[PATCH 00/32] tracing: Inter-event (e.g. latency) support

[PATCH 00/32] tracing: Inter-event (e.g. latency) support

[Tom Zanussi]

This patchset adds support for 'inter-event' quantities to the trace
event subsystem.  The most important example of inter-event quantities
are latencies, or the time differences between two events.

This is a follow-up to the initial RFC patchset and subsequent
discussion at ELC.  I think I've covered all the basic suggestions
from both those sources - thanks to everyone who reviewed and
contributed suggestions.  Also, thanks to Vedang Patel for testing and
providing real-user input and scripts - a number of the new patches
such as extended error reporting, cpu fields, and aliases address his
input directly.

The current patchset has been fairly well tested and I'm not aware of
any major problems with it, but there is one problem/feature to be
aware of, which has to do with the fact that currently the tracing map
can naturally have duplicate entries.  Normally this is expected and
isn't a problem for histograms without variables attached, as
duplicates are merged on output.  If a histogram has variables though
and gets a duplicate entry, the variable associated with that record
can't be trusted, since it can't be retrieved again.  Luckily
duplicates are normally very rare occurrences - I've never personally
seen one in practice - but it does mean that you always need to check
that the 'Duplicates' value on the histogram summary is 0 if that
histogram has variables attached.  We're currently working on a 'fix'
for this that basically eliminates the possibility of duplicates, but
for now the 'Duplicates' total will alert users to that rare situation
should it occur.

One of the main motivations for adding this capability is to provide a
general-purpose base that existing existing tools such as the -RT
latency_hist patchset can be built upon, while at the same time
providing a simple way for users to track latencies (or any
inter-event quantity) generically between any two events.

Previous -RT latency_hist patchsets that take advantage of the trace
event subsystem have been submitted, but they essentially hard-code
special-case tracepoints and application logic in ways that can't be
reused.  It seemed to me that rather than providing a one-off patchset
devoted specifically to generating the specific histograms in the
latency_hist patchset, it should be possible to build the same
functionality on top of a generic layer allowing users to do similar
things for other non-latency_hist applications.

In addition to preliminary patches that add some basic missing
functionality such as a common ringbuffer-derived timestamp and
dynamically-creatable tracepoints, the overall patchset is divided up
into a few different areas that combine to produce the overall goal
(The Documentation patch explains all the details):

  - variables and simple expressions required to calculate a latency

    In order to calculate a latency or any inter-event value,
    something from one event needs to be saved and later retrieved,
    and some operation such as subtraction or addition is performed on
    it.  This means some minimal form of variables and expressions,
    which the first set of patches implements.  Saving and retrieving
    events to use in a latency calculation is normally done using a
    hash table, and that's exactly what we have with trace event hist
    triggers, so that's where variables are instantiated, set, and
    retrieved.  Basically, variables are set on one entry and
    retrieved and used by a 'matching' event.

  - 'synthetic' events, combining variables from other events

    The trace event interface is based on pseudo-files associated with
    individual events, so it wouldn't really make sense to have
    quantities derived from multiple events attached to any one of
    those events.  For that reason, the patchset implements a means of
    combining variables from other events into a separate 'synthetic'
    event, which can be treated as if it were just like any other
    trace event in the system.

  - 'actions' generating synthetic events, among other things

    Variables and synthetic events provide the data and data structure
    for new events, but something still needs to actually generate an
    event using that data.  'Actions' are expanded to provide that
    capability.  Though it hasn't been explicitly called as much
    before, the default 'action' currently for a hist trigger is to
    update the matching histogram entry's sum values.  This patchset
    essentially expands that to provide a new 'onmatch.event(params)'
    action that can be used to have one event generate another.  The
    mechanism is extensible to other actions, and in fact the patchset
    also includes another, 'onmax(var).save(field,...)' that can be
    used to save context whenever a value exceeds the previous maximum
    (something also needed by latency_hist).

Here are some examples that should make things less abstract.

  ====
  Example - wakeup latency
  ====

  This basically implements the -RT latency_hist 'wakeup_latency'
  histogram using the synthetic events, variables, and actions
  described.  The output below is from a run of cyclictest using the
  following command:

    # rt-tests/cyclictest -p 80 -n -s -t 2

  What we're measuring the latency of is the time between when a
  thread (of cyclictest) is awakened and when it's scheduled in.  To
  do that we add triggers to sched_wakeup and sched_switch with the
  appropriate variables, and on a matching sched_switch event,
  generate a synthetic 'wakeup_latency' event.  Since it's just
  another trace event like any other, we can also define a histogram
  on that event, the output of which is what we see displayed when
  reading the wakeup_latency 'hist' file.

  First, we create a synthetic event called wakeup_latency, that
  creates 3 fields which will reference variables from other events:

    # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
        /sys/kernel/debug/tracing/synthetic_events

  Next we add a trigger to sched_wakeup, which saves the value of the
  '$common_timestamp' when that event is hit in a variable, ts0.  Note
  that this happens only when 'comm==cyclictest'.

  Also, '$common_timestamp' is a new field defined on every event (if
  needed - if there are no users of timestamps in a trace, timestamps
  won't be saved and there's no additional overhead from that).

    # echo 'hist:keys=pid:ts0=$common_timestamp.usecs if comm=="cyclictest"' >> \
        /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger

  Next, we add a trigger to sched_switch.  When the pid being switched
  to matches the pid woken up by a previous sched_wakeup event, this
  event grabs the ts0 variable saved on that event, takes the
  difference between it and the current sched_switch's
  $common_timestamp, and assigns it to a new 'wakeup_lat' variable.
  It then generates the wakeup_latency synthetic event defined earlier
  by 'invoking' it as a function using as parameters the wakeup_lat
  variable and two sched_switch event fields directly:

    # echo 'hist:keys=next_pid:wakeup_lat=$common_timestamp.usecs-$ts0: \
        onmatch(sched.sched_wakeup).wakeup_latency($wakeup_lat,next_pid,next_prio) \
        if next_comm=="cyclictest"' >> \
        /sys/kernel/debug/tracing/events/sched/sched_switch/trigger

  Finally, all we have left to do is create a standard histogram
  simply naming the fields of the wakeup_latency synthetic event:

    # echo 'hist:keys=pid,prio,lat:sort=pid,lat' >> \
        /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger

  At any time, we can see the histogram output by simply reading the
  synthetic/wakeup_latency/hist file:

    # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist

    # event histogram
    #
    # trigger info: hist:keys=pid,prio,lat:vals=hitcount:sort=pid,lat:size=2048 [active]
    #

    { pid:       2519, prio:        120, lat:          1 } hitcount:         12
    { pid:       2519, prio:        120, lat:          2 } hitcount:        671
    { pid:       2519, prio:        120, lat:          3 } hitcount:        588
    { pid:       2519, prio:        120, lat:          4 } hitcount:        202
    { pid:       2519, prio:        120, lat:          5 } hitcount:         28
    { pid:       2519, prio:        120, lat:          6 } hitcount:         13
    { pid:       2519, prio:        120, lat:          7 } hitcount:         12
    { pid:       2519, prio:        120, lat:          8 } hitcount:          7
    { pid:       2519, prio:        120, lat:          9 } hitcount:         12
    { pid:       2519, prio:        120, lat:         10 } hitcount:         11
    { pid:       2519, prio:        120, lat:         11 } hitcount:          7
    { pid:       2519, prio:        120, lat:         12 } hitcount:          6
    { pid:       2519, prio:        120, lat:         13 } hitcount:          1
    { pid:       2519, prio:        120, lat:         17 } hitcount:          1
    { pid:       2519, prio:        120, lat:         18 } hitcount:          3
    { pid:       2519, prio:        120, lat:         19 } hitcount:          2
    { pid:       2519, prio:        120, lat:         22 } hitcount:          2
    { pid:       2519, prio:        120, lat:         23 } hitcount:          1
    { pid:       2519, prio:        120, lat:         24 } hitcount:          1
    { pid:       2519, prio:        120, lat:         27 } hitcount:          1
    { pid:       2519, prio:        120, lat:         34 } hitcount:          1
    { pid:       2519, prio:        120, lat:         53 } hitcount:          1
    { pid:       2519, prio:        120, lat:         67 } hitcount:          1
    { pid:       2519, prio:        120, lat:         69 } hitcount:          1
    { pid:       2521, prio:         19, lat:          1 } hitcount:        735
    { pid:       2521, prio:         19, lat:          2 } hitcount:       8978
    { pid:       2521, prio:         19, lat:          3 } hitcount:       4798
    { pid:       2521, prio:         19, lat:          4 } hitcount:        716
    { pid:       2521, prio:         19, lat:          5 } hitcount:        298
    { pid:       2521, prio:         19, lat:          6 } hitcount:        136
    { pid:       2521, prio:         19, lat:          7 } hitcount:         93
    { pid:       2521, prio:         19, lat:          8 } hitcount:         51
    { pid:       2521, prio:         19, lat:          9 } hitcount:         20
    { pid:       2521, prio:         19, lat:         10 } hitcount:         18
    { pid:       2521, prio:         19, lat:         11 } hitcount:          3
    { pid:       2521, prio:         19, lat:         12 } hitcount:          1
    { pid:       2521, prio:         19, lat:         13 } hitcount:          3
    { pid:       2521, prio:         19, lat:         15 } hitcount:          1
    { pid:       2521, prio:         19, lat:         17 } hitcount:          1
    { pid:       2521, prio:         19, lat:         18 } hitcount:          1
    { pid:       2521, prio:         19, lat:         20 } hitcount:          2
    { pid:       2521, prio:         19, lat:         22 } hitcount:          1
    { pid:       2521, prio:         19, lat:         25 } hitcount:          1
    { pid:       2521, prio:         19, lat:         26 } hitcount:          1
    { pid:       2522, prio:         19, lat:          1 } hitcount:        392
    { pid:       2522, prio:         19, lat:          2 } hitcount:       5376
    { pid:       2522, prio:         19, lat:          3 } hitcount:       3982
    { pid:       2522, prio:         19, lat:          4 } hitcount:        500
    { pid:       2522, prio:         19, lat:          5 } hitcount:        202
    { pid:       2522, prio:         19, lat:          6 } hitcount:         67
    { pid:       2522, prio:         19, lat:          7 } hitcount:         35
    { pid:       2522, prio:         19, lat:          8 } hitcount:         12
    { pid:       2522, prio:         19, lat:          9 } hitcount:          9
    { pid:       2522, prio:         19, lat:         10 } hitcount:          4
    { pid:       2522, prio:         19, lat:         11 } hitcount:          3
    { pid:       2522, prio:         19, lat:         12 } hitcount:          1
    { pid:       2522, prio:         19, lat:         13 } hitcount:          1
    { pid:       2522, prio:         19, lat:         16 } hitcount:          1
    { pid:       2522, prio:         19, lat:         18 } hitcount:          2
    { pid:       2522, prio:         19, lat:         19 } hitcount:          1
    { pid:       2522, prio:         19, lat:         21 } hitcount:          2
    { pid:       2522, prio:         19, lat:         22 } hitcount:          1
    { pid:       2522, prio:         19, lat:         23 } hitcount:          1
    { pid:       2522, prio:         19, lat:         45 } hitcount:          1
    { pid:       2522, prio:         19, lat:         82 } hitcount:          1

    Totals:
        Hits: 28037
        Entries: 65
        Dropped: 0
        Duplicates: 0

  The above output uses the .usecs modifier to common_timestamp, so
  the latencies are reported in microseconds.  The default, without
  the modifier, is nanoseconds, but that's too fine-grained to put
  directly into a histogram - for that however we can use the .log2
  modifier on the 'lat' key.  Otherwise the rest is the same:

    # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
        /sys/kernel/debug/tracing/synthetic_events

    # echo 'hist:keys=pid:ts0=$common_timestamp if comm=="cyclictest"' >> \
        /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger

    # echo 'hist:keys=next_pid:wakeup_lat=$common_timestamp-$ts0: \
        onmatch(sched.sched_wakeup).wakeup_latency($wakeup_lat,next_pid,next_prio) \
        if next_comm=="cyclictest"' >> \
        /sys/kernel/debug/tracing/events/sched/sched_switch/trigger

    # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
        /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger

    # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist

    # event histogram
    #
    # trigger info: hist:keys=pid,prio,lat.log2:vals=hitcount:sort=pid,lat.log2:size=2048 [active]
    #

    { pid:       2585, prio:        120, lat: ~ 2^10 } hitcount:          1
    { pid:       2585, prio:        120, lat: ~ 2^11 } hitcount:        379
    { pid:       2585, prio:        120, lat: ~ 2^12 } hitcount:       1008
    { pid:       2585, prio:        120, lat: ~ 2^13 } hitcount:         42
    { pid:       2585, prio:        120, lat: ~ 2^14 } hitcount:         18
    { pid:       2585, prio:        120, lat: ~ 2^15 } hitcount:          3
    { pid:       2585, prio:        120, lat: ~ 2^16 } hitcount:          1
    { pid:       2586, prio:         19, lat: ~ 2^11 } hitcount:       4715
    { pid:       2586, prio:         19, lat: ~ 2^12 } hitcount:       9161
    { pid:       2586, prio:         19, lat: ~ 2^13 } hitcount:        632
    { pid:       2586, prio:         19, lat: ~ 2^14 } hitcount:         47
    { pid:       2586, prio:         19, lat: ~ 2^15 } hitcount:          3
    { pid:       2586, prio:         19, lat: ~ 2^17 } hitcount:          1
    { pid:       2587, prio:         19, lat: ~ 2^11 } hitcount:       3398
    { pid:       2587, prio:         19, lat: ~ 2^12 } hitcount:       5762
    { pid:       2587, prio:         19, lat: ~ 2^13 } hitcount:        505
    { pid:       2587, prio:         19, lat: ~ 2^14 } hitcount:         58
    { pid:       2587, prio:         19, lat: ~ 2^15 } hitcount:          3
    { pid:       2587, prio:         19, lat: ~ 2^17 } hitcount:          1

    Totals:
        Hits: 25738
        Entries: 19
        Dropped: 0
        Duplicates: 0

  ====
  Example - wakeup latency with onmax()
  ====

  This example is the same as the previous ones, but here we're
  additionally using the onmax() action to save some context (several
  fields of the sched_switch event) whenever the latency (wakeup_lat)
  exceeds the previous maximum.

  As with the similar functionality of the -RT latency_hist
  histograms, it's useful to be able to capture information about the
  previous process, which potentially could have contributed to the
  maximum latency that was saved.

    # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
        /sys/kernel/debug/tracing/synthetic_events

    # echo 'hist:keys=pid:ts0=$common_timestamp.usecs if comm=="cyclictest"' >> \
        /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger

  Here we add an onmax() action that saves some important fields of
  the sched_switch event along with the maximum, in addition to
  sending some of the same data to the synthetic event:

    # echo 'hist:keys=next_pid:wakeup_lat=$common_timestamp.usecs-$ts0: \
        onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm): \
	onmatch(sched.sched_wakeup).wakeup_latency($wakeup_lat,next_pid,next_prio) \
	if next_comm=="cyclictest"' >> \
	/sys/kernel/debug/tracing/events/sched/sched_switch/trigger

    # echo 'hist:keys=pid,prio,lat:sort=pid,lat' >> \
        /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger

  To see the maximums and associated data for each pid, cat the
  sched_switch event, as that's the event the onmax() action is
  associated with:

    # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist

    # event histogram
    #

    { next_pid:       6173 } hitcount:        199
      max:         14  next_comm: cyclictest  prev_pid:          0 \
      prev_prio:        120  prev_comm: swapper/2
    { next_pid:       6175 } hitcount:       1327
      max:         15  next_comm: cyclictest  prev_pid:          0 \
      prev_prio:        120  prev_comm: swapper/2
    { next_pid:       6174 } hitcount:       1985
      max:         30  next_comm: cyclictest  prev_pid:          0 \
      prev_prio:        120  prev_comm: swapper/3

    Totals:
        Hits: 17555
        Entries: 3
        Dropped: 0
        Duplicates: 0

  And, verifying, we can see that the max latencies captured above
  match the highest latencies for each thread in the wakeup_latency
  histogram:

    # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist

    # event histogram
    #
    # trigger info: hist:keys=pid,prio,lat:vals=hitcount:sort=pid,lat:size=2048 [active]
    #

    { pid:       6173, prio:        120, lat:          1 } hitcount:          2
    { pid:       6173, prio:        120, lat:          2 } hitcount:         82
    { pid:       6173, prio:        120, lat:          3 } hitcount:         84
    ...
    { pid:       6173, prio:        120, lat:         14 } hitcount:          1
    { pid:       6174, prio:         19, lat:          1 } hitcount:         23
    { pid:       6174, prio:         19, lat:          2 } hitcount:        749
    ...
    { pid:       6174, prio:         19, lat:         30 } hitcount:          1
    { pid:       6175, prio:         19, lat:          1 } hitcount:         20
    { pid:       6175, prio:         19, lat:          2 } hitcount:        633
    ...
    { pid:       6175, prio:         19, lat:         15 } hitcount:          1

    Totals:
        Hits: 3511
        Entries: 38
        Dropped: 0
        Duplicates: 0

  ====
  Example - combined wakeup and switchtime (wakeupswitch) latency
  ====

  Finally, this example is quite a bit more involved, but that's
  because it implements 3 latencies, one which is a combination of the
  other two.  This also, is something that the -RT latency_hist
  patchset does and which this patchset adds generic support for.

  The latency_hist patchset creates a few individual latency
  histograms but also combines them into larger overall combined
  histograms.  For example, the time between when a thread is awakened
  and when it actually continues executing in userspace is something
  covered by a histogram, but it's also broken down into two
  sub-histograms, one covering the time between sched_wakeup and the
  time the thread is scheduled in (wakeup_latency as above), and the
  time between when the thread is scheduled in and the time it
  actually begins executing again (return from sys_nanosleep), covered
  by a separate switchtime_latency histogram.

  The below combines the wakeup_latency histogram from before, adds a
  new switchtime_latency histogram, and another, wakeupswitch_latency,
  that's a combination of the other two.

  There isn't anything really new here, other than that the use of the
  addition operator to add two latencies to produce the
  wakeupswitch_latency.

  First, we create the familiar wakeup_latency histogram:

    # echo 'wakeup_latency u64 lat; pid_t pid' >> \
        /sys/kernel/debug/tracing/synthetic_events

    # echo 'hist:keys=pid:ts0=$common_timestamp.usecs \
        if comm=="cyclictest"' >> \
	/sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger

    # echo 'hist:keys=next_pid:wakeup_lat=$common_timestamp.usecs-$ts0:\
        onmatch(sched.sched_wakeup).wakeup_latency($wakeup_lat,next_pid) \
	if next_comm=="cyclictest"' >> \
	/sys/kernel/debug/tracing/events/sched/sched_switch/trigger

  Here we save the wakeup_latency lat value as wakeup_lat for use
  later in the combined latency:

    # echo 'hist:keys=pid,lat:wakeup_lat=lat:sort=pid,lat' \
        >> /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger

  Next, we create the switchtime_latency histogram:

    # echo 'switchtime_latency u64 lat; pid_t pid' >> \
        /sys/kernel/debug/tracing/synthetic_events

  Here we save the sched_switch next_pid field as 'pid'.  This is so
  we can access the next_pid in the matching sys_exit_nanosleep event.

    # echo 'hist:keys=next_pid:pid=next_pid:ts0=$common_timestamp.usecs \
        if next_comm=="cyclictest"' >> \
	/sys/kernel/debug/tracing/events/sched/sched_switch/trigger

    # echo 'hist:keys=common_pid:switchtime_lat=$common_timestamp.usecs-$ts0: \
        onmatch(sched.sched_switch).switchtime_latency($switchtime_lat,$pid)' \
	>> /sys/kernel/debug/tracing/events/syscalls/sys_exit_nanosleep/trigger

    # echo 'hist:keys=pid,lat:sort=pid,lat' \
        >> /sys/kernel/debug/tracing/events/synthetic/switchtime_latency/trigger

  Finally, we create the combined wakeupswitch_latency:

    # echo 'wakeupswitch_latency u64 lat; pid_t pid' >> \
        /sys/kernel/debug/tracing/synthetic_events

  Here we calculate the combined latency using the saved $wakeup_lat
  variable from the wakeup_latency histogram and the lat value of the
  switchtime_latency, save it as ws_lat and then use it to generate
  the combined wakeupswitch latency:

    # echo 'hist:keys=pid,lat:sort=pid,lat:ws_lat=$wakeup_lat+lat: \
        onmatch(synthetic.wakeup_latency).wakeupswitch_latency($ws_lat,pid)' \
	>> /sys/kernel/debug/tracing/events/synthetic/switchtime_latency/trigger

    # echo 'hist:keys=pid,lat:sort=pid,lat' >> \
    /sys/kernel/debug/tracing/events/synthetic/wakeupswitch_latency/trigger


  After running our cyclictest workload, we can now look at each
  histogram, starting with wakeup_latency:

    # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist

    # event histogram
    #
    # trigger info: hist:keys=pid,lat:vals=hitcount:wakeup_lat=lat:sort=pid,lat:size=2048 [active]
    #

    { pid:       6852, lat:          1 } hitcount:          2
    { pid:       6852, lat:          2 } hitcount:         88
    { pid:       6852, lat:          3 } hitcount:         72
    { pid:       6852, lat:          4 } hitcount:         19
    { pid:       6852, lat:          5 } hitcount:         10
    { pid:       6852, lat:          6 } hitcount:          1
    { pid:       6852, lat:          7 } hitcount:          4
    { pid:       6852, lat:          9 } hitcount:          2
    { pid:       6852, lat:         10 } hitcount:          1
    { pid:       6853, lat:          1 } hitcount:          1
    { pid:       6853, lat:          2 } hitcount:        535
    { pid:       6853, lat:          3 } hitcount:       1007
    ...
    { pid:       6853, lat:         19 } hitcount:          1
    { pid:       6853, lat:         20 } hitcount:          1
    { pid:       6853, lat:         29 } hitcount:          1
    { pid:       6854, lat:          1 } hitcount:          5
    { pid:       6854, lat:          2 } hitcount:        552
    { pid:       6854, lat:          3 } hitcount:        532
    { pid:       6854, lat:          4 } hitcount:        135
    { pid:       6854, lat:          5 } hitcount:         48
    { pid:       6854, lat:          6 } hitcount:         18
    { pid:       6854, lat:          7 } hitcount:         12
    { pid:       6854, lat:          8 } hitcount:          5
    ...
    { pid:       6854, lat:         29 } hitcount:          2
    { pid:       6854, lat:         48 } hitcount:          1

    Totals:
    Hits: 3501
    Entries: 46
    Dropped: 0
    Duplicates: 0

  Here's the switchtime histogram:

    # cat /sys/kernel/debug/tracing/events/synthetic/switchtime_latency/hist

    # event histogram
    #
    # trigger info: hist:keys=pid,lat:vals=hitcount:sort=pid,lat:size=2048 [active]
    #

    { pid:       6852, lat:          1 } hitcount:          1
    { pid:       6852, lat:          2 } hitcount:         33
    { pid:       6852, lat:          3 } hitcount:         73
    { pid:       6852, lat:          4 } hitcount:         49
    { pid:       6852, lat:          5 } hitcount:         28
    { pid:       6852, lat:          6 } hitcount:          4
    ...
    { pid:       6852, lat:         16 } hitcount:          1
    { pid:       6853, lat:          1 } hitcount:         76
    { pid:       6853, lat:          2 } hitcount:       1190
    { pid:       6853, lat:          3 } hitcount:        475
    { pid:       6853, lat:          4 } hitcount:        125
    { pid:       6853, lat:          5 } hitcount:         40
    { pid:       6853, lat:          6 } hitcount:         21
    { pid:       6853, lat:          7 } hitcount:         13
    { pid:       6853, lat:          8 } hitcount:          5
    { pid:       6853, lat:          9 } hitcount:         11
    ...
    { pid:       6853, lat:         20 } hitcount:          2
    { pid:       6854, lat:          1 } hitcount:         13
    { pid:       6854, lat:          2 } hitcount:        799
    { pid:       6854, lat:          3 } hitcount:        332
    { pid:       6854, lat:          4 } hitcount:         97
    { pid:       6854, lat:          5 } hitcount:         29
    { pid:       6854, lat:          6 } hitcount:         16
    ...
    { pid:       6854, lat:         22 } hitcount:          1
    { pid:       6854, lat:         26 } hitcount:          1

    Totals:
    Hits: 3501
    Entries: 48
    Dropped: 0
    Duplicates: 0

  And here's the combined wakeupswitch latency histogram:

    # cat /sys/kernel/debug/tracing/events/synthetic/wakeupswitch_latency/hist

    # event histogram
    #
    # trigger info: hist:keys=pid,lat:vals=hitcount:sort=pid,lat:size=2048 [active]
    #

    { pid:       6852, lat:          4 } hitcount:         24
    { pid:       6852, lat:          5 } hitcount:         47
    { pid:       6852, lat:          6 } hitcount:         53
    { pid:       6852, lat:          7 } hitcount:         29
    ...
    { pid:       6852, lat:         25 } hitcount:          1
    { pid:       6853, lat:          3 } hitcount:          5
    { pid:       6853, lat:          4 } hitcount:        504
    { pid:       6853, lat:          5 } hitcount:        753
    { pid:       6853, lat:          6 } hitcount:        337
    { pid:       6853, lat:          7 } hitcount:        149
    { pid:       6853, lat:          8 } hitcount:         66
    { pid:       6853, lat:          9 } hitcount:         45
    { pid:       6853, lat:         10 } hitcount:         24
    { pid:       6853, lat:         11 } hitcount:         26
    { pid:       6853, lat:         12 } hitcount:          9
    { pid:       6853, lat:         13 } hitcount:         13
    { pid:       6853, lat:         14 } hitcount:          9
    { pid:       6853, lat:         15 } hitcount:          3
    { pid:       6853, lat:         17 } hitcount:          3
    { pid:       6853, lat:         18 } hitcount:          5
    { pid:       6853, lat:         19 } hitcount:          2
    ...
    { pid:       6853, lat:         37 } hitcount:          1
    { pid:       6853, lat:         38 } hitcount:          1
    { pid:       6854, lat:          3 } hitcount:          7
    { pid:       6854, lat:          4 } hitcount:        418
    { pid:       6854, lat:          5 } hitcount:        493
    { pid:       6854, lat:          6 } hitcount:        165
    { pid:       6854, lat:          7 } hitcount:         81
    { pid:       6854, lat:          8 } hitcount:         57
    { pid:       6854, lat:          9 } hitcount:         27
    { pid:       6854, lat:         10 } hitcount:         15
    { pid:       6854, lat:         11 } hitcount:         13
    { pid:       6854, lat:         12 } hitcount:          7
    { pid:       6854, lat:         13 } hitcount:         10
    { pid:       6854, lat:         14 } hitcount:          6
    { pid:       6854, lat:         15 } hitcount:          5
    { pid:       6854, lat:         16 } hitcount:          5
    { pid:       6854, lat:         17 } hitcount:          2
    { pid:       6854, lat:         18 } hitcount:          1
    ...
    { pid:       6854, lat:         55 } hitcount:          1

    Totals:
    Hits: 3501
    Entries: 70
    Dropped: 0
    Duplicates: 0

  Finally, just to show that synthetic events are indeed just like any
  other event as far as the event subsystem is concerned, we can
  enable the synthetic events and see the events appear in the trace
  buffer:

    # echo 1 > /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/enable
    # echo 1 > /sys/kernel/debug/tracing/events/synthetic/switchtime_latency/enable
    # echo 1 > /sys/kernel/debug/tracing/events/synthetic/wakeupswitch_latency/enable

  Below is a snippet of the contents of the trace file produced when
  the above histograms were generated:

    # cat /sys/kernel/debug/tracing/trace

    # tracer: nop
    #
    # entries-in-buffer/entries-written: 10503/10503   #P:4
    #
    #                              _-----=> irqs-off
    #                             / _----=> need-resched
    #                            | / _---=> hardirq/softirq
    #                            || / _--=> preempt-depth
    #                            ||| /     delay
    #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
    #              | |       |   ||||       |         |
              <idle>-0     [001] d..2 23532.240146: wakeup_latency: lat=4, pid=6853
          cyclictest-6853  [001] .... 23532.240153: switchtime_latency: lat=7, pid=6853
          cyclictest-6853  [001] .... 23532.240157: wakeupswitch_latency: lat=11, pid=6853
     gnome-terminal--2500  [001] d..2 23532.240672: wakeup_latency: lat=5, pid=6854
          cyclictest-6854  [001] .... 23532.240676: switchtime_latency: lat=4, pid=6854
          cyclictest-6854  [001] .... 23532.240677: wakeupswitch_latency: lat=9, pid=6854
     gnome-terminal--2500  [001] d..2 23532.241169: wakeup_latency: lat=4, pid=6853
          cyclictest-6853  [001] .... 23532.241172: switchtime_latency: lat=3, pid=6853
          cyclictest-6853  [001] .... 23532.241174: wakeupswitch_latency: lat=7, pid=6853
              <idle>-0     [001] d..2 23532.242189: wakeup_latency: lat=6, pid=6853
          cyclictest-6853  [001] .... 23532.242195: switchtime_latency: lat=8, pid=6853
              <idle>-0     [000] d..2 23532.242196: wakeup_latency: lat=12, pid=6854
          cyclictest-6853  [001] .... 23532.240146: wakeupswitch_latency: lat=14, pid=6853
          cyclictest-6854  [000] .... 23532.242196: switchtime_latency: lat=4, pid=6854
              <idle>-0     [001] d..2 23532.240146: wakeup_latency: lat=2, pid=6853
          cyclictest-6854  [000] .... 23532.242196: wakeupswitch_latency: lat=16, pid=6854
          cyclictest-6853  [001] .... 23532.240146: switchtime_latency: lat=3, pid=6853
    ...

  One quick note about usage - the introduction of variables and
  actions obviously makes it harder to determine the cause of a hist
  trigger command failure - 'Invalid argument' is no longer sufficient
  in many cases.

  For that reason, a new 'extended error' mechanism has been added to
  hist triggers, initially focused on variable and action-related
  errors, but something that could possibly expanded to other error
  conditions later.

  To make use of it, simply read the 'hist' file of the event that was
  the target of the command.

  In this example, we've entered the same command twice, resulting in
  an attempt to define the same variable (ts0) twice.  After seeing
  the 'Invalid argument' error for the command, we read the same
  event's hist file and see a message to that effect at the bottom of
  the file:

    # echo 'hist:keys=pid:ts0=$common_timestamp.usecs if comm=="cyclictest"' >> \
        /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger

    # echo 'hist:keys=pid:ts0=$common_timestamp.usecs if comm=="cyclictest"' >> \
        /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger

    -su: echo: write error: Invalid argument

    # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
    # event histogram
    #
    #

    Totals:
    Hits: 0
    Entries: 0
    Dropped: 0
    Duplicates: 0

    ERROR: Variable already defined: ts0
      Last command: keys=pid:ts0=$common_timestamp.usecs if comm=="cyclictest"


The following changes since commit 681bec0367c2606b6154060310a2ffa543175980:

  tracing: Rename update the enum_map file (2017-06-13 17:13:06 -0400)

are available in the git repository at:

  https://github.com/tzanussi/linux-trace-inter-event.git tzanussi/inter-event-v01
  https://github.com/tzanussi/linux-trace-inter-event/tree/tzanussi/inter-event-v01

Tom Zanussi (32):
  tracing: Add hist_field_name() accessor
  tracing: Reimplement log2
  ring-buffer: Add interface for setting absolute time stamps
  ring-buffer: Redefine the unimplemented RINGBUF_TIME_TIME_STAMP
  tracing: Give event triggers access to ring_buffer_event
  tracing: Add ring buffer event param to hist field functions
  tracing: Increase tracing map KEYS_MAX size
  tracing: Break out hist trigger assignment parsing
  tracing: Make traceprobe parsing code reusable
  tracing: Add NO_DISCARD event file flag
  tracing: Add post-trigger flag to hist trigger command
  tracing: Add hist trigger timestamp support
  tracing: Add per-element variable support to tracing_map
  tracing: Add hist_data member to hist_field
  tracing: Add usecs modifier for hist trigger timestamps
  tracing: Add variable support to hist triggers
  tracing: Account for variables in named trigger compatibility
  tracing: Add simple expression support to hist triggers
  tracing: Add variable reference handling to hist triggers
  tracing: Add support for dynamic tracepoints
  tracing: Add hist trigger action hook
  tracing: Add support for 'synthetic' events
  tracing: Add 'onmatch' hist trigger action support
  tracing: Add 'onmax' hist trigger action support
  tracing: Allow whitespace to surround hist trigger filter
  tracing: Make duplicate count from tracing_map available
  tracing: Add cpu field for hist triggers
  tracing: Add hist trigger support for variable reference aliases
  tracing: Add 'last error' error facility for hist triggers
  tracing: Add inter-event hist trigger Documentation
  tracing: Make tracing_set_clock() non-static
  tracing: Add a clock attribute for hist triggers

 Documentation/trace/events.txt      |  422 ++++
 include/linux/ring_buffer.h         |   14 +-
 include/linux/trace_events.h        |   17 +-
 include/linux/tracepoint.h          |   11 +-
 kernel/trace/ring_buffer.c          |  118 +-
 kernel/trace/trace.c                |  121 +-
 kernel/trace/trace.h                |   36 +-
 kernel/trace/trace_events.c         |    4 +-
 kernel/trace/trace_events_hist.c    | 4107 ++++++++++++++++++++++++++++++++---
 kernel/trace/trace_events_trigger.c |   69 +-
 kernel/trace/trace_kprobe.c         |   18 +-
 kernel/trace/trace_probe.c          |   86 -
 kernel/trace/trace_probe.h          |    7 -
 kernel/trace/trace_uprobe.c         |    2 +-
 kernel/trace/tracing_map.c          |  125 +-
 kernel/trace/tracing_map.h          |   16 +-
 kernel/tracepoint.c                 |   42 +-
 17 files changed, 4684 insertions(+), 531 deletions(-)

-- 
1.9.3

[PATCH 01/32] tracing: Add hist_field_name() accessor

[Tom Zanussi]

In preparation for hist_fields that won't be strictly based on
trace_event_fields, add a new hist_field_name() accessor to allow that
flexibility and update associated users.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 68 +++++++++++++++++++++++++++-------------
 1 file changed, 46 insertions(+), 22 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 1c21d0e..91ffc39 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -146,6 +146,23 @@ struct hist_trigger_data {
 	struct tracing_map		*map;
 };
 
+static const char *hist_field_name(struct hist_field *field,
+				   unsigned int level)
+{
+	const char *field_name = "";
+
+	if (level > 1)
+		return field_name;
+
+	if (field->field)
+		field_name = field->field->name;
+
+	if (field_name == NULL)
+		field_name = "";
+
+	return field_name;
+}
+
 static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)
 {
 	hist_field_fn_t fn = NULL;
@@ -653,7 +670,6 @@ static int is_descending(const char *str)
 static int create_sort_keys(struct hist_trigger_data *hist_data)
 {
 	char *fields_str = hist_data->attrs->sort_key_str;
-	struct ftrace_event_field *field = NULL;
 	struct tracing_map_sort_key *sort_key;
 	int descending, ret = 0;
 	unsigned int i, j;
@@ -670,7 +686,9 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 	}
 
 	for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
+		struct hist_field *hist_field;
 		char *field_str, *field_name;
+		const char *test_name;
 
 		sort_key = &hist_data->sort_keys[i];
 
@@ -703,8 +721,11 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 		}
 
 		for (j = 1; j < hist_data->n_fields; j++) {
-			field = hist_data->fields[j]->field;
-			if (field && (strcmp(field_name, field->name) == 0)) {
+			hist_field = hist_data->fields[j];
+			test_name = hist_field_name(hist_field, 0);
+			if (test_name == NULL)
+				continue;
+			if (strcmp(field_name, test_name) == 0) {
 				sort_key->field_idx = j;
 				descending = is_descending(field_str);
 				if (descending < 0) {
@@ -952,6 +973,7 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 	struct hist_field *key_field;
 	char str[KSYM_SYMBOL_LEN];
 	bool multiline = false;
+	const char *field_name;
 	unsigned int i;
 	u64 uval;
 
@@ -963,26 +985,27 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 		if (i > hist_data->n_vals)
 			seq_puts(m, ", ");
 
+		field_name = hist_field_name(key_field, 0);
+
 		if (key_field->flags & HIST_FIELD_FL_HEX) {
 			uval = *(u64 *)(key + key_field->offset);
-			seq_printf(m, "%s: %llx",
-				   key_field->field->name, uval);
+			seq_printf(m, "%s: %llx", field_name, uval);
 		} else if (key_field->flags & HIST_FIELD_FL_SYM) {
 			uval = *(u64 *)(key + key_field->offset);
 			sprint_symbol_no_offset(str, uval);
-			seq_printf(m, "%s: [%llx] %-45s",
-				   key_field->field->name, uval, str);
+			seq_printf(m, "%s: [%llx] %-45s", field_name,
+				   uval, str);
 		} else if (key_field->flags & HIST_FIELD_FL_SYM_OFFSET) {
 			uval = *(u64 *)(key + key_field->offset);
 			sprint_symbol(str, uval);
-			seq_printf(m, "%s: [%llx] %-55s",
-				   key_field->field->name, uval, str);
+			seq_printf(m, "%s: [%llx] %-55s", field_name,
+				   uval, str);
 		} else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
 			char *comm = elt->private_data;
 
 			uval = *(u64 *)(key + key_field->offset);
-			seq_printf(m, "%s: %-16s[%10llu]",
-				   key_field->field->name, comm, uval);
+			seq_printf(m, "%s: %-16s[%10llu]", field_name,
+				   comm, uval);
 		} else if (key_field->flags & HIST_FIELD_FL_SYSCALL) {
 			const char *syscall_name;
 
@@ -991,8 +1014,8 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 			if (!syscall_name)
 				syscall_name = "unknown_syscall";
 
-			seq_printf(m, "%s: %-30s[%3llu]",
-				   key_field->field->name, syscall_name, uval);
+			seq_printf(m, "%s: %-30s[%3llu]", field_name,
+				   syscall_name, uval);
 		} else if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
 			seq_puts(m, "stacktrace:\n");
 			hist_trigger_stacktrace_print(m,
@@ -1000,15 +1023,14 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 						      HIST_STACKTRACE_DEPTH);
 			multiline = true;
 		} else if (key_field->flags & HIST_FIELD_FL_LOG2) {
-			seq_printf(m, "%s: ~ 2^%-2llu", key_field->field->name,
+			seq_printf(m, "%s: ~ 2^%-2llu", field_name,
 				   *(u64 *)(key + key_field->offset));
 		} else if (key_field->flags & HIST_FIELD_FL_STRING) {
-			seq_printf(m, "%s: %-50s", key_field->field->name,
+			seq_printf(m, "%s: %-50s", field_name,
 				   (char *)(key + key_field->offset));
 		} else {
 			uval = *(u64 *)(key + key_field->offset);
-			seq_printf(m, "%s: %10llu", key_field->field->name,
-				   uval);
+			seq_printf(m, "%s: %10llu", field_name, uval);
 		}
 	}
 
@@ -1021,13 +1043,13 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 		   tracing_map_read_sum(elt, HITCOUNT_IDX));
 
 	for (i = 1; i < hist_data->n_vals; i++) {
+		field_name = hist_field_name(hist_data->fields[i], 0);
+
 		if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
-			seq_printf(m, "  %s: %10llx",
-				   hist_data->fields[i]->field->name,
+			seq_printf(m, "  %s: %10llx", field_name,
 				   tracing_map_read_sum(elt, i));
 		} else {
-			seq_printf(m, "  %s: %10llu",
-				   hist_data->fields[i]->field->name,
+			seq_printf(m, "  %s: %10llu", field_name,
 				   tracing_map_read_sum(elt, i));
 		}
 	}
@@ -1142,7 +1164,9 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
 
 static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
 {
-	seq_printf(m, "%s", hist_field->field->name);
+	const char *field_name = hist_field_name(hist_field, 0);
+
+	seq_printf(m, "%s", field_name);
 	if (hist_field->flags) {
 		const char *flags_str = get_hist_field_flags(hist_field);
 
-- 
1.9.3

RE: [PATCH 01/32] tracing: Add hist_field_name() accessor

[Piotr Gregor]

Hi Tom,

Which repo and branch do you push these changes into?

cheers,
Piotr

-----Original Message-----
From: linux-rt-users-owner@vger.kernel.org [mailto:linux-rt-users-owner@vger.kernel.org] On Behalf Of Tom Zanussi
Sent: 26 June 2017 23:49
To: rostedt@goodmis.org
Cc: tglx@linutronix.de; mhiramat@kernel.org; namhyung@kernel.org; vedang.patel@intel.com; linux-kernel@vger.kernel.org; linux-rt-users@vger.kernel.org; Tom Zanussi <tom.zanussi@linux.intel.com>
Subject: [PATCH 01/32] tracing: Add hist_field_name() accessor

In preparation for hist_fields that won't be strictly based on trace_event_fields, add a new hist_field_name() accessor to allow that flexibility and update associated users.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 68 +++++++++++++++++++++++++++-------------
 1 file changed, 46 insertions(+), 22 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 1c21d0e..91ffc39 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -146,6 +146,23 @@ struct hist_trigger_data {
 	struct tracing_map		*map;
 };
 
+static const char *hist_field_name(struct hist_field *field,
+				   unsigned int level)
+{
+	const char *field_name = "";
+
+	if (level > 1)
+		return field_name;
+
+	if (field->field)
+		field_name = field->field->name;
+
+	if (field_name == NULL)
+		field_name = "";
+
+	return field_name;
+}
+
 static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)  {
 	hist_field_fn_t fn = NULL;
@@ -653,7 +670,6 @@ static int is_descending(const char *str)  static int create_sort_keys(struct hist_trigger_data *hist_data)  {
 	char *fields_str = hist_data->attrs->sort_key_str;
-	struct ftrace_event_field *field = NULL;
 	struct tracing_map_sort_key *sort_key;
 	int descending, ret = 0;
 	unsigned int i, j;
@@ -670,7 +686,9 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 	}
 
 	for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
+		struct hist_field *hist_field;
 		char *field_str, *field_name;
+		const char *test_name;
 
 		sort_key = &hist_data->sort_keys[i];
 
@@ -703,8 +721,11 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 		}
 
 		for (j = 1; j < hist_data->n_fields; j++) {
-			field = hist_data->fields[j]->field;
-			if (field && (strcmp(field_name, field->name) == 0)) {
+			hist_field = hist_data->fields[j];
+			test_name = hist_field_name(hist_field, 0);
+			if (test_name == NULL)
+				continue;
+			if (strcmp(field_name, test_name) == 0) {
 				sort_key->field_idx = j;
 				descending = is_descending(field_str);
 				if (descending < 0) {
@@ -952,6 +973,7 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 	struct hist_field *key_field;
 	char str[KSYM_SYMBOL_LEN];
 	bool multiline = false;
+	const char *field_name;
 	unsigned int i;
 	u64 uval;
 
@@ -963,26 +985,27 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 		if (i > hist_data->n_vals)
 			seq_puts(m, ", ");
 
+		field_name = hist_field_name(key_field, 0);
+
 		if (key_field->flags & HIST_FIELD_FL_HEX) {
 			uval = *(u64 *)(key + key_field->offset);
-			seq_printf(m, "%s: %llx",
-				   key_field->field->name, uval);
+			seq_printf(m, "%s: %llx", field_name, uval);
 		} else if (key_field->flags & HIST_FIELD_FL_SYM) {
 			uval = *(u64 *)(key + key_field->offset);
 			sprint_symbol_no_offset(str, uval);
-			seq_printf(m, "%s: [%llx] %-45s",
-				   key_field->field->name, uval, str);
+			seq_printf(m, "%s: [%llx] %-45s", field_name,
+				   uval, str);
 		} else if (key_field->flags & HIST_FIELD_FL_SYM_OFFSET) {
 			uval = *(u64 *)(key + key_field->offset);
 			sprint_symbol(str, uval);
-			seq_printf(m, "%s: [%llx] %-55s",
-				   key_field->field->name, uval, str);
+			seq_printf(m, "%s: [%llx] %-55s", field_name,
+				   uval, str);
 		} else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
 			char *comm = elt->private_data;
 
 			uval = *(u64 *)(key + key_field->offset);
-			seq_printf(m, "%s: %-16s[%10llu]",
-				   key_field->field->name, comm, uval);
+			seq_printf(m, "%s: %-16s[%10llu]", field_name,
+				   comm, uval);
 		} else if (key_field->flags & HIST_FIELD_FL_SYSCALL) {
 			const char *syscall_name;
 
@@ -991,8 +1014,8 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 			if (!syscall_name)
 				syscall_name = "unknown_syscall";
 
-			seq_printf(m, "%s: %-30s[%3llu]",
-				   key_field->field->name, syscall_name, uval);
+			seq_printf(m, "%s: %-30s[%3llu]", field_name,
+				   syscall_name, uval);
 		} else if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
 			seq_puts(m, "stacktrace:\n");
 			hist_trigger_stacktrace_print(m,
@@ -1000,15 +1023,14 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 						      HIST_STACKTRACE_DEPTH);
 			multiline = true;
 		} else if (key_field->flags & HIST_FIELD_FL_LOG2) {
-			seq_printf(m, "%s: ~ 2^%-2llu", key_field->field->name,
+			seq_printf(m, "%s: ~ 2^%-2llu", field_name,
 				   *(u64 *)(key + key_field->offset));
 		} else if (key_field->flags & HIST_FIELD_FL_STRING) {
-			seq_printf(m, "%s: %-50s", key_field->field->name,
+			seq_printf(m, "%s: %-50s", field_name,
 				   (char *)(key + key_field->offset));
 		} else {
 			uval = *(u64 *)(key + key_field->offset);
-			seq_printf(m, "%s: %10llu", key_field->field->name,
-				   uval);
+			seq_printf(m, "%s: %10llu", field_name, uval);
 		}
 	}
 
@@ -1021,13 +1043,13 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 		   tracing_map_read_sum(elt, HITCOUNT_IDX));
 
 	for (i = 1; i < hist_data->n_vals; i++) {
+		field_name = hist_field_name(hist_data->fields[i], 0);
+
 		if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
-			seq_printf(m, "  %s: %10llx",
-				   hist_data->fields[i]->field->name,
+			seq_printf(m, "  %s: %10llx", field_name,
 				   tracing_map_read_sum(elt, i));
 		} else {
-			seq_printf(m, "  %s: %10llu",
-				   hist_data->fields[i]->field->name,
+			seq_printf(m, "  %s: %10llu", field_name,
 				   tracing_map_read_sum(elt, i));
 		}
 	}
@@ -1142,7 +1164,9 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
 
 static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)  {
-	seq_printf(m, "%s", hist_field->field->name);
+	const char *field_name = hist_field_name(hist_field, 0);
+
+	seq_printf(m, "%s", field_name);
 	if (hist_field->flags) {
 		const char *flags_str = get_hist_field_flags(hist_field);
 
--
1.9.3

--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@vger.kernel.org More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 01/32] tracing: Add hist_field_name() accessor

[Tom Zanussi]

Hi Piotr,

On Thu, 2017-07-13 at 06:49 +0000, Piotr Gregor wrote:
> Hi Tom,
> 
> Which repo and branch do you push these changes into?
> 

  https://github.com/tzanussi/linux-trace-inter-event.git tzanussi/inter-event-v01

Tom

> cheers,
> Piotr
> 
> -----Original Message-----
> From: linux-rt-users-owner@vger.kernel.org [mailto:linux-rt-users-owner@vger.kernel.org] On Behalf Of Tom Zanussi
> Sent: 26 June 2017 23:49
> To: rostedt@goodmis.org
> Cc: tglx@linutronix.de; mhiramat@kernel.org; namhyung@kernel.org; vedang.patel@intel.com; linux-kernel@vger.kernel.org; linux-rt-users@vger.kernel.org; Tom Zanussi <tom.zanussi@linux.intel.com>
> Subject: [PATCH 01/32] tracing: Add hist_field_name() accessor
> 
> In preparation for hist_fields that won't be strictly based on trace_event_fields, add a new hist_field_name() accessor to allow that flexibility and update associated users.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  kernel/trace/trace_events_hist.c | 68 +++++++++++++++++++++++++++-------------
>  1 file changed, 46 insertions(+), 22 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 1c21d0e..91ffc39 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -146,6 +146,23 @@ struct hist_trigger_data {
>  	struct tracing_map		*map;
>  };
>  
> +static const char *hist_field_name(struct hist_field *field,
> +				   unsigned int level)
> +{
> +	const char *field_name = "";
> +
> +	if (level > 1)
> +		return field_name;
> +
> +	if (field->field)
> +		field_name = field->field->name;
> +
> +	if (field_name == NULL)
> +		field_name = "";
> +
> +	return field_name;
> +}
> +
>  static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)  {
>  	hist_field_fn_t fn = NULL;
> @@ -653,7 +670,6 @@ static int is_descending(const char *str)  static int create_sort_keys(struct hist_trigger_data *hist_data)  {
>  	char *fields_str = hist_data->attrs->sort_key_str;
> -	struct ftrace_event_field *field = NULL;
>  	struct tracing_map_sort_key *sort_key;
>  	int descending, ret = 0;
>  	unsigned int i, j;
> @@ -670,7 +686,9 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
>  	}
>  
>  	for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
> +		struct hist_field *hist_field;
>  		char *field_str, *field_name;
> +		const char *test_name;
>  
>  		sort_key = &hist_data->sort_keys[i];
>  
> @@ -703,8 +721,11 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
>  		}
>  
>  		for (j = 1; j < hist_data->n_fields; j++) {
> -			field = hist_data->fields[j]->field;
> -			if (field && (strcmp(field_name, field->name) == 0)) {
> +			hist_field = hist_data->fields[j];
> +			test_name = hist_field_name(hist_field, 0);
> +			if (test_name == NULL)
> +				continue;
> +			if (strcmp(field_name, test_name) == 0) {
>  				sort_key->field_idx = j;
>  				descending = is_descending(field_str);
>  				if (descending < 0) {
> @@ -952,6 +973,7 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
>  	struct hist_field *key_field;
>  	char str[KSYM_SYMBOL_LEN];
>  	bool multiline = false;
> +	const char *field_name;
>  	unsigned int i;
>  	u64 uval;
>  
> @@ -963,26 +985,27 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
>  		if (i > hist_data->n_vals)
>  			seq_puts(m, ", ");
>  
> +		field_name = hist_field_name(key_field, 0);
> +
>  		if (key_field->flags & HIST_FIELD_FL_HEX) {
>  			uval = *(u64 *)(key + key_field->offset);
> -			seq_printf(m, "%s: %llx",
> -				   key_field->field->name, uval);
> +			seq_printf(m, "%s: %llx", field_name, uval);
>  		} else if (key_field->flags & HIST_FIELD_FL_SYM) {
>  			uval = *(u64 *)(key + key_field->offset);
>  			sprint_symbol_no_offset(str, uval);
> -			seq_printf(m, "%s: [%llx] %-45s",
> -				   key_field->field->name, uval, str);
> +			seq_printf(m, "%s: [%llx] %-45s", field_name,
> +				   uval, str);
>  		} else if (key_field->flags & HIST_FIELD_FL_SYM_OFFSET) {
>  			uval = *(u64 *)(key + key_field->offset);
>  			sprint_symbol(str, uval);
> -			seq_printf(m, "%s: [%llx] %-55s",
> -				   key_field->field->name, uval, str);
> +			seq_printf(m, "%s: [%llx] %-55s", field_name,
> +				   uval, str);
>  		} else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
>  			char *comm = elt->private_data;
>  
>  			uval = *(u64 *)(key + key_field->offset);
> -			seq_printf(m, "%s: %-16s[%10llu]",
> -				   key_field->field->name, comm, uval);
> +			seq_printf(m, "%s: %-16s[%10llu]", field_name,
> +				   comm, uval);
>  		} else if (key_field->flags & HIST_FIELD_FL_SYSCALL) {
>  			const char *syscall_name;
>  
> @@ -991,8 +1014,8 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
>  			if (!syscall_name)
>  				syscall_name = "unknown_syscall";
>  
> -			seq_printf(m, "%s: %-30s[%3llu]",
> -				   key_field->field->name, syscall_name, uval);
> +			seq_printf(m, "%s: %-30s[%3llu]", field_name,
> +				   syscall_name, uval);
>  		} else if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
>  			seq_puts(m, "stacktrace:\n");
>  			hist_trigger_stacktrace_print(m,
> @@ -1000,15 +1023,14 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
>  						      HIST_STACKTRACE_DEPTH);
>  			multiline = true;
>  		} else if (key_field->flags & HIST_FIELD_FL_LOG2) {
> -			seq_printf(m, "%s: ~ 2^%-2llu", key_field->field->name,
> +			seq_printf(m, "%s: ~ 2^%-2llu", field_name,
>  				   *(u64 *)(key + key_field->offset));
>  		} else if (key_field->flags & HIST_FIELD_FL_STRING) {
> -			seq_printf(m, "%s: %-50s", key_field->field->name,
> +			seq_printf(m, "%s: %-50s", field_name,
>  				   (char *)(key + key_field->offset));
>  		} else {
>  			uval = *(u64 *)(key + key_field->offset);
> -			seq_printf(m, "%s: %10llu", key_field->field->name,
> -				   uval);
> +			seq_printf(m, "%s: %10llu", field_name, uval);
>  		}
>  	}
>  
> @@ -1021,13 +1043,13 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
>  		   tracing_map_read_sum(elt, HITCOUNT_IDX));
>  
>  	for (i = 1; i < hist_data->n_vals; i++) {
> +		field_name = hist_field_name(hist_data->fields[i], 0);
> +
>  		if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
> -			seq_printf(m, "  %s: %10llx",
> -				   hist_data->fields[i]->field->name,
> +			seq_printf(m, "  %s: %10llx", field_name,
>  				   tracing_map_read_sum(elt, i));
>  		} else {
> -			seq_printf(m, "  %s: %10llu",
> -				   hist_data->fields[i]->field->name,
> +			seq_printf(m, "  %s: %10llu", field_name,
>  				   tracing_map_read_sum(elt, i));
>  		}
>  	}
> @@ -1142,7 +1164,9 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
>  
>  static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)  {
> -	seq_printf(m, "%s", hist_field->field->name);
> +	const char *field_name = hist_field_name(hist_field, 0);
> +
> +	seq_printf(m, "%s", field_name);
>  	if (hist_field->flags) {
>  		const char *flags_str = get_hist_field_flags(hist_field);
>  
> --
> 1.9.3
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@vger.kernel.org More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 01/32] tracing: Add hist_field_name() accessor

[Namhyung Kim]

Hi Tom,

On Mon, Jun 26, 2017 at 05:49:02PM -0500, Tom Zanussi wrote:
> In preparation for hist_fields that won't be strictly based on
> trace_event_fields, add a new hist_field_name() accessor to allow that
> flexibility and update associated users.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  kernel/trace/trace_events_hist.c | 68 +++++++++++++++++++++++++++-------------
>  1 file changed, 46 insertions(+), 22 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 1c21d0e..91ffc39 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -146,6 +146,23 @@ struct hist_trigger_data {
>  	struct tracing_map		*map;
>  };
>  
> +static const char *hist_field_name(struct hist_field *field,
> +				   unsigned int level)
> +{
> +	const char *field_name = "";
> +
> +	if (level > 1)
> +		return field_name;
> +
> +	if (field->field)
> +		field_name = field->field->name;
> +
> +	if (field_name == NULL)
> +		field_name = "";
> +
> +	return field_name;
> +}
> +
>  static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)
>  {
>  	hist_field_fn_t fn = NULL;
> @@ -653,7 +670,6 @@ static int is_descending(const char *str)
>  static int create_sort_keys(struct hist_trigger_data *hist_data)
>  {
>  	char *fields_str = hist_data->attrs->sort_key_str;
> -	struct ftrace_event_field *field = NULL;
>  	struct tracing_map_sort_key *sort_key;
>  	int descending, ret = 0;
>  	unsigned int i, j;
> @@ -670,7 +686,9 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
>  	}
>  
>  	for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
> +		struct hist_field *hist_field;
>  		char *field_str, *field_name;
> +		const char *test_name;
>  
>  		sort_key = &hist_data->sort_keys[i];
>  
> @@ -703,8 +721,11 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
>  		}
>  
>  		for (j = 1; j < hist_data->n_fields; j++) {
> -			field = hist_data->fields[j]->field;
> -			if (field && (strcmp(field_name, field->name) == 0)) {
> +			hist_field = hist_data->fields[j];
> +			test_name = hist_field_name(hist_field, 0);
> +			if (test_name == NULL)
> +				continue;

The hist_field_name() don't return NULL.

Thanks,
Namhyung

[PATCH 02/32] tracing: Reimplement log2

[Tom Zanussi]

log2 as currently implemented applies only to u64 trace_event_field
derived fields, and assumes that anything it's applied to is a u64
field.

To prepare for synthetic fields like latencies, log2 should be
applicable to those as well, so take the opportunity now to fix the
current problems as well as expand to more general uses.

log2 should be thought of as a chaining function rather than a field
type.  To enable this as well as possible future function
implementations, add a hist_field operand array into the hist_field
definition for this purpose, and make use of it to implement the log2
'function'.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 91ffc39..7b55956 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -28,12 +28,16 @@
 
 typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event);
 
+#define HIST_FIELD_OPERANDS_MAX	2
+
 struct hist_field {
 	struct ftrace_event_field	*field;
 	unsigned long			flags;
 	hist_field_fn_t			fn;
 	unsigned int			size;
 	unsigned int			offset;
+	unsigned int                    is_signed;
+	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
 };
 
 static u64 hist_field_none(struct hist_field *field, void *event)
@@ -71,7 +75,9 @@ static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
 
 static u64 hist_field_log2(struct hist_field *hist_field, void *event)
 {
-	u64 val = *(u64 *)(event + hist_field->field->offset);
+	struct hist_field *operand = hist_field->operands[0];
+
+	u64 val = operand->fn(operand, event);
 
 	return (u64) ilog2(roundup_pow_of_two(val));
 }
@@ -156,6 +162,8 @@ static const char *hist_field_name(struct hist_field *field,
 
 	if (field->field)
 		field_name = field->field->name;
+	else if (field->flags & HIST_FIELD_FL_LOG2)
+		field_name = hist_field_name(field->operands[0], ++level);
 
 	if (field_name == NULL)
 		field_name = "";
@@ -357,8 +365,20 @@ static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
 	.elt_init	= hist_trigger_elt_comm_init,
 };
 
-static void destroy_hist_field(struct hist_field *hist_field)
+static void destroy_hist_field(struct hist_field *hist_field,
+			       unsigned int level)
 {
+	unsigned int i;
+
+	if (level > 2)
+		return;
+
+	if (!hist_field)
+		return;
+
+	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
+		destroy_hist_field(hist_field->operands[i], ++level);
+
 	kfree(hist_field);
 }
 
@@ -385,7 +405,10 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 	}
 
 	if (flags & HIST_FIELD_FL_LOG2) {
+		unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
 		hist_field->fn = hist_field_log2;
+		hist_field->operands[0] = create_hist_field(field, fl);
+		hist_field->size = hist_field->operands[0]->size;
 		goto out;
 	}
 
@@ -405,7 +428,7 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 		hist_field->fn = select_value_fn(field->size,
 						 field->is_signed);
 		if (!hist_field->fn) {
-			destroy_hist_field(hist_field);
+			destroy_hist_field(hist_field, 0);
 			return NULL;
 		}
 	}
@@ -422,7 +445,7 @@ static void destroy_hist_fields(struct hist_trigger_data *hist_data)
 
 	for (i = 0; i < TRACING_MAP_FIELDS_MAX; i++) {
 		if (hist_data->fields[i]) {
-			destroy_hist_field(hist_data->fields[i]);
+			destroy_hist_field(hist_data->fields[i], 0);
 			hist_data->fields[i] = NULL;
 		}
 	}
-- 
1.9.3

Re: [PATCH 02/32] tracing: Reimplement log2

[Namhyung Kim]

On Mon, Jun 26, 2017 at 05:49:03PM -0500, Tom Zanussi wrote:
> log2 as currently implemented applies only to u64 trace_event_field
> derived fields, and assumes that anything it's applied to is a u64
> field.
> 
> To prepare for synthetic fields like latencies, log2 should be
> applicable to those as well, so take the opportunity now to fix the
> current problems as well as expand to more general uses.
> 
> log2 should be thought of as a chaining function rather than a field
> type.  To enable this as well as possible future function
> implementations, add a hist_field operand array into the hist_field
> definition for this purpose, and make use of it to implement the log2
> 'function'.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  kernel/trace/trace_events_hist.c | 31 +++++++++++++++++++++++++++----
>  1 file changed, 27 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 91ffc39..7b55956 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -28,12 +28,16 @@
>  
>  typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event);
>  
> +#define HIST_FIELD_OPERANDS_MAX	2
> +
>  struct hist_field {
>  	struct ftrace_event_field	*field;
>  	unsigned long			flags;
>  	hist_field_fn_t			fn;
>  	unsigned int			size;
>  	unsigned int			offset;
> +	unsigned int                    is_signed;
> +	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
>  };
>  
>  static u64 hist_field_none(struct hist_field *field, void *event)
> @@ -71,7 +75,9 @@ static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
>  
>  static u64 hist_field_log2(struct hist_field *hist_field, void *event)
>  {
> -	u64 val = *(u64 *)(event + hist_field->field->offset);
> +	struct hist_field *operand = hist_field->operands[0];
> +
> +	u64 val = operand->fn(operand, event);
>  
>  	return (u64) ilog2(roundup_pow_of_two(val));
>  }
> @@ -156,6 +162,8 @@ static const char *hist_field_name(struct hist_field *field,
>  
>  	if (field->field)
>  		field_name = field->field->name;
> +	else if (field->flags & HIST_FIELD_FL_LOG2)
> +		field_name = hist_field_name(field->operands[0], ++level);
>  
>  	if (field_name == NULL)
>  		field_name = "";
> @@ -357,8 +365,20 @@ static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
>  	.elt_init	= hist_trigger_elt_comm_init,
>  };
>  
> -static void destroy_hist_field(struct hist_field *hist_field)
> +static void destroy_hist_field(struct hist_field *hist_field,
> +			       unsigned int level)
>  {
> +	unsigned int i;
> +
> +	if (level > 2)
> +		return;
> +
> +	if (!hist_field)
> +		return;
> +
> +	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
> +		destroy_hist_field(hist_field->operands[i], ++level);

Wouldn't it be 'level + 1' ?

Thanks,
Namhyung


> +
>  	kfree(hist_field);
>  }

Re: [PATCH 02/32] tracing: Reimplement log2

[Tom Zanussi]

Hi Namhyung,

On Fri, 2017-07-14 at 11:33 +0900, Namhyung Kim wrote:
> On Mon, Jun 26, 2017 at 05:49:03PM -0500, Tom Zanussi wrote:
> > log2 as currently implemented applies only to u64 trace_event_field
> > derived fields, and assumes that anything it's applied to is a u64
> > field.
> > 
> > To prepare for synthetic fields like latencies, log2 should be
> > applicable to those as well, so take the opportunity now to fix the
> > current problems as well as expand to more general uses.
> > 
> > log2 should be thought of as a chaining function rather than a field
> > type.  To enable this as well as possible future function
> > implementations, add a hist_field operand array into the hist_field
> > definition for this purpose, and make use of it to implement the log2
> > 'function'.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> >  kernel/trace/trace_events_hist.c | 31 +++++++++++++++++++++++++++----
> >  1 file changed, 27 insertions(+), 4 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index 91ffc39..7b55956 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> > @@ -28,12 +28,16 @@
> >  
> >  typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event);
> >  
> > +#define HIST_FIELD_OPERANDS_MAX	2
> > +
> >  struct hist_field {
> >  	struct ftrace_event_field	*field;
> >  	unsigned long			flags;
> >  	hist_field_fn_t			fn;
> >  	unsigned int			size;
> >  	unsigned int			offset;
> > +	unsigned int                    is_signed;
> > +	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
> >  };
> >  
> >  static u64 hist_field_none(struct hist_field *field, void *event)
> > @@ -71,7 +75,9 @@ static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
> >  
> >  static u64 hist_field_log2(struct hist_field *hist_field, void *event)
> >  {
> > -	u64 val = *(u64 *)(event + hist_field->field->offset);
> > +	struct hist_field *operand = hist_field->operands[0];
> > +
> > +	u64 val = operand->fn(operand, event);
> >  
> >  	return (u64) ilog2(roundup_pow_of_two(val));
> >  }
> > @@ -156,6 +162,8 @@ static const char *hist_field_name(struct hist_field *field,
> >  
> >  	if (field->field)
> >  		field_name = field->field->name;
> > +	else if (field->flags & HIST_FIELD_FL_LOG2)
> > +		field_name = hist_field_name(field->operands[0], ++level);
> >  
> >  	if (field_name == NULL)
> >  		field_name = "";
> > @@ -357,8 +365,20 @@ static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
> >  	.elt_init	= hist_trigger_elt_comm_init,
> >  };
> >  
> > -static void destroy_hist_field(struct hist_field *hist_field)
> > +static void destroy_hist_field(struct hist_field *hist_field,
> > +			       unsigned int level)
> >  {
> > +	unsigned int i;
> > +
> > +	if (level > 2)
> > +		return;
> > +
> > +	if (!hist_field)
> > +		return;
> > +
> > +	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
> > +		destroy_hist_field(hist_field->operands[i], ++level);
> 
> Wouldn't it be 'level + 1' ?
> 

Yeah, we're in a loop here, so definitely.  Thanks for catching this.

Tom

> Thanks,
> Namhyung
> 
> 
> > +
> >  	kfree(hist_field);
> >  }

[PATCH 03/32] ring-buffer: Add interface for setting absolute time stamps

[Tom Zanussi]

Define a new function, tracing_set_time_stamp_abs(), which can be used
to enable or disable the use of absolute timestamps rather than time
deltas for a trace array.

This resets the buffer to prevent a mix of time deltas and absolute
timestamps.

Only the interface is added here; a subsequent patch will add the
underlying implementation.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 include/linux/ring_buffer.h |  2 ++
 kernel/trace/ring_buffer.c  | 11 +++++++++++
 kernel/trace/trace.c        | 25 ++++++++++++++++++++++++-
 kernel/trace/trace.h        |  2 ++
 4 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index ee9b461..28e3472 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -180,6 +180,8 @@ void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
 				      int cpu, u64 *ts);
 void ring_buffer_set_clock(struct ring_buffer *buffer,
 			   u64 (*clock)(void));
+void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs);
+bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer);
 
 size_t ring_buffer_page_len(void *page);
 
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 4ae268e..f544738 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -485,6 +485,7 @@ struct ring_buffer {
 	u64				(*clock)(void);
 
 	struct rb_irq_work		irq_work;
+	bool				time_stamp_abs;
 };
 
 struct ring_buffer_iter {
@@ -1379,6 +1380,16 @@ void ring_buffer_set_clock(struct ring_buffer *buffer,
 	buffer->clock = clock;
 }
 
+void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
+{
+	buffer->time_stamp_abs = abs;
+}
+
+bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
+{
+	return buffer->time_stamp_abs;
+}
+
 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
 
 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 19ac208..da8cd51 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2169,7 +2169,7 @@ struct ring_buffer_event *
 
 	*current_rb = trace_file->tr->trace_buffer.buffer;
 
-	if ((trace_file->flags &
+	if (!ring_buffer_time_stamp_abs(*current_rb) && (trace_file->flags &
 	     (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
 	    (entry = this_cpu_read(trace_buffered_event))) {
 		/* Try to use the per cpu buffer first */
@@ -6079,6 +6079,29 @@ static int tracing_clock_open(struct inode *inode, struct file *file)
 	return ret;
 }
 
+int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs)
+{
+	mutex_lock(&trace_types_lock);
+
+	ring_buffer_set_time_stamp_abs(tr->trace_buffer.buffer, abs);
+
+	/*
+	 * New timestamps may not be consistent with the previous setting.
+	 * Reset the buffer so that it doesn't have incomparable timestamps.
+	 */
+	tracing_reset_online_cpus(&tr->trace_buffer);
+
+#ifdef CONFIG_TRACER_MAX_TRACE
+	if (tr->flags & TRACE_ARRAY_FL_GLOBAL && tr->max_buffer.buffer)
+		ring_buffer_set_time_stamp_abs(tr->max_buffer.buffer, abs);
+	tracing_reset_online_cpus(&tr->max_buffer);
+#endif
+
+	mutex_unlock(&trace_types_lock);
+
+	return 0;
+}
+
 struct ftrace_buffer_info {
 	struct trace_iterator	iter;
 	void			*spare;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 69a3ab3..155ad9a 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -281,6 +281,8 @@ enum {
 extern int trace_array_get(struct trace_array *tr);
 extern void trace_array_put(struct trace_array *tr);
 
+extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
+
 /*
  * The global tracer (top) should be the first trace array added,
  * but we check the flag anyway.
-- 
1.9.3

Re: [PATCH 03/32] ring-buffer: Add interface for setting absolute time stamps

[Namhyung Kim]

On Mon, Jun 26, 2017 at 05:49:04PM -0500, Tom Zanussi wrote:
> Define a new function, tracing_set_time_stamp_abs(), which can be used
> to enable or disable the use of absolute timestamps rather than time
> deltas for a trace array.
> 
> This resets the buffer to prevent a mix of time deltas and absolute
> timestamps.
> 
> Only the interface is added here; a subsequent patch will add the
> underlying implementation.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  include/linux/ring_buffer.h |  2 ++
>  kernel/trace/ring_buffer.c  | 11 +++++++++++
>  kernel/trace/trace.c        | 25 ++++++++++++++++++++++++-
>  kernel/trace/trace.h        |  2 ++
>  4 files changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
> index ee9b461..28e3472 100644
> --- a/include/linux/ring_buffer.h
> +++ b/include/linux/ring_buffer.h
> @@ -180,6 +180,8 @@ void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
>  				      int cpu, u64 *ts);
>  void ring_buffer_set_clock(struct ring_buffer *buffer,
>  			   u64 (*clock)(void));
> +void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs);
> +bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer);
>  
>  size_t ring_buffer_page_len(void *page);
>  
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 4ae268e..f544738 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -485,6 +485,7 @@ struct ring_buffer {
>  	u64				(*clock)(void);
>  
>  	struct rb_irq_work		irq_work;
> +	bool				time_stamp_abs;
>  };
>  
>  struct ring_buffer_iter {
> @@ -1379,6 +1380,16 @@ void ring_buffer_set_clock(struct ring_buffer *buffer,
>  	buffer->clock = clock;
>  }
>  
> +void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
> +{
> +	buffer->time_stamp_abs = abs;
> +}
> +
> +bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
> +{
> +	return buffer->time_stamp_abs;
> +}
> +
>  static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
>  
>  static inline unsigned long rb_page_entries(struct buffer_page *bpage)
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 19ac208..da8cd51 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2169,7 +2169,7 @@ struct ring_buffer_event *
>  
>  	*current_rb = trace_file->tr->trace_buffer.buffer;
>  
> -	if ((trace_file->flags &
> +	if (!ring_buffer_time_stamp_abs(*current_rb) && (trace_file->flags &
>  	     (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
>  	    (entry = this_cpu_read(trace_buffered_event))) {
>  		/* Try to use the per cpu buffer first */
> @@ -6079,6 +6079,29 @@ static int tracing_clock_open(struct inode *inode, struct file *file)
>  	return ret;
>  }
>  
> +int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs)
> +{
> +	mutex_lock(&trace_types_lock);
> +
> +	ring_buffer_set_time_stamp_abs(tr->trace_buffer.buffer, abs);
> +
> +	/*
> +	 * New timestamps may not be consistent with the previous setting.
> +	 * Reset the buffer so that it doesn't have incomparable timestamps.
> +	 */
> +	tracing_reset_online_cpus(&tr->trace_buffer);
> +
> +#ifdef CONFIG_TRACER_MAX_TRACE
> +	if (tr->flags & TRACE_ARRAY_FL_GLOBAL && tr->max_buffer.buffer)
> +		ring_buffer_set_time_stamp_abs(tr->max_buffer.buffer, abs);
> +	tracing_reset_online_cpus(&tr->max_buffer);

Why do you do this only for the global array?  AFAIK instance arrays
can have the max buffer too.  Am I missing something?

Thanks,
Namhyung


> +#endif
> +
> +	mutex_unlock(&trace_types_lock);
> +
> +	return 0;
> +}
> +
>  struct ftrace_buffer_info {
>  	struct trace_iterator	iter;
>  	void			*spare;
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 69a3ab3..155ad9a 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -281,6 +281,8 @@ enum {
>  extern int trace_array_get(struct trace_array *tr);
>  extern void trace_array_put(struct trace_array *tr);
>  
> +extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
> +
>  /*
>   * The global tracer (top) should be the first trace array added,
>   * but we check the flag anyway.
> -- 
> 1.9.3
> 

Re: [PATCH 03/32] ring-buffer: Add interface for setting absolute time stamps

[Tom Zanussi]

Hi Namhyung,

On Fri, 2017-07-14 at 14:25 +0900, Namhyung Kim wrote:
> On Mon, Jun 26, 2017 at 05:49:04PM -0500, Tom Zanussi wrote:
> > Define a new function, tracing_set_time_stamp_abs(), which can be used
> > to enable or disable the use of absolute timestamps rather than time
> > deltas for a trace array.
> > 
> > This resets the buffer to prevent a mix of time deltas and absolute
> > timestamps.
> > 
> > Only the interface is added here; a subsequent patch will add the
> > underlying implementation.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> >  include/linux/ring_buffer.h |  2 ++
> >  kernel/trace/ring_buffer.c  | 11 +++++++++++
> >  kernel/trace/trace.c        | 25 ++++++++++++++++++++++++-
> >  kernel/trace/trace.h        |  2 ++
> >  4 files changed, 39 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
> > index ee9b461..28e3472 100644
> > --- a/include/linux/ring_buffer.h
> > +++ b/include/linux/ring_buffer.h
> > @@ -180,6 +180,8 @@ void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
> >  				      int cpu, u64 *ts);
> >  void ring_buffer_set_clock(struct ring_buffer *buffer,
> >  			   u64 (*clock)(void));
> > +void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs);
> > +bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer);
> >  
> >  size_t ring_buffer_page_len(void *page);
> >  
> > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> > index 4ae268e..f544738 100644
> > --- a/kernel/trace/ring_buffer.c
> > +++ b/kernel/trace/ring_buffer.c
> > @@ -485,6 +485,7 @@ struct ring_buffer {
> >  	u64				(*clock)(void);
> >  
> >  	struct rb_irq_work		irq_work;
> > +	bool				time_stamp_abs;
> >  };
> >  
> >  struct ring_buffer_iter {
> > @@ -1379,6 +1380,16 @@ void ring_buffer_set_clock(struct ring_buffer *buffer,
> >  	buffer->clock = clock;
> >  }
> >  
> > +void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
> > +{
> > +	buffer->time_stamp_abs = abs;
> > +}
> > +
> > +bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
> > +{
> > +	return buffer->time_stamp_abs;
> > +}
> > +
> >  static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
> >  
> >  static inline unsigned long rb_page_entries(struct buffer_page *bpage)
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 19ac208..da8cd51 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -2169,7 +2169,7 @@ struct ring_buffer_event *
> >  
> >  	*current_rb = trace_file->tr->trace_buffer.buffer;
> >  
> > -	if ((trace_file->flags &
> > +	if (!ring_buffer_time_stamp_abs(*current_rb) && (trace_file->flags &
> >  	     (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
> >  	    (entry = this_cpu_read(trace_buffered_event))) {
> >  		/* Try to use the per cpu buffer first */
> > @@ -6079,6 +6079,29 @@ static int tracing_clock_open(struct inode *inode, struct file *file)
> >  	return ret;
> >  }
> >  
> > +int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs)
> > +{
> > +	mutex_lock(&trace_types_lock);
> > +
> > +	ring_buffer_set_time_stamp_abs(tr->trace_buffer.buffer, abs);
> > +
> > +	/*
> > +	 * New timestamps may not be consistent with the previous setting.
> > +	 * Reset the buffer so that it doesn't have incomparable timestamps.
> > +	 */
> > +	tracing_reset_online_cpus(&tr->trace_buffer);
> > +
> > +#ifdef CONFIG_TRACER_MAX_TRACE
> > +	if (tr->flags & TRACE_ARRAY_FL_GLOBAL && tr->max_buffer.buffer)
> > +		ring_buffer_set_time_stamp_abs(tr->max_buffer.buffer, abs);
> > +	tracing_reset_online_cpus(&tr->max_buffer);
> 
> Why do you do this only for the global array?  AFAIK instance arrays
> can have the max buffer too.  Am I missing something?
> 

Yes, I think you're right.  Will take a closer look and change as
needed.

Thanks,

Tom

[PATCH 04/32] ring-buffer: Redefine the unimplemented RINGBUF_TIME_TIME_STAMP

[Tom Zanussi]

RINGBUF_TYPE_TIME_STAMP is defined but not used, and from what I can
gather was reserved for something like an absolute timestamp feature
for the ring buffer, if not a complete replacement of the current
time_delta scheme.

This code redefines RINGBUF_TYPE_TIME_STAMP to implement absolute time
stamps.  Another way to look at it is that it essentially forces
extended time_deltas for all events.

The motivation for doing this is to enable time_deltas that aren't
dependent on previous events in the ring buffer, making it feasible to
use the ring_buffer_event timetamps in a more random-access way, for
purposes other than serial event printing.

To set/reset this mode, use tracing_set_timestamp_abs() from the
previous interface patch.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 include/linux/ring_buffer.h |  12 ++---
 kernel/trace/ring_buffer.c  | 107 +++++++++++++++++++++++++++++++-------------
 2 files changed, 83 insertions(+), 36 deletions(-)

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 28e3472..74bc276 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -36,10 +36,12 @@ struct ring_buffer_event {
  *				 array[0] = time delta (28 .. 59)
  *				 size = 8 bytes
  *
- * @RINGBUF_TYPE_TIME_STAMP:	Sync time stamp with external clock
- *				 array[0]    = tv_nsec
- *				 array[1..2] = tv_sec
- *				 size = 16 bytes
+ * @RINGBUF_TYPE_TIME_STAMP:	Absolute timestamp
+ *				 Same format as TIME_EXTEND except that the
+ *				 value is an absolute timestamp, not a delta
+ *				 event.time_delta contains bottom 27 bits
+ *				 array[0] = top (28 .. 59) bits
+ *				 size = 8 bytes
  *
  * <= @RINGBUF_TYPE_DATA_TYPE_LEN_MAX:
  *				Data record
@@ -56,12 +58,12 @@ enum ring_buffer_type {
 	RINGBUF_TYPE_DATA_TYPE_LEN_MAX = 28,
 	RINGBUF_TYPE_PADDING,
 	RINGBUF_TYPE_TIME_EXTEND,
-	/* FIXME: RINGBUF_TYPE_TIME_STAMP not implemented */
 	RINGBUF_TYPE_TIME_STAMP,
 };
 
 unsigned ring_buffer_event_length(struct ring_buffer_event *event);
 void *ring_buffer_event_data(struct ring_buffer_event *event);
+u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event);
 
 /*
  * ring_buffer_discard_commit will remove an event that has not
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index f544738..df848f0 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -42,6 +42,8 @@ int ring_buffer_print_entry_header(struct trace_seq *s)
 			 RINGBUF_TYPE_PADDING);
 	trace_seq_printf(s, "\ttime_extend : type == %d\n",
 			 RINGBUF_TYPE_TIME_EXTEND);
+	trace_seq_printf(s, "\ttime_stamp : type == %d\n",
+			 RINGBUF_TYPE_TIME_STAMP);
 	trace_seq_printf(s, "\tdata max type_len  == %d\n",
 			 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
 
@@ -147,6 +149,9 @@ enum {
 #define skip_time_extend(event) \
 	((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
 
+#define extended_time(event) \
+	(event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
+
 static inline int rb_null_event(struct ring_buffer_event *event)
 {
 	return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
@@ -187,10 +192,8 @@ static void rb_event_set_padding(struct ring_buffer_event *event)
 		return  event->array[0] + RB_EVNT_HDR_SIZE;
 
 	case RINGBUF_TYPE_TIME_EXTEND:
-		return RB_LEN_TIME_EXTEND;
-
 	case RINGBUF_TYPE_TIME_STAMP:
-		return RB_LEN_TIME_STAMP;
+		return RB_LEN_TIME_EXTEND;
 
 	case RINGBUF_TYPE_DATA:
 		return rb_event_data_length(event);
@@ -210,7 +213,7 @@ static void rb_event_set_padding(struct ring_buffer_event *event)
 {
 	unsigned len = 0;
 
-	if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
+	if (extended_time(event)) {
 		/* time extends include the data event after it */
 		len = RB_LEN_TIME_EXTEND;
 		event = skip_time_extend(event);
@@ -232,7 +235,7 @@ unsigned ring_buffer_event_length(struct ring_buffer_event *event)
 {
 	unsigned length;
 
-	if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+	if (extended_time(event))
 		event = skip_time_extend(event);
 
 	length = rb_event_length(event);
@@ -249,7 +252,7 @@ unsigned ring_buffer_event_length(struct ring_buffer_event *event)
 static __always_inline void *
 rb_event_data(struct ring_buffer_event *event)
 {
-	if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+	if (extended_time(event))
 		event = skip_time_extend(event);
 	BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
 	/* If length is in len field, then array[0] has the data */
@@ -276,6 +279,27 @@ void *ring_buffer_event_data(struct ring_buffer_event *event)
 #define TS_MASK		((1ULL << TS_SHIFT) - 1)
 #define TS_DELTA_TEST	(~TS_MASK)
 
+/**
+ * ring_buffer_event_time_stamp - return the event's extended timestamp
+ * @event: the event to get the timestamp of
+ *
+ * Returns the extended timestamp associated with a data event.
+ * An extended time_stamp is a 64-bit timestamp represented
+ * internally in a special way that makes the best use of space
+ * contained within a ring buffer event.  This function decodes
+ * it and maps it to a straight u64 value.
+ */
+u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
+{
+	u64 ts;
+
+	ts = event->array[0];
+	ts <<= TS_SHIFT;
+	ts += event->time_delta;
+
+	return ts;
+}
+
 /* Flag when events were overwritten */
 #define RB_MISSED_EVENTS	(1 << 31)
 /* Missed count stored at end */
@@ -2220,13 +2244,16 @@ static void rb_inc_iter(struct ring_buffer_iter *iter)
 }
 
 /* Slow path, do not inline */
-static noinline struct ring_buffer_event *
-rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
+static struct noinline ring_buffer_event *
+rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
 {
-	event->type_len = RINGBUF_TYPE_TIME_EXTEND;
+	if (abs)
+		event->type_len = RINGBUF_TYPE_TIME_STAMP;
+	else
+		event->type_len = RINGBUF_TYPE_TIME_EXTEND;
 
-	/* Not the first event on the page? */
-	if (rb_event_index(event)) {
+	/* Not the first event on the page, or not delta? */
+	if (abs || rb_event_index(event)) {
 		event->time_delta = delta & TS_MASK;
 		event->array[0] = delta >> TS_SHIFT;
 	} else {
@@ -2269,7 +2296,9 @@ static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
 	 * add it to the start of the resevered space.
 	 */
 	if (unlikely(info->add_timestamp)) {
-		event = rb_add_time_stamp(event, delta);
+		bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer);
+
+		event = rb_add_time_stamp(event, info->delta, abs);
 		length -= RB_LEN_TIME_EXTEND;
 		delta = 0;
 	}
@@ -2457,7 +2486,7 @@ static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer
 
 static inline void rb_event_discard(struct ring_buffer_event *event)
 {
-	if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+	if (extended_time(event))
 		event = skip_time_extend(event);
 
 	/* array[0] holds the actual length for the discarded event */
@@ -2488,6 +2517,10 @@ static inline void rb_event_discard(struct ring_buffer_event *event)
 {
 	u64 delta;
 
+	/* In TIME_STAMP mode, write_stamp is unused, nothing to do */
+	if (event->type_len == RINGBUF_TYPE_TIME_STAMP)
+		return;
+
 	/*
 	 * The event first in the commit queue updates the
 	 * time stamp.
@@ -2501,9 +2534,7 @@ static inline void rb_event_discard(struct ring_buffer_event *event)
 			cpu_buffer->write_stamp =
 				cpu_buffer->commit_page->page->time_stamp;
 		else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
-			delta = event->array[0];
-			delta <<= TS_SHIFT;
-			delta += event->time_delta;
+			delta = ring_buffer_event_time_stamp(event);
 			cpu_buffer->write_stamp += delta;
 		} else
 			cpu_buffer->write_stamp += event->time_delta;
@@ -2687,7 +2718,7 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer,
 	 * If this is the first commit on the page, then it has the same
 	 * timestamp as the page itself.
 	 */
-	if (!tail)
+	if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer))
 		info->delta = 0;
 
 	/* See if we shot pass the end of this buffer page */
@@ -2765,8 +2796,11 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer,
 	/* make sure this diff is calculated here */
 	barrier();
 
-	/* Did the write stamp get updated already? */
-	if (likely(info.ts >= cpu_buffer->write_stamp)) {
+	if (ring_buffer_time_stamp_abs(buffer)) {
+		info.delta = info.ts;
+		rb_handle_timestamp(cpu_buffer, &info);
+	} else /* Did the write stamp get updated already? */
+		if (likely(info.ts >= cpu_buffer->write_stamp)) {
 		info.delta = diff;
 		if (unlikely(test_time_stamp(info.delta)))
 			rb_handle_timestamp(cpu_buffer, &info);
@@ -3448,14 +3482,12 @@ int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
 		return;
 
 	case RINGBUF_TYPE_TIME_EXTEND:
-		delta = event->array[0];
-		delta <<= TS_SHIFT;
-		delta += event->time_delta;
+		delta = ring_buffer_event_time_stamp(event);
 		cpu_buffer->read_stamp += delta;
 		return;
 
 	case RINGBUF_TYPE_TIME_STAMP:
-		/* FIXME: not implemented */
+		/* In TIME_STAMP mode, write_stamp is unused, nothing to do */
 		return;
 
 	case RINGBUF_TYPE_DATA:
@@ -3479,14 +3511,12 @@ int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
 		return;
 
 	case RINGBUF_TYPE_TIME_EXTEND:
-		delta = event->array[0];
-		delta <<= TS_SHIFT;
-		delta += event->time_delta;
+		delta = ring_buffer_event_time_stamp(event);
 		iter->read_stamp += delta;
 		return;
 
 	case RINGBUF_TYPE_TIME_STAMP:
-		/* FIXME: not implemented */
+		/* In TIME_STAMP mode, write_stamp is unused, nothing to do */
 		return;
 
 	case RINGBUF_TYPE_DATA:
@@ -3710,6 +3740,8 @@ static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
 	struct buffer_page *reader;
 	int nr_loops = 0;
 
+	if (ts)
+		*ts = 0;
  again:
 	/*
 	 * We repeat when a time extend is encountered.
@@ -3746,12 +3778,17 @@ static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
 		goto again;
 
 	case RINGBUF_TYPE_TIME_STAMP:
-		/* FIXME: not implemented */
+		if (ts) {
+			*ts = ring_buffer_event_time_stamp(event);
+			ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
+							 cpu_buffer->cpu, ts);
+		}
+		/* Internal data, OK to advance */
 		rb_advance_reader(cpu_buffer);
 		goto again;
 
 	case RINGBUF_TYPE_DATA:
-		if (ts) {
+		if (ts && !(*ts)) {
 			*ts = cpu_buffer->read_stamp + event->time_delta;
 			ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
 							 cpu_buffer->cpu, ts);
@@ -3776,6 +3813,9 @@ static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
 	struct ring_buffer_event *event;
 	int nr_loops = 0;
 
+	if (ts)
+		*ts = 0;
+
 	cpu_buffer = iter->cpu_buffer;
 	buffer = cpu_buffer->buffer;
 
@@ -3828,12 +3868,17 @@ static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
 		goto again;
 
 	case RINGBUF_TYPE_TIME_STAMP:
-		/* FIXME: not implemented */
+		if (ts) {
+			*ts = ring_buffer_event_time_stamp(event);
+			ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
+							 cpu_buffer->cpu, ts);
+		}
+		/* Internal data, OK to advance */
 		rb_advance_iter(iter);
 		goto again;
 
 	case RINGBUF_TYPE_DATA:
-		if (ts) {
+		if (ts && !(*ts)) {
 			*ts = iter->read_stamp + event->time_delta;
 			ring_buffer_normalize_time_stamp(buffer,
 							 cpu_buffer->cpu, ts);
-- 
1.9.3

Re: [PATCH 04/32] ring-buffer: Redefine the unimplemented RINGBUF_TIME_TIME_STAMP

[Joel Fernandes (Google)]

On Mon, Jun 26, 2017 at 3:49 PM, Tom Zanussi
<tom.zanussi@linux.intel.com> wrote:
> RINGBUF_TYPE_TIME_STAMP is defined but not used, and from what I can
> gather was reserved for something like an absolute timestamp feature
> for the ring buffer, if not a complete replacement of the current
> time_delta scheme.
>
> This code redefines RINGBUF_TYPE_TIME_STAMP to implement absolute time
> stamps.  Another way to look at it is that it essentially forces
> extended time_deltas for all events.
>
> The motivation for doing this is to enable time_deltas that aren't
> dependent on previous events in the ring buffer, making it feasible to
> use the ring_buffer_event timetamps in a more random-access way, for
> purposes other than serial event printing.
>
> To set/reset this mode, use tracing_set_timestamp_abs() from the
> previous interface patch.
>
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  include/linux/ring_buffer.h |  12 ++---
>  kernel/trace/ring_buffer.c  | 107 +++++++++++++++++++++++++++++++-------------
>  2 files changed, 83 insertions(+), 36 deletions(-)
>
> diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
> index 28e3472..74bc276 100644
> --- a/include/linux/ring_buffer.h
> +++ b/include/linux/ring_buffer.h
> @@ -36,10 +36,12 @@ struct ring_buffer_event {
>   *                              array[0] = time delta (28 .. 59)
>   *                              size = 8 bytes
>   *
> - * @RINGBUF_TYPE_TIME_STAMP:   Sync time stamp with external clock
> - *                              array[0]    = tv_nsec
> - *                              array[1..2] = tv_sec
> - *                              size = 16 bytes
> + * @RINGBUF_TYPE_TIME_STAMP:   Absolute timestamp
> + *                              Same format as TIME_EXTEND except that the
> + *                              value is an absolute timestamp, not a delta
> + *                              event.time_delta contains bottom 27 bits
> + *                              array[0] = top (28 .. 59) bits
> + *                              size = 8 bytes
>   *

Let's also change it here in ring_buffer.c?

enum {
        RB_LEN_TIME_EXTEND = 8,
        RB_LEN_TIME_STAMP = 16,    <- change to 8
};


>   * <= @RINGBUF_TYPE_DATA_TYPE_LEN_MAX:
>   *                             Data record
> @@ -56,12 +58,12 @@ enum ring_buffer_type {
>         RINGBUF_TYPE_DATA_TYPE_LEN_MAX = 28,
>         RINGBUF_TYPE_PADDING,
>         RINGBUF_TYPE_TIME_EXTEND,
> -       /* FIXME: RINGBUF_TYPE_TIME_STAMP not implemented */
>         RINGBUF_TYPE_TIME_STAMP,
>  };
>
>  unsigned ring_buffer_event_length(struct ring_buffer_event *event);
>  void *ring_buffer_event_data(struct ring_buffer_event *event);
> +u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event);
>
>  /*
>   * ring_buffer_discard_commit will remove an event that has not
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index f544738..df848f0 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -42,6 +42,8 @@ int ring_buffer_print_entry_header(struct trace_seq *s)
>                          RINGBUF_TYPE_PADDING);
>         trace_seq_printf(s, "\ttime_extend : type == %d\n",
>                          RINGBUF_TYPE_TIME_EXTEND);
> +       trace_seq_printf(s, "\ttime_stamp : type == %d\n",
> +                        RINGBUF_TYPE_TIME_STAMP);
>         trace_seq_printf(s, "\tdata max type_len  == %d\n",
>                          RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
>
> @@ -147,6 +149,9 @@ enum {
>  #define skip_time_extend(event) \
>         ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
>
> +#define extended_time(event) \
> +       (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
> +
>  static inline int rb_null_event(struct ring_buffer_event *event)
>  {
>         return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
> @@ -187,10 +192,8 @@ static void rb_event_set_padding(struct ring_buffer_event *event)
>                 return  event->array[0] + RB_EVNT_HDR_SIZE;
>
>         case RINGBUF_TYPE_TIME_EXTEND:
> -               return RB_LEN_TIME_EXTEND;
> -
>         case RINGBUF_TYPE_TIME_STAMP:
> -               return RB_LEN_TIME_STAMP;
> +               return RB_LEN_TIME_EXTEND;

And then this change can be dropped. Or a new single enum can be
defined for both TIME_EXTEND and TIME_STAMP and then used.

thanks,

-Joel

[PATCH 05/32] tracing: Give event triggers access to ring_buffer_event

[Tom Zanussi]

The ring_buffer event can provide a timestamp that may be useful to
various triggers - pass it into the handlers for that purpose.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 include/linux/trace_events.h        | 14 ++++++-----
 kernel/trace/trace.h                |  9 +++----
 kernel/trace/trace_events_hist.c    | 11 +++++----
 kernel/trace/trace_events_trigger.c | 47 +++++++++++++++++++++++--------------
 4 files changed, 49 insertions(+), 32 deletions(-)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index a556805..f333114 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -391,11 +391,13 @@ enum event_trigger_type {
 
 extern int filter_match_preds(struct event_filter *filter, void *rec);
 
-extern enum event_trigger_type event_triggers_call(struct trace_event_file *file,
-						   void *rec);
-extern void event_triggers_post_call(struct trace_event_file *file,
-				     enum event_trigger_type tt,
-				     void *rec);
+extern enum event_trigger_type
+event_triggers_call(struct trace_event_file *file, void *rec,
+		    struct ring_buffer_event *event);
+extern void
+event_triggers_post_call(struct trace_event_file *file,
+			 enum event_trigger_type tt,
+			 void *rec, struct ring_buffer_event *event);
 
 bool trace_event_ignore_this_pid(struct trace_event_file *trace_file);
 
@@ -415,7 +417,7 @@ extern void event_triggers_post_call(struct trace_event_file *file,
 
 	if (!(eflags & EVENT_FILE_FL_TRIGGER_COND)) {
 		if (eflags & EVENT_FILE_FL_TRIGGER_MODE)
-			event_triggers_call(file, NULL);
+			event_triggers_call(file, NULL, NULL);
 		if (eflags & EVENT_FILE_FL_SOFT_DISABLED)
 			return true;
 		if (eflags & EVENT_FILE_FL_PID_FILTER)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 155ad9a..fc892b9 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1269,7 +1269,7 @@ static inline void trace_buffer_unlock_commit(struct trace_array *tr,
 	unsigned long eflags = file->flags;
 
 	if (eflags & EVENT_FILE_FL_TRIGGER_COND)
-		*tt = event_triggers_call(file, entry);
+		*tt = event_triggers_call(file, entry, event);
 
 	if (test_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags) ||
 	    (unlikely(file->flags & EVENT_FILE_FL_FILTERED) &&
@@ -1306,7 +1306,7 @@ static inline void trace_buffer_unlock_commit(struct trace_array *tr,
 		trace_buffer_unlock_commit(file->tr, buffer, event, irq_flags, pc);
 
 	if (tt)
-		event_triggers_post_call(file, tt, entry);
+		event_triggers_post_call(file, tt, entry, event);
 }
 
 /**
@@ -1339,7 +1339,7 @@ static inline void trace_buffer_unlock_commit(struct trace_array *tr,
 						irq_flags, pc, regs);
 
 	if (tt)
-		event_triggers_post_call(file, tt, entry);
+		event_triggers_post_call(file, tt, entry, event);
 }
 
 #define FILTER_PRED_INVALID	((unsigned short)-1)
@@ -1562,7 +1562,8 @@ extern void set_named_trigger_data(struct event_trigger_data *data,
  */
 struct event_trigger_ops {
 	void			(*func)(struct event_trigger_data *data,
-					void *rec);
+					void *rec,
+					struct ring_buffer_event *rbe);
 	int			(*init)(struct event_trigger_ops *ops,
 					struct event_trigger_data *data);
 	void			(*free)(struct event_trigger_ops *ops,
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 7b55956..655c412 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -921,7 +921,8 @@ static inline void add_to_key(char *compound_key, void *key,
 	memcpy(compound_key + key_field->offset, key, size);
 }
 
-static void event_hist_trigger(struct event_trigger_data *data, void *rec)
+static void event_hist_trigger(struct event_trigger_data *data, void *rec,
+			       struct ring_buffer_event *event)
 {
 	struct hist_trigger_data *hist_data = data->private_data;
 	bool use_compound_key = (hist_data->n_keys > 1);
@@ -1672,7 +1673,8 @@ __init int register_trigger_hist_cmd(void)
 }
 
 static void
-hist_enable_trigger(struct event_trigger_data *data, void *rec)
+hist_enable_trigger(struct event_trigger_data *data, void *rec,
+		    struct ring_buffer_event *event)
 {
 	struct enable_trigger_data *enable_data = data->private_data;
 	struct event_trigger_data *test;
@@ -1688,7 +1690,8 @@ __init int register_trigger_hist_cmd(void)
 }
 
 static void
-hist_enable_count_trigger(struct event_trigger_data *data, void *rec)
+hist_enable_count_trigger(struct event_trigger_data *data, void *rec,
+			  struct ring_buffer_event *event)
 {
 	if (!data->count)
 		return;
@@ -1696,7 +1699,7 @@ __init int register_trigger_hist_cmd(void)
 	if (data->count != -1)
 		(data->count)--;
 
-	hist_enable_trigger(data, rec);
+	hist_enable_trigger(data, rec, event);
 }
 
 static struct event_trigger_ops hist_enable_trigger_ops = {
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index f2ac9d4..9b0fe31 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -63,7 +63,8 @@ void trigger_data_free(struct event_trigger_data *data)
  * any trigger that should be deferred, ETT_NONE if nothing to defer.
  */
 enum event_trigger_type
-event_triggers_call(struct trace_event_file *file, void *rec)
+event_triggers_call(struct trace_event_file *file, void *rec,
+		    struct ring_buffer_event *event)
 {
 	struct event_trigger_data *data;
 	enum event_trigger_type tt = ETT_NONE;
@@ -76,7 +77,7 @@ enum event_trigger_type
 		if (data->paused)
 			continue;
 		if (!rec) {
-			data->ops->func(data, rec);
+			data->ops->func(data, rec, event);
 			continue;
 		}
 		filter = rcu_dereference_sched(data->filter);
@@ -86,7 +87,7 @@ enum event_trigger_type
 			tt |= data->cmd_ops->trigger_type;
 			continue;
 		}
-		data->ops->func(data, rec);
+		data->ops->func(data, rec, event);
 	}
 	return tt;
 }
@@ -108,7 +109,7 @@ enum event_trigger_type
 void
 event_triggers_post_call(struct trace_event_file *file,
 			 enum event_trigger_type tt,
-			 void *rec)
+			 void *rec, struct ring_buffer_event *event)
 {
 	struct event_trigger_data *data;
 
@@ -116,7 +117,7 @@ enum event_trigger_type
 		if (data->paused)
 			continue;
 		if (data->cmd_ops->trigger_type & tt)
-			data->ops->func(data, rec);
+			data->ops->func(data, rec, event);
 	}
 }
 EXPORT_SYMBOL_GPL(event_triggers_post_call);
@@ -909,7 +910,8 @@ void set_named_trigger_data(struct event_trigger_data *data,
 }
 
 static void
-traceon_trigger(struct event_trigger_data *data, void *rec)
+traceon_trigger(struct event_trigger_data *data, void *rec,
+		struct ring_buffer_event *event)
 {
 	if (tracing_is_on())
 		return;
@@ -918,7 +920,8 @@ void set_named_trigger_data(struct event_trigger_data *data,
 }
 
 static void
-traceon_count_trigger(struct event_trigger_data *data, void *rec)
+traceon_count_trigger(struct event_trigger_data *data, void *rec,
+		      struct ring_buffer_event *event)
 {
 	if (tracing_is_on())
 		return;
@@ -933,7 +936,8 @@ void set_named_trigger_data(struct event_trigger_data *data,
 }
 
 static void
-traceoff_trigger(struct event_trigger_data *data, void *rec)
+traceoff_trigger(struct event_trigger_data *data, void *rec,
+		 struct ring_buffer_event *event)
 {
 	if (!tracing_is_on())
 		return;
@@ -942,7 +946,8 @@ void set_named_trigger_data(struct event_trigger_data *data,
 }
 
 static void
-traceoff_count_trigger(struct event_trigger_data *data, void *rec)
+traceoff_count_trigger(struct event_trigger_data *data, void *rec,
+		       struct ring_buffer_event *event)
 {
 	if (!tracing_is_on())
 		return;
@@ -1039,13 +1044,15 @@ void set_named_trigger_data(struct event_trigger_data *data,
 
 #ifdef CONFIG_TRACER_SNAPSHOT
 static void
-snapshot_trigger(struct event_trigger_data *data, void *rec)
+snapshot_trigger(struct event_trigger_data *data, void *rec,
+		 struct ring_buffer_event *event)
 {
 	tracing_snapshot();
 }
 
 static void
-snapshot_count_trigger(struct event_trigger_data *data, void *rec)
+snapshot_count_trigger(struct event_trigger_data *data, void *rec,
+		       struct ring_buffer_event *event)
 {
 	if (!data->count)
 		return;
@@ -1053,7 +1060,7 @@ void set_named_trigger_data(struct event_trigger_data *data,
 	if (data->count != -1)
 		(data->count)--;
 
-	snapshot_trigger(data, rec);
+	snapshot_trigger(data, rec, event);
 }
 
 static int
@@ -1132,13 +1139,15 @@ static __init int register_trigger_snapshot_cmd(void)
 #define STACK_SKIP 3
 
 static void
-stacktrace_trigger(struct event_trigger_data *data, void *rec)
+stacktrace_trigger(struct event_trigger_data *data, void *rec,
+		   struct ring_buffer_event *event)
 {
 	trace_dump_stack(STACK_SKIP);
 }
 
 static void
-stacktrace_count_trigger(struct event_trigger_data *data, void *rec)
+stacktrace_count_trigger(struct event_trigger_data *data, void *rec,
+			 struct ring_buffer_event *event)
 {
 	if (!data->count)
 		return;
@@ -1146,7 +1155,7 @@ static __init int register_trigger_snapshot_cmd(void)
 	if (data->count != -1)
 		(data->count)--;
 
-	stacktrace_trigger(data, rec);
+	stacktrace_trigger(data, rec, event);
 }
 
 static int
@@ -1208,7 +1217,8 @@ static __init void unregister_trigger_traceon_traceoff_cmds(void)
 }
 
 static void
-event_enable_trigger(struct event_trigger_data *data, void *rec)
+event_enable_trigger(struct event_trigger_data *data, void *rec,
+		     struct ring_buffer_event *event)
 {
 	struct enable_trigger_data *enable_data = data->private_data;
 
@@ -1219,7 +1229,8 @@ static __init void unregister_trigger_traceon_traceoff_cmds(void)
 }
 
 static void
-event_enable_count_trigger(struct event_trigger_data *data, void *rec)
+event_enable_count_trigger(struct event_trigger_data *data, void *rec,
+			   struct ring_buffer_event *event)
 {
 	struct enable_trigger_data *enable_data = data->private_data;
 
@@ -1233,7 +1244,7 @@ static __init void unregister_trigger_traceon_traceoff_cmds(void)
 	if (data->count != -1)
 		(data->count)--;
 
-	event_enable_trigger(data, rec);
+	event_enable_trigger(data, rec, event);
 }
 
 int event_enable_trigger_print(struct seq_file *m,
-- 
1.9.3

[PATCH 06/32] tracing: Add ring buffer event param to hist field functions

[Tom Zanussi]

Some events such as timestamps require access to a ring_buffer_event
struct; add a param so that hist field functions can access that.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 655c412..613ff05 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -26,7 +26,8 @@
 
 struct hist_field;
 
-typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event);
+typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event,
+				struct ring_buffer_event *rbe);
 
 #define HIST_FIELD_OPERANDS_MAX	2
 
@@ -40,24 +41,28 @@ struct hist_field {
 	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
 };
 
-static u64 hist_field_none(struct hist_field *field, void *event)
+static u64 hist_field_none(struct hist_field *field, void *event,
+			   struct ring_buffer_event *rbe)
 {
 	return 0;
 }
 
-static u64 hist_field_counter(struct hist_field *field, void *event)
+static u64 hist_field_counter(struct hist_field *field, void *event,
+			      struct ring_buffer_event *rbe)
 {
 	return 1;
 }
 
-static u64 hist_field_string(struct hist_field *hist_field, void *event)
+static u64 hist_field_string(struct hist_field *hist_field, void *event,
+			     struct ring_buffer_event *rbe)
 {
 	char *addr = (char *)(event + hist_field->field->offset);
 
 	return (u64)(unsigned long)addr;
 }
 
-static u64 hist_field_dynstring(struct hist_field *hist_field, void *event)
+static u64 hist_field_dynstring(struct hist_field *hist_field, void *event,
+				struct ring_buffer_event *rbe)
 {
 	u32 str_item = *(u32 *)(event + hist_field->field->offset);
 	int str_loc = str_item & 0xffff;
@@ -66,24 +71,28 @@ static u64 hist_field_dynstring(struct hist_field *hist_field, void *event)
 	return (u64)(unsigned long)addr;
 }
 
-static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
+static u64 hist_field_pstring(struct hist_field *hist_field, void *event,
+			      struct ring_buffer_event *rbe)
 {
 	char **addr = (char **)(event + hist_field->field->offset);
 
 	return (u64)(unsigned long)*addr;
 }
 
-static u64 hist_field_log2(struct hist_field *hist_field, void *event)
+static u64 hist_field_log2(struct hist_field *hist_field, void *event,
+			   struct ring_buffer_event *rbe)
 {
 	struct hist_field *operand = hist_field->operands[0];
 
-	u64 val = operand->fn(operand, event);
+	u64 val = operand->fn(operand, event, rbe);
 
 	return (u64) ilog2(roundup_pow_of_two(val));
 }
 
 #define DEFINE_HIST_FIELD_FN(type)					\
-static u64 hist_field_##type(struct hist_field *hist_field, void *event)\
+	static u64 hist_field_##type(struct hist_field *hist_field,	\
+				     void *event,			\
+				     struct ring_buffer_event *rbe)	\
 {									\
 	type *addr = (type *)(event + hist_field->field->offset);	\
 									\
@@ -883,8 +892,8 @@ static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
 }
 
 static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
-				    struct tracing_map_elt *elt,
-				    void *rec)
+				    struct tracing_map_elt *elt, void *rec,
+				    struct ring_buffer_event *rbe)
 {
 	struct hist_field *hist_field;
 	unsigned int i;
@@ -892,7 +901,7 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
 
 	for_each_hist_val_field(i, hist_data) {
 		hist_field = hist_data->fields[i];
-		hist_val = hist_field->fn(hist_field, rec);
+		hist_val = hist_field->fn(hist_field, rec, rbe);
 		tracing_map_update_sum(elt, i, hist_val);
 	}
 }
@@ -922,7 +931,7 @@ static inline void add_to_key(char *compound_key, void *key,
 }
 
 static void event_hist_trigger(struct event_trigger_data *data, void *rec,
-			       struct ring_buffer_event *event)
+			       struct ring_buffer_event *rbe)
 {
 	struct hist_trigger_data *hist_data = data->private_data;
 	bool use_compound_key = (hist_data->n_keys > 1);
@@ -951,7 +960,7 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec,
 
 			key = entries;
 		} else {
-			field_contents = key_field->fn(key_field, rec);
+			field_contents = key_field->fn(key_field, rec, rbe);
 			if (key_field->flags & HIST_FIELD_FL_STRING) {
 				key = (void *)(unsigned long)field_contents;
 				use_compound_key = true;
@@ -968,7 +977,7 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec,
 
 	elt = tracing_map_insert(hist_data->map, key);
 	if (elt)
-		hist_trigger_elt_update(hist_data, elt, rec);
+		hist_trigger_elt_update(hist_data, elt, rec, rbe);
 }
 
 static void hist_trigger_stacktrace_print(struct seq_file *m,
-- 
1.9.3

[PATCH 07/32] tracing: Increase tracing map KEYS_MAX size

[Tom Zanussi]

The current default for the number of subkeys in a compound key is 2,
which is too restrictive.  Increase it to a more realistic value of 3.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/tracing_map.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/tracing_map.h b/kernel/trace/tracing_map.h
index 618838f..f097511 100644
--- a/kernel/trace/tracing_map.h
+++ b/kernel/trace/tracing_map.h
@@ -5,7 +5,7 @@
 #define TRACING_MAP_BITS_MAX		17
 #define TRACING_MAP_BITS_MIN		7
 
-#define TRACING_MAP_KEYS_MAX		2
+#define TRACING_MAP_KEYS_MAX		3
 #define TRACING_MAP_VALS_MAX		3
 #define TRACING_MAP_FIELDS_MAX		(TRACING_MAP_KEYS_MAX + \
 					 TRACING_MAP_VALS_MAX)
-- 
1.9.3

[PATCH 08/32] tracing: Break out hist trigger assignment parsing

[Tom Zanussi]

This will make it easier to add variables, and makes the parsing code
cleaner regardless.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 56 +++++++++++++++++++++++++---------------
 1 file changed, 35 insertions(+), 21 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 613ff05..fccbffe 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -251,6 +251,35 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 	kfree(attrs);
 }
 
+static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
+{
+	int ret = 0;
+
+	if ((strncmp(str, "key=", strlen("key=")) == 0) ||
+	    (strncmp(str, "keys=", strlen("keys=")) == 0))
+		attrs->keys_str = kstrdup(str, GFP_KERNEL);
+	else if ((strncmp(str, "val=", strlen("val=")) == 0) ||
+		 (strncmp(str, "vals=", strlen("vals=")) == 0) ||
+		 (strncmp(str, "values=", strlen("values=")) == 0))
+		attrs->vals_str = kstrdup(str, GFP_KERNEL);
+	else if (strncmp(str, "sort=", strlen("sort=")) == 0)
+		attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
+	else if (strncmp(str, "name=", strlen("name=")) == 0)
+		attrs->name = kstrdup(str, GFP_KERNEL);
+	else if (strncmp(str, "size=", strlen("size=")) == 0) {
+		int map_bits = parse_map_size(str);
+
+		if (map_bits < 0) {
+			ret = map_bits;
+			goto out;
+		}
+		attrs->map_bits = map_bits;
+	} else
+		ret = -EINVAL;
+ out:
+	return ret;
+}
+
 static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
 {
 	struct hist_trigger_attrs *attrs;
@@ -263,33 +292,18 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
 	while (trigger_str) {
 		char *str = strsep(&trigger_str, ":");
 
-		if ((strncmp(str, "key=", strlen("key=")) == 0) ||
-		    (strncmp(str, "keys=", strlen("keys=")) == 0))
-			attrs->keys_str = kstrdup(str, GFP_KERNEL);
-		else if ((strncmp(str, "val=", strlen("val=")) == 0) ||
-			 (strncmp(str, "vals=", strlen("vals=")) == 0) ||
-			 (strncmp(str, "values=", strlen("values=")) == 0))
-			attrs->vals_str = kstrdup(str, GFP_KERNEL);
-		else if (strncmp(str, "sort=", strlen("sort=")) == 0)
-			attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
-		else if (strncmp(str, "name=", strlen("name=")) == 0)
-			attrs->name = kstrdup(str, GFP_KERNEL);
-		else if (strcmp(str, "pause") == 0)
+		if (strchr(str, '=')) {
+			ret = parse_assignment(str, attrs);
+			if (ret)
+				goto free;
+		} else if (strcmp(str, "pause") == 0)
 			attrs->pause = true;
 		else if ((strcmp(str, "cont") == 0) ||
 			 (strcmp(str, "continue") == 0))
 			attrs->cont = true;
 		else if (strcmp(str, "clear") == 0)
 			attrs->clear = true;
-		else if (strncmp(str, "size=", strlen("size=")) == 0) {
-			int map_bits = parse_map_size(str);
-
-			if (map_bits < 0) {
-				ret = map_bits;
-				goto free;
-			}
-			attrs->map_bits = map_bits;
-		} else {
+		else {
 			ret = -EINVAL;
 			goto free;
 		}
-- 
1.9.3

[PATCH 09/32] tracing: Make traceprobe parsing code reusable

[Tom Zanussi]

traceprobe_probes_write() and traceprobe_command() actually contain
nothing that ties them to kprobes - the code is generically useful for
similar types of parsing elsewhere, so separate it out and move it to
trace.c/trace.h.

Other than moving it, the only change is in naming:
traceprobe_probes_write() becomes trace_parse_run_command() and
traceprobe_command() becomes trace_run_command().

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace.c        | 86 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/trace/trace.h        |  7 ++++
 kernel/trace/trace_kprobe.c | 18 +++++-----
 kernel/trace/trace_probe.c  | 86 ---------------------------------------------
 kernel/trace/trace_probe.h  |  7 ----
 kernel/trace/trace_uprobe.c |  2 +-
 6 files changed, 103 insertions(+), 103 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index da8cd51..f66a3df 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8082,6 +8082,92 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
 }
 EXPORT_SYMBOL_GPL(ftrace_dump);
 
+int trace_run_command(const char *buf, int (*createfn)(int, char **))
+{
+	char **argv;
+	int argc, ret;
+
+	argc = 0;
+	ret = 0;
+	argv = argv_split(GFP_KERNEL, buf, &argc);
+	if (!argv)
+		return -ENOMEM;
+
+	if (argc)
+		ret = createfn(argc, argv);
+
+	argv_free(argv);
+
+	return ret;
+}
+
+#define WRITE_BUFSIZE  4096
+
+ssize_t trace_parse_run_command(struct file *file, const char __user *buffer,
+				size_t count, loff_t *ppos,
+				int (*createfn)(int, char **))
+{
+	char *kbuf, *buf, *tmp;
+	int ret = 0;
+	size_t done = 0;
+	size_t size;
+
+	kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	while (done < count) {
+		size = count - done;
+
+		if (size >= WRITE_BUFSIZE)
+			size = WRITE_BUFSIZE - 1;
+
+		if (copy_from_user(kbuf, buffer + done, size)) {
+			ret = -EFAULT;
+			goto out;
+		}
+		kbuf[size] = '\0';
+		buf = kbuf;
+		do {
+			tmp = strchr(buf, '\n');
+			if (tmp) {
+				*tmp = '\0';
+				size = tmp - buf + 1;
+			} else {
+				size = strlen(buf);
+				if (done + size < count) {
+					if (buf != kbuf)
+						break;
+					/* This can accept WRITE_BUFSIZE - 2 ('\n' + '\0') */
+					pr_warn("Line length is too long: Should be less than %d\n",
+						WRITE_BUFSIZE - 2);
+					ret = -EINVAL;
+					goto out;
+				}
+			}
+			done += size;
+
+			/* Remove comments */
+			tmp = strchr(buf, '#');
+
+			if (tmp)
+				*tmp = '\0';
+
+			ret = trace_run_command(buf, createfn);
+			if (ret)
+				goto out;
+			buf += size;
+
+		} while (done < count);
+	}
+	ret = done;
+
+out:
+	kfree(kbuf);
+
+	return ret;
+}
+
 __init static int tracer_alloc_buffers(void)
 {
 	int ring_buf_size;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index fc892b9..78c7694 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1730,6 +1730,13 @@ extern int trace_event_enable_disable(struct trace_event_file *file,
 int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set);
 int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled);
 
+#define MAX_EVENT_NAME_LEN	64
+
+extern int trace_run_command(const char *buf, int (*createfn)(int, char**));
+extern ssize_t trace_parse_run_command(struct file *file,
+		const char __user *buffer, size_t count, loff_t *ppos,
+		int (*createfn)(int, char**));
+
 /*
  * Normal trace_printk() and friends allocates special buffers
  * to do the manipulation, as well as saves the print formats
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index c129fca..577cc69 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -902,8 +902,8 @@ static int probes_open(struct inode *inode, struct file *file)
 static ssize_t probes_write(struct file *file, const char __user *buffer,
 			    size_t count, loff_t *ppos)
 {
-	return traceprobe_probes_write(file, buffer, count, ppos,
-			create_trace_kprobe);
+	return trace_parse_run_command(file, buffer, count, ppos,
+				       create_trace_kprobe);
 }
 
 static const struct file_operations kprobe_events_ops = {
@@ -1428,9 +1428,9 @@ static __init int kprobe_trace_self_tests_init(void)
 
 	pr_info("Testing kprobe tracing: ");
 
-	ret = traceprobe_command("p:testprobe kprobe_trace_selftest_target "
-				  "$stack $stack0 +0($stack)",
-				  create_trace_kprobe);
+	ret = trace_run_command("p:testprobe kprobe_trace_selftest_target "
+				"$stack $stack0 +0($stack)",
+				create_trace_kprobe);
 	if (WARN_ON_ONCE(ret)) {
 		pr_warn("error on probing function entry.\n");
 		warn++;
@@ -1450,8 +1450,8 @@ static __init int kprobe_trace_self_tests_init(void)
 		}
 	}
 
-	ret = traceprobe_command("r:testprobe2 kprobe_trace_selftest_target "
-				  "$retval", create_trace_kprobe);
+	ret = trace_run_command("r:testprobe2 kprobe_trace_selftest_target "
+				"$retval", create_trace_kprobe);
 	if (WARN_ON_ONCE(ret)) {
 		pr_warn("error on probing function return.\n");
 		warn++;
@@ -1521,13 +1521,13 @@ static __init int kprobe_trace_self_tests_init(void)
 			disable_trace_kprobe(tk, file);
 	}
 
-	ret = traceprobe_command("-:testprobe", create_trace_kprobe);
+	ret = trace_run_command("-:testprobe", create_trace_kprobe);
 	if (WARN_ON_ONCE(ret)) {
 		pr_warn("error on deleting a probe.\n");
 		warn++;
 	}
 
-	ret = traceprobe_command("-:testprobe2", create_trace_kprobe);
+	ret = trace_run_command("-:testprobe2", create_trace_kprobe);
 	if (WARN_ON_ONCE(ret)) {
 		pr_warn("error on deleting a probe.\n");
 		warn++;
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 52478f0..d593573 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -623,92 +623,6 @@ void traceprobe_free_probe_arg(struct probe_arg *arg)
 	kfree(arg->comm);
 }
 
-int traceprobe_command(const char *buf, int (*createfn)(int, char **))
-{
-	char **argv;
-	int argc, ret;
-
-	argc = 0;
-	ret = 0;
-	argv = argv_split(GFP_KERNEL, buf, &argc);
-	if (!argv)
-		return -ENOMEM;
-
-	if (argc)
-		ret = createfn(argc, argv);
-
-	argv_free(argv);
-
-	return ret;
-}
-
-#define WRITE_BUFSIZE  4096
-
-ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer,
-				size_t count, loff_t *ppos,
-				int (*createfn)(int, char **))
-{
-	char *kbuf, *buf, *tmp;
-	int ret = 0;
-	size_t done = 0;
-	size_t size;
-
-	kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL);
-	if (!kbuf)
-		return -ENOMEM;
-
-	while (done < count) {
-		size = count - done;
-
-		if (size >= WRITE_BUFSIZE)
-			size = WRITE_BUFSIZE - 1;
-
-		if (copy_from_user(kbuf, buffer + done, size)) {
-			ret = -EFAULT;
-			goto out;
-		}
-		kbuf[size] = '\0';
-		buf = kbuf;
-		do {
-			tmp = strchr(buf, '\n');
-			if (tmp) {
-				*tmp = '\0';
-				size = tmp - buf + 1;
-			} else {
-				size = strlen(buf);
-				if (done + size < count) {
-					if (buf != kbuf)
-						break;
-					/* This can accept WRITE_BUFSIZE - 2 ('\n' + '\0') */
-					pr_warn("Line length is too long: Should be less than %d\n",
-						WRITE_BUFSIZE - 2);
-					ret = -EINVAL;
-					goto out;
-				}
-			}
-			done += size;
-
-			/* Remove comments */
-			tmp = strchr(buf, '#');
-
-			if (tmp)
-				*tmp = '\0';
-
-			ret = traceprobe_command(buf, createfn);
-			if (ret)
-				goto out;
-			buf += size;
-
-		} while (done < count);
-	}
-	ret = done;
-
-out:
-	kfree(kbuf);
-
-	return ret;
-}
-
 static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
 			   bool is_return)
 {
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 903273c..fb66e3e 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -42,7 +42,6 @@
 
 #define MAX_TRACE_ARGS		128
 #define MAX_ARGSTR_LEN		63
-#define MAX_EVENT_NAME_LEN	64
 #define MAX_STRING_SIZE		PATH_MAX
 
 /* Reserved field names */
@@ -356,12 +355,6 @@ extern int traceprobe_conflict_field_name(const char *name,
 
 extern int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset);
 
-extern ssize_t traceprobe_probes_write(struct file *file,
-		const char __user *buffer, size_t count, loff_t *ppos,
-		int (*createfn)(int, char**));
-
-extern int traceprobe_command(const char *buf, int (*createfn)(int, char**));
-
 /* Sum up total data length for dynamic arraies (strings) */
 static nokprobe_inline int
 __get_data_size(struct trace_probe *tp, struct pt_regs *regs)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index a7581fe..402120b 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -651,7 +651,7 @@ static int probes_open(struct inode *inode, struct file *file)
 static ssize_t probes_write(struct file *file, const char __user *buffer,
 			    size_t count, loff_t *ppos)
 {
-	return traceprobe_probes_write(file, buffer, count, ppos, create_trace_uprobe);
+	return trace_parse_run_command(file, buffer, count, ppos, create_trace_uprobe);
 }
 
 static const struct file_operations uprobe_events_ops = {
-- 
1.9.3

[PATCH 10/32] tracing: Add NO_DISCARD event file flag

[Tom Zanussi]

Whenever an event_command has a post-trigger that needs access to the
event record, the event record can't be discarded, or the post-trigger
will eventually see bogus data.

In order to allow the discard check to treat this case separately, add
an EVENT_FILE_FL_NO_DISCARD flag to the event file flags, along with
code in the discard check that checks the flag and avoids the discard
when the flag is set.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 include/linux/trace_events.h        |  3 +++
 kernel/trace/trace.h                | 13 ++++++++++---
 kernel/trace/trace_events_trigger.c | 16 +++++++++++++---
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index f333114..d7b230b 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -297,6 +297,7 @@ enum {
 	EVENT_FILE_FL_TRIGGER_MODE_BIT,
 	EVENT_FILE_FL_TRIGGER_COND_BIT,
 	EVENT_FILE_FL_PID_FILTER_BIT,
+	EVENT_FILE_FL_NO_DISCARD_BIT,
 };
 
 /*
@@ -311,6 +312,7 @@ enum {
  *  TRIGGER_MODE  - When set, invoke the triggers associated with the event
  *  TRIGGER_COND  - When set, one or more triggers has an associated filter
  *  PID_FILTER    - When set, the event is filtered based on pid
+ *  NO_DISCARD    - When set, do not discard events, something needs them later
  */
 enum {
 	EVENT_FILE_FL_ENABLED		= (1 << EVENT_FILE_FL_ENABLED_BIT),
@@ -322,6 +324,7 @@ enum {
 	EVENT_FILE_FL_TRIGGER_MODE	= (1 << EVENT_FILE_FL_TRIGGER_MODE_BIT),
 	EVENT_FILE_FL_TRIGGER_COND	= (1 << EVENT_FILE_FL_TRIGGER_COND_BIT),
 	EVENT_FILE_FL_PID_FILTER	= (1 << EVENT_FILE_FL_PID_FILTER_BIT),
+	EVENT_FILE_FL_NO_DISCARD	= (1 << EVENT_FILE_FL_NO_DISCARD_BIT),
 };
 
 struct trace_event_file {
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 78c7694..81b1d07 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1271,9 +1271,16 @@ static inline void trace_buffer_unlock_commit(struct trace_array *tr,
 	if (eflags & EVENT_FILE_FL_TRIGGER_COND)
 		*tt = event_triggers_call(file, entry, event);
 
-	if (test_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags) ||
-	    (unlikely(file->flags & EVENT_FILE_FL_FILTERED) &&
-	     !filter_match_preds(file->filter, entry))) {
+	if (unlikely(file->flags & EVENT_FILE_FL_FILTERED) &&
+	    !filter_match_preds(file->filter, entry)) {
+		__trace_event_discard_commit(buffer, event);
+		return true;
+	}
+
+	if (test_bit(EVENT_FILE_FL_NO_DISCARD_BIT, &file->flags))
+		return false;
+
+	if (test_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags)) {
 		__trace_event_discard_commit(buffer, event);
 		return true;
 	}
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 9b0fe31..d345820 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -505,20 +505,30 @@ int trace_event_trigger_enable_disable(struct trace_event_file *file,
 void update_cond_flag(struct trace_event_file *file)
 {
 	struct event_trigger_data *data;
-	bool set_cond = false;
+	bool set_cond = false, set_no_discard = false;
 
 	list_for_each_entry_rcu(data, &file->triggers, list) {
 		if (data->filter || event_command_post_trigger(data->cmd_ops) ||
-		    event_command_needs_rec(data->cmd_ops)) {
+		    event_command_needs_rec(data->cmd_ops))
 			set_cond = true;
+
+		if (event_command_post_trigger(data->cmd_ops) &&
+		    event_command_needs_rec(data->cmd_ops))
+			set_no_discard = true;
+
+		if (set_cond && set_no_discard)
 			break;
-		}
 	}
 
 	if (set_cond)
 		set_bit(EVENT_FILE_FL_TRIGGER_COND_BIT, &file->flags);
 	else
 		clear_bit(EVENT_FILE_FL_TRIGGER_COND_BIT, &file->flags);
+
+	if (set_no_discard)
+		set_bit(EVENT_FILE_FL_NO_DISCARD_BIT, &file->flags);
+	else
+		clear_bit(EVENT_FILE_FL_NO_DISCARD_BIT, &file->flags);
 }
 
 /**
-- 
1.9.3

[PATCH 11/32] tracing: Add post-trigger flag to hist trigger command

[Tom Zanussi]

Add EVENT_CMD_FL_POST_TRIGGER to the hist trigger cmd - it doesn't
affect the hist trigger results, and allows further events such as
synthetic events to be generated from a hist trigger.

Without this change, generating an event from a hist trigger will
cause the generated event to fail a ring buffer trace_recursive_lock()
check and return without actually logging the event.
---
 kernel/trace/trace_events_hist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index fccbffe..dab6ff6 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1676,7 +1676,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 static struct event_command trigger_hist_cmd = {
 	.name			= "hist",
 	.trigger_type		= ETT_EVENT_HIST,
-	.flags			= EVENT_CMD_FL_NEEDS_REC,
+	.flags			= EVENT_CMD_FL_NEEDS_REC | EVENT_CMD_FL_POST_TRIGGER,
 	.func			= event_hist_trigger_func,
 	.reg			= hist_register_trigger,
 	.unreg			= hist_unregister_trigger,
-- 
1.9.3

[PATCH 12/32] tracing: Add hist trigger timestamp support

[Tom Zanussi]

Add support for a timestamp event field.  This is actually a 'pseudo-'
event field in that it behaves like it's part of the event record, but
is really part of the corresponding ring buffer event.

To make use of the timestamp field, users can specify
"$common_timestamp" as a field name for any histogram.  Note that this
doesn't make much sense on its own either as either a key or value,
but needs to be supported even so, since follow-on patches will add
support for making use of this field in time deltas.  The '$' is used
as a prefix on the variable name to indicate that it's not an bonafide
event field - so you won't find it in the event description - but
rather it's a synthetic field that can be used like a real field).

Note that the use of this field requires the ring buffer be put into
TIME_EXTEND_ABS mode, which saves the complete timestamp for each
event rather than an offset.  This mode will be enabled if and only if
a histogram makes use of the "$common_timestamp" field.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 90 +++++++++++++++++++++++++++++-----------
 1 file changed, 66 insertions(+), 24 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index dab6ff6..aeae3b4 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -89,6 +89,12 @@ static u64 hist_field_log2(struct hist_field *hist_field, void *event,
 	return (u64) ilog2(roundup_pow_of_two(val));
 }
 
+static u64 hist_field_timestamp(struct hist_field *hist_field, void *event,
+				struct ring_buffer_event *rbe)
+{
+	return ring_buffer_event_time_stamp(rbe);
+}
+
 #define DEFINE_HIST_FIELD_FN(type)					\
 	static u64 hist_field_##type(struct hist_field *hist_field,	\
 				     void *event,			\
@@ -135,6 +141,7 @@ enum hist_field_flags {
 	HIST_FIELD_FL_SYSCALL		= 128,
 	HIST_FIELD_FL_STACKTRACE	= 256,
 	HIST_FIELD_FL_LOG2		= 512,
+	HIST_FIELD_FL_TIMESTAMP		= 1024,
 };
 
 struct hist_trigger_attrs {
@@ -159,6 +166,7 @@ struct hist_trigger_data {
 	struct trace_event_file		*event_file;
 	struct hist_trigger_attrs	*attrs;
 	struct tracing_map		*map;
+	bool				enable_timestamps;
 };
 
 static const char *hist_field_name(struct hist_field *field,
@@ -173,6 +181,8 @@ static const char *hist_field_name(struct hist_field *field,
 		field_name = field->field->name;
 	else if (field->flags & HIST_FIELD_FL_LOG2)
 		field_name = hist_field_name(field->operands[0], ++level);
+	else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
+		field_name = "$common_timestamp";
 
 	if (field_name == NULL)
 		field_name = "";
@@ -435,6 +445,12 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 		goto out;
 	}
 
+	if (flags & HIST_FIELD_FL_TIMESTAMP) {
+		hist_field->fn = hist_field_timestamp;
+		hist_field->size = sizeof(u64);
+		goto out;
+	}
+
 	if (WARN_ON_ONCE(!field))
 		goto out;
 
@@ -512,10 +528,15 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 		}
 	}
 
-	field = trace_find_event_field(file->event_call, field_name);
-	if (!field) {
-		ret = -EINVAL;
-		goto out;
+	if (strcmp(field_name, "$common_timestamp") == 0) {
+		flags |= HIST_FIELD_FL_TIMESTAMP;
+		hist_data->enable_timestamps = true;
+	} else {
+		field = trace_find_event_field(file->event_call, field_name);
+		if (!field) {
+			ret = -EINVAL;
+			goto out;
+		}
 	}
 
 	hist_data->fields[val_idx] = create_hist_field(field, flags);
@@ -610,16 +631,22 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 			}
 		}
 
-		field = trace_find_event_field(file->event_call, field_name);
-		if (!field) {
-			ret = -EINVAL;
-			goto out;
-		}
+		if (strcmp(field_name, "$common_timestamp") == 0) {
+			flags |= HIST_FIELD_FL_TIMESTAMP;
+			hist_data->enable_timestamps = true;
+			key_size = sizeof(u64);
+		} else {
+			field = trace_find_event_field(file->event_call, field_name);
+			if (!field) {
+				ret = -EINVAL;
+				goto out;
+			}
 
-		if (is_string_field(field))
-			key_size = MAX_FILTER_STR_VAL;
-		else
-			key_size = field->size;
+			if (is_string_field(field))
+				key_size = MAX_FILTER_STR_VAL;
+			else
+				key_size = field->size;
+		}
 	}
 
 	hist_data->fields[key_idx] = create_hist_field(field, flags);
@@ -756,7 +783,7 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 			break;
 		}
 
-		if (strcmp(field_name, "hitcount") == 0) {
+		if ((strcmp(field_name, "hitcount") == 0)) {
 			descending = is_descending(field_str);
 			if (descending < 0) {
 				ret = descending;
@@ -816,6 +843,9 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
 
 			if (hist_field->flags & HIST_FIELD_FL_STACKTRACE)
 				cmp_fn = tracing_map_cmp_none;
+			else if (!field)
+				cmp_fn = tracing_map_cmp_num(hist_field->size,
+							     hist_field->is_signed);
 			else if (is_string_field(field))
 				cmp_fn = tracing_map_cmp_string;
 			else
@@ -1213,7 +1243,11 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
 {
 	const char *field_name = hist_field_name(hist_field, 0);
 
-	seq_printf(m, "%s", field_name);
+	if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP)
+		seq_puts(m, "$common_timestamp");
+	else if (field_name)
+		seq_printf(m, "%s", field_name);
+
 	if (hist_field->flags) {
 		const char *flags_str = get_hist_field_flags(hist_field);
 
@@ -1264,27 +1298,25 @@ static int event_hist_trigger_print(struct seq_file *m,
 
 	for (i = 0; i < hist_data->n_sort_keys; i++) {
 		struct tracing_map_sort_key *sort_key;
+		unsigned int idx;
 
 		sort_key = &hist_data->sort_keys[i];
+		idx = sort_key->field_idx;
+
+		if (WARN_ON(idx >= TRACING_MAP_FIELDS_MAX))
+			return -EINVAL;
 
 		if (i > 0)
 			seq_puts(m, ",");
 
-		if (sort_key->field_idx == HITCOUNT_IDX)
+		if (idx == HITCOUNT_IDX)
 			seq_puts(m, "hitcount");
-		else {
-			unsigned int idx = sort_key->field_idx;
-
-			if (WARN_ON(idx >= TRACING_MAP_FIELDS_MAX))
-				return -EINVAL;
-
+		else
 			hist_field_print(m, hist_data->fields[idx]);
-		}
 
 		if (sort_key->descending)
 			seq_puts(m, ".descending");
 	}
-
 	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
 
 	if (data->filter_str)
@@ -1452,6 +1484,10 @@ static bool hist_trigger_match(struct event_trigger_data *data,
 			return false;
 		if (key_field->offset != key_field_test->offset)
 			return false;
+		if (key_field->size != key_field_test->size)
+			return false;
+		if (key_field->is_signed != key_field_test->is_signed)
+			return false;
 	}
 
 	for (i = 0; i < hist_data->n_sort_keys; i++) {
@@ -1534,6 +1570,9 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
 
 	update_cond_flag(file);
 
+	if (hist_data->enable_timestamps)
+		tracing_set_time_stamp_abs(file->tr, true);
+
 	if (trace_event_trigger_enable_disable(file, 1) < 0) {
 		list_del_rcu(&data->list);
 		update_cond_flag(file);
@@ -1568,6 +1607,9 @@ static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
 
 	if (unregistered && test->ops->free)
 		test->ops->free(test->ops, test);
+
+	if (hist_data->enable_timestamps)
+		tracing_set_time_stamp_abs(file->tr, false);
 }
 
 static void hist_unreg_all(struct trace_event_file *file)
-- 
1.9.3

Re: [PATCH 12/32] tracing: Add hist trigger timestamp support

[Namhyung Kim]

On Mon, Jun 26, 2017 at 05:49:13PM -0500, Tom Zanussi wrote:
> Add support for a timestamp event field.  This is actually a 'pseudo-'
> event field in that it behaves like it's part of the event record, but
> is really part of the corresponding ring buffer event.
> 
> To make use of the timestamp field, users can specify
> "$common_timestamp" as a field name for any histogram.  Note that this
> doesn't make much sense on its own either as either a key or value,
> but needs to be supported even so, since follow-on patches will add
> support for making use of this field in time deltas.  The '$' is used
> as a prefix on the variable name to indicate that it's not an bonafide
> event field - so you won't find it in the event description - but
> rather it's a synthetic field that can be used like a real field).
> 
> Note that the use of this field requires the ring buffer be put into
> TIME_EXTEND_ABS mode, which saves the complete timestamp for each
> event rather than an offset.  This mode will be enabled if and only if
> a histogram makes use of the "$common_timestamp" field.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  kernel/trace/trace_events_hist.c | 90 +++++++++++++++++++++++++++++-----------
>  1 file changed, 66 insertions(+), 24 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index dab6ff6..aeae3b4 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c

[SNIP]
> @@ -756,7 +783,7 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
>  			break;
>  		}
>  
> -		if (strcmp(field_name, "hitcount") == 0) {
> +		if ((strcmp(field_name, "hitcount") == 0)) {

Seems like an unnecessary change.


>  			descending = is_descending(field_str);
>  			if (descending < 0) {
>  				ret = descending;
> @@ -816,6 +843,9 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
>  
>  			if (hist_field->flags & HIST_FIELD_FL_STACKTRACE)
>  				cmp_fn = tracing_map_cmp_none;
> +			else if (!field)
> +				cmp_fn = tracing_map_cmp_num(hist_field->size,
> +							     hist_field->is_signed);

I couldn't find where the hist_field->is_signed is set.


>  			else if (is_string_field(field))
>  				cmp_fn = tracing_map_cmp_string;
>  			else

[SNIP]
> @@ -1534,6 +1570,9 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
>  
>  	update_cond_flag(file);
>  
> +	if (hist_data->enable_timestamps)
> +		tracing_set_time_stamp_abs(file->tr, true);
> +
>  	if (trace_event_trigger_enable_disable(file, 1) < 0) {
>  		list_del_rcu(&data->list);
>  		update_cond_flag(file);
> @@ -1568,6 +1607,9 @@ static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
>  
>  	if (unregistered && test->ops->free)
>  		test->ops->free(test->ops, test);
> +
> +	if (hist_data->enable_timestamps)
> +		tracing_set_time_stamp_abs(file->tr, false);

I think it needs some kind of refcount to disable the absolute
timestamp.  Otherwise unregistering a timestamp-enabled hist might
corrupt others IMHO.

Thanks,
Namhyung


>  }
>  
>  static void hist_unreg_all(struct trace_event_file *file)
> -- 
> 1.9.3
> 

Re: [PATCH 12/32] tracing: Add hist trigger timestamp support

[Tom Zanussi]

Hi Namhyung,

On Mon, 2017-07-17 at 15:00 +0900, Namhyung Kim wrote:
> On Mon, Jun 26, 2017 at 05:49:13PM -0500, Tom Zanussi wrote:
> > Add support for a timestamp event field.  This is actually a 'pseudo-'
> > event field in that it behaves like it's part of the event record, but
> > is really part of the corresponding ring buffer event.
> > 
> > To make use of the timestamp field, users can specify
> > "$common_timestamp" as a field name for any histogram.  Note that this
> > doesn't make much sense on its own either as either a key or value,
> > but needs to be supported even so, since follow-on patches will add
> > support for making use of this field in time deltas.  The '$' is used
> > as a prefix on the variable name to indicate that it's not an bonafide
> > event field - so you won't find it in the event description - but
> > rather it's a synthetic field that can be used like a real field).
> > 
> > Note that the use of this field requires the ring buffer be put into
> > TIME_EXTEND_ABS mode, which saves the complete timestamp for each
> > event rather than an offset.  This mode will be enabled if and only if
> > a histogram makes use of the "$common_timestamp" field.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> >  kernel/trace/trace_events_hist.c | 90 +++++++++++++++++++++++++++++-----------
> >  1 file changed, 66 insertions(+), 24 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index dab6ff6..aeae3b4 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> 
> [SNIP]
> > @@ -756,7 +783,7 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
> >  			break;
> >  		}
> >  
> > -		if (strcmp(field_name, "hitcount") == 0) {
> > +		if ((strcmp(field_name, "hitcount") == 0)) {
> 
> Seems like an unnecessary change.
> 
> 
> >  			descending = is_descending(field_str);
> >  			if (descending < 0) {
> >  				ret = descending;
> > @@ -816,6 +843,9 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
> >  
> >  			if (hist_field->flags & HIST_FIELD_FL_STACKTRACE)
> >  				cmp_fn = tracing_map_cmp_none;
> > +			else if (!field)
> > +				cmp_fn = tracing_map_cmp_num(hist_field->size,
> > +							     hist_field->is_signed);
> 
> I couldn't find where the hist_field->is_signed is set.

It's set in a later patch (the one that adds onmatch).  I'll move the
code that defines and sets the field to the same patch.

> 
> 
> >  			else if (is_string_field(field))
> >  				cmp_fn = tracing_map_cmp_string;
> >  			else
> 
> [SNIP]
> > @@ -1534,6 +1570,9 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
> >  
> >  	update_cond_flag(file);
> >  
> > +	if (hist_data->enable_timestamps)
> > +		tracing_set_time_stamp_abs(file->tr, true);
> > +
> >  	if (trace_event_trigger_enable_disable(file, 1) < 0) {
> >  		list_del_rcu(&data->list);
> >  		update_cond_flag(file);
> > @@ -1568,6 +1607,9 @@ static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
> >  
> >  	if (unregistered && test->ops->free)
> >  		test->ops->free(test->ops, test);
> > +
> > +	if (hist_data->enable_timestamps)
> > +		tracing_set_time_stamp_abs(file->tr, false);
> 
> I think it needs some kind of refcount to disable the absolute
> timestamp.  Otherwise unregistering a timestamp-enabled hist might
> corrupt others IMHO.
> 

Good point, I'll add that.  Thanks,

Tom

> Thanks,
> Namhyung
> 
> 
> >  }
> >  
> >  static void hist_unreg_all(struct trace_event_file *file)
> > -- 
> > 1.9.3
> > 

[PATCH 13/32] tracing: Add per-element variable support to tracing_map

[Tom Zanussi]

In order to allow information to be passed between trace events, add
support for per-element variables to tracing_map.  This provides a
means for histograms to associate a value or values with an entry when
it's saved or updated, and retrieved by a subsequent event occurrences.

Variables can be set using tracing_map_set_var() and read using
tracing_map_read_var().  tracing_map_var_set() returns true or false
depending on whether or not the variable has been set or not, which is
important for event-matching applications.

tracing_map_read_var_once() reads the variable and resets it to the
'unset' state, implementing read-once variables, which are also
important for event-matching uses.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/tracing_map.c | 113 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/trace/tracing_map.h |  11 +++++
 2 files changed, 124 insertions(+)

diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
index 0a689bb..f987069 100644
--- a/kernel/trace/tracing_map.c
+++ b/kernel/trace/tracing_map.c
@@ -66,6 +66,73 @@ u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i)
 	return (u64)atomic64_read(&elt->fields[i].sum);
 }
 
+/**
+ * tracing_map_set_var - Assign a tracing_map_elt's variable field
+ * @elt: The tracing_map_elt
+ * @i: The index of the given variable associated with the tracing_map_elt
+ * @n: The value to assign
+ *
+ * Assign n to variable i associated with the specified tracing_map_elt
+ * instance.  The index i is the index returned by the call to
+ * tracing_map_add_var() when the tracing map was set up.
+ */
+void tracing_map_set_var(struct tracing_map_elt *elt, unsigned int i, u64 n)
+{
+	atomic64_set(&elt->vars[i], n);
+	elt->var_set[i] = true;
+}
+
+/**
+ * tracing_map_var_set - Return whether or not a variable has been set
+ * @elt: The tracing_map_elt
+ * @i: The index of the given variable associated with the tracing_map_elt
+ *
+ * Return true if the variable has been set, false otherwise.  The
+ * index i is the index returned by the call to tracing_map_add_var()
+ * when the tracing map was set up.
+ */
+bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i)
+{
+	return elt->var_set[i];
+}
+
+/**
+ * tracing_map_read_var - Return the value of a tracing_map_elt's variable field
+ * @elt: The tracing_map_elt
+ * @i: The index of the given variable associated with the tracing_map_elt
+ *
+ * Retrieve the value of the variable i associated with the specified
+ * tracing_map_elt instance.  The index i is the index returned by the
+ * call to tracing_map_add_var() when the tracing map was set
+ * up.
+ *
+ * Return: The variable value associated with field i for elt.
+ */
+u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i)
+{
+	return (u64)atomic64_read(&elt->vars[i]);
+}
+
+/**
+ * tracing_map_read_var_once - Return and reset a tracing_map_elt's variable field
+ * @elt: The tracing_map_elt
+ * @i: The index of the given variable associated with the tracing_map_elt
+ *
+ * Retrieve the value of the variable i associated with the specified
+ * tracing_map_elt instance, and reset the variable to the 'not set'
+ * state.  The index i is the index returned by the call to
+ * tracing_map_add_var() when the tracing map was set up.  The reset
+ * essentially makes the variable a read-once variable if it's only
+ * accessed using this function.
+ *
+ * Return: The variable value associated with field i for elt.
+ */
+u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i)
+{
+	elt->var_set[i] = false;
+	return (u64)atomic64_read(&elt->vars[i]);
+}
+
 int tracing_map_cmp_string(void *val_a, void *val_b)
 {
 	char *a = val_a;
@@ -171,6 +238,28 @@ int tracing_map_add_sum_field(struct tracing_map *map)
 }
 
 /**
+ * tracing_map_add_var - Add a field describing a tracing_map var
+ * @map: The tracing_map
+ *
+ * Add a var to the map and return the index identifying it in the map
+ * and associated tracing_map_elts.  This is the index used for
+ * instance to update a var for a particular tracing_map_elt using
+ * tracing_map_update_var() or reading it via tracing_map_read_var().
+ *
+ * Return: The index identifying the var in the map and associated
+ * tracing_map_elts, or -EINVAL on error.
+ */
+int tracing_map_add_var(struct tracing_map *map)
+{
+	int ret = -EINVAL;
+
+	if (map->n_vars < TRACING_MAP_VARS_MAX)
+		ret = map->n_vars++;
+
+	return ret;
+}
+
+/**
  * tracing_map_add_key_field - Add a field describing a tracing_map key
  * @map: The tracing_map
  * @offset: The offset within the key
@@ -277,6 +366,11 @@ static void tracing_map_elt_clear(struct tracing_map_elt *elt)
 		if (elt->fields[i].cmp_fn == tracing_map_cmp_atomic64)
 			atomic64_set(&elt->fields[i].sum, 0);
 
+	for (i = 0; i < elt->map->n_vars; i++) {
+		atomic64_set(&elt->vars[i], 0);
+		elt->var_set[i] = false;
+	}
+
 	if (elt->map->ops && elt->map->ops->elt_clear)
 		elt->map->ops->elt_clear(elt);
 }
@@ -303,6 +397,8 @@ static void tracing_map_elt_free(struct tracing_map_elt *elt)
 	if (elt->map->ops && elt->map->ops->elt_free)
 		elt->map->ops->elt_free(elt);
 	kfree(elt->fields);
+	kfree(elt->vars);
+	kfree(elt->var_set);
 	kfree(elt->key);
 	kfree(elt);
 }
@@ -330,6 +426,18 @@ static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
 		goto free;
 	}
 
+	elt->vars = kcalloc(map->n_vars, sizeof(*elt->vars), GFP_KERNEL);
+	if (!elt->vars) {
+		err = -ENOMEM;
+		goto free;
+	}
+
+	elt->var_set = kcalloc(map->n_vars, sizeof(*elt->var_set), GFP_KERNEL);
+	if (!elt->var_set) {
+		err = -ENOMEM;
+		goto free;
+	}
+
 	tracing_map_elt_init_fields(elt);
 
 	if (map->ops && map->ops->elt_alloc) {
@@ -833,6 +941,11 @@ static struct tracing_map_elt *copy_elt(struct tracing_map_elt *elt)
 		dup_elt->fields[i].cmp_fn = elt->fields[i].cmp_fn;
 	}
 
+	for (i = 0; i < elt->map->n_vars; i++) {
+		atomic64_set(&dup_elt->vars[i], atomic64_read(&elt->vars[i]));
+		dup_elt->var_set[i] = elt->var_set[i];
+	}
+
 	return dup_elt;
 }
 
diff --git a/kernel/trace/tracing_map.h b/kernel/trace/tracing_map.h
index f097511..303bc4f 100644
--- a/kernel/trace/tracing_map.h
+++ b/kernel/trace/tracing_map.h
@@ -9,6 +9,7 @@
 #define TRACING_MAP_VALS_MAX		3
 #define TRACING_MAP_FIELDS_MAX		(TRACING_MAP_KEYS_MAX + \
 					 TRACING_MAP_VALS_MAX)
+#define TRACING_MAP_VARS_MAX		16
 #define TRACING_MAP_SORT_KEYS_MAX	2
 
 typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b);
@@ -136,6 +137,8 @@ struct tracing_map_field {
 struct tracing_map_elt {
 	struct tracing_map		*map;
 	struct tracing_map_field	*fields;
+	atomic64_t			*vars;
+	bool				*var_set;
 	void				*key;
 	void				*private_data;
 };
@@ -191,6 +194,7 @@ struct tracing_map {
 	int				key_idx[TRACING_MAP_KEYS_MAX];
 	unsigned int			n_keys;
 	struct tracing_map_sort_key	sort_key;
+	unsigned int			n_vars;
 	atomic64_t			hits;
 	atomic64_t			drops;
 };
@@ -247,6 +251,7 @@ struct tracing_map_ops {
 extern int tracing_map_init(struct tracing_map *map);
 
 extern int tracing_map_add_sum_field(struct tracing_map *map);
+extern int tracing_map_add_var(struct tracing_map *map);
 extern int tracing_map_add_key_field(struct tracing_map *map,
 				     unsigned int offset,
 				     tracing_map_cmp_fn_t cmp_fn);
@@ -266,7 +271,13 @@ extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
 
 extern void tracing_map_update_sum(struct tracing_map_elt *elt,
 				   unsigned int i, u64 n);
+extern void tracing_map_set_var(struct tracing_map_elt *elt,
+				unsigned int i, u64 n);
+extern bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i);
 extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i);
+extern u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i);
+extern u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i);
+
 extern void tracing_map_set_field_descr(struct tracing_map *map,
 					unsigned int i,
 					unsigned int key_offset,
-- 
1.9.3

[PATCH 14/32] tracing: Add hist_data member to hist_field

[Tom Zanussi]

Allow hist_data access via hist_field.  Some users of hist_fields
require or will require more access to the associated hist_data.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index aeae3b4..fb08a75 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -39,6 +39,7 @@ struct hist_field {
 	unsigned int			offset;
 	unsigned int                    is_signed;
 	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
+	struct hist_trigger_data	*hist_data;
 };
 
 static u64 hist_field_none(struct hist_field *field, void *event,
@@ -415,7 +416,8 @@ static void destroy_hist_field(struct hist_field *hist_field,
 	kfree(hist_field);
 }
 
-static struct hist_field *create_hist_field(struct ftrace_event_field *field,
+static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
+					    struct ftrace_event_field *field,
 					    unsigned long flags)
 {
 	struct hist_field *hist_field;
@@ -427,6 +429,8 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 	if (!hist_field)
 		return NULL;
 
+	hist_field->hist_data = hist_data;
+
 	if (flags & HIST_FIELD_FL_HITCOUNT) {
 		hist_field->fn = hist_field_counter;
 		goto out;
@@ -440,7 +444,7 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 	if (flags & HIST_FIELD_FL_LOG2) {
 		unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
 		hist_field->fn = hist_field_log2;
-		hist_field->operands[0] = create_hist_field(field, fl);
+		hist_field->operands[0] = create_hist_field(hist_data, field, fl);
 		hist_field->size = hist_field->operands[0]->size;
 		goto out;
 	}
@@ -493,7 +497,7 @@ static void destroy_hist_fields(struct hist_trigger_data *hist_data)
 static int create_hitcount_val(struct hist_trigger_data *hist_data)
 {
 	hist_data->fields[HITCOUNT_IDX] =
-		create_hist_field(NULL, HIST_FIELD_FL_HITCOUNT);
+		create_hist_field(hist_data, NULL, HIST_FIELD_FL_HITCOUNT);
 	if (!hist_data->fields[HITCOUNT_IDX])
 		return -ENOMEM;
 
@@ -539,7 +543,7 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 		}
 	}
 
-	hist_data->fields[val_idx] = create_hist_field(field, flags);
+	hist_data->fields[val_idx] = create_hist_field(hist_data, field, flags);
 	if (!hist_data->fields[val_idx]) {
 		ret = -ENOMEM;
 		goto out;
@@ -649,7 +653,7 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 		}
 	}
 
-	hist_data->fields[key_idx] = create_hist_field(field, flags);
+	hist_data->fields[key_idx] = create_hist_field(hist_data, field, flags);
 	if (!hist_data->fields[key_idx]) {
 		ret = -ENOMEM;
 		goto out;
-- 
1.9.3

[PATCH 15/32] tracing: Add usecs modifier for hist trigger timestamps

[Tom Zanussi]

Appending .usecs onto a common_timestamp field will cause the
timestamp value to be in microseconds instead of the default
nanoseconds.  A typical latency histogram using usecs would look like
this:

   # echo 'hist:keys=pid,prio:ts0=$common_timestamp.usecs ...
   # echo 'hist:keys=next_pid:wakeup_lat=$common_timestamp.usecs-$ts0 ...

This also adds an external trace_clock_in_ns() to trace.c for the
timestamp conversion.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace.c             |  8 ++++++++
 kernel/trace/trace.h             |  2 ++
 kernel/trace/trace_events_hist.c | 28 ++++++++++++++++++++++------
 3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f66a3df..ec84822 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1170,6 +1170,14 @@ unsigned long nsecs_to_usecs(unsigned long nsecs)
 	ARCH_TRACE_CLOCKS
 };
 
+bool trace_clock_in_ns(struct trace_array *tr)
+{
+	if (trace_clocks[tr->clock_id].in_ns)
+		return true;
+
+	return false;
+}
+
 /*
  * trace_parser_get_init - gets the buffer for trace parser
  */
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 81b1d07..65f90b4 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -283,6 +283,8 @@ enum {
 
 extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
 
+extern bool trace_clock_in_ns(struct trace_array *tr);
+
 /*
  * The global tracer (top) should be the first trace array added,
  * but we check the flag anyway.
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index fb08a75..5c351d7 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -90,12 +90,6 @@ static u64 hist_field_log2(struct hist_field *hist_field, void *event,
 	return (u64) ilog2(roundup_pow_of_two(val));
 }
 
-static u64 hist_field_timestamp(struct hist_field *hist_field, void *event,
-				struct ring_buffer_event *rbe)
-{
-	return ring_buffer_event_time_stamp(rbe);
-}
-
 #define DEFINE_HIST_FIELD_FN(type)					\
 	static u64 hist_field_##type(struct hist_field *hist_field,	\
 				     void *event,			\
@@ -143,6 +137,7 @@ enum hist_field_flags {
 	HIST_FIELD_FL_STACKTRACE	= 256,
 	HIST_FIELD_FL_LOG2		= 512,
 	HIST_FIELD_FL_TIMESTAMP		= 1024,
+	HIST_FIELD_FL_TIMESTAMP_USECS	= 2048,
 };
 
 struct hist_trigger_attrs {
@@ -153,6 +148,7 @@ struct hist_trigger_attrs {
 	bool		pause;
 	bool		cont;
 	bool		clear;
+	bool		ts_in_usecs;
 	unsigned int	map_bits;
 };
 
@@ -170,6 +166,20 @@ struct hist_trigger_data {
 	bool				enable_timestamps;
 };
 
+static u64 hist_field_timestamp(struct hist_field *hist_field, void *event,
+				struct ring_buffer_event *rbe)
+{
+	struct hist_trigger_data *hist_data = hist_field->hist_data;
+	struct trace_array *tr = hist_data->event_file->tr;
+
+	u64 ts = ring_buffer_event_time_stamp(rbe);
+
+	if (hist_data->attrs->ts_in_usecs && trace_clock_in_ns(tr))
+		ts = ns2usecs(ts);
+
+	return ts;
+}
+
 static const char *hist_field_name(struct hist_field *field,
 				   unsigned int level)
 {
@@ -629,6 +639,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 				flags |= HIST_FIELD_FL_SYSCALL;
 			else if (strcmp(field_str, "log2") == 0)
 				flags |= HIST_FIELD_FL_LOG2;
+			else if (strcmp(field_str, "usecs") == 0)
+				flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
 			else {
 				ret = -EINVAL;
 				goto out;
@@ -638,6 +650,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 		if (strcmp(field_name, "$common_timestamp") == 0) {
 			flags |= HIST_FIELD_FL_TIMESTAMP;
 			hist_data->enable_timestamps = true;
+			if (flags & HIST_FIELD_FL_TIMESTAMP_USECS)
+				hist_data->attrs->ts_in_usecs = true;
 			key_size = sizeof(u64);
 		} else {
 			field = trace_find_event_field(file->event_call, field_name);
@@ -1239,6 +1253,8 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
 		flags_str = "syscall";
 	else if (hist_field->flags & HIST_FIELD_FL_LOG2)
 		flags_str = "log2";
+	else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP_USECS)
+		flags_str = "usecs";
 
 	return flags_str;
 }
-- 
1.9.3

[PATCH 16/32] tracing: Add variable support to hist triggers

[Tom Zanussi]

Add support for saving the value of a current event's event field by
assigning it to a variable that can be read by a subsequent event.

The basic syntax for saving a variable is to simply prefix a unique
variable name not corresponding to any keyword along with an '=' sign
to any event field.

Both keys and values can be saved and retrieved in this way:

    # echo 'hist:keys=next_pid:vals=ts0=common_timestamp ...
    # echo 'hist:key=timer_pid=common_pid ...'

If a variable isn't a key variable or prefixed with 'vals=', the
associated event field will be saved in a variable but won't be summed
as a value:

    # echo 'hist:keys=next_pid:ts1=common_timestamp:...

Multiple variables can be assigned at the same time:

    # echo 'hist:keys=pid:vals=ts0=common_timestamp,b=field1,field2 ...

Multiple (or single) variables can also be assigned at the same time
using separate assignments:

    # echo 'hist:keys=pid:vals=ts0=common_timestamp:b=field1:c=field2 ...

Variables set as above can be used by being referenced from another
event, as described in a subsequent patch.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 299 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 264 insertions(+), 35 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 5c351d7..75cac76 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -30,6 +30,13 @@ typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event,
 				struct ring_buffer_event *rbe);
 
 #define HIST_FIELD_OPERANDS_MAX	2
+#define HIST_FIELDS_MAX		(TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
+
+struct hist_var {
+	char				*name;
+	struct hist_trigger_data	*hist_data;
+	unsigned int			idx;
+};
 
 struct hist_field {
 	struct ftrace_event_field	*field;
@@ -40,6 +47,7 @@ struct hist_field {
 	unsigned int                    is_signed;
 	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
 	struct hist_trigger_data	*hist_data;
+	struct hist_var			var;
 };
 
 static u64 hist_field_none(struct hist_field *field, void *event,
@@ -138,6 +146,8 @@ enum hist_field_flags {
 	HIST_FIELD_FL_LOG2		= 512,
 	HIST_FIELD_FL_TIMESTAMP		= 1024,
 	HIST_FIELD_FL_TIMESTAMP_USECS	= 2048,
+	HIST_FIELD_FL_VAR		= 4096,
+	HIST_FIELD_FL_VAR_ONLY		= 8192,
 };
 
 struct hist_trigger_attrs {
@@ -150,13 +160,18 @@ struct hist_trigger_attrs {
 	bool		clear;
 	bool		ts_in_usecs;
 	unsigned int	map_bits;
+
+	char		*assignment_str[TRACING_MAP_VARS_MAX];
+	unsigned int	n_assignments;
 };
 
 struct hist_trigger_data {
-	struct hist_field               *fields[TRACING_MAP_FIELDS_MAX];
+	struct hist_field               *fields[HIST_FIELDS_MAX];
 	unsigned int			n_vals;
 	unsigned int			n_keys;
 	unsigned int			n_fields;
+	unsigned int			n_vars;
+	unsigned int			n_var_only;
 	unsigned int			key_size;
 	struct tracing_map_sort_key	sort_keys[TRACING_MAP_SORT_KEYS_MAX];
 	unsigned int			n_sort_keys;
@@ -164,6 +179,7 @@ struct hist_trigger_data {
 	struct hist_trigger_attrs	*attrs;
 	struct tracing_map		*map;
 	bool				enable_timestamps;
+	bool				remove;
 };
 
 static u64 hist_field_timestamp(struct hist_field *hist_field, void *event,
@@ -262,9 +278,14 @@ static int parse_map_size(char *str)
 
 static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 {
+	unsigned int i;
+
 	if (!attrs)
 		return;
 
+	for (i = 0; i < attrs->n_assignments; i++)
+		kfree(attrs->assignment_str[i]);
+
 	kfree(attrs->name);
 	kfree(attrs->sort_key_str);
 	kfree(attrs->keys_str);
@@ -295,8 +316,22 @@ static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
 			goto out;
 		}
 		attrs->map_bits = map_bits;
-	} else
-		ret = -EINVAL;
+	} else {
+		char *assignment;
+
+		if (attrs->n_assignments == TRACING_MAP_VARS_MAX) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		assignment = kstrdup(str, GFP_KERNEL);
+		if (!assignment) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		attrs->assignment_str[attrs->n_assignments++] = assignment;
+	}
  out:
 	return ret;
 }
@@ -423,12 +458,15 @@ static void destroy_hist_field(struct hist_field *hist_field,
 	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
 		destroy_hist_field(hist_field->operands[i], ++level);
 
+	kfree(hist_field->var.name);
+
 	kfree(hist_field);
 }
 
 static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 					    struct ftrace_event_field *field,
-					    unsigned long flags)
+					    unsigned long flags,
+					    char *var_name)
 {
 	struct hist_field *hist_field;
 
@@ -454,7 +492,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 	if (flags & HIST_FIELD_FL_LOG2) {
 		unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
 		hist_field->fn = hist_field_log2;
-		hist_field->operands[0] = create_hist_field(hist_data, field, fl);
+		hist_field->operands[0] = create_hist_field(hist_data, field, fl, NULL);
 		hist_field->size = hist_field->operands[0]->size;
 		goto out;
 	}
@@ -489,14 +527,23 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 	hist_field->field = field;
 	hist_field->flags = flags;
 
+	if (var_name) {
+		hist_field->var.name = kstrdup(var_name, GFP_KERNEL);
+		if (!hist_field->var.name)
+			goto free;
+	}
+
 	return hist_field;
+ free:
+	destroy_hist_field(hist_field, 0);
+	return NULL;
 }
 
 static void destroy_hist_fields(struct hist_trigger_data *hist_data)
 {
 	unsigned int i;
 
-	for (i = 0; i < TRACING_MAP_FIELDS_MAX; i++) {
+	for (i = 0; i < HIST_FIELDS_MAX; i++) {
 		if (hist_data->fields[i]) {
 			destroy_hist_field(hist_data->fields[i], 0);
 			hist_data->fields[i] = NULL;
@@ -507,11 +554,12 @@ static void destroy_hist_fields(struct hist_trigger_data *hist_data)
 static int create_hitcount_val(struct hist_trigger_data *hist_data)
 {
 	hist_data->fields[HITCOUNT_IDX] =
-		create_hist_field(hist_data, NULL, HIST_FIELD_FL_HITCOUNT);
+		create_hist_field(hist_data, NULL, HIST_FIELD_FL_HITCOUNT, NULL);
 	if (!hist_data->fields[HITCOUNT_IDX])
 		return -ENOMEM;
 
 	hist_data->n_vals++;
+	hist_data->n_fields++;
 
 	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX))
 		return -EINVAL;
@@ -519,19 +567,81 @@ static int create_hitcount_val(struct hist_trigger_data *hist_data)
 	return 0;
 }
 
+static struct hist_field *find_var_field(struct hist_trigger_data *hist_data,
+					 const char *var_name)
+{
+	struct hist_field *hist_field, *found = NULL;
+	int i;
+
+	for_each_hist_field(i, hist_data) {
+		hist_field = hist_data->fields[i];
+		if (hist_field && hist_field->flags & HIST_FIELD_FL_VAR &&
+		    strcmp(hist_field->var.name, var_name) == 0) {
+			found = hist_field;
+			break;
+		}
+	}
+
+	return found;
+}
+
+static struct hist_field *find_var(struct trace_event_file *file,
+				   const char *var_name)
+{
+	struct hist_trigger_data *hist_data;
+	struct event_trigger_data *test;
+	struct hist_field *hist_field;
+
+	list_for_each_entry_rcu(test, &file->triggers, list) {
+		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			hist_data = test->private_data;
+			hist_field = find_var_field(hist_data, var_name);
+			if (hist_field)
+				return hist_field;
+		}
+	}
+
+	return NULL;
+}
+
 static int create_val_field(struct hist_trigger_data *hist_data,
 			    unsigned int val_idx,
 			    struct trace_event_file *file,
-			    char *field_str)
+			    char *field_str, bool var_only)
 {
 	struct ftrace_event_field *field = NULL;
+	char *field_name, *var_name;
 	unsigned long flags = 0;
-	char *field_name;
 	int ret = 0;
 
-	if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX))
+	if (WARN_ON(!var_only && val_idx >= TRACING_MAP_VALS_MAX))
 		return -EINVAL;
 
+	var_name = strsep(&field_str, "=");
+	if (field_str && var_name) {
+		if (find_var(file, var_name) &&
+		    !hist_data->remove) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		flags |= HIST_FIELD_FL_VAR;
+		hist_data->n_vars++;
+		if (hist_data->n_vars > TRACING_MAP_VARS_MAX) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		if (var_only)
+			flags |= HIST_FIELD_FL_VAR_ONLY;
+	} else if (!var_only && var_name != NULL && field_str == NULL) {
+		field_str = var_name;
+		var_name = NULL;
+	} else {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	field_name = strsep(&field_str, ".");
 	if (field_str) {
 		if (strcmp(field_str, "hex") == 0)
@@ -553,15 +663,19 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 		}
 	}
 
-	hist_data->fields[val_idx] = create_hist_field(hist_data, field, flags);
+	hist_data->fields[val_idx] = create_hist_field(hist_data, field, flags, var_name);
 	if (!hist_data->fields[val_idx]) {
 		ret = -ENOMEM;
 		goto out;
 	}
 
 	++hist_data->n_vals;
+	++hist_data->n_fields;
 
-	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX))
+	if (hist_data->fields[val_idx]->flags & HIST_FIELD_FL_VAR_ONLY)
+		hist_data->n_var_only++;
+
+	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
 		ret = -EINVAL;
  out:
 	return ret;
@@ -571,7 +685,7 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
 			     struct trace_event_file *file)
 {
 	char *fields_str, *field_str;
-	unsigned int i, j;
+	unsigned int i, j = 1;
 	int ret;
 
 	ret = create_hitcount_val(hist_data);
@@ -591,12 +705,15 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
 		field_str = strsep(&fields_str, ",");
 		if (!field_str)
 			break;
+
 		if (strcmp(field_str, "hitcount") == 0)
 			continue;
-		ret = create_val_field(hist_data, j++, file, field_str);
+
+		ret = create_val_field(hist_data, j++, file, field_str, false);
 		if (ret)
 			goto out;
 	}
+
 	if (fields_str && (strcmp(fields_str, "hitcount") != 0))
 		ret = -EINVAL;
  out:
@@ -610,18 +727,32 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 			    char *field_str)
 {
 	struct ftrace_event_field *field = NULL;
+	struct hist_field *hist_field = NULL;
 	unsigned long flags = 0;
 	unsigned int key_size;
+	char *var_name;
 	int ret = 0;
 
-	if (WARN_ON(key_idx >= TRACING_MAP_FIELDS_MAX))
+	if (WARN_ON(key_idx >= HIST_FIELDS_MAX))
 		return -EINVAL;
 
 	flags |= HIST_FIELD_FL_KEY;
 
+	var_name = strsep(&field_str, "=");
+	if (field_str) {
+		if (find_var(file, var_name) &&
+		    !hist_data->remove)
+			return -EINVAL;
+		flags |= HIST_FIELD_FL_VAR;
+	} else {
+		field_str = var_name;
+		var_name = NULL;
+	}
+
 	if (strcmp(field_str, "stacktrace") == 0) {
 		flags |= HIST_FIELD_FL_STACKTRACE;
 		key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
+		hist_field = create_hist_field(hist_data, NULL, flags, var_name);
 	} else {
 		char *field_name = strsep(&field_str, ".");
 
@@ -667,7 +798,7 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 		}
 	}
 
-	hist_data->fields[key_idx] = create_hist_field(hist_data, field, flags);
+	hist_data->fields[key_idx] = create_hist_field(hist_data, field, flags, var_name);
 	if (!hist_data->fields[key_idx]) {
 		ret = -ENOMEM;
 		goto out;
@@ -683,6 +814,7 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 	}
 
 	hist_data->n_keys++;
+	hist_data->n_fields++;
 
 	if (WARN_ON(hist_data->n_keys > TRACING_MAP_KEYS_MAX))
 		return -EINVAL;
@@ -726,6 +858,29 @@ static int create_key_fields(struct hist_trigger_data *hist_data,
 	return ret;
 }
 
+static int create_var_fields(struct hist_trigger_data *hist_data,
+			     struct trace_event_file *file)
+{
+	unsigned int i, j, k = hist_data->n_vals;
+	char *str, *field_str;
+	int ret = 0;
+
+	for (i = 0; i < hist_data->attrs->n_assignments; i++) {
+		str = hist_data->attrs->assignment_str[i];
+
+		for (j = 0; j < TRACING_MAP_VARS_MAX; j++) {
+			field_str = strsep(&str, ",");
+			if (!field_str)
+				break;
+			ret = create_val_field(hist_data, k++, file, field_str, true);
+			if (ret)
+				goto out;
+		}
+	}
+ out:
+	return ret;
+}
+
 static int create_hist_fields(struct hist_trigger_data *hist_data,
 			      struct trace_event_file *file)
 {
@@ -735,11 +890,13 @@ static int create_hist_fields(struct hist_trigger_data *hist_data,
 	if (ret)
 		goto out;
 
-	ret = create_key_fields(hist_data, file);
+	ret = create_var_fields(hist_data, file);
 	if (ret)
 		goto out;
 
-	hist_data->n_fields = hist_data->n_vals + hist_data->n_keys;
+	ret = create_key_fields(hist_data, file);
+	if (ret)
+		goto out;
  out:
 	return ret;
 }
@@ -763,7 +920,7 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 	char *fields_str = hist_data->attrs->sort_key_str;
 	struct tracing_map_sort_key *sort_key;
 	int descending, ret = 0;
-	unsigned int i, j;
+	unsigned int i, j, k;
 
 	hist_data->n_sort_keys = 1; /* we always have at least one, hitcount */
 
@@ -811,13 +968,21 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 			continue;
 		}
 
-		for (j = 1; j < hist_data->n_fields; j++) {
+		for (j = 1, k = 1; j < hist_data->n_fields; j++) {
+			unsigned idx;
+
 			hist_field = hist_data->fields[j];
+			if (hist_field->flags & HIST_FIELD_FL_VAR_ONLY)
+				continue;
+
+			idx = k++;
+
 			test_name = hist_field_name(hist_field, 0);
+
 			if (test_name == NULL)
 				continue;
 			if (strcmp(field_name, test_name) == 0) {
-				sort_key->field_idx = j;
+				sort_key->field_idx = idx;
 				descending = is_descending(field_str);
 				if (descending < 0) {
 					ret = descending;
@@ -832,6 +997,7 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 			break;
 		}
 	}
+
 	hist_data->n_sort_keys = i;
  out:
 	return ret;
@@ -872,12 +1038,19 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
 			idx = tracing_map_add_key_field(map,
 							hist_field->offset,
 							cmp_fn);
-
-		} else
+		} else if (!(hist_field->flags & HIST_FIELD_FL_VAR))
 			idx = tracing_map_add_sum_field(map);
 
 		if (idx < 0)
 			return idx;
+
+		if (hist_field->flags & HIST_FIELD_FL_VAR) {
+			idx = tracing_map_add_var(map);
+			if (idx < 0)
+				return idx;
+			hist_field->var.idx = idx;
+			hist_field->var.hist_data = hist_data;
+		}
 	}
 
 	return 0;
@@ -901,7 +1074,8 @@ static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
 static struct hist_trigger_data *
 create_hist_data(unsigned int map_bits,
 		 struct hist_trigger_attrs *attrs,
-		 struct trace_event_file *file)
+		 struct trace_event_file *file,
+		 bool remove)
 {
 	const struct tracing_map_ops *map_ops = NULL;
 	struct hist_trigger_data *hist_data;
@@ -912,6 +1086,7 @@ static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
 		return ERR_PTR(-ENOMEM);
 
 	hist_data->attrs = attrs;
+	hist_data->remove = remove;
 
 	ret = create_hist_fields(hist_data, file);
 	if (ret)
@@ -958,14 +1133,29 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
 				    struct ring_buffer_event *rbe)
 {
 	struct hist_field *hist_field;
-	unsigned int i;
+	unsigned int i, var_idx;
 	u64 hist_val;
 
 	for_each_hist_val_field(i, hist_data) {
 		hist_field = hist_data->fields[i];
-		hist_val = hist_field->fn(hist_field, rec, rbe);
+		hist_val = hist_field->fn(hist_field, rbe, rec);
+		if (hist_field->flags & HIST_FIELD_FL_VAR) {
+			var_idx = hist_field->var.idx;
+			tracing_map_set_var(elt, var_idx, hist_val);
+			if (hist_field->flags & HIST_FIELD_FL_VAR_ONLY)
+				continue;
+		}
 		tracing_map_update_sum(elt, i, hist_val);
 	}
+
+	for_each_hist_key_field(i, hist_data) {
+		hist_field = hist_data->fields[i];
+		if (hist_field->flags & HIST_FIELD_FL_VAR) {
+			hist_val = hist_field->fn(hist_field, rbe, rec);
+			var_idx = hist_field->var.idx;
+			tracing_map_set_var(elt, var_idx, hist_val);
+		}
+	}
 }
 
 static inline void add_to_key(char *compound_key, void *key,
@@ -1140,6 +1330,9 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 	for (i = 1; i < hist_data->n_vals; i++) {
 		field_name = hist_field_name(hist_data->fields[i], 0);
 
+		if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR)
+			continue;
+
 		if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
 			seq_printf(m, "  %s: %10llx", field_name,
 				   tracing_map_read_sum(elt, i));
@@ -1263,6 +1456,9 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
 {
 	const char *field_name = hist_field_name(hist_field, 0);
 
+	if (hist_field->var.name)
+		seq_printf(m, "%s=", hist_field->var.name);
+
 	if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP)
 		seq_puts(m, "$common_timestamp");
 	else if (field_name)
@@ -1281,7 +1477,8 @@ static int event_hist_trigger_print(struct seq_file *m,
 				    struct event_trigger_data *data)
 {
 	struct hist_trigger_data *hist_data = data->private_data;
-	struct hist_field *key_field;
+	bool have_var_only = false;
+	struct hist_field *field;
 	unsigned int i;
 
 	seq_puts(m, "hist:");
@@ -1292,25 +1489,47 @@ static int event_hist_trigger_print(struct seq_file *m,
 	seq_puts(m, "keys=");
 
 	for_each_hist_key_field(i, hist_data) {
-		key_field = hist_data->fields[i];
+		field = hist_data->fields[i];
 
 		if (i > hist_data->n_vals)
 			seq_puts(m, ",");
 
-		if (key_field->flags & HIST_FIELD_FL_STACKTRACE)
+		if (field->flags & HIST_FIELD_FL_STACKTRACE)
 			seq_puts(m, "stacktrace");
 		else
-			hist_field_print(m, key_field);
+			hist_field_print(m, field);
 	}
 
 	seq_puts(m, ":vals=");
 
 	for_each_hist_val_field(i, hist_data) {
+		field = hist_data->fields[i];
+		if (field->flags & HIST_FIELD_FL_VAR_ONLY) {
+			have_var_only = true;
+			continue;
+		}
+
 		if (i == HITCOUNT_IDX)
 			seq_puts(m, "hitcount");
 		else {
 			seq_puts(m, ",");
-			hist_field_print(m, hist_data->fields[i]);
+			hist_field_print(m, field);
+		}
+	}
+
+	if (have_var_only) {
+		unsigned int n = 0;
+
+		seq_puts(m, ":");
+
+		for_each_hist_val_field(i, hist_data) {
+			field = hist_data->fields[i];
+
+			if (field->flags & HIST_FIELD_FL_VAR_ONLY) {
+				if (n++)
+					seq_puts(m, ",");
+				hist_field_print(m, field);
+			}
 		}
 	}
 
@@ -1318,7 +1537,10 @@ static int event_hist_trigger_print(struct seq_file *m,
 
 	for (i = 0; i < hist_data->n_sort_keys; i++) {
 		struct tracing_map_sort_key *sort_key;
-		unsigned int idx;
+		unsigned int idx, first_key_idx;
+
+		/* skip VAR_ONLY vals */
+		first_key_idx = hist_data->n_vals - hist_data->n_var_only;
 
 		sort_key = &hist_data->sort_keys[i];
 		idx = sort_key->field_idx;
@@ -1331,8 +1553,11 @@ static int event_hist_trigger_print(struct seq_file *m,
 
 		if (idx == HITCOUNT_IDX)
 			seq_puts(m, "hitcount");
-		else
+		else {
+			if (idx >= first_key_idx)
+				idx += hist_data->n_var_only;
 			hist_field_print(m, hist_data->fields[idx]);
+		}
 
 		if (sort_key->descending)
 			seq_puts(m, ".descending");
@@ -1656,12 +1881,16 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	struct hist_trigger_attrs *attrs;
 	struct event_trigger_ops *trigger_ops;
 	struct hist_trigger_data *hist_data;
+	bool remove = false;
 	char *trigger;
 	int ret = 0;
 
 	if (!param)
 		return -EINVAL;
 
+	if (glob[0] == '!')
+		remove = true;
+
 	/* separate the trigger from the filter (k:v [if filter]) */
 	trigger = strsep(&param, " \t");
 	if (!trigger)
@@ -1674,7 +1903,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	if (attrs->map_bits)
 		hist_trigger_bits = attrs->map_bits;
 
-	hist_data = create_hist_data(hist_trigger_bits, attrs, file);
+	hist_data = create_hist_data(hist_trigger_bits, attrs, file, remove);
 	if (IS_ERR(hist_data)) {
 		destroy_hist_trigger_attrs(attrs);
 		return PTR_ERR(hist_data);
@@ -1703,7 +1932,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 			goto out_free;
 	}
 
-	if (glob[0] == '!') {
+	if (remove) {
 		cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
 		ret = 0;
 		goto out_free;
-- 
1.9.3

Re: [PATCH 16/32] tracing: Add variable support to hist triggers

[Namhyung Kim]

Hi Tom,

On Mon, Jun 26, 2017 at 05:49:17PM -0500, Tom Zanussi wrote:
> Add support for saving the value of a current event's event field by
> assigning it to a variable that can be read by a subsequent event.
> 
> The basic syntax for saving a variable is to simply prefix a unique
> variable name not corresponding to any keyword along with an '=' sign
> to any event field.
> 
> Both keys and values can be saved and retrieved in this way:
> 
>     # echo 'hist:keys=next_pid:vals=ts0=common_timestamp ...
>     # echo 'hist:key=timer_pid=common_pid ...'
> 
> If a variable isn't a key variable or prefixed with 'vals=', the
> associated event field will be saved in a variable but won't be summed
> as a value:
> 
>     # echo 'hist:keys=next_pid:ts1=common_timestamp:...
> 
> Multiple variables can be assigned at the same time:
> 
>     # echo 'hist:keys=pid:vals=ts0=common_timestamp,b=field1,field2 ...
> 
> Multiple (or single) variables can also be assigned at the same time
> using separate assignments:
> 
>     # echo 'hist:keys=pid:vals=ts0=common_timestamp:b=field1:c=field2 ...

It seems the variable definition can be hard to read if multiple
variables with expression are used.  I think it'd be better to make it
clear what's the key and the values by separating the variable
definition.  For example, the above example can be written as

  # echo 'hist:key=pid:val=ts0:ts0=$common_timestamp:b=field1:...'

I know this is not a good example since the 'ts0' is a simple
reference to the timestamp but it can be more complex..

What do you think?

Thanks,
Namhyung


> 
> Variables set as above can be used by being referenced from another
> event, as described in a subsequent patch.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>

Re: [PATCH 16/32] tracing: Add variable support to hist triggers

[Tom Zanussi]

Hi Namhyung,

On Wed, 2017-07-19 at 10:07 +0900, Namhyung Kim wrote:
> Hi Tom,
> 
> On Mon, Jun 26, 2017 at 05:49:17PM -0500, Tom Zanussi wrote:
> > Add support for saving the value of a current event's event field by
> > assigning it to a variable that can be read by a subsequent event.
> > 
> > The basic syntax for saving a variable is to simply prefix a unique
> > variable name not corresponding to any keyword along with an '=' sign
> > to any event field.
> > 
> > Both keys and values can be saved and retrieved in this way:
> > 
> >     # echo 'hist:keys=next_pid:vals=ts0=common_timestamp ...
> >     # echo 'hist:key=timer_pid=common_pid ...'
> > 
> > If a variable isn't a key variable or prefixed with 'vals=', the
> > associated event field will be saved in a variable but won't be summed
> > as a value:
> > 
> >     # echo 'hist:keys=next_pid:ts1=common_timestamp:...
> > 
> > Multiple variables can be assigned at the same time:
> > 
> >     # echo 'hist:keys=pid:vals=ts0=common_timestamp,b=field1,field2 ...
> > 
> > Multiple (or single) variables can also be assigned at the same time
> > using separate assignments:
> > 
> >     # echo 'hist:keys=pid:vals=ts0=common_timestamp:b=field1:c=field2 ...
> 
> It seems the variable definition can be hard to read if multiple
> variables with expression are used.  I think it'd be better to make it
> clear what's the key and the values by separating the variable
> definition.  For example, the above example can be written as
> 
>   # echo 'hist:key=pid:val=ts0:ts0=$common_timestamp:b=field1:...'
> 
> I know this is not a good example since the 'ts0' is a simple
> reference to the timestamp but it can be more complex..
> 
> What do you think?
> 

Yes, I think that makes sense - I was never a big fan of that syntax
anyway.  I'll make that change in the next version.

Thanks,

Tom

[PATCH 17/32] tracing: Account for variables in named trigger compatibility

[Tom Zanussi]

Named triggers must also have the same set of variables in order to be
considered compatible - update the trigger match test to account for
that.

The reason for this requirement is that named triggers with variables
are meant to allow one or more events to set the same variable.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 75cac76..fa8f607 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1545,7 +1545,7 @@ static int event_hist_trigger_print(struct seq_file *m,
 		sort_key = &hist_data->sort_keys[i];
 		idx = sort_key->field_idx;
 
-		if (WARN_ON(idx >= TRACING_MAP_FIELDS_MAX))
+		if (WARN_ON(idx >= HIST_FIELDS_MAX))
 			return -EINVAL;
 
 		if (i > 0)
@@ -1733,6 +1733,12 @@ static bool hist_trigger_match(struct event_trigger_data *data,
 			return false;
 		if (key_field->is_signed != key_field_test->is_signed)
 			return false;
+		if ((key_field->var.name && !key_field_test->var.name) ||
+		    (!key_field->var.name && key_field_test->var.name))
+			return false;
+		if ((key_field->var.name && key_field_test->var.name) &&
+		     strcmp(key_field->var.name, key_field_test->var.name) != 0)
+			return false;
 	}
 
 	for (i = 0; i < hist_data->n_sort_keys; i++) {
-- 
1.9.3

[PATCH 18/32] tracing: Add simple expression support to hist triggers

[Tom Zanussi]

Add support for simple addition, subtraction, and unary expressions
(-(expr) and expr, where expr = b-a, a+b, a+b+c) to hist triggers, in
order to support a minimal set of useful inter-event calculations.

These operations are needed for calculating latencies between events
(timestamp1-timestamp0) and for combined latencies (latencies over 3
or more events).

In the process, factor out some common code from key and value
parsing.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 457 +++++++++++++++++++++++++++++++++------
 1 file changed, 390 insertions(+), 67 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index fa8f607..92a9d89 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -32,6 +32,13 @@ typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event,
 #define HIST_FIELD_OPERANDS_MAX	2
 #define HIST_FIELDS_MAX		(TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
 
+enum field_op_id {
+	FIELD_OP_NONE,
+	FIELD_OP_PLUS,
+	FIELD_OP_MINUS,
+	FIELD_OP_UNARY_MINUS,
+};
+
 struct hist_var {
 	char				*name;
 	struct hist_trigger_data	*hist_data;
@@ -48,6 +55,8 @@ struct hist_field {
 	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
 	struct hist_trigger_data	*hist_data;
 	struct hist_var			var;
+	enum field_op_id		operator;
+	char				*name;
 };
 
 static u64 hist_field_none(struct hist_field *field, void *event,
@@ -98,6 +107,41 @@ static u64 hist_field_log2(struct hist_field *hist_field, void *event,
 	return (u64) ilog2(roundup_pow_of_two(val));
 }
 
+static u64 hist_field_plus(struct hist_field *hist_field, void *event,
+			   struct ring_buffer_event *rbe)
+{
+	struct hist_field *operand1 = hist_field->operands[0];
+	struct hist_field *operand2 = hist_field->operands[1];
+
+	u64 val1 = operand1->fn(operand1, event, rbe);
+	u64 val2 = operand2->fn(operand2, event, rbe);
+
+	return val1 + val2;
+}
+
+static u64 hist_field_minus(struct hist_field *hist_field, void *event,
+			    struct ring_buffer_event *rbe)
+{
+	struct hist_field *operand1 = hist_field->operands[0];
+	struct hist_field *operand2 = hist_field->operands[1];
+
+	u64 val1 = operand1->fn(operand1, event, rbe);
+	u64 val2 = operand2->fn(operand2, event, rbe);
+
+	return val1 - val2;
+}
+
+static u64 hist_field_unary_minus(struct hist_field *hist_field, void *event,
+				  struct ring_buffer_event *rbe)
+{
+	struct hist_field *operand = hist_field->operands[0];
+
+	s64 sval = (s64)operand->fn(operand, event, rbe);
+	u64 val = (u64)-sval;
+
+	return val;
+}
+
 #define DEFINE_HIST_FIELD_FN(type)					\
 	static u64 hist_field_##type(struct hist_field *hist_field,	\
 				     void *event,			\
@@ -148,6 +192,7 @@ enum hist_field_flags {
 	HIST_FIELD_FL_TIMESTAMP_USECS	= 2048,
 	HIST_FIELD_FL_VAR		= 4096,
 	HIST_FIELD_FL_VAR_ONLY		= 8192,
+	HIST_FIELD_FL_EXPR		= 16384,
 };
 
 struct hist_trigger_attrs {
@@ -210,6 +255,8 @@ static const char *hist_field_name(struct hist_field *field,
 		field_name = hist_field_name(field->operands[0], ++level);
 	else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
 		field_name = "$common_timestamp";
+	else if (field->flags & HIST_FIELD_FL_EXPR)
+		field_name = field->name;
 
 	if (field_name == NULL)
 		field_name = "";
@@ -444,6 +491,73 @@ static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
 	.elt_init	= hist_trigger_elt_comm_init,
 };
 
+static char *expr_str(struct hist_field *field, unsigned int level)
+{
+	char *expr = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
+
+	if (!expr || level > 1)
+		return NULL;
+
+	if (field->operator == FIELD_OP_UNARY_MINUS) {
+		char *subexpr;
+
+		strcat(expr, "-(");
+		subexpr = expr_str(field->operands[0], ++level);
+		if (!subexpr) {
+			kfree(expr);
+			return NULL;
+		}
+		strcat(expr, subexpr);
+		strcat(expr, ")");
+
+		return expr;
+	}
+
+	strcat(expr, hist_field_name(field->operands[0], 0));
+
+	switch (field->operator) {
+	case FIELD_OP_MINUS:
+		strcat(expr, "-");
+		break;
+	case FIELD_OP_PLUS:
+		strcat(expr, "+");
+		break;
+	default:
+		kfree(expr);
+		return NULL;
+	}
+
+	strcat(expr, hist_field_name(field->operands[1], 0));
+
+	return expr;
+}
+
+static int contains_operator(char *str)
+{
+	enum field_op_id field_op = FIELD_OP_NONE;
+	char *op;
+
+	op = strpbrk(str, "+-");
+	if (!op)
+		return FIELD_OP_NONE;
+
+	switch (*op) {
+	case '-':
+		if (*str == '-')
+			field_op = FIELD_OP_UNARY_MINUS;
+		else
+			field_op = FIELD_OP_MINUS;
+		break;
+	case '+':
+		field_op = FIELD_OP_PLUS;
+		break;
+	default:
+		break;
+	}
+
+	return field_op;
+}
+
 static void destroy_hist_field(struct hist_field *hist_field,
 			       unsigned int level)
 {
@@ -459,6 +573,7 @@ static void destroy_hist_field(struct hist_field *hist_field,
 		destroy_hist_field(hist_field->operands[i], ++level);
 
 	kfree(hist_field->var.name);
+	kfree(hist_field->name);
 
 	kfree(hist_field);
 }
@@ -479,6 +594,9 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 
 	hist_field->hist_data = hist_data;
 
+	if (flags & HIST_FIELD_FL_EXPR)
+		goto out; /* caller will populate */
+
 	if (flags & HIST_FIELD_FL_HITCOUNT) {
 		hist_field->fn = hist_field_counter;
 		goto out;
@@ -551,6 +669,247 @@ static void destroy_hist_fields(struct hist_trigger_data *hist_data)
 	}
 }
 
+static struct ftrace_event_field *
+parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
+	    char *field_str, unsigned long *flags)
+{
+	struct ftrace_event_field *field = NULL;
+	char *field_name;
+
+	field_name = strsep(&field_str, ".");
+	if (field_str) {
+		if (strcmp(field_str, "hex") == 0)
+			*flags |= HIST_FIELD_FL_HEX;
+		else if (strcmp(field_str, "sym") == 0)
+			*flags |= HIST_FIELD_FL_SYM;
+		else if (strcmp(field_str, "sym-offset") == 0)
+			*flags |= HIST_FIELD_FL_SYM_OFFSET;
+		else if ((strcmp(field_str, "execname") == 0) &&
+			 (strcmp(field_name, "common_pid") == 0))
+			*flags |= HIST_FIELD_FL_EXECNAME;
+		else if (strcmp(field_str, "syscall") == 0)
+			*flags |= HIST_FIELD_FL_SYSCALL;
+		else if (strcmp(field_str, "log2") == 0)
+			*flags |= HIST_FIELD_FL_LOG2;
+		else if (strcmp(field_str, "usecs") == 0)
+			*flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
+		else
+			return ERR_PTR(-EINVAL);
+	}
+
+	if (strcmp(field_name, "$common_timestamp") == 0) {
+		*flags |= HIST_FIELD_FL_TIMESTAMP;
+		hist_data->enable_timestamps = true;
+		if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
+			hist_data->attrs->ts_in_usecs = true;
+	} else {
+		field = trace_find_event_field(file->event_call, field_name);
+		if (!field)
+			return ERR_PTR(-EINVAL);
+	}
+
+	return field;
+}
+
+struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
+			      struct trace_event_file *file, char *str,
+			      unsigned long *flags, char *var_name)
+{
+	struct ftrace_event_field *field = NULL;
+	struct hist_field *hist_field = NULL;
+	int ret = 0;
+
+	field = parse_field(hist_data, file, str, flags);
+	if (IS_ERR(field)) {
+		ret = PTR_ERR(field);
+		goto out;
+	}
+
+	hist_field = create_hist_field(hist_data, field, *flags, var_name);
+	if (!hist_field) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	return hist_field;
+ out:
+	return ERR_PTR(ret);
+}
+
+static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
+				     struct trace_event_file *file,
+				     char *str, unsigned long flags,
+				     char *var_name, unsigned int level);
+
+static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
+				      struct trace_event_file *file,
+				      char *str, unsigned long flags,
+				      char *var_name, unsigned int level)
+{
+	struct hist_field *operand1, *expr = NULL;
+	unsigned long operand_flags;
+	char *operand1_str;
+	int ret = 0;
+	char *s;
+
+	// we support only -(xxx) i.e. explicit parens required
+
+	if (level > 2) {
+		ret = -EINVAL;
+		goto free;
+	}
+
+	str++; // skip leading '-'
+
+	s = strchr(str, '(');
+	if (s)
+		str++;
+	else {
+		ret = -EINVAL;
+		goto free;
+	}
+
+	s = strchr(str, ')');
+	if (s)
+		*s = '\0';
+	else {
+		ret = -EINVAL; // no closing ')'
+		goto free;
+	}
+
+	operand1_str = strsep(&str, "(");
+	if (!operand1_str)
+		goto free;
+
+	flags |= HIST_FIELD_FL_EXPR;
+	expr = create_hist_field(hist_data, NULL, flags, var_name);
+	if (!expr) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	operand_flags = 0;
+	operand1 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
+	if (IS_ERR(operand1)) {
+		ret = PTR_ERR(operand1);
+		goto free;
+	}
+
+	if (operand1 == NULL) {
+		operand_flags = 0;
+		operand1 = parse_atom(hist_data, file, operand1_str,
+				      &operand_flags, NULL);
+		if (IS_ERR(operand1)) {
+			ret = PTR_ERR(operand1);
+			goto free;
+		}
+	}
+
+	expr->fn = hist_field_unary_minus;
+	expr->operands[0] = operand1;
+	expr->operator = FIELD_OP_UNARY_MINUS;
+	expr->name = expr_str(expr, 0);
+
+	return expr;
+ free:
+	return ERR_PTR(ret);
+}
+
+static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
+				     struct trace_event_file *file,
+				     char *str, unsigned long flags,
+				     char *var_name, unsigned int level)
+{
+	struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
+	unsigned long operand_flags;
+	int field_op, ret = -EINVAL;
+	char *sep, *operand1_str;
+
+	if (level > 2)
+		return NULL;
+
+	field_op = contains_operator(str);
+	if (field_op == FIELD_OP_NONE)
+		return NULL;
+
+	if (field_op == FIELD_OP_UNARY_MINUS)
+		return parse_unary(hist_data, file, str, flags, var_name, ++level);
+
+	switch (field_op) {
+	case FIELD_OP_MINUS:
+		sep = "-";
+		break;
+	case FIELD_OP_PLUS:
+		sep = "+";
+		break;
+	default:
+		goto free;
+	}
+
+	operand1_str = strsep(&str, sep);
+	if (!operand1_str || !str)
+		goto free;
+
+	operand_flags = 0;
+	operand1 = parse_atom(hist_data, file, operand1_str,
+			      &operand_flags, NULL);
+	if (IS_ERR(operand1)) {
+		ret = PTR_ERR(operand1);
+		operand1 = NULL;
+		goto free;
+	}
+
+	// rest of string could be another expression e.g. b+c in a+b+c
+	operand_flags = 0;
+	operand2 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
+	if (IS_ERR(operand2)) {
+		ret = PTR_ERR(operand2);
+		operand2 = NULL;
+		goto free;
+	}
+	if (!operand2) {
+		operand_flags = 0;
+		operand2 = parse_atom(hist_data, file, str,
+				      &operand_flags, NULL);
+		if (IS_ERR(operand2)) {
+			ret = PTR_ERR(operand2);
+			operand2 = NULL;
+			goto free;
+		}
+	}
+
+	flags |= HIST_FIELD_FL_EXPR;
+	expr = create_hist_field(hist_data, NULL, flags, var_name);
+	if (!expr) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	expr->operands[0] = operand1;
+	expr->operands[1] = operand2;
+	expr->operator = field_op;
+	expr->name = expr_str(expr, 0);
+
+	switch (field_op) {
+	case FIELD_OP_MINUS:
+		expr->fn = hist_field_minus;
+		break;
+	case FIELD_OP_PLUS:
+		expr->fn = hist_field_plus;
+		break;
+	default:
+		goto free;
+	}
+
+	return expr;
+ free:
+	destroy_hist_field(operand1, 0);
+	destroy_hist_field(operand2, 0);
+	destroy_hist_field(expr, 0);
+
+	return ERR_PTR(ret);
+}
+
 static int create_hitcount_val(struct hist_trigger_data *hist_data)
 {
 	hist_data->fields[HITCOUNT_IDX] =
@@ -609,9 +968,9 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 			    struct trace_event_file *file,
 			    char *field_str, bool var_only)
 {
-	struct ftrace_event_field *field = NULL;
-	char *field_name, *var_name;
+	struct hist_field *hist_field;
 	unsigned long flags = 0;
+	char *var_name;
 	int ret = 0;
 
 	if (WARN_ON(!var_only && val_idx >= TRACING_MAP_VALS_MAX))
@@ -642,37 +1001,27 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 		goto out;
 	}
 
-	field_name = strsep(&field_str, ".");
-	if (field_str) {
-		if (strcmp(field_str, "hex") == 0)
-			flags |= HIST_FIELD_FL_HEX;
-		else {
-			ret = -EINVAL;
-			goto out;
-		}
+	hist_field = parse_expr(hist_data, file, field_str, flags, var_name, 0);
+	if (IS_ERR(hist_field)) {
+		ret = PTR_ERR(hist_field);
+		goto out;
 	}
 
-	if (strcmp(field_name, "$common_timestamp") == 0) {
-		flags |= HIST_FIELD_FL_TIMESTAMP;
-		hist_data->enable_timestamps = true;
-	} else {
-		field = trace_find_event_field(file->event_call, field_name);
-		if (!field) {
-			ret = -EINVAL;
+	if (!hist_field) {
+		hist_field = parse_atom(hist_data, file, field_str,
+					&flags, var_name);
+		if (IS_ERR(hist_field)) {
+			ret = PTR_ERR(hist_field);
 			goto out;
 		}
 	}
 
-	hist_data->fields[val_idx] = create_hist_field(hist_data, field, flags, var_name);
-	if (!hist_data->fields[val_idx]) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	hist_data->fields[val_idx] = hist_field;
 
 	++hist_data->n_vals;
 	++hist_data->n_fields;
 
-	if (hist_data->fields[val_idx]->flags & HIST_FIELD_FL_VAR_ONLY)
+	if (hist_field->flags & HIST_FIELD_FL_VAR_ONLY)
 		hist_data->n_var_only++;
 
 	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
@@ -726,8 +1075,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 			    struct trace_event_file *file,
 			    char *field_str)
 {
-	struct ftrace_event_field *field = NULL;
 	struct hist_field *hist_field = NULL;
+
 	unsigned long flags = 0;
 	unsigned int key_size;
 	char *var_name;
@@ -754,60 +1103,33 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 		key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
 		hist_field = create_hist_field(hist_data, NULL, flags, var_name);
 	} else {
-		char *field_name = strsep(&field_str, ".");
-
-		if (field_str) {
-			if (strcmp(field_str, "hex") == 0)
-				flags |= HIST_FIELD_FL_HEX;
-			else if (strcmp(field_str, "sym") == 0)
-				flags |= HIST_FIELD_FL_SYM;
-			else if (strcmp(field_str, "sym-offset") == 0)
-				flags |= HIST_FIELD_FL_SYM_OFFSET;
-			else if ((strcmp(field_str, "execname") == 0) &&
-				 (strcmp(field_name, "common_pid") == 0))
-				flags |= HIST_FIELD_FL_EXECNAME;
-			else if (strcmp(field_str, "syscall") == 0)
-				flags |= HIST_FIELD_FL_SYSCALL;
-			else if (strcmp(field_str, "log2") == 0)
-				flags |= HIST_FIELD_FL_LOG2;
-			else if (strcmp(field_str, "usecs") == 0)
-				flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
-			else {
-				ret = -EINVAL;
-				goto out;
-			}
+		hist_field = parse_expr(hist_data, file, field_str, flags,
+					var_name, 0);
+		if (IS_ERR(hist_field)) {
+			ret = PTR_ERR(hist_field);
+			goto out;
 		}
 
-		if (strcmp(field_name, "$common_timestamp") == 0) {
-			flags |= HIST_FIELD_FL_TIMESTAMP;
-			hist_data->enable_timestamps = true;
-			if (flags & HIST_FIELD_FL_TIMESTAMP_USECS)
-				hist_data->attrs->ts_in_usecs = true;
-			key_size = sizeof(u64);
-		} else {
-			field = trace_find_event_field(file->event_call, field_name);
-			if (!field) {
-				ret = -EINVAL;
+		if (!hist_field) {
+			hist_field = parse_atom(hist_data, file, field_str,
+						&flags, var_name);
+			if (IS_ERR(hist_field)) {
+				ret = PTR_ERR(hist_field);
 				goto out;
 			}
-
-			if (is_string_field(field))
-				key_size = MAX_FILTER_STR_VAL;
-			else
-				key_size = field->size;
 		}
-	}
 
-	hist_data->fields[key_idx] = create_hist_field(hist_data, field, flags, var_name);
-	if (!hist_data->fields[key_idx]) {
-		ret = -ENOMEM;
-		goto out;
+		key_size = hist_field->size;
 	}
 
+	hist_data->fields[key_idx] = hist_field;
+
 	key_size = ALIGN(key_size, sizeof(u64));
 	hist_data->fields[key_idx]->size = key_size;
 	hist_data->fields[key_idx]->offset = key_offset;
+
 	hist_data->key_size += key_size;
+
 	if (hist_data->key_size > HIST_KEY_SIZE_MAX) {
 		ret = -EINVAL;
 		goto out;
@@ -1330,7 +1652,8 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 	for (i = 1; i < hist_data->n_vals; i++) {
 		field_name = hist_field_name(hist_data->fields[i], 0);
 
-		if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR)
+		if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR ||
+		    hist_data->fields[i]->flags & HIST_FIELD_FL_EXPR)
 			continue;
 
 		if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
-- 
1.9.3

Re: [PATCH 18/32] tracing: Add simple expression support to hist triggers

[Namhyung Kim]

Hi Tom,

On Mon, Jun 26, 2017 at 05:49:19PM -0500, Tom Zanussi wrote:
> Add support for simple addition, subtraction, and unary expressions
> (-(expr) and expr, where expr = b-a, a+b, a+b+c) to hist triggers, in
> order to support a minimal set of useful inter-event calculations.
> 
> These operations are needed for calculating latencies between events
> (timestamp1-timestamp0) and for combined latencies (latencies over 3
> or more events).
> 
> In the process, factor out some common code from key and value
> parsing.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---

[SNIP]
> +static char *expr_str(struct hist_field *field, unsigned int level)
> +{
> +	char *expr = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> +
> +	if (!expr || level > 1)
> +		return NULL;

Looks like a memory leak.


[SNIP]
> +static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
> +				     struct trace_event_file *file,
> +				     char *str, unsigned long flags,
> +				     char *var_name, unsigned int level)
> +{
> +	struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
> +	unsigned long operand_flags;
> +	int field_op, ret = -EINVAL;
> +	char *sep, *operand1_str;
> +
> +	if (level > 2)
> +		return NULL;
> +
> +	field_op = contains_operator(str);
> +	if (field_op == FIELD_OP_NONE)
> +		return NULL;

Why not calling parse_atom() here?  It'd make the code simpler IMHO.

Thanks,
Namhyung


> +
> +	if (field_op == FIELD_OP_UNARY_MINUS)
> +		return parse_unary(hist_data, file, str, flags, var_name, ++level);
> +
> +	switch (field_op) {
> +	case FIELD_OP_MINUS:
> +		sep = "-";
> +		break;
> +	case FIELD_OP_PLUS:
> +		sep = "+";
> +		break;
> +	default:
> +		goto free;
> +	}
> +
> +	operand1_str = strsep(&str, sep);
> +	if (!operand1_str || !str)
> +		goto free;
> +
> +	operand_flags = 0;
> +	operand1 = parse_atom(hist_data, file, operand1_str,
> +			      &operand_flags, NULL);
> +	if (IS_ERR(operand1)) {
> +		ret = PTR_ERR(operand1);
> +		operand1 = NULL;
> +		goto free;
> +	}
> +
> +	// rest of string could be another expression e.g. b+c in a+b+c
> +	operand_flags = 0;
> +	operand2 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
> +	if (IS_ERR(operand2)) {
> +		ret = PTR_ERR(operand2);
> +		operand2 = NULL;
> +		goto free;
> +	}
> +	if (!operand2) {
> +		operand_flags = 0;
> +		operand2 = parse_atom(hist_data, file, str,
> +				      &operand_flags, NULL);
> +		if (IS_ERR(operand2)) {
> +			ret = PTR_ERR(operand2);
> +			operand2 = NULL;
> +			goto free;
> +		}
> +	}
> +
> +	flags |= HIST_FIELD_FL_EXPR;
> +	expr = create_hist_field(hist_data, NULL, flags, var_name);
> +	if (!expr) {
> +		ret = -ENOMEM;
> +		goto free;
> +	}
> +
> +	expr->operands[0] = operand1;
> +	expr->operands[1] = operand2;
> +	expr->operator = field_op;
> +	expr->name = expr_str(expr, 0);
> +
> +	switch (field_op) {
> +	case FIELD_OP_MINUS:
> +		expr->fn = hist_field_minus;
> +		break;
> +	case FIELD_OP_PLUS:
> +		expr->fn = hist_field_plus;
> +		break;
> +	default:
> +		goto free;
> +	}
> +
> +	return expr;
> + free:
> +	destroy_hist_field(operand1, 0);
> +	destroy_hist_field(operand2, 0);
> +	destroy_hist_field(expr, 0);
> +
> +	return ERR_PTR(ret);
> +}

Re: [PATCH 18/32] tracing: Add simple expression support to hist triggers

[Tom Zanussi]

Hi Namhyung,

On Fri, 2017-07-21 at 11:02 +0900, Namhyung Kim wrote:
> Hi Tom,
> 
> On Mon, Jun 26, 2017 at 05:49:19PM -0500, Tom Zanussi wrote:
> > Add support for simple addition, subtraction, and unary expressions
> > (-(expr) and expr, where expr = b-a, a+b, a+b+c) to hist triggers, in
> > order to support a minimal set of useful inter-event calculations.
> > 
> > These operations are needed for calculating latencies between events
> > (timestamp1-timestamp0) and for combined latencies (latencies over 3
> > or more events).
> > 
> > In the process, factor out some common code from key and value
> > parsing.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> 
> [SNIP]
> > +static char *expr_str(struct hist_field *field, unsigned int level)
> > +{
> > +	char *expr = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> > +
> > +	if (!expr || level > 1)
> > +		return NULL;
> 
> Looks like a memory leak.
> 
> 

Indeed, and so obvious I can't believe I missed it.  Thanks for pointing
it out.

> [SNIP]
> > +static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
> > +				     struct trace_event_file *file,
> > +				     char *str, unsigned long flags,
> > +				     char *var_name, unsigned int level)
> > +{
> > +	struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
> > +	unsigned long operand_flags;
> > +	int field_op, ret = -EINVAL;
> > +	char *sep, *operand1_str;
> > +
> > +	if (level > 2)
> > +		return NULL;
> > +
> > +	field_op = contains_operator(str);
> > +	if (field_op == FIELD_OP_NONE)
> > +		return NULL;
> 
> Why not calling parse_atom() here?  It'd make the code simpler IMHO.
> 

Yeah, I think that would be much nicer, will do.

Thanks,

Tom

[PATCH 19/32] tracing: Add variable reference handling to hist triggers

[Tom Zanussi]

Add the necessary infrastructure to allow the variables defined on one
event to be referenced in another.  This allows variables set by a
previous event to be referenced and used in expressions combining the
variable values saved by that previous event and the event fields of
the current event.  For example, here's how a latency can be
calculated and saved into yet another variable named 'wakeup_lat':

    # echo 'hist:keys=pid,prio:ts0=common_timestamp ...
    # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...

In the first event, the event's timetamp is saved into the variable
ts0.  In the next line, ts0 is subtracted from the second event's
timestamp to produce the latency.

Further users of variable references will be described in subsequent
patches, such as for instance how the 'wakeup_lat' variable above can
be displayed in a latency histogram.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace.h                |   2 +
 kernel/trace/trace_events_hist.c    | 719 ++++++++++++++++++++++++++++++------
 kernel/trace/trace_events_trigger.c |   6 +
 3 files changed, 604 insertions(+), 123 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 65f90b4..7dc13fa 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1528,6 +1528,8 @@ extern int save_named_trigger(const char *name,
 extern void unpause_named_trigger(struct event_trigger_data *data);
 extern void set_named_trigger_data(struct event_trigger_data *data,
 				   struct event_trigger_data *named_data);
+extern struct event_trigger_data *
+get_named_trigger_data(struct event_trigger_data *data);
 extern int register_event_command(struct event_command *cmd);
 extern int unregister_event_command(struct event_command *cmd);
 extern int register_trigger_hist_enable_disable_cmds(void);
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 92a9d89..d83d4ca 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -26,8 +26,10 @@
 
 struct hist_field;
 
-typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event,
-				struct ring_buffer_event *rbe);
+typedef u64 (*hist_field_fn_t) (struct hist_field *field,
+				struct tracing_map_elt *elt,
+				struct ring_buffer_event *rbe,
+				void *event);
 
 #define HIST_FIELD_OPERANDS_MAX	2
 #define HIST_FIELDS_MAX		(TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
@@ -57,30 +59,41 @@ struct hist_field {
 	struct hist_var			var;
 	enum field_op_id		operator;
 	char				*name;
+	unsigned int			var_idx;
+	unsigned int			var_ref_idx;
+	bool                            read_once;
 };
 
-static u64 hist_field_none(struct hist_field *field, void *event,
-			   struct ring_buffer_event *rbe)
+static u64 hist_field_none(struct hist_field *field,
+			   struct tracing_map_elt *elt,
+			   struct ring_buffer_event *rbe,
+			   void *event)
 {
 	return 0;
 }
 
-static u64 hist_field_counter(struct hist_field *field, void *event,
-			      struct ring_buffer_event *rbe)
+static u64 hist_field_counter(struct hist_field *field,
+			      struct tracing_map_elt *elt,
+			      struct ring_buffer_event *rbe,
+			      void *event)
 {
 	return 1;
 }
 
-static u64 hist_field_string(struct hist_field *hist_field, void *event,
-			     struct ring_buffer_event *rbe)
+static u64 hist_field_string(struct hist_field *hist_field,
+			     struct tracing_map_elt *elt,
+			     struct ring_buffer_event *rbe,
+			     void *event)
 {
 	char *addr = (char *)(event + hist_field->field->offset);
 
 	return (u64)(unsigned long)addr;
 }
 
-static u64 hist_field_dynstring(struct hist_field *hist_field, void *event,
-				struct ring_buffer_event *rbe)
+static u64 hist_field_dynstring(struct hist_field *hist_field,
+				struct tracing_map_elt *elt,
+				struct ring_buffer_event *rbe,
+				void *event)
 {
 	u32 str_item = *(u32 *)(event + hist_field->field->offset);
 	int str_loc = str_item & 0xffff;
@@ -89,54 +102,64 @@ static u64 hist_field_dynstring(struct hist_field *hist_field, void *event,
 	return (u64)(unsigned long)addr;
 }
 
-static u64 hist_field_pstring(struct hist_field *hist_field, void *event,
-			      struct ring_buffer_event *rbe)
+static u64 hist_field_pstring(struct hist_field *hist_field,
+			      struct tracing_map_elt *elt,
+			      struct ring_buffer_event *rbe,
+			      void *event)
 {
 	char **addr = (char **)(event + hist_field->field->offset);
 
 	return (u64)(unsigned long)*addr;
 }
 
-static u64 hist_field_log2(struct hist_field *hist_field, void *event,
-			   struct ring_buffer_event *rbe)
+static u64 hist_field_log2(struct hist_field *hist_field,
+			   struct tracing_map_elt *elt,
+			   struct ring_buffer_event *rbe,
+			   void *event)
 {
 	struct hist_field *operand = hist_field->operands[0];
 
-	u64 val = operand->fn(operand, event, rbe);
+	u64 val = operand->fn(operand, elt, rbe, event);
 
 	return (u64) ilog2(roundup_pow_of_two(val));
 }
 
-static u64 hist_field_plus(struct hist_field *hist_field, void *event,
-			   struct ring_buffer_event *rbe)
+static u64 hist_field_plus(struct hist_field *hist_field,
+			   struct tracing_map_elt *elt,
+			   struct ring_buffer_event *rbe,
+			   void *event)
 {
 	struct hist_field *operand1 = hist_field->operands[0];
 	struct hist_field *operand2 = hist_field->operands[1];
 
-	u64 val1 = operand1->fn(operand1, event, rbe);
-	u64 val2 = operand2->fn(operand2, event, rbe);
+	u64 val1 = operand1->fn(operand1, elt, rbe, event);
+	u64 val2 = operand2->fn(operand2, elt, rbe, event);
 
 	return val1 + val2;
 }
 
-static u64 hist_field_minus(struct hist_field *hist_field, void *event,
-			    struct ring_buffer_event *rbe)
+static u64 hist_field_minus(struct hist_field *hist_field,
+			    struct tracing_map_elt *elt,
+			    struct ring_buffer_event *rbe,
+			    void *event)
 {
 	struct hist_field *operand1 = hist_field->operands[0];
 	struct hist_field *operand2 = hist_field->operands[1];
 
-	u64 val1 = operand1->fn(operand1, event, rbe);
-	u64 val2 = operand2->fn(operand2, event, rbe);
+	u64 val1 = operand1->fn(operand1, elt, rbe, event);
+	u64 val2 = operand2->fn(operand2, elt, rbe, event);
 
 	return val1 - val2;
 }
 
-static u64 hist_field_unary_minus(struct hist_field *hist_field, void *event,
-				  struct ring_buffer_event *rbe)
+static u64 hist_field_unary_minus(struct hist_field *hist_field,
+				  struct tracing_map_elt *elt,
+				  struct ring_buffer_event *rbe,
+				  void *event)
 {
 	struct hist_field *operand = hist_field->operands[0];
 
-	s64 sval = (s64)operand->fn(operand, event, rbe);
+	s64 sval = (s64)operand->fn(operand, elt, rbe, event);
 	u64 val = (u64)-sval;
 
 	return val;
@@ -144,8 +167,9 @@ static u64 hist_field_unary_minus(struct hist_field *hist_field, void *event,
 
 #define DEFINE_HIST_FIELD_FN(type)					\
 	static u64 hist_field_##type(struct hist_field *hist_field,	\
-				     void *event,			\
-				     struct ring_buffer_event *rbe)	\
+				     struct tracing_map_elt *elt,	\
+				     struct ring_buffer_event *rbe,	\
+				     void *event)			\
 {									\
 	type *addr = (type *)(event + hist_field->field->offset);	\
 									\
@@ -193,6 +217,7 @@ enum hist_field_flags {
 	HIST_FIELD_FL_VAR		= 4096,
 	HIST_FIELD_FL_VAR_ONLY		= 8192,
 	HIST_FIELD_FL_EXPR		= 16384,
+	HIST_FIELD_FL_VAR_REF		= 32768,
 };
 
 struct hist_trigger_attrs {
@@ -225,10 +250,14 @@ struct hist_trigger_data {
 	struct tracing_map		*map;
 	bool				enable_timestamps;
 	bool				remove;
+	struct hist_field               *var_refs[TRACING_MAP_VARS_MAX];
+	unsigned int			n_var_refs;
 };
 
-static u64 hist_field_timestamp(struct hist_field *hist_field, void *event,
-				struct ring_buffer_event *rbe)
+static u64 hist_field_timestamp(struct hist_field *hist_field,
+				struct tracing_map_elt *elt,
+				struct ring_buffer_event *rbe,
+				void *event)
 {
 	struct hist_trigger_data *hist_data = hist_field->hist_data;
 	struct trace_array *tr = hist_data->event_file->tr;
@@ -241,6 +270,324 @@ static u64 hist_field_timestamp(struct hist_field *hist_field, void *event,
 	return ts;
 }
 
+static LIST_HEAD(hist_var_list);
+
+struct hist_var_data {
+	struct list_head list;
+	struct hist_trigger_data *hist_data;
+};
+
+static struct hist_field *check_var_ref(struct hist_field *hist_field,
+					struct hist_trigger_data *var_data,
+					unsigned int var_idx)
+{
+	struct hist_field *found = NULL;
+
+	if (hist_field && hist_field->flags & HIST_FIELD_FL_VAR_REF) {
+		if (hist_field->var.idx == var_idx &&
+		    hist_field->var.hist_data == var_data) {
+			found = hist_field;
+		}
+	}
+
+	return found;
+}
+
+static struct hist_field *find_var_ref(struct hist_trigger_data *hist_data,
+				       struct hist_trigger_data *var_data,
+				       unsigned int var_idx)
+{
+	struct hist_field *hist_field, *found = NULL;
+	unsigned int i, j;
+
+	for_each_hist_field(i, hist_data) {
+		hist_field = hist_data->fields[i];
+		found = check_var_ref(hist_field, var_data, var_idx);
+		if (found)
+			return found;
+
+		for (j = 0; j < HIST_FIELD_OPERANDS_MAX; j++) {
+			struct hist_field *operand;
+
+			operand = hist_field->operands[j];
+			found = check_var_ref(operand, var_data, var_idx);
+			if (found)
+				return found;
+		}
+	}
+
+	return found;
+}
+
+static struct hist_field *find_any_var_ref(struct hist_trigger_data *hist_data,
+					   unsigned int var_idx)
+{
+	struct hist_field *found = NULL;
+	struct hist_var_data *var_data;
+
+	list_for_each_entry(var_data, &hist_var_list, list) {
+		found = find_var_ref(var_data->hist_data, hist_data, var_idx);
+		if (found)
+			break;
+	}
+
+	return found;
+}
+
+static bool check_var_refs(struct hist_trigger_data *hist_data)
+{
+	struct hist_field *field;
+	bool found = false;
+	int i;
+
+	for_each_hist_field(i, hist_data) {
+		field = hist_data->fields[i];
+		if (field && field->flags & HIST_FIELD_FL_VAR) {
+			if (find_any_var_ref(hist_data, field->var.idx)) {
+				found = true;
+				break;
+			}
+		}
+	}
+
+	return found;
+}
+
+static struct hist_var_data *find_hist_vars(struct hist_trigger_data *hist_data)
+{
+	struct hist_var_data *var_data, *found = NULL;
+
+	list_for_each_entry(var_data, &hist_var_list, list) {
+		if (var_data->hist_data == hist_data) {
+			found = var_data;
+			break;
+		}
+	}
+
+	return found;
+}
+
+static bool has_hist_vars(struct hist_trigger_data *hist_data)
+{
+	struct hist_field *hist_field;
+	bool found = false;
+	int i;
+
+	for_each_hist_field(i, hist_data) {
+		hist_field = hist_data->fields[i];
+		if (hist_field && hist_field->flags & HIST_FIELD_FL_VAR) {
+			found = true;
+			break;
+		}
+	}
+
+	return found;
+}
+
+static int save_hist_vars(struct hist_trigger_data *hist_data)
+{
+	struct hist_var_data *var_data;
+
+	var_data = find_hist_vars(hist_data);
+	if (var_data)
+		return 0;
+
+	var_data = kzalloc(sizeof(*var_data), GFP_KERNEL);
+	if (!var_data)
+		return -ENOMEM;
+
+	var_data->hist_data = hist_data;
+	list_add(&var_data->list, &hist_var_list);
+
+	return 0;
+}
+
+static void remove_hist_vars(struct hist_trigger_data *hist_data)
+{
+	struct hist_var_data *var_data;
+
+	var_data = find_hist_vars(hist_data);
+	if (!var_data)
+		return;
+
+	if (WARN_ON(check_var_refs(hist_data)))
+		return;
+
+	list_del(&var_data->list);
+
+	kfree(var_data);
+}
+
+static struct hist_field *find_var_field(struct hist_trigger_data *hist_data,
+					 const char *var_name)
+{
+	struct hist_field *hist_field, *found = NULL;
+	int i;
+
+	for_each_hist_field(i, hist_data) {
+		hist_field = hist_data->fields[i];
+		if (hist_field && hist_field->flags & HIST_FIELD_FL_VAR &&
+		    strcmp(hist_field->var.name, var_name) == 0) {
+			found = hist_field;
+			break;
+		}
+	}
+
+	return found;
+}
+
+static struct hist_field *find_var(struct trace_event_file *file,
+				   const char *var_name)
+{
+	struct hist_trigger_data *hist_data;
+	struct event_trigger_data *test;
+	struct hist_field *hist_field;
+
+	list_for_each_entry_rcu(test, &file->triggers, list) {
+		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			hist_data = test->private_data;
+			hist_field = find_var_field(hist_data, var_name);
+			if (hist_field)
+				return hist_field;
+		}
+	}
+
+	return NULL;
+}
+
+static struct trace_event_file *find_var_file(const char *system,
+					      const char *event_name,
+					      const char *var_name)
+{
+	struct hist_trigger_data *var_hist_data;
+	struct hist_var_data *var_data;
+	struct trace_event_call *call;
+	struct trace_event_file *file;
+	const char *name;
+
+	list_for_each_entry(var_data, &hist_var_list, list) {
+		var_hist_data = var_data->hist_data;
+		file = var_hist_data->event_file;
+		call = file->event_call;
+		name = trace_event_name(call);
+
+		if (!system || !event_name) {
+			if (find_var(file, var_name))
+				return file;
+			continue;
+		}
+
+		if (strcmp(event_name, name) != 0)
+			continue;
+		if (strcmp(system, call->class->system) != 0)
+			continue;
+
+		return file;
+	}
+
+	return NULL;
+}
+
+static struct hist_field *find_file_var(struct trace_event_file *file,
+					const char *var_name)
+{
+	struct hist_trigger_data *test_data;
+	struct event_trigger_data *test;
+	struct hist_field *hist_field;
+
+	list_for_each_entry_rcu(test, &file->triggers, list) {
+		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			test_data = test->private_data;
+			hist_field = find_var_field(test_data, var_name);
+			if (hist_field)
+				return hist_field;
+		}
+	}
+
+	return NULL;
+}
+
+static struct hist_field *find_event_var(const char *system,
+					 const char *event_name,
+					 const char *var_name)
+{
+	struct hist_field *hist_field = NULL;
+	struct trace_event_file *file;
+
+	file = find_var_file(system, event_name, var_name);
+	if (!file)
+		return NULL;
+
+	hist_field = find_file_var(file, var_name);
+
+	return hist_field;
+}
+
+struct hist_elt_data {
+	char *comm;
+	u64 *var_ref_vals;
+};
+
+static u64 hist_field_var_ref(struct hist_field *hist_field,
+			      struct tracing_map_elt *elt,
+			      struct ring_buffer_event *rbe,
+			      void *event)
+{
+	struct hist_elt_data *elt_data;
+	u64 var_val = 0;
+
+	elt_data = elt->private_data;
+	var_val = elt_data->var_ref_vals[hist_field->var_ref_idx];
+
+	return var_val;
+}
+
+static bool resolve_var_refs(struct hist_trigger_data *hist_data, void *key,
+			     u64 *var_ref_vals, bool self)
+{
+	struct hist_trigger_data *var_data;
+	struct tracing_map_elt *var_elt;
+	struct hist_field *hist_field;
+	unsigned int i, var_idx;
+	bool resolved = true;
+	u64 var_val = 0;
+
+	for (i = 0; i < hist_data->n_var_refs; i++) {
+		hist_field = hist_data->var_refs[i];
+		var_idx = hist_field->var.idx;
+		var_data = hist_field->var.hist_data;
+
+		if (var_data == NULL) {
+			resolved = false;
+			break;
+		}
+
+		if ((self && var_data != hist_data) ||
+		    (!self && var_data == hist_data))
+			continue;
+
+		var_elt = tracing_map_lookup(var_data->map, key);
+		if (!var_elt) {
+			resolved = false;
+			break;
+		}
+
+		if (!tracing_map_var_set(var_elt, var_idx)) {
+			resolved = false;
+			break;
+		}
+
+		if (self || !hist_field->read_once)
+			var_val = tracing_map_read_var(var_elt, var_idx);
+		else
+			var_val = tracing_map_read_var_once(var_elt, var_idx);
+
+		var_ref_vals[i] = var_val;
+	}
+
+	return resolved;
+}
+
 static const char *hist_field_name(struct hist_field *field,
 				   unsigned int level)
 {
@@ -255,7 +602,8 @@ static const char *hist_field_name(struct hist_field *field,
 		field_name = hist_field_name(field->operands[0], ++level);
 	else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
 		field_name = "$common_timestamp";
-	else if (field->flags & HIST_FIELD_FL_EXPR)
+	else if (field->flags & HIST_FIELD_FL_EXPR ||
+		 field->flags & HIST_FIELD_FL_VAR_REF)
 		field_name = field->name;
 
 	if (field_name == NULL)
@@ -439,26 +787,36 @@ static inline void save_comm(char *comm, struct task_struct *task)
 	memcpy(comm, task->comm, TASK_COMM_LEN);
 }
 
-static void hist_trigger_elt_comm_free(struct tracing_map_elt *elt)
+static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
 {
-	kfree((char *)elt->private_data);
+	struct hist_elt_data *private_data = elt->private_data;
+
+	kfree(private_data->comm);
+	kfree(private_data);
 }
 
-static int hist_trigger_elt_comm_alloc(struct tracing_map_elt *elt)
+static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
 {
 	struct hist_trigger_data *hist_data = elt->map->private_data;
+	unsigned int size = TASK_COMM_LEN + 1;
+	struct hist_elt_data *elt_data;
 	struct hist_field *key_field;
 	unsigned int i;
 
+	elt->private_data = elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
+	if (!elt_data)
+		return -ENOMEM;
+
 	for_each_hist_key_field(i, hist_data) {
 		key_field = hist_data->fields[i];
 
 		if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
-			unsigned int size = TASK_COMM_LEN + 1;
-
-			elt->private_data = kzalloc(size, GFP_KERNEL);
-			if (!elt->private_data)
+			elt_data->comm = kzalloc(size, GFP_KERNEL);
+			if (!elt_data->comm) {
+				kfree(elt_data);
+				elt->private_data = NULL;
 				return -ENOMEM;
+			}
 			break;
 		}
 	}
@@ -466,29 +824,31 @@ static int hist_trigger_elt_comm_alloc(struct tracing_map_elt *elt)
 	return 0;
 }
 
-static void hist_trigger_elt_comm_copy(struct tracing_map_elt *to,
+static void hist_trigger_elt_data_copy(struct tracing_map_elt *to,
 				       struct tracing_map_elt *from)
 {
-	char *comm_from = from->private_data;
-	char *comm_to = to->private_data;
+	struct hist_elt_data *from_data = from->private_data;
+	struct hist_elt_data *to_data = to->private_data;
 
-	if (comm_from)
-		memcpy(comm_to, comm_from, TASK_COMM_LEN + 1);
+	memcpy(to_data, from_data, sizeof(*to));
+
+	if (from_data->comm)
+		memcpy(to_data->comm, from_data->comm, TASK_COMM_LEN + 1);
 }
 
-static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
+static void hist_trigger_elt_data_init(struct tracing_map_elt *elt)
 {
-	char *comm = elt->private_data;
+	struct hist_elt_data *private_data = elt->private_data;
 
-	if (comm)
-		save_comm(comm, current);
+	if (private_data->comm)
+		save_comm(private_data->comm, current);
 }
 
-static const struct tracing_map_ops hist_trigger_elt_comm_ops = {
-	.elt_alloc	= hist_trigger_elt_comm_alloc,
-	.elt_copy	= hist_trigger_elt_comm_copy,
-	.elt_free	= hist_trigger_elt_comm_free,
-	.elt_init	= hist_trigger_elt_comm_init,
+static const struct tracing_map_ops hist_trigger_elt_data_ops = {
+	.elt_alloc	= hist_trigger_elt_data_alloc,
+	.elt_copy	= hist_trigger_elt_data_copy,
+	.elt_free	= hist_trigger_elt_data_free,
+	.elt_init	= hist_trigger_elt_data_init,
 };
 
 static char *expr_str(struct hist_field *field, unsigned int level)
@@ -513,6 +873,8 @@ static char *expr_str(struct hist_field *field, unsigned int level)
 		return expr;
 	}
 
+	if (field->operands[0]->flags & HIST_FIELD_FL_VAR_REF)
+		strcat(expr, "$");
 	strcat(expr, hist_field_name(field->operands[0], 0));
 
 	switch (field->operator) {
@@ -527,6 +889,8 @@ static char *expr_str(struct hist_field *field, unsigned int level)
 		return NULL;
 	}
 
+	if (field->operands[1]->flags & HIST_FIELD_FL_VAR_REF)
+		strcat(expr, "$");
 	strcat(expr, hist_field_name(field->operands[1], 0));
 
 	return expr;
@@ -597,6 +961,11 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 	if (flags & HIST_FIELD_FL_EXPR)
 		goto out; /* caller will populate */
 
+	if (flags & HIST_FIELD_FL_VAR_REF) {
+		hist_field->fn = hist_field_var_ref;
+		goto out;
+	}
+
 	if (flags & HIST_FIELD_FL_HITCOUNT) {
 		hist_field->fn = hist_field_counter;
 		goto out;
@@ -669,6 +1038,44 @@ static void destroy_hist_fields(struct hist_trigger_data *hist_data)
 	}
 }
 
+static struct hist_field *create_var_ref(struct hist_field *var_field)
+{
+	unsigned long flags = HIST_FIELD_FL_VAR_REF;
+	struct hist_field *ref_field;
+
+	ref_field = create_hist_field(var_field->hist_data, NULL, flags, NULL);
+	if (ref_field) {
+		ref_field->var.idx = var_field->var.idx;
+		ref_field->var.hist_data = var_field->hist_data;
+		ref_field->size = var_field->size;
+		ref_field->is_signed = var_field->is_signed;
+		ref_field->name = kstrdup(var_field->var.name, GFP_KERNEL);
+		if (!ref_field->name) {
+			destroy_hist_field(ref_field, 0);
+			return NULL;
+		}
+	}
+
+	return ref_field;
+}
+
+static struct hist_field *parse_var_ref(char *system, char *event_name,
+					char *var_name)
+{
+	struct hist_field *var_field = NULL, *ref_field = NULL;
+
+	if (!var_name || strlen(var_name) < 2 || var_name[0] != '$')
+		return NULL;
+
+	var_name++;
+
+	var_field = find_event_var(system, event_name, var_name);
+	if (var_field)
+		ref_field = create_var_ref(var_field);
+
+	return ref_field;
+}
+
 static struct ftrace_event_field *
 parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
 	    char *field_str, unsigned long *flags)
@@ -715,10 +1122,28 @@ struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
 			      struct trace_event_file *file, char *str,
 			      unsigned long *flags, char *var_name)
 {
+	char *s, *ref_system = NULL, *ref_event = NULL, *ref_var = str;
 	struct ftrace_event_field *field = NULL;
 	struct hist_field *hist_field = NULL;
 	int ret = 0;
 
+	s = strchr(str, '.');
+	if (s) {
+		s = strchr(++s, '.');
+		if (s) {
+			ref_system = strsep(&str, ".");
+			ref_event = strsep(&str, ".");
+			ref_var = str;
+		}
+	}
+
+	hist_field = parse_var_ref(ref_system, ref_event, ref_var);
+	if (hist_field) {
+		hist_data->var_refs[hist_data->n_var_refs] = hist_field;
+		hist_field->var_ref_idx = hist_data->n_var_refs++;
+		return hist_field;
+	}
+
 	field = parse_field(hist_data, file, str, flags);
 	if (IS_ERR(field)) {
 		ret = PTR_ERR(field);
@@ -885,6 +1310,9 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
 		goto free;
 	}
 
+	operand1->read_once = true;
+	operand2->read_once = true;
+
 	expr->operands[0] = operand1;
 	expr->operands[1] = operand2;
 	expr->operator = field_op;
@@ -926,43 +1354,6 @@ static int create_hitcount_val(struct hist_trigger_data *hist_data)
 	return 0;
 }
 
-static struct hist_field *find_var_field(struct hist_trigger_data *hist_data,
-					 const char *var_name)
-{
-	struct hist_field *hist_field, *found = NULL;
-	int i;
-
-	for_each_hist_field(i, hist_data) {
-		hist_field = hist_data->fields[i];
-		if (hist_field && hist_field->flags & HIST_FIELD_FL_VAR &&
-		    strcmp(hist_field->var.name, var_name) == 0) {
-			found = hist_field;
-			break;
-		}
-	}
-
-	return found;
-}
-
-static struct hist_field *find_var(struct trace_event_file *file,
-				   const char *var_name)
-{
-	struct hist_trigger_data *hist_data;
-	struct event_trigger_data *test;
-	struct hist_field *hist_field;
-
-	list_for_each_entry_rcu(test, &file->triggers, list) {
-		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
-			hist_data = test->private_data;
-			hist_field = find_var_field(hist_data, var_name);
-			if (hist_field)
-				return hist_field;
-		}
-	}
-
-	return NULL;
-}
-
 static int create_val_field(struct hist_trigger_data *hist_data,
 			    unsigned int val_idx,
 			    struct trace_event_file *file,
@@ -1119,6 +1510,12 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 			}
 		}
 
+		if (hist_field->flags & HIST_FIELD_FL_VAR_REF) {
+			destroy_hist_field(hist_field, 0);
+			ret = -EINVAL;
+			goto out;
+		}
+
 		key_size = hist_field->size;
 	}
 
@@ -1378,21 +1775,6 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
 	return 0;
 }
 
-static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
-{
-	struct hist_field *key_field;
-	unsigned int i;
-
-	for_each_hist_key_field(i, hist_data) {
-		key_field = hist_data->fields[i];
-
-		if (key_field->flags & HIST_FIELD_FL_EXECNAME)
-			return true;
-	}
-
-	return false;
-}
-
 static struct hist_trigger_data *
 create_hist_data(unsigned int map_bits,
 		 struct hist_trigger_attrs *attrs,
@@ -1418,8 +1800,7 @@ static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
 	if (ret)
 		goto free;
 
-	if (need_tracing_map_ops(hist_data))
-		map_ops = &hist_trigger_elt_comm_ops;
+	map_ops = &hist_trigger_elt_data_ops;
 
 	hist_data->map = tracing_map_create(map_bits, hist_data->key_size,
 					    map_ops, hist_data);
@@ -1433,10 +1814,6 @@ static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
 	if (ret)
 		goto free;
 
-	ret = tracing_map_init(hist_data->map);
-	if (ret)
-		goto free;
-
 	hist_data->event_file = file;
  out:
 	return hist_data;
@@ -1452,15 +1829,20 @@ static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
 
 static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
 				    struct tracing_map_elt *elt, void *rec,
-				    struct ring_buffer_event *rbe)
+				    struct ring_buffer_event *rbe,
+				    u64 *var_ref_vals)
 {
+	struct hist_elt_data *elt_data;
 	struct hist_field *hist_field;
 	unsigned int i, var_idx;
 	u64 hist_val;
 
+	elt_data = elt->private_data;
+	elt_data->var_ref_vals = var_ref_vals;
+
 	for_each_hist_val_field(i, hist_data) {
 		hist_field = hist_data->fields[i];
-		hist_val = hist_field->fn(hist_field, rbe, rec);
+		hist_val = hist_field->fn(hist_field, elt, rbe, rec);
 		if (hist_field->flags & HIST_FIELD_FL_VAR) {
 			var_idx = hist_field->var.idx;
 			tracing_map_set_var(elt, var_idx, hist_val);
@@ -1473,7 +1855,7 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
 	for_each_hist_key_field(i, hist_data) {
 		hist_field = hist_data->fields[i];
 		if (hist_field->flags & HIST_FIELD_FL_VAR) {
-			hist_val = hist_field->fn(hist_field, rbe, rec);
+			hist_val = hist_field->fn(hist_field, elt, rbe, rec);
 			var_idx = hist_field->var.idx;
 			tracing_map_set_var(elt, var_idx, hist_val);
 		}
@@ -1510,10 +1892,11 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec,
 	struct hist_trigger_data *hist_data = data->private_data;
 	bool use_compound_key = (hist_data->n_keys > 1);
 	unsigned long entries[HIST_STACKTRACE_DEPTH];
+	u64 var_ref_vals[TRACING_MAP_VARS_MAX];
 	char compound_key[HIST_KEY_SIZE_MAX];
+	struct tracing_map_elt *elt = NULL;
 	struct stack_trace stacktrace;
 	struct hist_field *key_field;
-	struct tracing_map_elt *elt;
 	u64 field_contents;
 	void *key = NULL;
 	unsigned int i;
@@ -1534,7 +1917,7 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec,
 
 			key = entries;
 		} else {
-			field_contents = key_field->fn(key_field, rec, rbe);
+			field_contents = key_field->fn(key_field, elt, rbe, rec);
 			if (key_field->flags & HIST_FIELD_FL_STRING) {
 				key = (void *)(unsigned long)field_contents;
 				use_compound_key = true;
@@ -1549,9 +1932,15 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec,
 	if (use_compound_key)
 		key = compound_key;
 
+	if (hist_data->n_var_refs &&
+	    !resolve_var_refs(hist_data, key, var_ref_vals, false))
+		return;
+
 	elt = tracing_map_insert(hist_data->map, key);
-	if (elt)
-		hist_trigger_elt_update(hist_data, elt, rec, rbe);
+	if (!elt)
+		return;
+
+	hist_trigger_elt_update(hist_data, elt, rec, rbe, var_ref_vals);
 }
 
 static void hist_trigger_stacktrace_print(struct seq_file *m,
@@ -1608,7 +1997,8 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 			seq_printf(m, "%s: [%llx] %-55s", field_name,
 				   uval, str);
 		} else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
-			char *comm = elt->private_data;
+			struct hist_elt_data *elt_data = elt->private_data;
+			char *comm = elt_data->comm;
 
 			uval = *(u64 *)(key + key_field->offset);
 			seq_printf(m, "%s: %-16s[%10llu]", field_name,
@@ -1653,7 +2043,8 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 		field_name = hist_field_name(hist_data->fields[i], 0);
 
 		if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR ||
-		    hist_data->fields[i]->flags & HIST_FIELD_FL_EXPR)
+		    hist_data->fields[i]->flags & HIST_FIELD_FL_EXPR ||
+		    hist_data->fields[i]->flags & HIST_FIELD_FL_VAR_REF)
 			continue;
 
 		if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
@@ -1925,7 +2316,11 @@ static void event_hist_trigger_free(struct event_trigger_ops *ops,
 	if (!data->ref) {
 		if (data->name)
 			del_named_trigger(data);
+
 		trigger_data_free(data);
+
+		remove_hist_vars(hist_data);
+
 		destroy_hist_data(hist_data);
 	}
 }
@@ -2139,23 +2534,55 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
 			goto out;
 	}
 
-	list_add_rcu(&data->list, &file->triggers);
 	ret++;
 
-	update_cond_flag(file);
-
 	if (hist_data->enable_timestamps)
 		tracing_set_time_stamp_abs(file->tr, true);
+ out:
+	return ret;
+}
+
+static int hist_trigger_enable(struct event_trigger_data *data,
+			       struct trace_event_file *file)
+{
+	int ret = 0;
+
+	list_add_rcu(&data->list, &file->triggers);
+
+	update_cond_flag(file);
 
 	if (trace_event_trigger_enable_disable(file, 1) < 0) {
 		list_del_rcu(&data->list);
 		update_cond_flag(file);
 		ret--;
 	}
- out:
+
 	return ret;
 }
 
+static bool hist_trigger_check_refs(struct event_trigger_data *data,
+				    struct trace_event_file *file)
+{
+	struct hist_trigger_data *hist_data = data->private_data;
+	struct event_trigger_data *test, *named_data = NULL;
+
+	if (hist_data->attrs->name)
+		named_data = find_named_trigger(hist_data->attrs->name);
+
+	list_for_each_entry_rcu(test, &file->triggers, list) {
+		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			if (!hist_trigger_match(data, test, named_data, false))
+				continue;
+			hist_data = test->private_data;
+			if (check_var_refs(hist_data))
+				return true;
+			break;
+		}
+	}
+
+	return false;
+}
+
 static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
 				    struct event_trigger_data *data,
 				    struct trace_event_file *file)
@@ -2186,10 +2613,32 @@ static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
 		tracing_set_time_stamp_abs(file->tr, false);
 }
 
+static bool hist_file_check_refs(struct trace_event_file *file)
+{
+	struct hist_trigger_data *hist_data;
+	struct event_trigger_data *test;
+
+	printk("func: %s\n", __func__);
+
+	list_for_each_entry_rcu(test, &file->triggers, list) {
+		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			hist_data = test->private_data;
+			if (check_var_refs(hist_data))
+				return true;
+			break;
+		}
+	}
+
+	return false;
+}
+
 static void hist_unreg_all(struct trace_event_file *file)
 {
 	struct event_trigger_data *test, *n;
 
+	if (hist_file_check_refs(file))
+	    return;
+
 	list_for_each_entry_safe(test, n, &file->triggers, list) {
 		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
 			list_del_rcu(&test->list);
@@ -2262,6 +2711,11 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	}
 
 	if (remove) {
+		if (hist_trigger_check_refs(trigger_data, file)) {
+			ret = -EBUSY;
+			goto out_free;
+		}
+
 		cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
 		ret = 0;
 		goto out_free;
@@ -2279,14 +2733,33 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 		goto out_free;
 	} else if (ret < 0)
 		goto out_free;
+
+	if (get_named_trigger_data(trigger_data))
+		goto enable;
+
+	if (has_hist_vars(hist_data))
+		save_hist_vars(hist_data);
+
+	ret = tracing_map_init(hist_data->map);
+	if (ret)
+		goto out_unreg;
+enable:
+	ret = hist_trigger_enable(trigger_data, file);
+	if (ret)
+		goto out_unreg;
+
 	/* Just return zero, not the number of registered triggers */
 	ret = 0;
  out:
 	return ret;
+ out_unreg:
+	cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
  out_free:
 	if (cmd_ops->set_filter)
 		cmd_ops->set_filter(NULL, trigger_data, NULL);
 
+	remove_hist_vars(hist_data);
+
 	kfree(trigger_data);
 
 	destroy_hist_data(hist_data);
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index d345820..4aefacf 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -919,6 +919,12 @@ void set_named_trigger_data(struct event_trigger_data *data,
 	data->named_data = named_data;
 }
 
+struct event_trigger_data *
+get_named_trigger_data(struct event_trigger_data *data)
+{
+	return data->named_data;
+}
+
 static void
 traceon_trigger(struct event_trigger_data *data, void *rec,
 		struct ring_buffer_event *event)
-- 
1.9.3

Re: [PATCH 19/32] tracing: Add variable reference handling to hist triggers

[Namhyung Kim]

On Mon, Jun 26, 2017 at 05:49:20PM -0500, Tom Zanussi wrote:
> Add the necessary infrastructure to allow the variables defined on one
> event to be referenced in another.  This allows variables set by a
> previous event to be referenced and used in expressions combining the
> variable values saved by that previous event and the event fields of
> the current event.  For example, here's how a latency can be
> calculated and saved into yet another variable named 'wakeup_lat':
> 
>     # echo 'hist:keys=pid,prio:ts0=common_timestamp ...
>     # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...
> 
> In the first event, the event's timetamp is saved into the variable
> ts0.  In the next line, ts0 is subtracted from the second event's
> timestamp to produce the latency.
> 
> Further users of variable references will be described in subsequent
> patches, such as for instance how the 'wakeup_lat' variable above can
> be displayed in a latency histogram.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---

I think it'd be better spliting this into 3 parts: add hist_elt_data,
pass tracing_map_elt to hist field func and add var ref logic.


[SNIP]
> @@ -241,6 +270,324 @@ static u64 hist_field_timestamp(struct hist_field *hist_field, void *event,
>  	return ts;
>  }
>  
> +static LIST_HEAD(hist_var_list);
> +
> +struct hist_var_data {
> +	struct list_head list;
> +	struct hist_trigger_data *hist_data;
> +};

Hmm.. I'm confused whether this list maintains reference of variable
or defintion (or both?).  It seems an entry is added only by
save_hist_vars() which is for definition.  But find_any_var_ref()
looks it up for references..  What am I missing?

Also I think it'd be better keeping this list for each instance rather
than globally.


[SNIP]
> @@ -2186,10 +2613,32 @@ static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
>  		tracing_set_time_stamp_abs(file->tr, false);
>  }
>  
> +static bool hist_file_check_refs(struct trace_event_file *file)
> +{
> +	struct hist_trigger_data *hist_data;
> +	struct event_trigger_data *test;
> +
> +	printk("func: %s\n", __func__);

Please remove this.

Thanks,
Namhyung


> +
> +	list_for_each_entry_rcu(test, &file->triggers, list) {
> +		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
> +			hist_data = test->private_data;
> +			if (check_var_refs(hist_data))
> +				return true;
> +			break;
> +		}
> +	}
> +
> +	return false;
> +}

Re: [PATCH 19/32] tracing: Add variable reference handling to hist triggers

[Tom Zanussi]

Hi Namhyung,

On Fri, 2017-07-21 at 12:31 +0900, Namhyung Kim wrote:
> On Mon, Jun 26, 2017 at 05:49:20PM -0500, Tom Zanussi wrote:
> > Add the necessary infrastructure to allow the variables defined on one
> > event to be referenced in another.  This allows variables set by a
> > previous event to be referenced and used in expressions combining the
> > variable values saved by that previous event and the event fields of
> > the current event.  For example, here's how a latency can be
> > calculated and saved into yet another variable named 'wakeup_lat':
> > 
> >     # echo 'hist:keys=pid,prio:ts0=common_timestamp ...
> >     # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...
> > 
> > In the first event, the event's timetamp is saved into the variable
> > ts0.  In the next line, ts0 is subtracted from the second event's
> > timestamp to produce the latency.
> > 
> > Further users of variable references will be described in subsequent
> > patches, such as for instance how the 'wakeup_lat' variable above can
> > be displayed in a latency histogram.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> 
> I think it'd be better spliting this into 3 parts: add hist_elt_data,
> pass tracing_map_elt to hist field func and add var ref logic.
> 

Yeah, that makes sense, will do.

> 
> [SNIP]
> > @@ -241,6 +270,324 @@ static u64 hist_field_timestamp(struct hist_field *hist_field, void *event,
> >  	return ts;
> >  }
> >  
> > +static LIST_HEAD(hist_var_list);
> > +
> > +struct hist_var_data {
> > +	struct list_head list;
> > +	struct hist_trigger_data *hist_data;
> > +};
> 
> Hmm.. I'm confused whether this list maintains reference of variable
> or defintion (or both?).  It seems an entry is added only by
> save_hist_vars() which is for definition.  But find_any_var_ref()
> looks it up for references..  What am I missing?
> 

Nothing - it should be both, but as you point out it's missing the
reference-only triggers.  Most of the time when you create a hist
trigger that references a variable, you also create a variable to
receive the result and use it later, which is why you don't normally
see a problem.  Thanks for noticing this..

Tom

[PATCH 20/32] tracing: Add support for dynamic tracepoints

[Tom Zanussi]

The tracepoint infrastructure assumes statically-defined tracepoints
and uses static_keys for tracepoint enablement.  In order to define
tracepoints on the fly, we need to have a dynamic counterpart.

Add a dynamic_tracepoint_probe_register() and a dynamic param onto
tracepoint_probe_unregister() for this purpose.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 include/linux/tracepoint.h  | 11 +++++++----
 kernel/trace/trace_events.c |  4 ++--
 kernel/tracepoint.c         | 42 ++++++++++++++++++++++++++++++------------
 3 files changed, 39 insertions(+), 18 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index a26ffbe..dfb07dd 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -37,9 +37,12 @@ struct trace_eval_map {
 tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
 extern int
 tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data,
-			       int prio);
+			       int prio, bool dynamic);
+extern int dynamic_tracepoint_probe_register(struct tracepoint *tp,
+					     void *probe, void *data);
 extern int
-tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data);
+tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data,
+			    bool dynamic);
 extern void
 for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
 		void *priv);
@@ -210,13 +213,13 @@ static inline void tracepoint_synchronize_unregister(void)
 				   int prio)				\
 	{								\
 		return tracepoint_probe_register_prio(&__tracepoint_##name, \
-					      (void *)probe, data, prio); \
+				      (void *)probe, data, prio, false); \
 	}								\
 	static inline int						\
 	unregister_trace_##name(void (*probe)(data_proto), void *data)	\
 	{								\
 		return tracepoint_probe_unregister(&__tracepoint_##name,\
-						(void *)probe, data);	\
+					   (void *)probe, data, false); \
 	}								\
 	static inline void						\
 	check_trace_callback_type_##name(void (*cb)(data_proto))	\
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 83dfd0d..1324393 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -297,7 +297,7 @@ int trace_event_reg(struct trace_event_call *call,
 	case TRACE_REG_UNREGISTER:
 		tracepoint_probe_unregister(call->tp,
 					    call->class->probe,
-					    file);
+					    file, false);
 		return 0;
 
 #ifdef CONFIG_PERF_EVENTS
@@ -308,7 +308,7 @@ int trace_event_reg(struct trace_event_call *call,
 	case TRACE_REG_PERF_UNREGISTER:
 		tracepoint_probe_unregister(call->tp,
 					    call->class->perf_probe,
-					    call);
+					    call, false);
 		return 0;
 	case TRACE_REG_PERF_OPEN:
 	case TRACE_REG_PERF_CLOSE:
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 685c50a..4068809 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -192,12 +192,15 @@ static void *func_remove(struct tracepoint_func **funcs,
  * Add the probe function to a tracepoint.
  */
 static int tracepoint_add_func(struct tracepoint *tp,
-			       struct tracepoint_func *func, int prio)
+			       struct tracepoint_func *func, int prio,
+			       bool dynamic)
 {
 	struct tracepoint_func *old, *tp_funcs;
 	int ret;
 
-	if (tp->regfunc && !static_key_enabled(&tp->key)) {
+	if (tp->regfunc &&
+	    ((dynamic && !(atomic_read(&tp->key.enabled) > 0)) ||
+	     !static_key_enabled(&tp->key))) {
 		ret = tp->regfunc();
 		if (ret < 0)
 			return ret;
@@ -219,7 +222,9 @@ static int tracepoint_add_func(struct tracepoint *tp,
 	 * is used.
 	 */
 	rcu_assign_pointer(tp->funcs, tp_funcs);
-	if (!static_key_enabled(&tp->key))
+	if (dynamic && !(atomic_read(&tp->key.enabled) > 0))
+		atomic_inc(&tp->key.enabled);
+	else if (!dynamic && !static_key_enabled(&tp->key))
 		static_key_slow_inc(&tp->key);
 	release_probes(old);
 	return 0;
@@ -232,7 +237,7 @@ static int tracepoint_add_func(struct tracepoint *tp,
  * by preempt_disable around the call site.
  */
 static int tracepoint_remove_func(struct tracepoint *tp,
-		struct tracepoint_func *func)
+				  struct tracepoint_func *func, bool dynamic)
 {
 	struct tracepoint_func *old, *tp_funcs;
 
@@ -246,10 +251,14 @@ static int tracepoint_remove_func(struct tracepoint *tp,
 
 	if (!tp_funcs) {
 		/* Removed last function */
-		if (tp->unregfunc && static_key_enabled(&tp->key))
+		if (tp->unregfunc &&
+		    ((dynamic && (atomic_read(&tp->key.enabled) > 0)) ||
+		     static_key_enabled(&tp->key)))
 			tp->unregfunc();
 
-		if (static_key_enabled(&tp->key))
+		if (dynamic && (atomic_read(&tp->key.enabled) > 0))
+			atomic_dec(&tp->key.enabled);
+		else if (!dynamic && static_key_enabled(&tp->key))
 			static_key_slow_dec(&tp->key);
 	}
 	rcu_assign_pointer(tp->funcs, tp_funcs);
@@ -258,7 +267,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
 }
 
 /**
- * tracepoint_probe_register -  Connect a probe to a tracepoint
+ * tracepoint_probe_register_prio -  Connect a probe to a tracepoint
  * @tp: tracepoint
  * @probe: probe handler
  * @data: tracepoint data
@@ -271,7 +280,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
  * within module exit functions.
  */
 int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
-				   void *data, int prio)
+				   void *data, int prio, bool dynamic)
 {
 	struct tracepoint_func tp_func;
 	int ret;
@@ -280,7 +289,7 @@ int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
 	tp_func.func = probe;
 	tp_func.data = data;
 	tp_func.prio = prio;
-	ret = tracepoint_add_func(tp, &tp_func, prio);
+	ret = tracepoint_add_func(tp, &tp_func, prio, dynamic);
 	mutex_unlock(&tracepoints_mutex);
 	return ret;
 }
@@ -301,10 +310,18 @@ int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
  */
 int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
 {
-	return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
+	return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO, false);
 }
 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
 
+int dynamic_tracepoint_probe_register(struct tracepoint *tp, void *probe,
+				      void *data)
+{
+	return tracepoint_probe_register_prio(tp, probe, data,
+					      TRACEPOINT_DEFAULT_PRIO, true);
+}
+EXPORT_SYMBOL_GPL(dynamic_tracepoint_probe_register);
+
 /**
  * tracepoint_probe_unregister -  Disconnect a probe from a tracepoint
  * @tp: tracepoint
@@ -313,7 +330,8 @@ int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
  *
  * Returns 0 if ok, error value on error.
  */
-int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
+int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data,
+				bool dynamic)
 {
 	struct tracepoint_func tp_func;
 	int ret;
@@ -321,7 +339,7 @@ int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
 	mutex_lock(&tracepoints_mutex);
 	tp_func.func = probe;
 	tp_func.data = data;
-	ret = tracepoint_remove_func(tp, &tp_func);
+	ret = tracepoint_remove_func(tp, &tp_func, dynamic);
 	mutex_unlock(&tracepoints_mutex);
 	return ret;
 }
-- 
1.9.3

[PATCH 21/32] tracing: Add hist trigger action hook

[Tom Zanussi]

Add a hook for executing extra actions whenever a histogram entry is
added or updated.

The default 'action' when a hist entry is added to a histogram is to
update the set of values associated with it.  Some applications may
want to perform additional actions at that point, such as generate
another event, or compare and save a maximum.

Add a simple framework for doing that; specific actions will be
implemented on top of it in later patches.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 114 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 111 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index d83d4ca..338a9d5 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -33,6 +33,7 @@ typedef u64 (*hist_field_fn_t) (struct hist_field *field,
 
 #define HIST_FIELD_OPERANDS_MAX	2
 #define HIST_FIELDS_MAX		(TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
+#define HIST_ACTIONS_MAX	8
 
 enum field_op_id {
 	FIELD_OP_NONE,
@@ -233,6 +234,9 @@ struct hist_trigger_attrs {
 
 	char		*assignment_str[TRACING_MAP_VARS_MAX];
 	unsigned int	n_assignments;
+
+	char		*action_str[HIST_ACTIONS_MAX];
+	unsigned int	n_actions;
 };
 
 struct hist_trigger_data {
@@ -252,6 +256,21 @@ struct hist_trigger_data {
 	bool				remove;
 	struct hist_field               *var_refs[TRACING_MAP_VARS_MAX];
 	unsigned int			n_var_refs;
+
+	struct action_data		*actions[HIST_ACTIONS_MAX];
+	unsigned int			n_actions;
+};
+
+struct action_data;
+
+typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
+			     struct tracing_map_elt *elt, void *rec,
+			     struct ring_buffer_event *rbe,
+			     struct action_data *data, u64 *var_ref_vals);
+
+struct action_data {
+	action_fn_t		fn;
+	unsigned int		var_ref_idx;
 };
 
 static u64 hist_field_timestamp(struct hist_field *hist_field,
@@ -681,6 +700,9 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 	for (i = 0; i < attrs->n_assignments; i++)
 		kfree(attrs->assignment_str[i]);
 
+	for (i = 0; i < attrs->n_actions; i++)
+		kfree(attrs->action_str[i]);
+
 	kfree(attrs->name);
 	kfree(attrs->sort_key_str);
 	kfree(attrs->keys_str);
@@ -688,6 +710,16 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 	kfree(attrs);
 }
 
+static int parse_action(char *str, struct hist_trigger_attrs *attrs)
+{
+	int ret = 0;
+
+	if (attrs->n_actions >= HIST_ACTIONS_MAX)
+		return ret;
+
+	return ret;
+}
+
 static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
 {
 	int ret = 0;
@@ -755,8 +787,9 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
 		else if (strcmp(str, "clear") == 0)
 			attrs->clear = true;
 		else {
-			ret = -EINVAL;
-			goto free;
+			ret = parse_action(str, attrs);
+			if (ret)
+				goto free;
 		}
 	}
 
@@ -1722,11 +1755,63 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
 	return ret;
 }
 
+static void destroy_actions(struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+
+		kfree(data);
+	}
+}
+
+static int create_actions(struct hist_trigger_data *hist_data,
+			  struct trace_event_file *file)
+{
+	unsigned int i;
+	int ret = 0;
+	char *str;
+
+	for (i = 0; i < hist_data->attrs->n_actions; i++) {
+		str = hist_data->attrs->action_str[i];
+	}
+
+	return ret;
+}
+
+static void print_actions(struct seq_file *m,
+			  struct hist_trigger_data *hist_data,
+			  struct tracing_map_elt *elt)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+	}
+}
+
+static void print_actions_spec(struct seq_file *m,
+			       struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+	}
+}
+
 static void destroy_hist_data(struct hist_trigger_data *hist_data)
 {
+	if (!hist_data)
+		return;
+
 	destroy_hist_trigger_attrs(hist_data->attrs);
 	destroy_hist_fields(hist_data);
 	tracing_map_destroy(hist_data->map);
+
+	destroy_actions(hist_data);
+
 	kfree(hist_data);
 }
 
@@ -1886,6 +1971,20 @@ static inline void add_to_key(char *compound_key, void *key,
 	memcpy(compound_key + key_field->offset, key, size);
 }
 
+static void
+hist_trigger_actions(struct hist_trigger_data *hist_data,
+		     struct tracing_map_elt *elt, void *rec,
+		     struct ring_buffer_event *rbe, u64 *var_ref_vals)
+{
+	struct action_data *data;
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		data = hist_data->actions[i];
+		data->fn(hist_data, elt, rec, rbe, data, var_ref_vals);
+	}
+}
+
 static void event_hist_trigger(struct event_trigger_data *data, void *rec,
 			       struct ring_buffer_event *rbe)
 {
@@ -1941,6 +2040,9 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec,
 		return;
 
 	hist_trigger_elt_update(hist_data, elt, rec, rbe, var_ref_vals);
+
+	if (resolve_var_refs(hist_data, key, var_ref_vals, true))
+		hist_trigger_actions(hist_data, elt, rec, rbe, var_ref_vals);
 }
 
 static void hist_trigger_stacktrace_print(struct seq_file *m,
@@ -2278,6 +2380,8 @@ static int event_hist_trigger_print(struct seq_file *m,
 	}
 	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
 
+	print_actions_spec(m, hist_data);
+
 	if (data->filter_str)
 		seq_printf(m, " if %s", data->filter_str);
 
@@ -2740,6 +2844,10 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	if (has_hist_vars(hist_data))
 		save_hist_vars(hist_data);
 
+	ret = create_actions(hist_data, file);
+	if (ret)
+		goto out_unreg;
+
 	ret = tracing_map_init(hist_data->map);
 	if (ret)
 		goto out_unreg;
@@ -2761,8 +2869,8 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	remove_hist_vars(hist_data);
 
 	kfree(trigger_data);
-
 	destroy_hist_data(hist_data);
+
 	goto out;
 }
 
-- 
1.9.3

[PATCH 22/32] tracing: Add support for 'synthetic' events

[Tom Zanussi]

Synthetic events are user-defined events generated from hist trigger
variables saved from one or more other events.

To define a synthetic event, the user writes a simple specification
consisting of the name of the new event along with one or more
variables and their type(s), to the tracing/synthetic_events file.

For instance, the following creates a new event named 'wakeup_latency'
with 3 fields: lat, pid, and prio:

    # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
      /sys/kernel/debug/tracing/synthetic_events

Reading the tracing/synthetic_events file lists all the
currently-defined synthetic events, in this case the event we defined
above:

    # cat /sys/kernel/debug/tracing/synthetic_events
    wakeup_latency u64 lat; pid_t pid; int prio

At this point, the synthetic event is ready to use, and a histogram
can be defined using it:

    # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
    /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger

The new event is created under the tracing/events/synthetic/ directory
and looks and behaves just like any other event:

    # ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency
      enable  filter  format  hist  id  trigger

Although a histogram can be defined for it, nothing will happen until
an action tracing that event via the trace_synth() function occurs.
The trace_synth() function is very similar to all the other trace_*
invocations spread throughout the kernel, except in this case the
trace_ function and its corresponding tracepoint isn't statically
generated but defined by the user at run-time.

How this can be automatically hooked up via a hist trigger 'action' is
discussed in a subsequent patch.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 738 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 738 insertions(+)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 338a9d5..e11b3a3 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -20,10 +20,14 @@
 #include <linux/slab.h>
 #include <linux/stacktrace.h>
 #include <linux/rculist.h>
+#include <linux/tracefs.h>
 
 #include "tracing_map.h"
 #include "trace.h"
 
+#define SYNTH_SYSTEM		"synthetic"
+#define SYNTH_FIELDS_MAX	16
+
 struct hist_field;
 
 typedef u64 (*hist_field_fn_t) (struct hist_field *field,
@@ -261,6 +265,23 @@ struct hist_trigger_data {
 	unsigned int			n_actions;
 };
 
+struct synth_field {
+	char *type;
+	char *name;
+	unsigned int size;
+	bool is_signed;
+};
+
+struct synth_event {
+	struct list_head			list;
+	char					*name;
+	struct synth_field			**fields;
+	unsigned int				n_fields;
+	struct trace_event_class		class;
+	struct trace_event_call			call;
+	struct tracepoint			*tp;
+};
+
 struct action_data;
 
 typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
@@ -273,6 +294,688 @@ struct action_data {
 	unsigned int		var_ref_idx;
 };
 
+static LIST_HEAD(synth_event_list);
+static DEFINE_MUTEX(synth_event_mutex);
+
+struct synth_trace_event {
+	struct trace_entry	ent;
+	int			n_fields;
+	u64			fields[];
+};
+
+static int synth_event_define_fields(struct trace_event_call *call)
+{
+	struct synth_trace_event trace;
+	int offset = offsetof(typeof(trace), fields);
+	struct synth_event *event = call->data;
+	unsigned int i, size;
+	char *name, *type;
+	bool is_signed;
+	int ret = 0;
+
+	for (i = 0; i < event->n_fields; i++) {
+		size = event->fields[i]->size;
+		is_signed = event->fields[i]->is_signed;
+		type = event->fields[i]->type;
+		name = event->fields[i]->name;
+		ret = trace_define_field(call, type, name, offset, size,
+					 is_signed, FILTER_OTHER);
+		offset += sizeof(u64);
+	}
+
+	return ret;
+}
+
+static enum print_line_t print_synth_event(struct trace_iterator *iter,
+					   int flags,
+					   struct trace_event *event)
+{
+	struct trace_array *tr = iter->tr;
+	struct trace_seq *s = &iter->seq;
+	struct synth_trace_event *entry;
+	struct synth_event *se;
+	unsigned int i;
+
+	entry = (struct synth_trace_event *)iter->ent;
+	se = container_of(event, struct synth_event, call.event);
+
+	trace_seq_printf(s, "%s: ", se->name);
+
+	for (i = 0; i < entry->n_fields; i++) {
+		if (trace_seq_has_overflowed(s))
+			goto end;
+
+		/* parameter types */
+		if (tr->trace_flags & TRACE_ITER_VERBOSE)
+			trace_seq_printf(s, "%s ", "u64");
+
+		/* parameter values */
+		trace_seq_printf(s, "%s=%llu%s", se->fields[i]->name,
+				 entry->fields[i],
+				 i == entry->n_fields - 1 ? "" : ", ");
+	}
+end:
+	trace_seq_putc(s, '\n');
+
+	return trace_handle_return(s);
+}
+
+static struct trace_event_functions synth_event_funcs = {
+	.trace		= print_synth_event
+};
+
+static notrace void trace_event_raw_event_synth(void *__data,
+						u64 *var_ref_vals,
+						unsigned int var_ref_idx)
+{
+	struct trace_event_file *trace_file = __data;
+	struct synth_trace_event *entry;
+	struct trace_event_buffer fbuffer;
+	int fields_size;
+	unsigned int i;
+
+	struct synth_event *event;
+
+	event = trace_file->event_call->data;
+
+	if (trace_trigger_soft_disabled(trace_file))
+		return;
+
+	fields_size = event->n_fields * sizeof(u64);
+
+	entry = trace_event_buffer_reserve(&fbuffer, trace_file,
+					   sizeof(*entry) + fields_size);
+	if (!entry)
+		return;
+
+	entry->n_fields = event->n_fields;
+
+	for (i = 0; i < event->n_fields; i++)
+		entry->fields[i] = var_ref_vals[var_ref_idx + i];
+
+	trace_event_buffer_commit(&fbuffer);
+}
+
+static void free_synth_event_print_fmt(struct trace_event_call *call)
+{
+	if (call)
+		kfree(call->print_fmt);
+}
+
+static int __set_synth_event_print_fmt(struct synth_event *event,
+				       char *buf, int len)
+{
+	int pos = 0;
+	int i;
+
+	/* When len=0, we just calculate the needed length */
+#define LEN_OR_ZERO (len ? len - pos : 0)
+
+	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
+	for (i = 0; i < event->n_fields; i++) {
+		pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
+				event->fields[i]->name, sizeof(u64),
+				i == event->n_fields - 1 ? "" : ", ");
+	}
+	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
+
+	for (i = 0; i < event->n_fields; i++) {
+		pos += snprintf(buf + pos, LEN_OR_ZERO,
+				", ((u64)(REC->%s))", event->fields[i]->name);
+	}
+
+#undef LEN_OR_ZERO
+
+	/* return the length of print_fmt */
+	return pos;
+}
+
+static int set_synth_event_print_fmt(struct trace_event_call *call)
+{
+	struct synth_event *event = call->data;
+	char *print_fmt;
+	int len;
+
+	/* First: called with 0 length to calculate the needed length */
+	len = __set_synth_event_print_fmt(event, NULL, 0);
+
+	print_fmt = kmalloc(len + 1, GFP_KERNEL);
+	if (!print_fmt)
+		return -ENOMEM;
+
+	/* Second: actually write the @print_fmt */
+	__set_synth_event_print_fmt(event, print_fmt, len + 1);
+	call->print_fmt = print_fmt;
+
+	return 0;
+}
+
+int dynamic_trace_event_reg(struct trace_event_call *call,
+			    enum trace_reg type, void *data)
+{
+	struct trace_event_file *file = data;
+
+	WARN_ON(!(call->flags & TRACE_EVENT_FL_TRACEPOINT));
+	switch (type) {
+	case TRACE_REG_REGISTER:
+		return dynamic_tracepoint_probe_register(call->tp,
+							 call->class->probe,
+							 file);
+	case TRACE_REG_UNREGISTER:
+		tracepoint_probe_unregister(call->tp,
+					    call->class->probe,
+					    file, true);
+		return 0;
+
+#ifdef CONFIG_PERF_EVENTS
+	case TRACE_REG_PERF_REGISTER:
+		return dynamic_tracepoint_probe_register(call->tp,
+							 call->class->perf_probe,
+							 call);
+	case TRACE_REG_PERF_UNREGISTER:
+		tracepoint_probe_unregister(call->tp,
+					    call->class->perf_probe,
+					    call, true);
+		return 0;
+	case TRACE_REG_PERF_OPEN:
+	case TRACE_REG_PERF_CLOSE:
+	case TRACE_REG_PERF_ADD:
+	case TRACE_REG_PERF_DEL:
+		return 0;
+#endif
+	}
+	return 0;
+}
+
+static void free_synth_field(struct synth_field *field)
+{
+	kfree(field->type);
+	kfree(field->name);
+	kfree(field);
+}
+
+static bool synth_field_signed(char *type)
+{
+	if (strncmp(type, "u", 1) == 0)
+		return false;
+
+	return true;
+}
+
+static unsigned int synth_field_size(char *type)
+{
+	unsigned int size = 0;
+
+	if (strcmp(type, "s64") == 0)
+		size = sizeof(s64);
+	else if (strcmp(type, "u64") == 0)
+		size = sizeof(u64);
+	else if (strcmp(type, "s32") == 0)
+		size = sizeof(s32);
+	else if (strcmp(type, "u32") == 0)
+		size = sizeof(u32);
+	else if (strcmp(type, "s16") == 0)
+		size = sizeof(s16);
+	else if (strcmp(type, "u16") == 0)
+		size = sizeof(u16);
+	else if (strcmp(type, "s8") == 0)
+		size = sizeof(s8);
+	else if (strcmp(type, "u8") == 0)
+		size = sizeof(u8);
+	else if (strcmp(type, "char") == 0)
+		size = sizeof(char);
+	else if (strcmp(type, "unsigned char") == 0)
+		size = sizeof(unsigned char);
+	else if (strcmp(type, "int") == 0)
+		size = sizeof(int);
+	else if (strcmp(type, "unsigned int") == 0)
+		size = sizeof(unsigned int);
+	else if (strcmp(type, "long") == 0)
+		size = sizeof(long);
+	else if (strcmp(type, "unsigned long") == 0)
+		size = sizeof(unsigned long);
+	else if (strcmp(type, "pid_t") == 0)
+		size = sizeof(pid_t);
+	else if (strstr(type, "[") == 0)
+		size = sizeof(u64);
+
+	return size;
+}
+
+static struct synth_field *parse_synth_field(char *field_type,
+					     char *field_name)
+{
+	struct synth_field *field;
+	int len, ret = 0;
+	char *array;
+
+	if (field_type[0] == ';')
+		field_type++;
+
+	len = strlen(field_name);
+	if (field_name[len - 1] == ';')
+		field_name[len - 1] = '\0';
+
+	field = kzalloc(sizeof(*field), GFP_KERNEL);
+	if (!field)
+		return ERR_PTR(-ENOMEM);
+
+	len = strlen(field_type) + 1;
+	array = strchr(field_name, '[');
+	if (array)
+		len += strlen(array);
+	field->type = kzalloc(len, GFP_KERNEL);
+	if (!field->type) {
+		ret = -ENOMEM;
+		goto free;
+	}
+	strcat(field->type, field_type);
+	if (array)
+		strcat(field->type, array);
+
+	field->size = synth_field_size(field->type);
+	if (!field->size) {
+		ret = -EINVAL;
+		goto free;
+	}
+
+	field->is_signed = synth_field_signed(field->type);
+
+	field->name = kstrdup(field_name, GFP_KERNEL);
+	if (!field->name) {
+		ret = -ENOMEM;
+		goto free;
+	}
+ out:
+	return field;
+ free:
+	free_synth_field(field);
+	field = ERR_PTR(ret);
+	goto out;
+}
+
+static void free_synth_tracepoint(struct tracepoint *tp)
+{
+	if (!tp)
+		return;
+
+	kfree(tp->name);
+	kfree(tp);
+}
+
+static struct tracepoint *alloc_synth_tracepoint(char *name)
+{
+	struct tracepoint *tp;
+	int ret = 0;
+
+	tp = kzalloc(sizeof(*tp), GFP_KERNEL);
+	if (!tp) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	tp->name = kstrdup(name, GFP_KERNEL);
+	if (!tp->name) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	return tp;
+ free:
+	free_synth_tracepoint(tp);
+
+	return ERR_PTR(ret);
+}
+
+static inline void trace_synth(struct synth_event *event, u64 *var_ref_vals,
+			       unsigned int var_ref_idx)
+{
+	struct tracepoint *tp = event->tp;
+
+	if (unlikely(atomic_read(&tp->key.enabled) > 0)) {
+		struct tracepoint_func *it_func_ptr;
+		void *it_func;
+		void *__data;
+
+		if (!(cpu_online(raw_smp_processor_id())))
+			return;
+
+		it_func_ptr = rcu_dereference_sched((tp)->funcs);
+		if (it_func_ptr) {
+			do {
+				it_func = (it_func_ptr)->func;
+				__data = (it_func_ptr)->data;
+				((void(*)(void *__data, u64 *var_ref_vals, unsigned int var_ref_idx))(it_func))(__data, var_ref_vals, var_ref_idx);
+			} while ((++it_func_ptr)->func);
+		}
+	}
+}
+
+static struct synth_event *find_synth_event(const char *name)
+{
+	struct synth_event *event;
+
+	list_for_each_entry(event, &synth_event_list, list) {
+		if (strcmp(event->name, name) == 0)
+			return event;
+	}
+
+	return NULL;
+}
+
+static int register_synth_event(struct synth_event *event)
+{
+	struct trace_event_call *call = &event->call;
+	int ret = 0;
+
+	event->call.class = &event->class;
+	event->class.system = kstrdup(SYNTH_SYSTEM, GFP_KERNEL);
+	if (!event->class.system) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	event->tp = alloc_synth_tracepoint(event->name);
+	if (IS_ERR(event->tp)) {
+		ret = PTR_ERR(event->tp);
+		event->tp = NULL;
+		goto out;
+	}
+
+	INIT_LIST_HEAD(&call->class->fields);
+	call->event.funcs = &synth_event_funcs;
+	call->class->define_fields = synth_event_define_fields;
+
+	ret = register_trace_event(&call->event);
+	if (!ret) {
+		ret = -ENODEV;
+		goto out;
+	}
+	call->flags = TRACE_EVENT_FL_TRACEPOINT;
+	call->class->reg = dynamic_trace_event_reg;
+	call->class->probe = trace_event_raw_event_synth;
+	call->data = event;
+	call->tp = event->tp;
+	ret = trace_add_event_call(call);
+	if (ret) {
+		pr_warn("Failed to register synthetic event: %s\n",
+			trace_event_name(call));
+		goto err;
+	}
+
+	ret = set_synth_event_print_fmt(call);
+	if (ret < 0) {
+		trace_remove_event_call(call);
+		goto err;
+	}
+ out:
+	return ret;
+ err:
+	unregister_trace_event(&call->event);
+	goto out;
+}
+
+static int unregister_synth_event(struct synth_event *event)
+{
+	struct trace_event_call *call = &event->call;
+	int ret;
+
+	ret = trace_remove_event_call(call);
+	if (ret) {
+		pr_warn("Failed to remove synthetic event: %s\n",
+			trace_event_name(call));
+		free_synth_event_print_fmt(call);
+		unregister_trace_event(&call->event);
+	}
+
+	return ret;
+}
+
+static void remove_synth_event(struct synth_event *event)
+{
+	unregister_synth_event(event);
+	list_del(&event->list);
+}
+
+static int add_synth_event(struct synth_event *event)
+{
+	int ret;
+
+	ret = register_synth_event(event);
+	if (ret)
+		return ret;
+
+	list_add(&event->list, &synth_event_list);
+
+	return 0;
+}
+
+static void free_synth_event(struct synth_event *event)
+{
+	unsigned int i;
+
+	if (!event)
+		return;
+
+	for (i = 0; i < event->n_fields; i++)
+		free_synth_field(event->fields[i]);
+
+	kfree(event->fields);
+	kfree(event->name);
+	kfree(event->class.system);
+	free_synth_tracepoint(event->tp);
+	free_synth_event_print_fmt(&event->call);
+	kfree(event);
+}
+
+static struct synth_event *alloc_synth_event(char *event_name, int n_fields,
+					     struct synth_field **fields)
+{
+	struct synth_event *event;
+	unsigned int i;
+
+	event = kzalloc(sizeof(*event), GFP_KERNEL);
+	if (!event) {
+		event = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	event->name = kstrdup(event_name, GFP_KERNEL);
+	if (!event->name) {
+		kfree(event);
+		event = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	event->fields = kcalloc(n_fields, sizeof(event->fields), GFP_KERNEL);
+	if (!event->fields) {
+		free_synth_event(event);
+		event = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	for (i = 0; i < n_fields; i++)
+		event->fields[i] = fields[i];
+
+	event->n_fields = n_fields;
+ out:
+	return event;
+}
+
+static int create_synth_event(int argc, char **argv)
+{
+	struct synth_field *fields[SYNTH_FIELDS_MAX];
+	struct synth_event *event = NULL;
+	bool delete_event = false;
+	int i, n_fields = 0, ret = 0;
+	char *name;
+
+	mutex_lock(&synth_event_mutex);
+
+	/*
+	 * Argument syntax:
+	 *  - Add synthetic event: <event_name> field[;field] ...
+	 *  - Remove synthetic event: !<event_name> field[;field] ...
+	 *      where 'field' = type field_name
+	 */
+	if (argc < 1) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	name = argv[0];
+	if (name[0] == '!') {
+		delete_event = true;
+		name++;
+	}
+
+	event = find_synth_event(name);
+	if (event) {
+		if (delete_event) {
+			remove_synth_event(event);
+			goto err;
+		} else
+			ret = -EEXIST;
+		goto out;
+	} else if (delete_event) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (argc < 2) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	for (i = 1; i < argc - 1; i++) {
+		if (strcmp(argv[i], ";") == 0)
+			continue;
+		if (n_fields == SYNTH_FIELDS_MAX) {
+			ret = -EINVAL;
+			goto out;
+		}
+		fields[n_fields] = parse_synth_field(argv[i], argv[i + 1]);
+		if (!fields[n_fields])
+			goto err;
+		i++; n_fields++;
+	}
+	if (i < argc) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	event = alloc_synth_event(name, n_fields, fields);
+	if (IS_ERR(event)) {
+		ret = PTR_ERR(event);
+		event = NULL;
+		goto err;
+	}
+
+	add_synth_event(event);
+ out:
+	mutex_unlock(&synth_event_mutex);
+
+	return ret;
+ err:
+	for (i = 0; i < n_fields; i++)
+		free_synth_field(fields[i]);
+	free_synth_event(event);
+
+	goto out;
+}
+
+static int release_all_synth_events(void)
+{
+	struct synth_event *event, *e;
+	int ret = 0;
+
+	mutex_lock(&synth_event_mutex);
+
+	list_for_each_entry_safe(event, e, &synth_event_list, list) {
+		remove_synth_event(event);
+		free_synth_event(event);
+	}
+
+	mutex_unlock(&synth_event_mutex);
+
+	return ret;
+}
+
+
+static void *synth_events_seq_start(struct seq_file *m, loff_t *pos)
+{
+	mutex_lock(&synth_event_mutex);
+
+	return seq_list_start(&synth_event_list, *pos);
+}
+
+static void *synth_events_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	return seq_list_next(v, &synth_event_list, pos);
+}
+
+static void synth_events_seq_stop(struct seq_file *m, void *v)
+{
+	mutex_unlock(&synth_event_mutex);
+}
+
+static int synth_events_seq_show(struct seq_file *m, void *v)
+{
+	struct synth_field *field;
+	struct synth_event *event = v;
+	unsigned int i;
+
+	seq_printf(m, "%s\t", event->name);
+
+	for (i = 0; i < event->n_fields; i++) {
+		field = event->fields[i];
+
+		/* parameter values */
+		seq_printf(m, "%s %s%s", field->type, field->name,
+			   i == event->n_fields - 1 ? "" : "; ");
+	}
+
+	seq_putc(m, '\n');
+
+	return 0;
+}
+
+static const struct seq_operations synth_events_seq_op = {
+	.start  = synth_events_seq_start,
+	.next   = synth_events_seq_next,
+	.stop   = synth_events_seq_stop,
+	.show   = synth_events_seq_show
+};
+
+static int synth_events_open(struct inode *inode, struct file *file)
+{
+	int ret;
+
+	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
+		ret = release_all_synth_events();
+		if (ret < 0)
+			return ret;
+	}
+
+	return seq_open(file, &synth_events_seq_op);
+}
+
+static ssize_t synth_events_write(struct file *file,
+				  const char __user *buffer,
+				  size_t count, loff_t *ppos)
+{
+	return trace_parse_run_command(file, buffer, count, ppos,
+				       create_synth_event);
+}
+
+static const struct file_operations synth_events_fops = {
+	.open           = synth_events_open,
+	.write		= synth_events_write,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = seq_release,
+};
+
 static u64 hist_field_timestamp(struct hist_field *hist_field,
 				struct tracing_map_elt *elt,
 				struct ring_buffer_event *rbe,
@@ -3028,3 +3731,38 @@ __init int register_trigger_hist_enable_disable_cmds(void)
 
 	return ret;
 }
+
+static __init int trace_events_hist_init(void)
+{
+	struct dentry *entry = NULL;
+	struct trace_array *tr;
+	struct dentry *d_tracer;
+	int err = 0;
+
+	tr = top_trace_array();
+	if (!tr) {
+		err = -ENODEV;
+		goto err;
+	}
+
+	d_tracer = tracing_init_dentry();
+	if (IS_ERR(d_tracer)) {
+		err = PTR_ERR(d_tracer);
+		goto err;
+	}
+
+	entry = tracefs_create_file("synthetic_events", 0644, d_tracer,
+				    tr, &synth_events_fops);
+	if (!entry) {
+		err = -ENODEV;
+		goto err;
+	}
+
+	return err;
+ err:
+	pr_warn("Could not create tracefs 'synthetic_events' entry\n");
+
+	return err;
+}
+
+fs_initcall(trace_events_hist_init);
-- 
1.9.3

Re: [PATCH 22/32] tracing: Add support for 'synthetic' events

[Namhyung Kim]

Hi Tom,

On Mon, Jun 26, 2017 at 05:49:23PM -0500, Tom Zanussi wrote:
> Synthetic events are user-defined events generated from hist trigger
> variables saved from one or more other events.
> 
> To define a synthetic event, the user writes a simple specification
> consisting of the name of the new event along with one or more
> variables and their type(s), to the tracing/synthetic_events file.
> 
> For instance, the following creates a new event named 'wakeup_latency'
> with 3 fields: lat, pid, and prio:
> 
>     # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
>       /sys/kernel/debug/tracing/synthetic_events
> 
> Reading the tracing/synthetic_events file lists all the
> currently-defined synthetic events, in this case the event we defined
> above:
> 
>     # cat /sys/kernel/debug/tracing/synthetic_events
>     wakeup_latency u64 lat; pid_t pid; int prio
> 
> At this point, the synthetic event is ready to use, and a histogram
> can be defined using it:
> 
>     # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
>     /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
> 
> The new event is created under the tracing/events/synthetic/ directory
> and looks and behaves just like any other event:
> 
>     # ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency
>       enable  filter  format  hist  id  trigger
> 
> Although a histogram can be defined for it, nothing will happen until
> an action tracing that event via the trace_synth() function occurs.
> The trace_synth() function is very similar to all the other trace_*
> invocations spread throughout the kernel, except in this case the
> trace_ function and its corresponding tracepoint isn't statically
> generated but defined by the user at run-time.
> 
> How this can be automatically hooked up via a hist trigger 'action' is
> discussed in a subsequent patch.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  kernel/trace/trace_events_hist.c | 738 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 738 insertions(+)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 338a9d5..e11b3a3 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c

[SNIP]
> @@ -273,6 +294,688 @@ struct action_data {
>  	unsigned int		var_ref_idx;
>  };
>  
> +static LIST_HEAD(synth_event_list);
> +static DEFINE_MUTEX(synth_event_mutex);
> +
> +struct synth_trace_event {
> +	struct trace_entry	ent;
> +	int			n_fields;
> +	u64			fields[];
> +};
> +
> +static int synth_event_define_fields(struct trace_event_call *call)
> +{
> +	struct synth_trace_event trace;
> +	int offset = offsetof(typeof(trace), fields);
> +	struct synth_event *event = call->data;
> +	unsigned int i, size;
> +	char *name, *type;
> +	bool is_signed;
> +	int ret = 0;
> +
> +	for (i = 0; i < event->n_fields; i++) {
> +		size = event->fields[i]->size;
> +		is_signed = event->fields[i]->is_signed;
> +		type = event->fields[i]->type;
> +		name = event->fields[i]->name;
> +		ret = trace_define_field(call, type, name, offset, size,
> +					 is_signed, FILTER_OTHER);
> +		offset += sizeof(u64);

So you assume size of a field is up to 64-bit, right?  Does it
guaranteed somewhere?


> +	}
> +
> +	return ret;
> +}
> +
> +static enum print_line_t print_synth_event(struct trace_iterator *iter,
> +					   int flags,
> +					   struct trace_event *event)
> +{
> +	struct trace_array *tr = iter->tr;
> +	struct trace_seq *s = &iter->seq;
> +	struct synth_trace_event *entry;
> +	struct synth_event *se;
> +	unsigned int i;
> +
> +	entry = (struct synth_trace_event *)iter->ent;
> +	se = container_of(event, struct synth_event, call.event);
> +
> +	trace_seq_printf(s, "%s: ", se->name);
> +
> +	for (i = 0; i < entry->n_fields; i++) {
> +		if (trace_seq_has_overflowed(s))
> +			goto end;
> +
> +		/* parameter types */
> +		if (tr->trace_flags & TRACE_ITER_VERBOSE)
> +			trace_seq_printf(s, "%s ", "u64");

Why did you hardcode 'u64' here?

> +
> +		/* parameter values */
> +		trace_seq_printf(s, "%s=%llu%s", se->fields[i]->name,
> +				 entry->fields[i],
> +				 i == entry->n_fields - 1 ? "" : ", ");
> +	}
> +end:
> +	trace_seq_putc(s, '\n');
> +
> +	return trace_handle_return(s);
> +}
> +
> +static struct trace_event_functions synth_event_funcs = {
> +	.trace		= print_synth_event
> +};
> +

[SNIP]
> +static unsigned int synth_field_size(char *type)
> +{
> +	unsigned int size = 0;
> +
> +	if (strcmp(type, "s64") == 0)
> +		size = sizeof(s64);
> +	else if (strcmp(type, "u64") == 0)
> +		size = sizeof(u64);
> +	else if (strcmp(type, "s32") == 0)
> +		size = sizeof(s32);
> +	else if (strcmp(type, "u32") == 0)
> +		size = sizeof(u32);
> +	else if (strcmp(type, "s16") == 0)
> +		size = sizeof(s16);
> +	else if (strcmp(type, "u16") == 0)
> +		size = sizeof(u16);
> +	else if (strcmp(type, "s8") == 0)
> +		size = sizeof(s8);
> +	else if (strcmp(type, "u8") == 0)
> +		size = sizeof(u8);
> +	else if (strcmp(type, "char") == 0)
> +		size = sizeof(char);
> +	else if (strcmp(type, "unsigned char") == 0)
> +		size = sizeof(unsigned char);
> +	else if (strcmp(type, "int") == 0)
> +		size = sizeof(int);
> +	else if (strcmp(type, "unsigned int") == 0)
> +		size = sizeof(unsigned int);
> +	else if (strcmp(type, "long") == 0)
> +		size = sizeof(long);
> +	else if (strcmp(type, "unsigned long") == 0)
> +		size = sizeof(unsigned long);
> +	else if (strcmp(type, "pid_t") == 0)
> +		size = sizeof(pid_t);
> +	else if (strstr(type, "[") == 0)
> +		size = sizeof(u64);

Ah ok, so you don't accept arrays and all supported fields are less
than or equal to 8 bytes.

> +
> +	return size;
> +}
> +

[SNIP]
> +static inline void trace_synth(struct synth_event *event, u64 *var_ref_vals,
> +			       unsigned int var_ref_idx)
> +{
> +	struct tracepoint *tp = event->tp;
> +
> +	if (unlikely(atomic_read(&tp->key.enabled) > 0)) {
> +		struct tracepoint_func *it_func_ptr;
> +		void *it_func;
> +		void *__data;
> +
> +		if (!(cpu_online(raw_smp_processor_id())))
> +			return;
> +
> +		it_func_ptr = rcu_dereference_sched((tp)->funcs);
> +		if (it_func_ptr) {
> +			do {
> +				it_func = (it_func_ptr)->func;
> +				__data = (it_func_ptr)->data;
> +				((void(*)(void *__data, u64 *var_ref_vals, unsigned int var_ref_idx))(it_func))(__data, var_ref_vals, var_ref_idx);

Ouch, why not defining a function pointer?

Thanks,
Namhyung


> +			} while ((++it_func_ptr)->func);
> +		}
> +	}
> +}

Re: [PATCH 22/32] tracing: Add support for 'synthetic' events

[Tom Zanussi]

Hi Namhyung,

On Sun, 2017-07-23 at 21:00 +0900, Namhyung Kim wrote:
> Hi Tom,
> 
> On Mon, Jun 26, 2017 at 05:49:23PM -0500, Tom Zanussi wrote:
> > Synthetic events are user-defined events generated from hist trigger
> > variables saved from one or more other events.
> > 
> > To define a synthetic event, the user writes a simple specification
> > consisting of the name of the new event along with one or more
> > variables and their type(s), to the tracing/synthetic_events file.
> > 
> > For instance, the following creates a new event named 'wakeup_latency'
> > with 3 fields: lat, pid, and prio:
> > 
> >     # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
> >       /sys/kernel/debug/tracing/synthetic_events
> > 
> > Reading the tracing/synthetic_events file lists all the
> > currently-defined synthetic events, in this case the event we defined
> > above:
> > 
> >     # cat /sys/kernel/debug/tracing/synthetic_events
> >     wakeup_latency u64 lat; pid_t pid; int prio
> > 
> > At this point, the synthetic event is ready to use, and a histogram
> > can be defined using it:
> > 
> >     # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
> >     /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
> > 
> > The new event is created under the tracing/events/synthetic/ directory
> > and looks and behaves just like any other event:
> > 
> >     # ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency
> >       enable  filter  format  hist  id  trigger
> > 
> > Although a histogram can be defined for it, nothing will happen until
> > an action tracing that event via the trace_synth() function occurs.
> > The trace_synth() function is very similar to all the other trace_*
> > invocations spread throughout the kernel, except in this case the
> > trace_ function and its corresponding tracepoint isn't statically
> > generated but defined by the user at run-time.
> > 
> > How this can be automatically hooked up via a hist trigger 'action' is
> > discussed in a subsequent patch.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> >  kernel/trace/trace_events_hist.c | 738 +++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 738 insertions(+)
> > 
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index 338a9d5..e11b3a3 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> 
> [SNIP]
> > @@ -273,6 +294,688 @@ struct action_data {
> >  	unsigned int		var_ref_idx;
> >  };
> >  
> > +static LIST_HEAD(synth_event_list);
> > +static DEFINE_MUTEX(synth_event_mutex);
> > +
> > +struct synth_trace_event {
> > +	struct trace_entry	ent;
> > +	int			n_fields;
> > +	u64			fields[];
> > +};
> > +
> > +static int synth_event_define_fields(struct trace_event_call *call)
> > +{
> > +	struct synth_trace_event trace;
> > +	int offset = offsetof(typeof(trace), fields);
> > +	struct synth_event *event = call->data;
> > +	unsigned int i, size;
> > +	char *name, *type;
> > +	bool is_signed;
> > +	int ret = 0;
> > +
> > +	for (i = 0; i < event->n_fields; i++) {
> > +		size = event->fields[i]->size;
> > +		is_signed = event->fields[i]->is_signed;
> > +		type = event->fields[i]->type;
> > +		name = event->fields[i]->name;
> > +		ret = trace_define_field(call, type, name, offset, size,
> > +					 is_signed, FILTER_OTHER);
> > +		offset += sizeof(u64);
> 
> So you assume size of a field is up to 64-bit, right?  Does it
> guaranteed somewhere?
> 
> 
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static enum print_line_t print_synth_event(struct trace_iterator *iter,
> > +					   int flags,
> > +					   struct trace_event *event)
> > +{
> > +	struct trace_array *tr = iter->tr;
> > +	struct trace_seq *s = &iter->seq;
> > +	struct synth_trace_event *entry;
> > +	struct synth_event *se;
> > +	unsigned int i;
> > +
> > +	entry = (struct synth_trace_event *)iter->ent;
> > +	se = container_of(event, struct synth_event, call.event);
> > +
> > +	trace_seq_printf(s, "%s: ", se->name);
> > +
> > +	for (i = 0; i < entry->n_fields; i++) {
> > +		if (trace_seq_has_overflowed(s))
> > +			goto end;
> > +
> > +		/* parameter types */
> > +		if (tr->trace_flags & TRACE_ITER_VERBOSE)
> > +			trace_seq_printf(s, "%s ", "u64");
> 
> Why did you hardcode 'u64' here?
> 

Originally everything was u64 but now we have actual types, so this
needs to be updated.

> > +
> > +		/* parameter values */
> > +		trace_seq_printf(s, "%s=%llu%s", se->fields[i]->name,
> > +				 entry->fields[i],
> > +				 i == entry->n_fields - 1 ? "" : ", ");
> > +	}
> > +end:
> > +	trace_seq_putc(s, '\n');
> > +
> > +	return trace_handle_return(s);
> > +}
> > +
> > +static struct trace_event_functions synth_event_funcs = {
> > +	.trace		= print_synth_event
> > +};
> > +
> 
> [SNIP]
> > +static unsigned int synth_field_size(char *type)
> > +{
> > +	unsigned int size = 0;
> > +
> > +	if (strcmp(type, "s64") == 0)
> > +		size = sizeof(s64);
> > +	else if (strcmp(type, "u64") == 0)
> > +		size = sizeof(u64);
> > +	else if (strcmp(type, "s32") == 0)
> > +		size = sizeof(s32);
> > +	else if (strcmp(type, "u32") == 0)
> > +		size = sizeof(u32);
> > +	else if (strcmp(type, "s16") == 0)
> > +		size = sizeof(s16);
> > +	else if (strcmp(type, "u16") == 0)
> > +		size = sizeof(u16);
> > +	else if (strcmp(type, "s8") == 0)
> > +		size = sizeof(s8);
> > +	else if (strcmp(type, "u8") == 0)
> > +		size = sizeof(u8);
> > +	else if (strcmp(type, "char") == 0)
> > +		size = sizeof(char);
> > +	else if (strcmp(type, "unsigned char") == 0)
> > +		size = sizeof(unsigned char);
> > +	else if (strcmp(type, "int") == 0)
> > +		size = sizeof(int);
> > +	else if (strcmp(type, "unsigned int") == 0)
> > +		size = sizeof(unsigned int);
> > +	else if (strcmp(type, "long") == 0)
> > +		size = sizeof(long);
> > +	else if (strcmp(type, "unsigned long") == 0)
> > +		size = sizeof(unsigned long);
> > +	else if (strcmp(type, "pid_t") == 0)
> > +		size = sizeof(pid_t);
> > +	else if (strstr(type, "[") == 0)
> > +		size = sizeof(u64);
> 
> Ah ok, so you don't accept arrays and all supported fields are less
> than or equal to 8 bytes.
> 
> > +
> > +	return size;
> > +}
> > +
> 
> [SNIP]
> > +static inline void trace_synth(struct synth_event *event, u64 *var_ref_vals,
> > +			       unsigned int var_ref_idx)
> > +{
> > +	struct tracepoint *tp = event->tp;
> > +
> > +	if (unlikely(atomic_read(&tp->key.enabled) > 0)) {
> > +		struct tracepoint_func *it_func_ptr;
> > +		void *it_func;
> > +		void *__data;
> > +
> > +		if (!(cpu_online(raw_smp_processor_id())))
> > +			return;
> > +
> > +		it_func_ptr = rcu_dereference_sched((tp)->funcs);
> > +		if (it_func_ptr) {
> > +			do {
> > +				it_func = (it_func_ptr)->func;
> > +				__data = (it_func_ptr)->data;
> > +				((void(*)(void *__data, u64 *var_ref_vals, unsigned int var_ref_idx))(it_func))(__data, var_ref_vals, var_ref_idx);
> 
> Ouch, why not defining a function pointer?
> 

Good point, will do.

Thanks,

Tom

[PATCH 23/32] tracing: Add 'onmatch' hist trigger action support

[Tom Zanussi]

Add an 'onmatch(matching.event).<synthetic_event_name>(param list)'
hist trigger action which is invoked with the set of variables or
event fields named in the 'param list'.  The result is the generation
of a synthetic event that consists of the values contained in those
variables and/or fields at the time the invoking event was hit.

As an example the below defines a simple synthetic event using a
variable defined on the sched_wakeup_new event, and shows the event
definition with unresolved fields, since the sched_wakeup_new event
with the testpid variable hasn't been defined yet:

    # echo 'wakeup_new_test pid_t pid; int prio' >> \
      /sys/kernel/debug/tracing/synthetic_events

    # cat /sys/kernel/debug/tracing/synthetic_events
      wakeup_new_test pid_t pid; int prio

The following hist trigger both defines a testpid variable and
specifies an onmatch() trace action that uses that variable along with
a non-variable field to generate a wakeup_new_test synthetic event
whenever a sched_wakeup_new event occurs, which because of the 'if
comm == "cyclictest"' filter only happens when the executable is
cyclictest:

    # echo 'hist:keys=testpid=pid:\
      onmatch(sched.sched_wakeup_new).wakeup_new_test($testpid, prio) \
        if comm=="cyclictest"' >> \
      /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger

Creating and displaying a histogram based on those events is now just
a matter of using the fields and new synthetic event in the
tracing/events/synthetic directory, as usual:

    # echo 'hist:keys=pid,prio:sort=pid,prio' >> \
      /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 955 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 940 insertions(+), 15 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index e11b3a3..b1f859c 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -59,6 +59,7 @@ struct hist_field {
 	unsigned int			size;
 	unsigned int			offset;
 	unsigned int                    is_signed;
+	const char			*type;
 	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
 	struct hist_trigger_data	*hist_data;
 	struct hist_var			var;
@@ -243,6 +244,16 @@ struct hist_trigger_attrs {
 	unsigned int	n_actions;
 };
 
+struct field_var {
+	struct hist_field	*var;
+	struct hist_field	*val;
+};
+
+struct field_var_hist {
+	struct hist_trigger_data	*hist_data;
+	char				*cmd;
+};
+
 struct hist_trigger_data {
 	struct hist_field               *fields[HIST_FIELDS_MAX];
 	unsigned int			n_vals;
@@ -263,6 +274,14 @@ struct hist_trigger_data {
 
 	struct action_data		*actions[HIST_ACTIONS_MAX];
 	unsigned int			n_actions;
+
+	struct hist_field		*synth_var_refs[SYNTH_FIELDS_MAX];
+	unsigned int			n_synth_var_refs;
+	struct field_var		*field_vars[SYNTH_FIELDS_MAX];
+	unsigned int			n_field_vars;
+	unsigned int			n_field_var_str;
+	struct field_var_hist		*field_var_hists[SYNTH_FIELDS_MAX];
+	unsigned int			n_field_var_hists;
 };
 
 struct synth_field {
@@ -291,7 +310,14 @@ typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
 
 struct action_data {
 	action_fn_t		fn;
+	unsigned int		n_params;
+	char			*params[SYNTH_FIELDS_MAX];
+
 	unsigned int		var_ref_idx;
+	char			*match_event;
+	char			*match_event_system;
+	char			*synth_event_name;
+	struct synth_event	*synth_event;
 };
 
 static LIST_HEAD(synth_event_list);
@@ -802,6 +828,50 @@ static struct synth_event *alloc_synth_event(char *event_name, int n_fields,
 	return event;
 }
 
+static void action_trace(struct hist_trigger_data *hist_data,
+			 struct tracing_map_elt *elt, void *rec,
+			 struct ring_buffer_event *rbe,
+			 struct action_data *data, u64 *var_ref_vals)
+{
+	struct synth_event *event = data->synth_event;
+
+	trace_synth(event, var_ref_vals, data->var_ref_idx);
+}
+
+static bool check_hist_action_refs(struct hist_trigger_data *hist_data,
+				   struct synth_event *event)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+
+		if (data->fn == action_trace && data->synth_event == event)
+			return true;
+	}
+
+	return false;
+}
+
+static LIST_HEAD(hist_action_list);
+static LIST_HEAD(hist_var_list);
+
+struct hist_var_data {
+	struct list_head list;
+	struct hist_trigger_data *hist_data;
+};
+
+static bool check_synth_action_refs(struct synth_event *event)
+{
+	struct hist_var_data *var_data;
+
+	list_for_each_entry(var_data, &hist_action_list, list)
+		if (check_hist_action_refs(var_data->hist_data, event))
+			return true;
+
+	return false;
+}
+
 static int create_synth_event(int argc, char **argv)
 {
 	struct synth_field *fields[SYNTH_FIELDS_MAX];
@@ -832,15 +902,17 @@ static int create_synth_event(int argc, char **argv)
 	event = find_synth_event(name);
 	if (event) {
 		if (delete_event) {
+			if (check_synth_action_refs(event)) {
+				ret = -EBUSY;
+				goto out;
+			}
 			remove_synth_event(event);
 			goto err;
 		} else
 			ret = -EEXIST;
 		goto out;
-	} else if (delete_event) {
-		ret = -EINVAL;
+	} else if (delete_event)
 		goto out;
-	}
 
 	if (argc < 2) {
 		ret = -EINVAL;
@@ -891,11 +963,18 @@ static int release_all_synth_events(void)
 
 	mutex_lock(&synth_event_mutex);
 
+	list_for_each_entry(event, &synth_event_list, list) {
+		if (check_synth_action_refs(event)) {
+			ret = -EBUSY;
+			goto out;
+		}
+	}
+
 	list_for_each_entry_safe(event, e, &synth_event_list, list) {
 		remove_synth_event(event);
 		free_synth_event(event);
 	}
-
+ out:
 	mutex_unlock(&synth_event_mutex);
 
 	return ret;
@@ -992,13 +1071,6 @@ static u64 hist_field_timestamp(struct hist_field *hist_field,
 	return ts;
 }
 
-static LIST_HEAD(hist_var_list);
-
-struct hist_var_data {
-	struct list_head list;
-	struct hist_trigger_data *hist_data;
-};
-
 static struct hist_field *check_var_ref(struct hist_field *hist_field,
 					struct hist_trigger_data *var_data,
 					unsigned int var_idx)
@@ -1248,6 +1320,7 @@ static struct hist_field *find_event_var(const char *system,
 struct hist_elt_data {
 	char *comm;
 	u64 *var_ref_vals;
+	char *field_var_str[SYNTH_FIELDS_MAX];
 };
 
 static u64 hist_field_var_ref(struct hist_field *hist_field,
@@ -1415,11 +1488,21 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 
 static int parse_action(char *str, struct hist_trigger_attrs *attrs)
 {
-	int ret = 0;
+	int ret = -EINVAL;
 
 	if (attrs->n_actions >= HIST_ACTIONS_MAX)
 		return ret;
 
+	if ((strncmp(str, "onmatch(", strlen("onmatch(")) == 0)) {
+		attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
+		if (!attrs->action_str[attrs->n_actions]) {
+			ret = -ENOMEM;
+			return ret;
+		}
+		attrs->n_actions++;
+		ret = 0;
+	}
+
 	return ret;
 }
 
@@ -1525,7 +1608,14 @@ static inline void save_comm(char *comm, struct task_struct *task)
 
 static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
 {
+	struct hist_trigger_data *hist_data = elt->map->private_data;
 	struct hist_elt_data *private_data = elt->private_data;
+	unsigned int i, n_str;
+
+	n_str = hist_data->n_field_var_str;
+
+	for (i = 0; i < n_str; i++)
+		kfree(private_data->field_var_str[i]);
 
 	kfree(private_data->comm);
 	kfree(private_data);
@@ -1537,7 +1627,7 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
 	unsigned int size = TASK_COMM_LEN + 1;
 	struct hist_elt_data *elt_data;
 	struct hist_field *key_field;
-	unsigned int i;
+	unsigned int i, n_str;
 
 	elt->private_data = elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
 	if (!elt_data)
@@ -1557,6 +1647,16 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
 		}
 	}
 
+	n_str = hist_data->n_field_var_str;
+
+	for (i = 0; i < n_str; i++) {
+		elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);
+		if (!elt_data->field_var_str[i]) {
+			hist_trigger_elt_data_free(elt);
+			return -ENOMEM;
+		}
+	}
+
 	return 0;
 }
 
@@ -1674,6 +1774,7 @@ static void destroy_hist_field(struct hist_field *hist_field,
 
 	kfree(hist_field->var.name);
 	kfree(hist_field->name);
+	kfree(hist_field->type);
 
 	kfree(hist_field);
 }
@@ -1704,6 +1805,10 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 
 	if (flags & HIST_FIELD_FL_HITCOUNT) {
 		hist_field->fn = hist_field_counter;
+		hist_field->size = sizeof(u64);
+		hist_field->type = kstrdup("u64", GFP_KERNEL);
+		if (!hist_field->type)
+			goto free;
 		goto out;
 	}
 
@@ -1717,12 +1822,18 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 		hist_field->fn = hist_field_log2;
 		hist_field->operands[0] = create_hist_field(hist_data, field, fl, NULL);
 		hist_field->size = hist_field->operands[0]->size;
+		hist_field->type = kstrdup(hist_field->operands[0]->type, GFP_KERNEL);
+		if (!hist_field->type)
+			goto free;
 		goto out;
 	}
 
 	if (flags & HIST_FIELD_FL_TIMESTAMP) {
 		hist_field->fn = hist_field_timestamp;
 		hist_field->size = sizeof(u64);
+		hist_field->type = kstrdup("u64", GFP_KERNEL);
+		if (!hist_field->type)
+			goto free;
 		goto out;
 	}
 
@@ -1731,6 +1842,10 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 
 	if (is_string_field(field)) {
 		flags |= HIST_FIELD_FL_STRING;
+		hist_field->size = MAX_FILTER_STR_VAL;
+		hist_field->type = kstrdup(field->type, GFP_KERNEL);
+		if (!hist_field->type)
+			goto free;
 
 		if (field->filter_type == FILTER_STATIC_STRING)
 			hist_field->fn = hist_field_string;
@@ -1739,6 +1854,12 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 		else
 			hist_field->fn = hist_field_pstring;
 	} else {
+		hist_field->size = field->size;
+		hist_field->is_signed = field->is_signed;
+		hist_field->type = kstrdup(field->type, GFP_KERNEL);
+		if (!hist_field->type)
+			goto free;
+
 		hist_field->fn = select_value_fn(field->size,
 						 field->is_signed);
 		if (!hist_field->fn) {
@@ -1786,7 +1907,10 @@ static struct hist_field *create_var_ref(struct hist_field *var_field)
 		ref_field->size = var_field->size;
 		ref_field->is_signed = var_field->is_signed;
 		ref_field->name = kstrdup(var_field->var.name, GFP_KERNEL);
-		if (!ref_field->name) {
+		ref_field->type = kstrdup(var_field->type, GFP_KERNEL);
+		if (!ref_field->name || !ref_field->type) {
+			kfree(ref_field->name);
+			kfree(ref_field->type);
 			destroy_hist_field(ref_field, 0);
 			return NULL;
 		}
@@ -1970,6 +2094,11 @@ static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
 	expr->operands[0] = operand1;
 	expr->operator = FIELD_OP_UNARY_MINUS;
 	expr->name = expr_str(expr, 0);
+	expr->type = kstrdup(operand1->type, GFP_KERNEL);
+	if (!expr->type) {
+		ret = -ENOMEM;
+		goto free;
+	}
 
 	return expr;
  free:
@@ -2053,6 +2182,11 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
 	expr->operands[1] = operand2;
 	expr->operator = field_op;
 	expr->name = expr_str(expr, 0);
+	expr->type = kstrdup(operand1->type, GFP_KERNEL);
+	if (!expr->type) {
+		ret = -ENOMEM;
+		goto free;
+	}
 
 	switch (field_op) {
 	case FIELD_OP_MINUS:
@@ -2074,6 +2208,718 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
 	return ERR_PTR(ret);
 }
 
+static struct hist_var_data *find_actions(struct hist_trigger_data *hist_data)
+{
+	struct hist_var_data *var_data, *found = NULL;
+
+	list_for_each_entry(var_data, &hist_action_list, list) {
+		if (var_data->hist_data == hist_data) {
+			found = var_data;
+			break;
+		}
+	}
+
+	return found;
+}
+
+static int save_hist_actions(struct hist_trigger_data *hist_data)
+{
+	struct hist_var_data *var_data;
+
+	var_data = find_actions(hist_data);
+	if (var_data)
+		return 0;
+
+	var_data = kzalloc(sizeof(*var_data), GFP_KERNEL);
+	if (!var_data)
+		return -ENOMEM;
+
+	var_data->hist_data = hist_data;
+	list_add(&var_data->list, &hist_action_list);
+
+	return 0;
+}
+
+static void remove_hist_actions(struct hist_trigger_data *hist_data)
+{
+	struct hist_var_data *var_data;
+
+	var_data = find_actions(hist_data);
+	if (!var_data)
+		return;
+
+	list_del(&var_data->list);
+
+	kfree(var_data);
+}
+
+static char *find_trigger_filter(struct hist_trigger_data *hist_data,
+				 struct trace_event_file *file)
+{
+	struct event_trigger_data *test;
+
+	list_for_each_entry_rcu(test, &file->triggers, list) {
+		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			if (test->private_data == hist_data)
+				return test->filter_str;
+		}
+	}
+
+	return NULL;
+}
+
+static struct event_command trigger_hist_cmd;
+static int event_hist_trigger_func(struct event_command *cmd_ops,
+				   struct trace_event_file *file,
+				   char *glob, char *cmd, char *param);
+
+static bool compatible_keys(struct hist_trigger_data *target_hist_data,
+			    struct hist_trigger_data *hist_data,
+			    unsigned int n_keys)
+{
+	struct hist_field *target_hist_field, *hist_field;
+	unsigned int n, i, j;
+
+	if (hist_data->n_fields - hist_data->n_vals != n_keys)
+		return false;
+
+	i = hist_data->n_vals;
+	j = target_hist_data->n_vals;
+
+	for (n = 0; n < n_keys; n++) {
+		hist_field = hist_data->fields[i + n];
+		target_hist_field = hist_data->fields[j + n];
+
+		if (strcmp(hist_field->type, target_hist_field->type) != 0)
+			return false;
+		if (hist_field->size != target_hist_field->size)
+			return false;
+		if (hist_field->is_signed != target_hist_field->is_signed)
+			return false;
+	}
+
+	return true;
+}
+
+static struct hist_trigger_data *
+find_compatible_hist(struct hist_trigger_data *target_hist_data,
+		     struct trace_event_file *file)
+{
+	struct hist_trigger_data *hist_data;
+	struct event_trigger_data *test;
+	unsigned int n_keys;
+
+	n_keys = target_hist_data->n_fields - target_hist_data->n_vals;
+
+	list_for_each_entry_rcu(test, &file->triggers, list) {
+		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			hist_data = test->private_data;
+
+			if (compatible_keys(target_hist_data, hist_data, n_keys))
+				return hist_data;
+		}
+	}
+
+	return NULL;
+}
+
+static struct trace_event_file *event_file(char *system, char *event_name)
+{
+	struct trace_event_file *file;
+	struct trace_array *tr;
+
+	tr = top_trace_array();
+	if (!tr)
+		return ERR_PTR(-ENODEV);
+
+	file = find_event_file(tr, system, event_name);
+	if (!file)
+		return ERR_PTR(-EINVAL);
+
+	return file;
+}
+
+static struct hist_field *
+create_field_var_hist(struct hist_trigger_data *target_hist_data,
+		      char *system, char *event_name, char *field_name)
+{
+	struct hist_field *event_var = ERR_PTR(-EINVAL);
+	struct hist_trigger_data *hist_data;
+	unsigned int i, n, first = true;
+	struct field_var_hist *var_hist;
+	struct trace_event_file *file;
+	struct hist_field *key_field;
+	struct trace_array *tr;
+	char *saved_filter;
+	char *cmd;
+	int ret;
+
+	if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX)
+		return ERR_PTR(-EINVAL);
+
+	tr = top_trace_array();
+	if (!tr)
+		return ERR_PTR(-ENODEV);
+
+	file = event_file(system, event_name);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		return ERR_PTR(ret);
+	}
+
+	hist_data = find_compatible_hist(target_hist_data, file);
+	if (!hist_data)
+		return ERR_PTR(-EINVAL);
+
+	var_hist = kzalloc(sizeof(*var_hist), GFP_KERNEL);
+	if (!var_hist)
+		return ERR_PTR(-ENOMEM);
+
+	cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
+	if (!cmd) {
+		kfree(var_hist);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	strcat(cmd, "keys=");
+
+	for_each_hist_key_field(i, hist_data) {
+		key_field = hist_data->fields[i];
+		if (!first)
+			strcat(cmd, ",");
+		strcat(cmd, key_field->field->name);
+		first = false;
+	}
+
+	strcat(cmd, ":synthetic_");
+	strcat(cmd, field_name);
+	strcat(cmd, "=");
+	strcat(cmd, field_name);
+
+	saved_filter = find_trigger_filter(hist_data, file);
+	if (saved_filter) {
+		strcat(cmd, " if ");
+		strcat(cmd, saved_filter);
+	}
+
+	var_hist->cmd = kstrdup(cmd, GFP_KERNEL);
+	if (!var_hist->cmd) {
+		kfree(cmd);
+		kfree(var_hist);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	var_hist->hist_data = hist_data;
+
+	ret = event_hist_trigger_func(&trigger_hist_cmd, file,
+				      "", "hist", cmd);
+	if (ret) {
+		kfree(cmd);
+		kfree(var_hist->cmd);
+		kfree(var_hist);
+		return ERR_PTR(ret);
+	}
+
+	strcpy(cmd, "synthetic_");
+	strcat(cmd, field_name);
+
+	event_var = find_event_var(system, event_name, cmd);
+	if (!event_var) {
+		kfree(cmd);
+		kfree(var_hist->cmd);
+		kfree(var_hist);
+		return ERR_PTR(-EINVAL);
+	}
+
+	n = target_hist_data->n_field_var_hists;
+	target_hist_data->field_var_hists[n] = var_hist;
+	target_hist_data->n_field_var_hists++;
+
+	return event_var;
+}
+
+static struct hist_field *
+find_target_event_var(struct hist_trigger_data *hist_data,
+		      char *system, char *event_name, char *var_name)
+{
+	struct trace_event_file *file = hist_data->event_file;
+	struct hist_field *hist_field = NULL;
+
+	if (system) {
+		struct trace_event_call *call;
+
+		if (!event_name)
+			return NULL;
+
+		call = file->event_call;
+
+		if (strcmp(system, call->class->system) != 0)
+			return NULL;
+
+		if (strcmp(event_name, trace_event_name(call)) != 0)
+			return NULL;
+	}
+
+	hist_field = find_var_field(hist_data, var_name);
+
+	return hist_field;
+}
+
+static inline void __update_field_vars(struct tracing_map_elt *elt,
+				       struct ring_buffer_event *rbe,
+				       void *rec,
+				       struct field_var **field_vars,
+				       unsigned int n_field_vars,
+				       unsigned int field_var_str_start)
+{
+	struct hist_elt_data *elt_data = elt->private_data;
+	unsigned int i, j, var_idx;
+	u64 var_val;
+
+	for (i = 0, j = field_var_str_start; i < n_field_vars; i++) {
+		struct field_var *field_var = field_vars[i];
+		struct hist_field *var = field_var->var;
+		struct hist_field *val = field_var->val;
+
+		var_val = val->fn(val, elt, rbe, rec);
+		var_idx = var->var.idx;
+
+		if (val->flags & HIST_FIELD_FL_STRING) {
+			char *str = elt_data->field_var_str[j++];
+
+			memcpy(str, (char *)(uintptr_t)var_val,
+			       TASK_COMM_LEN + 1);
+			var_val = (u64)(uintptr_t)str;
+		}
+		tracing_map_set_var(elt, var_idx, var_val);
+	}
+}
+
+static void update_field_vars(struct hist_trigger_data *hist_data,
+			      struct tracing_map_elt *elt,
+			      struct ring_buffer_event *rbe,
+			      void *rec)
+{
+	__update_field_vars(elt, rbe, rec, hist_data->field_vars,
+			    hist_data->n_field_vars, 0);
+}
+
+static struct hist_field *create_var(struct hist_trigger_data *hist_data,
+				     struct trace_event_file *file,
+				     char *name, int size, const char *type)
+{
+	struct hist_field *var;
+	int idx;
+
+	if (find_var(file, name) && !hist_data->remove) {
+		var = ERR_PTR(-EINVAL);
+		goto out;
+	}
+
+	var = kzalloc(sizeof(struct hist_field), GFP_KERNEL);
+	if (!var) {
+		var = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	idx = tracing_map_add_var(hist_data->map);
+	if (idx < 0) {
+		kfree(var);
+		var = ERR_PTR(-EINVAL);
+		goto out;
+	}
+
+	var->flags = HIST_FIELD_FL_VAR;
+	var->var.idx = idx;
+	var->var.hist_data = var->hist_data = hist_data;
+	var->size = size;
+	var->var.name = kstrdup(name, GFP_KERNEL);
+	var->type = kstrdup(type, GFP_KERNEL);
+	if (!var->var.name || !var->type) {
+		kfree(var->var.name);
+		kfree(var->type);
+		kfree(var);
+		var = ERR_PTR(-ENOMEM);
+	}
+ out:
+	return var;
+}
+
+static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
+					  struct trace_event_file *file,
+					  char *field_name)
+{
+	struct hist_field *val = NULL, *var = NULL;
+	unsigned long flags = HIST_FIELD_FL_VAR;
+	struct field_var *field_var;
+	int ret = 0;
+
+	if (hist_data->n_field_vars >= SYNTH_FIELDS_MAX) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	val = parse_atom(hist_data, file, field_name, &flags, NULL);
+	if (IS_ERR(val)) {
+		ret = PTR_ERR(val);
+		goto err;
+	}
+
+	var = create_var(hist_data, file, field_name, val->size, val->type);
+	if (IS_ERR(var)) {
+		kfree(val);
+		ret = PTR_ERR(var);
+		goto err;
+	}
+
+	field_var = kzalloc(sizeof(struct field_var), GFP_KERNEL);
+	if (!field_var) {
+		kfree(val);
+		kfree(var);
+		ret =  -ENOMEM;
+		goto err;
+	}
+
+	field_var->var = var;
+	field_var->val = val;
+ out:
+	return field_var;
+ err:
+	field_var = ERR_PTR(ret);
+	goto out;
+}
+
+static struct field_var *
+create_target_field_var(struct hist_trigger_data *hist_data,
+			char *system, char *event_name, char *var_name)
+{
+	struct trace_event_file *file = hist_data->event_file;
+
+	if (system) {
+		struct trace_event_call *call;
+
+		if (!event_name)
+			return NULL;
+
+		call = file->event_call;
+
+		if (strcmp(system, call->class->system) != 0)
+			return NULL;
+
+		if (strcmp(event_name, trace_event_name(call)) != 0)
+			return NULL;
+	}
+
+	return create_field_var(hist_data, file, var_name);
+}
+
+static void onmatch_destroy(struct action_data *data)
+{
+	unsigned int i;
+
+	kfree(data->match_event);
+	kfree(data->match_event_system);
+	kfree(data->synth_event_name);
+
+	for (i = 0; i < data->n_params; i++)
+		kfree(data->params[i]);
+
+	kfree(data);
+}
+
+static void destroy_field_var(struct field_var *field_var)
+{
+	if (!field_var)
+		return;
+
+	destroy_hist_field(field_var->var, 0);
+	destroy_hist_field(field_var->val, 0);
+
+	kfree(field_var);
+}
+
+static void destroy_field_vars(struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_field_vars; i++)
+		destroy_field_var(hist_data->field_vars[i]);
+}
+
+static void save_field_var(struct hist_trigger_data *hist_data,
+			   struct field_var *field_var)
+{
+	hist_data->field_vars[hist_data->n_field_vars++] = field_var;
+
+	if (field_var->val->flags & HIST_FIELD_FL_STRING)
+		hist_data->n_field_var_str++;
+}
+
+static void destroy_synth_var_refs(struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_synth_var_refs; i++)
+		destroy_hist_field(hist_data->synth_var_refs[i], 0);
+}
+
+static void save_synth_var_ref(struct hist_trigger_data *hist_data,
+			 struct hist_field *var_ref)
+{
+	hist_data->synth_var_refs[hist_data->n_synth_var_refs++] = var_ref;
+
+	hist_data->var_refs[hist_data->n_var_refs] = var_ref;
+	var_ref->var_ref_idx = hist_data->n_var_refs++;
+}
+
+static int check_synth_field(struct synth_event *event,
+			     struct hist_field *hist_field,
+			     unsigned int field_pos)
+{
+	struct synth_field *field;
+
+	if (field_pos >= event->n_fields)
+		return -EINVAL;
+
+	field = event->fields[field_pos];
+
+	if (strcmp(field->type, hist_field->type) != 0)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int parse_action_params(char *params, struct action_data *data)
+{
+	char *param, *saved_param;
+	int ret = 0;
+
+	while (params) {
+		if (data->n_params >= SYNTH_FIELDS_MAX)
+			goto out;
+
+		param = strsep(&params, ",");
+		if (!param)
+			goto out;
+
+		param = strstrip(param);
+		if (strlen(param) < 2) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		saved_param = kstrdup(param, GFP_KERNEL);
+		if (!saved_param) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		data->params[data->n_params++] = saved_param;
+	}
+ out:
+	return ret;
+}
+
+static struct hist_field *
+onmatch_find_var(struct hist_trigger_data *hist_data, struct action_data *data,
+		 char *system, char *event, char *var)
+{
+	struct hist_field *hist_field;
+
+	var++; /* skip '$' */
+
+	hist_field = find_target_event_var(hist_data, system, event, var);
+	if (!hist_field) {
+		if (!system) {
+			system = data->match_event_system;
+			event = data->match_event;
+		}
+
+		hist_field = find_event_var(system, event, var);
+	}
+
+	return hist_field;
+}
+
+static struct hist_field *
+onmatch_create_field_var(struct hist_trigger_data *hist_data,
+			 struct action_data *data, char *system,
+			 char *event, char *var)
+{
+	struct hist_field *hist_field = NULL;
+	struct field_var *field_var;
+
+	field_var = create_target_field_var(hist_data, system, event, var);
+	if (IS_ERR(field_var))
+		goto out;
+
+	if (field_var) {
+		save_field_var(hist_data, field_var);
+		hist_field = field_var->var;
+	} else {
+		if (!system) {
+			system = data->match_event_system;
+			event = data->match_event;
+		}
+
+		hist_field = create_field_var_hist(hist_data, system, event, var);
+		if (IS_ERR(hist_field))
+			goto free;
+	}
+ out:
+	return hist_field;
+ free:
+	destroy_field_var(field_var);
+	hist_field = NULL;
+	goto out;
+}
+
+static int onmatch_create(struct hist_trigger_data *hist_data,
+			  struct trace_event_file *file,
+			  struct action_data *data)
+{
+	char *event_name, *param, *system = NULL;
+	struct hist_field *hist_field, *var_ref;
+	unsigned int i, var_ref_idx;
+	unsigned int field_pos = 0;
+	struct synth_event *event;
+	int ret = 0;
+
+	mutex_lock(&synth_event_mutex);
+
+	event = find_synth_event(data->synth_event_name);
+	if (!event) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	var_ref_idx = hist_data->n_var_refs;
+
+	for (i = 0; i < data->n_params; i++) {
+		char *p;
+
+		p = param = kstrdup(data->params[i], GFP_KERNEL);
+		if (!param)
+			goto out;
+
+		system = strsep(&param, ".");
+		if (!param) {
+			param = (char *)system;
+			system = event_name = NULL;
+		} else {
+			event_name = strsep(&param, ".");
+			if (!param) {
+				kfree(p);
+				ret = -EINVAL;
+				goto out;
+			}
+		}
+
+		if (param[0] == '$')
+			hist_field = onmatch_find_var(hist_data, data, system,
+						      event_name, param);
+		else
+			hist_field = onmatch_create_field_var(hist_data, data,
+							      system,
+							      event_name,
+							      param);
+
+		if (!hist_field) {
+			kfree(p);
+			ret = -EINVAL;
+			goto out;
+		}
+
+		if (check_synth_field(event, hist_field, field_pos) == 0) {
+			var_ref = create_var_ref(hist_field);
+			if (!var_ref) {
+				kfree(p);
+				ret = -ENOMEM;
+				goto out;
+			}
+
+			save_synth_var_ref(hist_data, var_ref);
+			field_pos++;
+			kfree(p);
+			continue;
+		}
+
+		kfree(p);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (field_pos != event->n_fields) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	data->fn = action_trace;
+	data->synth_event = event;
+	data->var_ref_idx = var_ref_idx;
+	hist_data->actions[hist_data->n_actions++] = data;
+	save_hist_actions(hist_data);
+ out:
+	mutex_unlock(&synth_event_mutex);
+
+	return ret;
+}
+
+static struct action_data *onmatch_parse(char *str)
+{
+	char *match_event, *match_event_system;
+	char *synth_event_name, *params;
+	struct action_data *data;
+	int ret = -EINVAL;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return ERR_PTR(-ENOMEM);
+
+	match_event = strsep(&str, ")");
+	if (!match_event || !str)
+		goto free;
+
+	match_event_system = strsep(&match_event, ".");
+	if (!match_event)
+		goto free;
+
+	if (IS_ERR(event_file(match_event_system, match_event)))
+		goto free;
+
+	data->match_event = kstrdup(match_event, GFP_KERNEL);
+	data->match_event_system = kstrdup(match_event_system, GFP_KERNEL);
+
+	strsep(&str, ".");
+	if (!str)
+		goto free;
+
+	synth_event_name = strsep(&str, "(");
+	if (!synth_event_name || !str)
+		goto free;
+	data->synth_event_name = kstrdup(synth_event_name, GFP_KERNEL);
+
+	params = strsep(&str, ")");
+	if (!params || !str || (str && strlen(str)))
+		goto free;
+
+	ret = parse_action_params(params, data);
+	if (ret)
+		goto free;
+
+	if (!data->match_event_system || !data->match_event ||
+	    !data->synth_event_name) {
+		ret = -ENOMEM;
+		goto free;
+	}
+ out:
+	return data;
+ free:
+	onmatch_destroy(data);
+	data = ERR_PTR(ret);
+	goto out;
+}
+
 static int create_hitcount_val(struct hist_trigger_data *hist_data)
 {
 	hist_data->fields[HITCOUNT_IDX] =
@@ -2465,19 +3311,37 @@ static void destroy_actions(struct hist_trigger_data *hist_data)
 	for (i = 0; i < hist_data->n_actions; i++) {
 		struct action_data *data = hist_data->actions[i];
 
-		kfree(data);
+		if (data->fn == action_trace)
+			onmatch_destroy(data);
+		else
+			kfree(data);
 	}
 }
 
 static int create_actions(struct hist_trigger_data *hist_data,
 			  struct trace_event_file *file)
 {
+	struct action_data *data;
 	unsigned int i;
 	int ret = 0;
 	char *str;
 
 	for (i = 0; i < hist_data->attrs->n_actions; i++) {
 		str = hist_data->attrs->action_str[i];
+
+		if (strncmp(str, "onmatch(", strlen("onmatch(")) == 0) {
+			char *action_str = str + strlen("onmatch(");
+
+			data = onmatch_parse(action_str);
+			if (IS_ERR(data))
+				return PTR_ERR(data);
+
+			ret = onmatch_create(hist_data, file, data);
+			if (ret) {
+				onmatch_destroy(data);
+				return ret;
+			}
+		}
 	}
 
 	return ret;
@@ -2494,6 +3358,26 @@ static void print_actions(struct seq_file *m,
 	}
 }
 
+static void print_onmatch_spec(struct seq_file *m,
+			       struct hist_trigger_data *hist_data,
+			       struct action_data *data)
+{
+	unsigned int i;
+
+	seq_printf(m, ":onmatch(%s.%s).", data->match_event_system,
+		   data->match_event);
+
+	seq_printf(m, "%s(", data->synth_event->name);
+
+	for (i = 0; i < data->n_params; i++) {
+		if (i)
+			seq_puts(m, ",");
+		seq_printf(m, "%s", data->params[i]);
+	}
+
+	seq_puts(m, ")");
+}
+
 static void print_actions_spec(struct seq_file *m,
 			       struct hist_trigger_data *hist_data)
 {
@@ -2501,6 +3385,19 @@ static void print_actions_spec(struct seq_file *m,
 
 	for (i = 0; i < hist_data->n_actions; i++) {
 		struct action_data *data = hist_data->actions[i];
+
+		if (data->fn == action_trace)
+			print_onmatch_spec(m, hist_data, data);
+	}
+}
+
+static void destroy_field_var_hists(struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_field_var_hists; i++) {
+		kfree(hist_data->field_var_hists[i]->cmd);
+		kfree(hist_data->field_var_hists[i]);
 	}
 }
 
@@ -2514,6 +3411,9 @@ static void destroy_hist_data(struct hist_trigger_data *hist_data)
 	tracing_map_destroy(hist_data->map);
 
 	destroy_actions(hist_data);
+	destroy_field_vars(hist_data);
+	destroy_field_var_hists(hist_data);
+	destroy_synth_var_refs(hist_data);
 
 	kfree(hist_data);
 }
@@ -2648,6 +3548,8 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
 			tracing_map_set_var(elt, var_idx, hist_val);
 		}
 	}
+
+	update_field_vars(hist_data, elt, rbe, rec);
 }
 
 static inline void add_to_key(char *compound_key, void *key,
@@ -2861,6 +3763,8 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 		}
 	}
 
+	print_actions(m, hist_data, elt);
+
 	seq_puts(m, "\n");
 }
 
@@ -3128,6 +4032,8 @@ static void event_hist_trigger_free(struct event_trigger_ops *ops,
 
 		remove_hist_vars(hist_data);
 
+		remove_hist_actions(hist_data);
+
 		destroy_hist_data(hist_data);
 	}
 }
@@ -3390,6 +4296,21 @@ static bool hist_trigger_check_refs(struct event_trigger_data *data,
 	return false;
 }
 
+static void unregister_field_var_hists(struct hist_trigger_data *hist_data)
+{
+	struct trace_event_file *file;
+	unsigned int i;
+	char *cmd;
+	int ret;
+
+	for (i = 0; i < hist_data->n_field_var_hists; i++) {
+		file = hist_data->field_var_hists[i]->hist_data->event_file;
+		cmd = hist_data->field_var_hists[i]->cmd;
+		ret = event_hist_trigger_func(&trigger_hist_cmd, file,
+					      "!hist", "hist", cmd);
+	}
+}
+
 static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
 				    struct event_trigger_data *data,
 				    struct trace_event_file *file)
@@ -3405,6 +4326,7 @@ static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
 		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
 			if (!hist_trigger_match(data, test, named_data, false))
 				continue;
+			unregister_field_var_hists(test->private_data);
 			unregistered = true;
 			list_del_rcu(&test->list);
 			trace_event_trigger_enable_disable(file, 0);
@@ -3448,6 +4370,7 @@ static void hist_unreg_all(struct trace_event_file *file)
 
 	list_for_each_entry_safe(test, n, &file->triggers, list) {
 		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			unregister_field_var_hists(test->private_data);
 			list_del_rcu(&test->list);
 			trace_event_trigger_enable_disable(file, 0);
 			update_cond_flag(file);
@@ -3571,6 +4494,8 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 
 	remove_hist_vars(hist_data);
 
+	remove_hist_actions(hist_data);
+
 	kfree(trigger_data);
 	destroy_hist_data(hist_data);
 
-- 
1.9.3

Re: [PATCH 23/32] tracing: Add 'onmatch' hist trigger action support

[Namhyung Kim]

On Mon, Jun 26, 2017 at 05:49:24PM -0500, Tom Zanussi wrote:
> Add an 'onmatch(matching.event).<synthetic_event_name>(param list)'
> hist trigger action which is invoked with the set of variables or
> event fields named in the 'param list'.  The result is the generation
> of a synthetic event that consists of the values contained in those
> variables and/or fields at the time the invoking event was hit.
> 
> As an example the below defines a simple synthetic event using a
> variable defined on the sched_wakeup_new event, and shows the event
> definition with unresolved fields, since the sched_wakeup_new event
> with the testpid variable hasn't been defined yet:
> 
>     # echo 'wakeup_new_test pid_t pid; int prio' >> \
>       /sys/kernel/debug/tracing/synthetic_events
> 
>     # cat /sys/kernel/debug/tracing/synthetic_events
>       wakeup_new_test pid_t pid; int prio
> 
> The following hist trigger both defines a testpid variable and
> specifies an onmatch() trace action that uses that variable along with
> a non-variable field to generate a wakeup_new_test synthetic event
> whenever a sched_wakeup_new event occurs, which because of the 'if
> comm == "cyclictest"' filter only happens when the executable is
> cyclictest:
> 
>     # echo 'hist:keys=testpid=pid:\
>       onmatch(sched.sched_wakeup_new).wakeup_new_test($testpid, prio) \
>         if comm=="cyclictest"' >> \
>       /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
> 
> Creating and displaying a histogram based on those events is now just
> a matter of using the fields and new synthetic event in the
> tracing/events/synthetic directory, as usual:
> 
>     # echo 'hist:keys=pid,prio:sort=pid,prio' >> \
>       /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---

This patch is also big and it'd be better splitting - add type to
hist_field, add variable handling and implement onmatch() action.


>  kernel/trace/trace_events_hist.c | 955 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 940 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index e11b3a3..b1f859c 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -59,6 +59,7 @@ struct hist_field {
>  	unsigned int			size;
>  	unsigned int			offset;
>  	unsigned int                    is_signed;
> +	const char			*type;
>  	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
>  	struct hist_trigger_data	*hist_data;
>  	struct hist_var			var;
> @@ -243,6 +244,16 @@ struct hist_trigger_attrs {
>  	unsigned int	n_actions;
>  };
>  
> +struct field_var {
> +	struct hist_field	*var;
> +	struct hist_field	*val;
> +};
> +
> +struct field_var_hist {
> +	struct hist_trigger_data	*hist_data;
> +	char				*cmd;
> +};
> +
>  struct hist_trigger_data {
>  	struct hist_field               *fields[HIST_FIELDS_MAX];
>  	unsigned int			n_vals;
> @@ -263,6 +274,14 @@ struct hist_trigger_data {
>  
>  	struct action_data		*actions[HIST_ACTIONS_MAX];
>  	unsigned int			n_actions;
> +
> +	struct hist_field		*synth_var_refs[SYNTH_FIELDS_MAX];
> +	unsigned int			n_synth_var_refs;
> +	struct field_var		*field_vars[SYNTH_FIELDS_MAX];
> +	unsigned int			n_field_vars;
> +	unsigned int			n_field_var_str;
> +	struct field_var_hist		*field_var_hists[SYNTH_FIELDS_MAX];
> +	unsigned int			n_field_var_hists;
>  };
>  
>  struct synth_field {
> @@ -291,7 +310,14 @@ typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
>  
>  struct action_data {
>  	action_fn_t		fn;
> +	unsigned int		n_params;
> +	char			*params[SYNTH_FIELDS_MAX];
> +
>  	unsigned int		var_ref_idx;
> +	char			*match_event;
> +	char			*match_event_system;
> +	char			*synth_event_name;
> +	struct synth_event	*synth_event;
>  };
>  
>  static LIST_HEAD(synth_event_list);
> @@ -802,6 +828,50 @@ static struct synth_event *alloc_synth_event(char *event_name, int n_fields,
>  	return event;
>  }
>  
> +static void action_trace(struct hist_trigger_data *hist_data,
> +			 struct tracing_map_elt *elt, void *rec,
> +			 struct ring_buffer_event *rbe,
> +			 struct action_data *data, u64 *var_ref_vals)
> +{
> +	struct synth_event *event = data->synth_event;
> +
> +	trace_synth(event, var_ref_vals, data->var_ref_idx);
> +}
> +
> +static bool check_hist_action_refs(struct hist_trigger_data *hist_data,
> +				   struct synth_event *event)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < hist_data->n_actions; i++) {
> +		struct action_data *data = hist_data->actions[i];
> +
> +		if (data->fn == action_trace && data->synth_event == event)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +static LIST_HEAD(hist_action_list);
> +static LIST_HEAD(hist_var_list);
> +
> +struct hist_var_data {
> +	struct list_head list;
> +	struct hist_trigger_data *hist_data;
> +};
> +
> +static bool check_synth_action_refs(struct synth_event *event)
> +{
> +	struct hist_var_data *var_data;
> +
> +	list_for_each_entry(var_data, &hist_action_list, list)
> +		if (check_hist_action_refs(var_data->hist_data, event))
> +			return true;
> +
> +	return false;
> +}
> +
>  static int create_synth_event(int argc, char **argv)
>  {
>  	struct synth_field *fields[SYNTH_FIELDS_MAX];
> @@ -832,15 +902,17 @@ static int create_synth_event(int argc, char **argv)
>  	event = find_synth_event(name);
>  	if (event) {
>  		if (delete_event) {
> +			if (check_synth_action_refs(event)) {
> +				ret = -EBUSY;
> +				goto out;
> +			}
>  			remove_synth_event(event);
>  			goto err;
>  		} else
>  			ret = -EEXIST;
>  		goto out;
> -	} else if (delete_event) {
> -		ret = -EINVAL;
> +	} else if (delete_event)
>  		goto out;
> -	}

Why is it changed?

Thanks,
Namhyung


>  
>  	if (argc < 2) {
>  		ret = -EINVAL;

Re: [PATCH 23/32] tracing: Add 'onmatch' hist trigger action support

[Tom Zanussi]

Hi Namhyung,

On Mon, 2017-07-24 at 00:12 +0900, Namhyung Kim wrote:
> On Mon, Jun 26, 2017 at 05:49:24PM -0500, Tom Zanussi wrote:
> > Add an 'onmatch(matching.event).<synthetic_event_name>(param list)'
> > hist trigger action which is invoked with the set of variables or
> > event fields named in the 'param list'.  The result is the generation
> > of a synthetic event that consists of the values contained in those
> > variables and/or fields at the time the invoking event was hit.
> > 
> > As an example the below defines a simple synthetic event using a
> > variable defined on the sched_wakeup_new event, and shows the event
> > definition with unresolved fields, since the sched_wakeup_new event
> > with the testpid variable hasn't been defined yet:
> > 
> >     # echo 'wakeup_new_test pid_t pid; int prio' >> \
> >       /sys/kernel/debug/tracing/synthetic_events
> > 
> >     # cat /sys/kernel/debug/tracing/synthetic_events
> >       wakeup_new_test pid_t pid; int prio
> > 
> > The following hist trigger both defines a testpid variable and
> > specifies an onmatch() trace action that uses that variable along with
> > a non-variable field to generate a wakeup_new_test synthetic event
> > whenever a sched_wakeup_new event occurs, which because of the 'if
> > comm == "cyclictest"' filter only happens when the executable is
> > cyclictest:
> > 
> >     # echo 'hist:keys=testpid=pid:\
> >       onmatch(sched.sched_wakeup_new).wakeup_new_test($testpid, prio) \
> >         if comm=="cyclictest"' >> \
> >       /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
> > 
> > Creating and displaying a histogram based on those events is now just
> > a matter of using the fields and new synthetic event in the
> > tracing/events/synthetic directory, as usual:
> > 
> >     # echo 'hist:keys=pid,prio:sort=pid,prio' >> \
> >       /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> 
> This patch is also big and it'd be better splitting - add type to
> hist_field, add variable handling and implement onmatch() action.
> 

Yeah, makes sense, will do.

> 
> >  kernel/trace/trace_events_hist.c | 955 ++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 940 insertions(+), 15 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index e11b3a3..b1f859c 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> > @@ -59,6 +59,7 @@ struct hist_field {
> >  	unsigned int			size;
> >  	unsigned int			offset;
> >  	unsigned int                    is_signed;
> > +	const char			*type;
> >  	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
> >  	struct hist_trigger_data	*hist_data;
> >  	struct hist_var			var;
> > @@ -243,6 +244,16 @@ struct hist_trigger_attrs {
> >  	unsigned int	n_actions;
> >  };
> >  
> > +struct field_var {
> > +	struct hist_field	*var;
> > +	struct hist_field	*val;
> > +};
> > +
> > +struct field_var_hist {
> > +	struct hist_trigger_data	*hist_data;
> > +	char				*cmd;
> > +};
> > +
> >  struct hist_trigger_data {
> >  	struct hist_field               *fields[HIST_FIELDS_MAX];
> >  	unsigned int			n_vals;
> > @@ -263,6 +274,14 @@ struct hist_trigger_data {
> >  
> >  	struct action_data		*actions[HIST_ACTIONS_MAX];
> >  	unsigned int			n_actions;
> > +
> > +	struct hist_field		*synth_var_refs[SYNTH_FIELDS_MAX];
> > +	unsigned int			n_synth_var_refs;
> > +	struct field_var		*field_vars[SYNTH_FIELDS_MAX];
> > +	unsigned int			n_field_vars;
> > +	unsigned int			n_field_var_str;
> > +	struct field_var_hist		*field_var_hists[SYNTH_FIELDS_MAX];
> > +	unsigned int			n_field_var_hists;
> >  };
> >  
> >  struct synth_field {
> > @@ -291,7 +310,14 @@ typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
> >  
> >  struct action_data {
> >  	action_fn_t		fn;
> > +	unsigned int		n_params;
> > +	char			*params[SYNTH_FIELDS_MAX];
> > +
> >  	unsigned int		var_ref_idx;
> > +	char			*match_event;
> > +	char			*match_event_system;
> > +	char			*synth_event_name;
> > +	struct synth_event	*synth_event;
> >  };
> >  
> >  static LIST_HEAD(synth_event_list);
> > @@ -802,6 +828,50 @@ static struct synth_event *alloc_synth_event(char *event_name, int n_fields,
> >  	return event;
> >  }
> >  
> > +static void action_trace(struct hist_trigger_data *hist_data,
> > +			 struct tracing_map_elt *elt, void *rec,
> > +			 struct ring_buffer_event *rbe,
> > +			 struct action_data *data, u64 *var_ref_vals)
> > +{
> > +	struct synth_event *event = data->synth_event;
> > +
> > +	trace_synth(event, var_ref_vals, data->var_ref_idx);
> > +}
> > +
> > +static bool check_hist_action_refs(struct hist_trigger_data *hist_data,
> > +				   struct synth_event *event)
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < hist_data->n_actions; i++) {
> > +		struct action_data *data = hist_data->actions[i];
> > +
> > +		if (data->fn == action_trace && data->synth_event == event)
> > +			return true;
> > +	}
> > +
> > +	return false;
> > +}
> > +
> > +static LIST_HEAD(hist_action_list);
> > +static LIST_HEAD(hist_var_list);
> > +
> > +struct hist_var_data {
> > +	struct list_head list;
> > +	struct hist_trigger_data *hist_data;
> > +};
> > +
> > +static bool check_synth_action_refs(struct synth_event *event)
> > +{
> > +	struct hist_var_data *var_data;
> > +
> > +	list_for_each_entry(var_data, &hist_action_list, list)
> > +		if (check_hist_action_refs(var_data->hist_data, event))
> > +			return true;
> > +
> > +	return false;
> > +}
> > +
> >  static int create_synth_event(int argc, char **argv)
> >  {
> >  	struct synth_field *fields[SYNTH_FIELDS_MAX];
> > @@ -832,15 +902,17 @@ static int create_synth_event(int argc, char **argv)
> >  	event = find_synth_event(name);
> >  	if (event) {
> >  		if (delete_event) {
> > +			if (check_synth_action_refs(event)) {
> > +				ret = -EBUSY;
> > +				goto out;
> > +			}
> >  			remove_synth_event(event);
> >  			goto err;
> >  		} else
> >  			ret = -EEXIST;
> >  		goto out;
> > -	} else if (delete_event) {
> > -		ret = -EINVAL;
> > +	} else if (delete_event)
> >  		goto out;
> > -	}
> 
> Why is it changed?
> 

Yeah, shouldn't have been, thanks for pointing this out.

Tom

Re: [PATCH 23/32] tracing: Add 'onmatch' hist trigger action support

[Namhyung Kim]

Hi Tom,

On Mon, Jun 26, 2017 at 05:49:24PM -0500, Tom Zanussi wrote:
> Add an 'onmatch(matching.event).<synthetic_event_name>(param list)'
> hist trigger action which is invoked with the set of variables or
> event fields named in the 'param list'.  The result is the generation
> of a synthetic event that consists of the values contained in those
> variables and/or fields at the time the invoking event was hit.
> 
> As an example the below defines a simple synthetic event using a
> variable defined on the sched_wakeup_new event, and shows the event
> definition with unresolved fields, since the sched_wakeup_new event
> with the testpid variable hasn't been defined yet:
> 
>     # echo 'wakeup_new_test pid_t pid; int prio' >> \
>       /sys/kernel/debug/tracing/synthetic_events
> 
>     # cat /sys/kernel/debug/tracing/synthetic_events
>       wakeup_new_test pid_t pid; int prio
> 
> The following hist trigger both defines a testpid variable and
> specifies an onmatch() trace action that uses that variable along with
> a non-variable field to generate a wakeup_new_test synthetic event
> whenever a sched_wakeup_new event occurs, which because of the 'if
> comm == "cyclictest"' filter only happens when the executable is
> cyclictest:
> 
>     # echo 'hist:keys=testpid=pid:\
>       onmatch(sched.sched_wakeup_new).wakeup_new_test($testpid, prio) \
>         if comm=="cyclictest"' >> \
>       /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
> 
> Creating and displaying a histogram based on those events is now just
> a matter of using the fields and new synthetic event in the
> tracing/events/synthetic directory, as usual:
> 
>     # echo 'hist:keys=pid,prio:sort=pid,prio' >> \
>       /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---

[SNIP]
>  static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
>  {
> +	struct hist_trigger_data *hist_data = elt->map->private_data;
>  	struct hist_elt_data *private_data = elt->private_data;
> +	unsigned int i, n_str;
> +
> +	n_str = hist_data->n_field_var_str;
> +
> +	for (i = 0; i < n_str; i++)
> +		kfree(private_data->field_var_str[i]);
>  
>  	kfree(private_data->comm);
>  	kfree(private_data);
> @@ -1537,7 +1627,7 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
>  	unsigned int size = TASK_COMM_LEN + 1;
>  	struct hist_elt_data *elt_data;
>  	struct hist_field *key_field;
> -	unsigned int i;
> +	unsigned int i, n_str;
>  
>  	elt->private_data = elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
>  	if (!elt_data)
> @@ -1557,6 +1647,16 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
>  		}
>  	}
>  
> +	n_str = hist_data->n_field_var_str;
> +
> +	for (i = 0; i < n_str; i++) {
> +		elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);

So the max length of a string variable is TASK_COMM_LEN, right?

In addition, isn't it necessary for hist_trigger_elt_data_copy() to
copy the field_var_str array?


> +		if (!elt_data->field_var_str[i]) {
> +			hist_trigger_elt_data_free(elt);
> +			return -ENOMEM;
> +		}
> +	}
> +
>  	return 0;
>  }

[SNIP]
> +static bool compatible_keys(struct hist_trigger_data *target_hist_data,
> +			    struct hist_trigger_data *hist_data,
> +			    unsigned int n_keys)
> +{
> +	struct hist_field *target_hist_field, *hist_field;
> +	unsigned int n, i, j;
> +
> +	if (hist_data->n_fields - hist_data->n_vals != n_keys)
> +		return false;
> +
> +	i = hist_data->n_vals;
> +	j = target_hist_data->n_vals;
> +
> +	for (n = 0; n < n_keys; n++) {
> +		hist_field = hist_data->fields[i + n];
> +		target_hist_field = hist_data->fields[j + n];

Shouldn't it be 'target_hist_field = target_hist_data->fields[j + n]'?
                                     ^^^^^^^^^^^^^^^^

> +
> +		if (strcmp(hist_field->type, target_hist_field->type) != 0)
> +			return false;
> +		if (hist_field->size != target_hist_field->size)
> +			return false;
> +		if (hist_field->is_signed != target_hist_field->is_signed)
> +			return false;
> +	}
> +
> +	return true;
> +}
> +
> +static struct hist_trigger_data *
> +find_compatible_hist(struct hist_trigger_data *target_hist_data,
> +		     struct trace_event_file *file)
> +{
> +	struct hist_trigger_data *hist_data;
> +	struct event_trigger_data *test;
> +	unsigned int n_keys;
> +
> +	n_keys = target_hist_data->n_fields - target_hist_data->n_vals;
> +
> +	list_for_each_entry_rcu(test, &file->triggers, list) {
> +		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
> +			hist_data = test->private_data;
> +
> +			if (compatible_keys(target_hist_data, hist_data, n_keys))
> +				return hist_data;
> +		}
> +	}
> +
> +	return NULL;
> +}
> +
> +static struct trace_event_file *event_file(char *system, char *event_name)
> +{
> +	struct trace_event_file *file;
> +	struct trace_array *tr;
> +
> +	tr = top_trace_array();
> +	if (!tr)
> +		return ERR_PTR(-ENODEV);
> +
> +	file = find_event_file(tr, system, event_name);
> +	if (!file)
> +		return ERR_PTR(-EINVAL);
> +
> +	return file;
> +}
> +
> +static struct hist_field *
> +create_field_var_hist(struct hist_trigger_data *target_hist_data,
> +		      char *system, char *event_name, char *field_name)

IIUC this is needed to create a new hist on a match_event only to
provide a variable for a field, right?  I guess it's needed because
adding a new variable is dangerous/unsafe for a running hist.

It'd be nice if you could add more comments though.

Thanks,
Namhyung


> +{
> +	struct hist_field *event_var = ERR_PTR(-EINVAL);
> +	struct hist_trigger_data *hist_data;
> +	unsigned int i, n, first = true;
> +	struct field_var_hist *var_hist;
> +	struct trace_event_file *file;
> +	struct hist_field *key_field;
> +	struct trace_array *tr;
> +	char *saved_filter;
> +	char *cmd;
> +	int ret;
> +
> +	if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX)
> +		return ERR_PTR(-EINVAL);
> +
> +	tr = top_trace_array();
> +	if (!tr)
> +		return ERR_PTR(-ENODEV);
> +
> +	file = event_file(system, event_name);
> +	if (IS_ERR(file)) {
> +		ret = PTR_ERR(file);
> +		return ERR_PTR(ret);
> +	}
> +
> +	hist_data = find_compatible_hist(target_hist_data, file);
> +	if (!hist_data)
> +		return ERR_PTR(-EINVAL);
> +
> +	var_hist = kzalloc(sizeof(*var_hist), GFP_KERNEL);
> +	if (!var_hist)
> +		return ERR_PTR(-ENOMEM);
> +
> +	cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> +	if (!cmd) {
> +		kfree(var_hist);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	strcat(cmd, "keys=");
> +
> +	for_each_hist_key_field(i, hist_data) {
> +		key_field = hist_data->fields[i];
> +		if (!first)
> +			strcat(cmd, ",");
> +		strcat(cmd, key_field->field->name);
> +		first = false;
> +	}
> +
> +	strcat(cmd, ":synthetic_");
> +	strcat(cmd, field_name);
> +	strcat(cmd, "=");
> +	strcat(cmd, field_name);
> +
> +	saved_filter = find_trigger_filter(hist_data, file);
> +	if (saved_filter) {
> +		strcat(cmd, " if ");
> +		strcat(cmd, saved_filter);
> +	}
> +
> +	var_hist->cmd = kstrdup(cmd, GFP_KERNEL);
> +	if (!var_hist->cmd) {
> +		kfree(cmd);
> +		kfree(var_hist);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	var_hist->hist_data = hist_data;
> +
> +	ret = event_hist_trigger_func(&trigger_hist_cmd, file,
> +				      "", "hist", cmd);
> +	if (ret) {
> +		kfree(cmd);
> +		kfree(var_hist->cmd);
> +		kfree(var_hist);
> +		return ERR_PTR(ret);
> +	}
> +
> +	strcpy(cmd, "synthetic_");
> +	strcat(cmd, field_name);
> +
> +	event_var = find_event_var(system, event_name, cmd);
> +	if (!event_var) {
> +		kfree(cmd);
> +		kfree(var_hist->cmd);
> +		kfree(var_hist);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	n = target_hist_data->n_field_var_hists;
> +	target_hist_data->field_var_hists[n] = var_hist;
> +	target_hist_data->n_field_var_hists++;
> +
> +	return event_var;
> +}

Re: [PATCH 23/32] tracing: Add 'onmatch' hist trigger action support

[Tom Zanussi]

Hi Namhyung,

On Wed, 2017-07-26 at 11:40 +0900, Namhyung Kim wrote:
> Hi Tom,
> 
> On Mon, Jun 26, 2017 at 05:49:24PM -0500, Tom Zanussi wrote:
> > Add an 'onmatch(matching.event).<synthetic_event_name>(param list)'
> > hist trigger action which is invoked with the set of variables or
> > event fields named in the 'param list'.  The result is the generation
> > of a synthetic event that consists of the values contained in those
> > variables and/or fields at the time the invoking event was hit.
> > 
> > As an example the below defines a simple synthetic event using a
> > variable defined on the sched_wakeup_new event, and shows the event
> > definition with unresolved fields, since the sched_wakeup_new event
> > with the testpid variable hasn't been defined yet:
> > 
> >     # echo 'wakeup_new_test pid_t pid; int prio' >> \
> >       /sys/kernel/debug/tracing/synthetic_events
> > 
> >     # cat /sys/kernel/debug/tracing/synthetic_events
> >       wakeup_new_test pid_t pid; int prio
> > 
> > The following hist trigger both defines a testpid variable and
> > specifies an onmatch() trace action that uses that variable along with
> > a non-variable field to generate a wakeup_new_test synthetic event
> > whenever a sched_wakeup_new event occurs, which because of the 'if
> > comm == "cyclictest"' filter only happens when the executable is
> > cyclictest:
> > 
> >     # echo 'hist:keys=testpid=pid:\
> >       onmatch(sched.sched_wakeup_new).wakeup_new_test($testpid, prio) \
> >         if comm=="cyclictest"' >> \
> >       /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
> > 
> > Creating and displaying a histogram based on those events is now just
> > a matter of using the fields and new synthetic event in the
> > tracing/events/synthetic directory, as usual:
> > 
> >     # echo 'hist:keys=pid,prio:sort=pid,prio' >> \
> >       /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> 
> [SNIP]
> >  static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
> >  {
> > +	struct hist_trigger_data *hist_data = elt->map->private_data;
> >  	struct hist_elt_data *private_data = elt->private_data;
> > +	unsigned int i, n_str;
> > +
> > +	n_str = hist_data->n_field_var_str;
> > +
> > +	for (i = 0; i < n_str; i++)
> > +		kfree(private_data->field_var_str[i]);
> >  
> >  	kfree(private_data->comm);
> >  	kfree(private_data);
> > @@ -1537,7 +1627,7 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
> >  	unsigned int size = TASK_COMM_LEN + 1;
> >  	struct hist_elt_data *elt_data;
> >  	struct hist_field *key_field;
> > -	unsigned int i;
> > +	unsigned int i, n_str;
> >  
> >  	elt->private_data = elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
> >  	if (!elt_data)
> > @@ -1557,6 +1647,16 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
> >  		}
> >  	}
> >  
> > +	n_str = hist_data->n_field_var_str;
> > +
> > +	for (i = 0; i < n_str; i++) {
> > +		elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);
> 
> So the max length of a string variable is TASK_COMM_LEN, right?
> 

Yes, but I think it should be a bit larger - looking at existing events,
I also see 32 as a common length, so it would probably be good to up it
to that.  Unless you have a better idea...

> In addition, isn't it necessary for hist_trigger_elt_data_copy() to
> copy the field_var_str array?
> 

Yep, missed that, will add.

> 
> > +		if (!elt_data->field_var_str[i]) {
> > +			hist_trigger_elt_data_free(elt);
> > +			return -ENOMEM;
> > +		}
> > +	}
> > +
> >  	return 0;
> >  }
> 
> [SNIP]
> > +static bool compatible_keys(struct hist_trigger_data *target_hist_data,
> > +			    struct hist_trigger_data *hist_data,
> > +			    unsigned int n_keys)
> > +{
> > +	struct hist_field *target_hist_field, *hist_field;
> > +	unsigned int n, i, j;
> > +
> > +	if (hist_data->n_fields - hist_data->n_vals != n_keys)
> > +		return false;
> > +
> > +	i = hist_data->n_vals;
> > +	j = target_hist_data->n_vals;
> > +
> > +	for (n = 0; n < n_keys; n++) {
> > +		hist_field = hist_data->fields[i + n];
> > +		target_hist_field = hist_data->fields[j + n];
> 
> Shouldn't it be 'target_hist_field = target_hist_data->fields[j + n]'?
>                                      ^^^^^^^^^^^^^^^^
> 

Yeah, thanks for point out the typo.

> > +
> > +		if (strcmp(hist_field->type, target_hist_field->type) != 0)
> > +			return false;
> > +		if (hist_field->size != target_hist_field->size)
> > +			return false;
> > +		if (hist_field->is_signed != target_hist_field->is_signed)
> > +			return false;
> > +	}
> > +
> > +	return true;
> > +}
> > +
> > +static struct hist_trigger_data *
> > +find_compatible_hist(struct hist_trigger_data *target_hist_data,
> > +		     struct trace_event_file *file)
> > +{
> > +	struct hist_trigger_data *hist_data;
> > +	struct event_trigger_data *test;
> > +	unsigned int n_keys;
> > +
> > +	n_keys = target_hist_data->n_fields - target_hist_data->n_vals;
> > +
> > +	list_for_each_entry_rcu(test, &file->triggers, list) {
> > +		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
> > +			hist_data = test->private_data;
> > +
> > +			if (compatible_keys(target_hist_data, hist_data, n_keys))
> > +				return hist_data;
> > +		}
> > +	}
> > +
> > +	return NULL;
> > +}
> > +
> > +static struct trace_event_file *event_file(char *system, char *event_name)
> > +{
> > +	struct trace_event_file *file;
> > +	struct trace_array *tr;
> > +
> > +	tr = top_trace_array();
> > +	if (!tr)
> > +		return ERR_PTR(-ENODEV);
> > +
> > +	file = find_event_file(tr, system, event_name);
> > +	if (!file)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	return file;
> > +}
> > +
> > +static struct hist_field *
> > +create_field_var_hist(struct hist_trigger_data *target_hist_data,
> > +		      char *system, char *event_name, char *field_name)
> 
> IIUC this is needed to create a new hist on a match_event only to
> provide a variable for a field, right?  I guess it's needed because
> adding a new variable is dangerous/unsafe for a running hist.
> 

Exactly.  I'll add a comment to make that clear.

Thanks,

Tom

[PATCH 24/32] tracing: Add 'onmax' hist trigger action support

[Tom Zanussi]

Add an 'onmax(var).save(field,...)' hist trigger action which is
invoked whenever an event exceeds the current maximum.

The end result is that the trace event fields or variables specified
as the onmax.save() params will be saved if 'var' exceeds the current
maximum for that hist trigger entry.  This allows context from the
event that exhibited the new maximum to be saved for later reference.
When the histogram is displayed, additional fields displaying the
saved values will be printed.

As an example the below defines a couple of hist triggers, one for
sched_wakeup and another for sched_switch, keyed on pid.  Whenever a
sched_wakeup occurs, the timestamp is saved in the entry corresponding
to the current pid, and when the scheduler switches back to that pid,
the timestamp difference is calculated.  If the resulting latency
exceeds the current maximum latency, the specified save() values are
saved:

    # echo 'hist:keys=pid:ts0=common_timestamp.usecs \
        if comm=="cyclictest"' >> \
      /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger

    # echo 'hist:keys=next_pid:\
      wakeup_lat=common_timestamp.usecs-$ts0:\
      onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm) \
        if next_comm=="cyclictest"' >> \
      /sys/kernel/debug/tracing/events/sched/sched_switch/trigger

When the histogram is displayed, the max value and the saved values
corresponding to the max are displayed following the rest of the
fields:

    # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
      { next_pid:       2255 } hitcount:        239 \
        common_timestamp-$ts0:          0
        max:         27  next_comm: cyclictest \
        prev_pid:          0  prev_prio:        120  prev_comm: swapper/1 \
      { next_pid:       2256 } hitcount:       2355  common_timestamp-$ts0: 0 \
      	max:         49  next_comm: cyclictest \
        prev_pid:          0  prev_prio:        120  prev_comm: swapper/0

    Totals:
        Hits: 12970
        Entries: 2
        Dropped: 0

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 310 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 276 insertions(+), 34 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index b1f859c..d191f1a 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -282,6 +282,10 @@ struct hist_trigger_data {
 	unsigned int			n_field_var_str;
 	struct field_var_hist		*field_var_hists[SYNTH_FIELDS_MAX];
 	unsigned int			n_field_var_hists;
+
+	struct field_var		*max_vars[SYNTH_FIELDS_MAX];
+	unsigned int			n_max_vars;
+	unsigned int			n_max_var_str;
 };
 
 struct synth_field {
@@ -318,6 +322,12 @@ struct action_data {
 	char			*match_event_system;
 	char			*synth_event_name;
 	struct synth_event	*synth_event;
+
+	char			*onmax_var_str;
+	char			*onmax_fn_name;
+	unsigned int		max_var_ref_idx;
+	struct hist_field	*max_var;
+	struct hist_field	*onmax_var;
 };
 
 static LIST_HEAD(synth_event_list);
@@ -1493,7 +1503,8 @@ static int parse_action(char *str, struct hist_trigger_attrs *attrs)
 	if (attrs->n_actions >= HIST_ACTIONS_MAX)
 		return ret;
 
-	if ((strncmp(str, "onmatch(", strlen("onmatch(")) == 0)) {
+	if ((strncmp(str, "onmatch(", strlen("onmatch(")) == 0) ||
+	    (strncmp(str, "onmax(", strlen("onmax(")) == 0)) {
 		attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
 		if (!attrs->action_str[attrs->n_actions]) {
 			ret = -ENOMEM;
@@ -1612,7 +1623,7 @@ static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
 	struct hist_elt_data *private_data = elt->private_data;
 	unsigned int i, n_str;
 
-	n_str = hist_data->n_field_var_str;
+	n_str = hist_data->n_field_var_str + hist_data->n_max_var_str;
 
 	for (i = 0; i < n_str; i++)
 		kfree(private_data->field_var_str[i]);
@@ -1647,7 +1658,7 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
 		}
 	}
 
-	n_str = hist_data->n_field_var_str;
+	n_str = hist_data->n_field_var_str + hist_data->n_max_var_str;
 
 	for (i = 0; i < n_str; i++) {
 		elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);
@@ -2504,6 +2515,15 @@ static void update_field_vars(struct hist_trigger_data *hist_data,
 			    hist_data->n_field_vars, 0);
 }
 
+static void update_max_vars(struct hist_trigger_data *hist_data,
+			    struct tracing_map_elt *elt,
+			    struct ring_buffer_event *rbe,
+			    void *rec)
+{
+	__update_field_vars(elt, rbe, rec, hist_data->max_vars,
+			    hist_data->n_max_vars, hist_data->n_field_var_str);
+}
+
 static struct hist_field *create_var(struct hist_trigger_data *hist_data,
 				     struct trace_event_file *file,
 				     char *name, int size, const char *type)
@@ -2613,6 +2633,222 @@ static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
 	return create_field_var(hist_data, file, var_name);
 }
 
+static void onmax_print(struct seq_file *m,
+			struct hist_trigger_data *hist_data,
+			struct tracing_map_elt *elt,
+			struct action_data *data)
+{
+	unsigned int i, save_var_idx, max_idx = data->max_var->var.idx;
+
+	seq_printf(m, "\n\tmax: %10llu", tracing_map_read_var(elt, max_idx));
+
+	for (i = 0; i < hist_data->n_max_vars; i++) {
+		struct hist_field *save_val = hist_data->max_vars[i]->val;
+		struct hist_field *save_var = hist_data->max_vars[i]->var;
+		u64 val;
+
+		save_var_idx = save_var->var.idx;
+
+		val = tracing_map_read_var(elt, save_var_idx);
+
+		if (save_val->flags & HIST_FIELD_FL_STRING) {
+			seq_printf(m, "  %s: %-50s", save_var->var.name,
+				   (char *)(uintptr_t)(val));
+		} else
+			seq_printf(m, "  %s: %10llu", save_var->var.name, val);
+	}
+}
+
+static void onmax_save(struct hist_trigger_data *hist_data,
+		       struct tracing_map_elt *elt, void *rec,
+		       struct ring_buffer_event *rbe,
+		       struct action_data *data, u64 *var_ref_vals)
+{
+	unsigned int max_idx = data->max_var->var.idx;
+	unsigned int max_var_ref_idx = data->max_var_ref_idx;
+
+	u64 var_val, max_val;
+
+	var_val = var_ref_vals[max_var_ref_idx];
+	max_val = tracing_map_read_var(elt, max_idx);
+
+	if (var_val <= max_val)
+		return;
+
+	tracing_map_set_var(elt, max_idx, var_val);
+
+	update_max_vars(hist_data, elt, rbe, rec);
+}
+
+static void onmax_destroy(struct action_data *data)
+{
+	unsigned int i;
+
+	destroy_hist_field(data->max_var, 0);
+	destroy_hist_field(data->onmax_var, 0);
+
+	kfree(data->onmax_var_str);
+	kfree(data->onmax_fn_name);
+
+	for (i = 0; i < data->n_params; i++)
+		kfree(data->params[i]);
+
+	kfree(data);
+}
+
+static int onmax_create(struct hist_trigger_data *hist_data,
+			struct action_data *data)
+{
+	struct trace_event_call *call = hist_data->event_file->event_call;
+	struct trace_event_file *file = hist_data->event_file;
+	struct hist_field *var_field, *ref_field, *max_var;
+	unsigned int var_ref_idx = hist_data->n_var_refs;
+	struct field_var *field_var;
+	char *onmax_var_str, *param;
+	const char *event_name;
+	unsigned long flags;
+	unsigned int i;
+	int ret = 0;
+
+	onmax_var_str = data->onmax_var_str;
+	if (onmax_var_str[0] != '$')
+		return -EINVAL;
+	onmax_var_str++;
+
+	event_name = trace_event_name(call);
+	var_field = find_target_event_var(hist_data, NULL, NULL, onmax_var_str);
+	if (!var_field)
+		return -EINVAL;
+
+	flags = HIST_FIELD_FL_VAR_REF;
+	ref_field = create_hist_field(hist_data, NULL, flags, NULL);
+	if (!ref_field)
+		return -ENOMEM;
+
+	ref_field->var.idx = var_field->var.idx;
+	ref_field->var.hist_data = hist_data;
+	ref_field->name = kstrdup(var_field->var.name, GFP_KERNEL);
+	ref_field->type = kstrdup(var_field->type, GFP_KERNEL);
+	if (!ref_field->name || !ref_field->type) {
+		destroy_hist_field(ref_field, 0);
+		ret = -ENOMEM;
+		goto out;
+	}
+	hist_data->var_refs[hist_data->n_var_refs] = ref_field;
+	ref_field->var_ref_idx = hist_data->n_var_refs++;
+	data->onmax_var = ref_field;
+
+	data->fn = onmax_save;
+	data->max_var_ref_idx = var_ref_idx;
+	max_var = create_var(hist_data, file, "max", sizeof(u64), "u64");
+	if (IS_ERR(max_var)) {
+		ret = PTR_ERR(max_var);
+		goto out;
+	}
+	data->max_var = max_var;
+
+	for (i = 0; i < data->n_params; i++) {
+		param = kstrdup(data->params[i], GFP_KERNEL);
+		if (!param)
+			goto out;
+
+		field_var = create_target_field_var(hist_data, NULL, NULL, param);
+		if (IS_ERR(field_var)) {
+			ret = PTR_ERR(field_var);
+			kfree(param);
+			goto out;
+		}
+
+		hist_data->max_vars[hist_data->n_max_vars++] = field_var;
+		if (field_var->val->flags & HIST_FIELD_FL_STRING)
+			hist_data->n_max_var_str++;
+
+		kfree(param);
+	}
+
+	hist_data->actions[hist_data->n_actions++] = data;
+ out:
+	return ret;
+}
+
+static int parse_action_params(char *params, struct action_data *data)
+{
+	char *param, *saved_param;
+	int ret = 0;
+
+	while (params) {
+		if (data->n_params >= SYNTH_FIELDS_MAX)
+			goto out;
+
+		param = strsep(&params, ",");
+		if (!param)
+			goto out;
+
+		param = strstrip(param);
+		if (strlen(param) < 2) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		saved_param = kstrdup(param, GFP_KERNEL);
+		if (!saved_param) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		data->params[data->n_params++] = saved_param;
+	}
+ out:
+	return ret;
+}
+
+static struct action_data *onmax_parse(char *str)
+{
+	char *onmax_fn_name, *onmax_var_str;
+	struct action_data *data;
+	int ret = -EINVAL;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return ERR_PTR(-ENOMEM);
+
+	onmax_var_str = strsep(&str, ")");
+	if (!onmax_var_str || !str)
+		return ERR_PTR(-EINVAL);
+	data->onmax_var_str = kstrdup(onmax_var_str, GFP_KERNEL);
+
+	strsep(&str, ".");
+	if (!str)
+		goto free;
+
+	onmax_fn_name = strsep(&str, "(");
+	if (!onmax_fn_name || !str)
+		goto free;
+
+	if (strncmp(onmax_fn_name, "save", strlen("save")) == 0) {
+		char *params = strsep(&str, ")");
+
+		if (!params)
+			goto free;
+
+		ret = parse_action_params(params, data);
+		if (ret)
+			goto free;
+	}
+	data->onmax_fn_name = kstrdup(onmax_fn_name, GFP_KERNEL);
+
+	if (!data->onmax_var_str || !data->onmax_fn_name) {
+		ret = -ENOMEM;
+		goto free;
+	}
+ out:
+	return data;
+ free:
+	onmax_destroy(data);
+	data = ERR_PTR(ret);
+	goto out;
+}
+
 static void onmatch_destroy(struct action_data *data)
 {
 	unsigned int i;
@@ -2689,37 +2925,6 @@ static int check_synth_field(struct synth_event *event,
 	return 0;
 }
 
-static int parse_action_params(char *params, struct action_data *data)
-{
-	char *param, *saved_param;
-	int ret = 0;
-
-	while (params) {
-		if (data->n_params >= SYNTH_FIELDS_MAX)
-			goto out;
-
-		param = strsep(&params, ",");
-		if (!param)
-			goto out;
-
-		param = strstrip(param);
-		if (strlen(param) < 2) {
-			ret = -EINVAL;
-			goto out;
-		}
-
-		saved_param = kstrdup(param, GFP_KERNEL);
-		if (!saved_param) {
-			ret = -ENOMEM;
-			goto out;
-		}
-
-		data->params[data->n_params++] = saved_param;
-	}
- out:
-	return ret;
-}
-
 static struct hist_field *
 onmatch_find_var(struct hist_trigger_data *hist_data, struct action_data *data,
 		 char *system, char *event, char *var)
@@ -3313,6 +3518,8 @@ static void destroy_actions(struct hist_trigger_data *hist_data)
 
 		if (data->fn == action_trace)
 			onmatch_destroy(data);
+		else if (data->fn == onmax_save)
+			onmax_destroy(data);
 		else
 			kfree(data);
 	}
@@ -3341,6 +3548,18 @@ static int create_actions(struct hist_trigger_data *hist_data,
 				onmatch_destroy(data);
 				return ret;
 			}
+		} else if (strncmp(str, "onmax(", strlen("onmax(")) == 0) {
+			char *action_str = str + strlen("onmax(");
+
+			data = onmax_parse(action_str);
+			if (IS_ERR(data))
+				return PTR_ERR(data);
+
+			ret = onmax_create(hist_data, data);
+			if (ret) {
+				onmax_destroy(data);
+				return ret;
+			}
 		}
 	}
 
@@ -3355,9 +3574,30 @@ static void print_actions(struct seq_file *m,
 
 	for (i = 0; i < hist_data->n_actions; i++) {
 		struct action_data *data = hist_data->actions[i];
+
+		if (data->fn == onmax_save)
+			onmax_print(m, hist_data, elt, data);
 	}
 }
 
+static void print_onmax_spec(struct seq_file *m,
+			     struct hist_trigger_data *hist_data,
+			     struct action_data *data)
+{
+	unsigned int i;
+
+	seq_puts(m, ":onmax(");
+	seq_printf(m, "%s", data->onmax_var_str);
+	seq_printf(m, ").%s(", data->onmax_fn_name);
+
+	for (i = 0; i < hist_data->n_max_vars; i++) {
+		seq_printf(m, "%s", hist_data->max_vars[i]->var->var.name);
+		if (i < hist_data->n_max_vars - 1)
+			seq_puts(m, ",");
+	}
+	seq_puts(m, ")");
+}
+
 static void print_onmatch_spec(struct seq_file *m,
 			       struct hist_trigger_data *hist_data,
 			       struct action_data *data)
@@ -3388,6 +3628,8 @@ static void print_actions_spec(struct seq_file *m,
 
 		if (data->fn == action_trace)
 			print_onmatch_spec(m, hist_data, data);
+		else if (data->fn == onmax_save)
+			print_onmax_spec(m, hist_data, data);
 	}
 }
 
-- 
1.9.3

Re: [PATCH 24/32] tracing: Add 'onmax' hist trigger action support

[Namhyung Kim]

On Mon, Jun 26, 2017 at 05:49:25PM -0500, Tom Zanussi wrote:
> Add an 'onmax(var).save(field,...)' hist trigger action which is
> invoked whenever an event exceeds the current maximum.
> 
> The end result is that the trace event fields or variables specified
> as the onmax.save() params will be saved if 'var' exceeds the current
> maximum for that hist trigger entry.  This allows context from the
> event that exhibited the new maximum to be saved for later reference.
> When the histogram is displayed, additional fields displaying the
> saved values will be printed.
> 
> As an example the below defines a couple of hist triggers, one for
> sched_wakeup and another for sched_switch, keyed on pid.  Whenever a
> sched_wakeup occurs, the timestamp is saved in the entry corresponding
> to the current pid, and when the scheduler switches back to that pid,
> the timestamp difference is calculated.  If the resulting latency
> exceeds the current maximum latency, the specified save() values are
> saved:
> 
>     # echo 'hist:keys=pid:ts0=common_timestamp.usecs \
>         if comm=="cyclictest"' >> \
>       /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
> 
>     # echo 'hist:keys=next_pid:\
>       wakeup_lat=common_timestamp.usecs-$ts0:\
>       onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm) \
>         if next_comm=="cyclictest"' >> \
>       /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
> 
> When the histogram is displayed, the max value and the saved values
> corresponding to the max are displayed following the rest of the
> fields:
> 
>     # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
>       { next_pid:       2255 } hitcount:        239 \
>         common_timestamp-$ts0:          0

What is this, wakeup_lat?  If so, it'd be better showing the variable name.


>         max:         27  next_comm: cyclictest \
>         prev_pid:          0  prev_prio:        120  prev_comm: swapper/1 \
>       { next_pid:       2256 } hitcount:       2355  common_timestamp-$ts0: 0 \
>       	max:         49  next_comm: cyclictest \
>         prev_pid:          0  prev_prio:        120  prev_comm: swapper/0
> 
>     Totals:
>         Hits: 12970

Why total hits is different than the sum of two?

>         Entries: 2
>         Dropped: 0
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  kernel/trace/trace_events_hist.c | 310 ++++++++++++++++++++++++++++++++++-----
>  1 file changed, 276 insertions(+), 34 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index b1f859c..d191f1a 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -282,6 +282,10 @@ struct hist_trigger_data {
>  	unsigned int			n_field_var_str;
>  	struct field_var_hist		*field_var_hists[SYNTH_FIELDS_MAX];
>  	unsigned int			n_field_var_hists;
> +
> +	struct field_var		*max_vars[SYNTH_FIELDS_MAX];
> +	unsigned int			n_max_vars;
> +	unsigned int			n_max_var_str;
>  };
>  
>  struct synth_field {
> @@ -318,6 +322,12 @@ struct action_data {
>  	char			*match_event_system;
>  	char			*synth_event_name;
>  	struct synth_event	*synth_event;
> +
> +	char			*onmax_var_str;
> +	char			*onmax_fn_name;
> +	unsigned int		max_var_ref_idx;
> +	struct hist_field	*max_var;
> +	struct hist_field	*onmax_var;

Couldn't it be a union?

>  };

[SNIP]
> @@ -2613,6 +2633,222 @@ static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
>  	return create_field_var(hist_data, file, var_name);
>  }
>  
> +static void onmax_print(struct seq_file *m,
> +			struct hist_trigger_data *hist_data,
> +			struct tracing_map_elt *elt,
> +			struct action_data *data)
> +{
> +	unsigned int i, save_var_idx, max_idx = data->max_var->var.idx;
> +
> +	seq_printf(m, "\n\tmax: %10llu", tracing_map_read_var(elt, max_idx));
> +
> +	for (i = 0; i < hist_data->n_max_vars; i++) {
> +		struct hist_field *save_val = hist_data->max_vars[i]->val;
> +		struct hist_field *save_var = hist_data->max_vars[i]->var;
> +		u64 val;
> +
> +		save_var_idx = save_var->var.idx;
> +
> +		val = tracing_map_read_var(elt, save_var_idx);
> +
> +		if (save_val->flags & HIST_FIELD_FL_STRING) {
> +			seq_printf(m, "  %s: %-50s", save_var->var.name,

It seems TASK_COMM_LEN is enough.  Or please define STR_VAR_LEN or
something.


> +				   (char *)(uintptr_t)(val));
> +		} else
> +			seq_printf(m, "  %s: %10llu", save_var->var.name, val);
> +	}
> +}

[SNIP]
> +static struct action_data *onmax_parse(char *str)
> +{
> +	char *onmax_fn_name, *onmax_var_str;
> +	struct action_data *data;
> +	int ret = -EINVAL;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return ERR_PTR(-ENOMEM);
> +
> +	onmax_var_str = strsep(&str, ")");
> +	if (!onmax_var_str || !str)
> +		return ERR_PTR(-EINVAL);
> +	data->onmax_var_str = kstrdup(onmax_var_str, GFP_KERNEL);
> +
> +	strsep(&str, ".");
> +	if (!str)
> +		goto free;
> +
> +	onmax_fn_name = strsep(&str, "(");
> +	if (!onmax_fn_name || !str)
> +		goto free;
> +
> +	if (strncmp(onmax_fn_name, "save", strlen("save")) == 0) {
> +		char *params = strsep(&str, ")");
> +
> +		if (!params)
> +			goto free;
> +
> +		ret = parse_action_params(params, data);
> +		if (ret)
> +			goto free;
> +	}

Hmm.. is it ok to give a function name other than 'save'?

Thanks,
Namhyung


> +	data->onmax_fn_name = kstrdup(onmax_fn_name, GFP_KERNEL);
> +
> +	if (!data->onmax_var_str || !data->onmax_fn_name) {
> +		ret = -ENOMEM;
> +		goto free;
> +	}
> + out:
> +	return data;
> + free:
> +	onmax_destroy(data);
> +	data = ERR_PTR(ret);
> +	goto out;
> +}

Re: [PATCH 24/32] tracing: Add 'onmax' hist trigger action support

[Tom Zanussi]

Hi Namhyung,

On Wed, 2017-07-26 at 12:04 +0900, Namhyung Kim wrote:
> On Mon, Jun 26, 2017 at 05:49:25PM -0500, Tom Zanussi wrote:
> > Add an 'onmax(var).save(field,...)' hist trigger action which is
> > invoked whenever an event exceeds the current maximum.
> > 
> > The end result is that the trace event fields or variables specified
> > as the onmax.save() params will be saved if 'var' exceeds the current
> > maximum for that hist trigger entry.  This allows context from the
> > event that exhibited the new maximum to be saved for later reference.
> > When the histogram is displayed, additional fields displaying the
> > saved values will be printed.
> > 
> > As an example the below defines a couple of hist triggers, one for
> > sched_wakeup and another for sched_switch, keyed on pid.  Whenever a
> > sched_wakeup occurs, the timestamp is saved in the entry corresponding
> > to the current pid, and when the scheduler switches back to that pid,
> > the timestamp difference is calculated.  If the resulting latency
> > exceeds the current maximum latency, the specified save() values are
> > saved:
> > 
> >     # echo 'hist:keys=pid:ts0=common_timestamp.usecs \
> >         if comm=="cyclictest"' >> \
> >       /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
> > 
> >     # echo 'hist:keys=next_pid:\
> >       wakeup_lat=common_timestamp.usecs-$ts0:\
> >       onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm) \
> >         if next_comm=="cyclictest"' >> \
> >       /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
> > 
> > When the histogram is displayed, the max value and the saved values
> > corresponding to the max are displayed following the rest of the
> > fields:
> > 
> >     # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
> >       { next_pid:       2255 } hitcount:        239 \
> >         common_timestamp-$ts0:          0
> 
> What is this, wakeup_lat?  If so, it'd be better showing the variable name.
> 

Yeah, this is actually old output - I need to update the examples in the
commit messages.  Anyway, this kind of thing is no longer displayed at
all in the current version.

> 
> >         max:         27  next_comm: cyclictest \
> >         prev_pid:          0  prev_prio:        120  prev_comm: swapper/1 \
> >       { next_pid:       2256 } hitcount:       2355  common_timestamp-$ts0: 0 \
> >       	max:         49  next_comm: cyclictest \
> >         prev_pid:          0  prev_prio:        120  prev_comm: swapper/0
> > 
> >     Totals:
> >         Hits: 12970
> 
> Why total hits is different than the sum of two?
> 

The reason for differences like this is that the tracing map counts
lookups as 'hits', and we're using lookups to resolve variable
references, so this number no longer matches the actual number of
updates to elements.  I'm going to add a patch that doesn't account
lookups in the hitcount, as I don't think it should.

> >         Entries: 2
> >         Dropped: 0
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> >  kernel/trace/trace_events_hist.c | 310 ++++++++++++++++++++++++++++++++++-----
> >  1 file changed, 276 insertions(+), 34 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index b1f859c..d191f1a 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> > @@ -282,6 +282,10 @@ struct hist_trigger_data {
> >  	unsigned int			n_field_var_str;
> >  	struct field_var_hist		*field_var_hists[SYNTH_FIELDS_MAX];
> >  	unsigned int			n_field_var_hists;
> > +
> > +	struct field_var		*max_vars[SYNTH_FIELDS_MAX];
> > +	unsigned int			n_max_vars;
> > +	unsigned int			n_max_var_str;
> >  };
> >  
> >  struct synth_field {
> > @@ -318,6 +322,12 @@ struct action_data {
> >  	char			*match_event_system;
> >  	char			*synth_event_name;
> >  	struct synth_event	*synth_event;
> > +
> > +	char			*onmax_var_str;
> > +	char			*onmax_fn_name;
> > +	unsigned int		max_var_ref_idx;
> > +	struct hist_field	*max_var;
> > +	struct hist_field	*onmax_var;
> 
> Couldn't it be a union?
> 

Yeah, I think that makes more sense.

> >  };
> 
> [SNIP]
> > @@ -2613,6 +2633,222 @@ static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
> >  	return create_field_var(hist_data, file, var_name);
> >  }
> >  
> > +static void onmax_print(struct seq_file *m,
> > +			struct hist_trigger_data *hist_data,
> > +			struct tracing_map_elt *elt,
> > +			struct action_data *data)
> > +{
> > +	unsigned int i, save_var_idx, max_idx = data->max_var->var.idx;
> > +
> > +	seq_printf(m, "\n\tmax: %10llu", tracing_map_read_var(elt, max_idx));
> > +
> > +	for (i = 0; i < hist_data->n_max_vars; i++) {
> > +		struct hist_field *save_val = hist_data->max_vars[i]->val;
> > +		struct hist_field *save_var = hist_data->max_vars[i]->var;
> > +		u64 val;
> > +
> > +		save_var_idx = save_var->var.idx;
> > +
> > +		val = tracing_map_read_var(elt, save_var_idx);
> > +
> > +		if (save_val->flags & HIST_FIELD_FL_STRING) {
> > +			seq_printf(m, "  %s: %-50s", save_var->var.name,
> 
> It seems TASK_COMM_LEN is enough.  Or please define STR_VAR_LEN or
> something.
> 
> 
> > +				   (char *)(uintptr_t)(val));
> > +		} else
> > +			seq_printf(m, "  %s: %10llu", save_var->var.name, val);
> > +	}
> > +}
> 
> [SNIP]
> > +static struct action_data *onmax_parse(char *str)
> > +{
> > +	char *onmax_fn_name, *onmax_var_str;
> > +	struct action_data *data;
> > +	int ret = -EINVAL;
> > +
> > +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> > +	if (!data)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	onmax_var_str = strsep(&str, ")");
> > +	if (!onmax_var_str || !str)
> > +		return ERR_PTR(-EINVAL);
> > +	data->onmax_var_str = kstrdup(onmax_var_str, GFP_KERNEL);
> > +
> > +	strsep(&str, ".");
> > +	if (!str)
> > +		goto free;
> > +
> > +	onmax_fn_name = strsep(&str, "(");
> > +	if (!onmax_fn_name || !str)
> > +		goto free;
> > +
> > +	if (strncmp(onmax_fn_name, "save", strlen("save")) == 0) {
> > +		char *params = strsep(&str, ")");
> > +
> > +		if (!params)
> > +			goto free;
> > +
> > +		ret = parse_action_params(params, data);
> > +		if (ret)
> > +			goto free;
> > +	}
> 
> Hmm.. is it ok to give a function name other than 'save'?
> 

No, good point, thanks for pointing it out.

Tom

[PATCH 25/32] tracing: Allow whitespace to surround hist trigger filter

[Tom Zanussi]

The existing code only allows for one space before and after the 'if'
specifying the filter for a hist trigger.  Add code to make that more
permissive as far as whitespace goes.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index d191f1a..53a0634 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -4632,7 +4632,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	struct event_trigger_ops *trigger_ops;
 	struct hist_trigger_data *hist_data;
 	bool remove = false;
-	char *trigger;
+	char *trigger, *p;
 	int ret = 0;
 
 	if (!param)
@@ -4642,9 +4642,19 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 		remove = true;
 
 	/* separate the trigger from the filter (k:v [if filter]) */
-	trigger = strsep(&param, " \t");
-	if (!trigger)
-		return -EINVAL;
+	trigger = param;
+	p = strstr(param, " if");
+	if (!p)
+		p = strstr(param, "\tif");
+	if (p) {
+		if (p == trigger)
+			return -EINVAL;
+		param = p + 1;
+		param = strstrip(param);
+		*p = '\0';
+		trigger = strstrip(trigger);
+	} else
+		param = NULL;
 
 	attrs = parse_hist_trigger_attrs(trigger);
 	if (IS_ERR(attrs))
@@ -4694,6 +4704,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	}
 
 	ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
+
 	/*
 	 * The above returns on success the # of triggers registered,
 	 * but if it didn't register any it returns zero.  Consider no
-- 
1.9.3

[PATCH 26/32] tracing: Make duplicate count from tracing_map available

[Tom Zanussi]

Though extremely rare, there can be duplicate entries in the tracing
map.  This isn't normally a problem, as the sorting code makes this
transparent by merging them during the sort.

It's useful to know however, as a check on that assumption - if a
non-zero duplicate count is seen more than rarely, it might indicate
an unexpected change to the algorithm, or a pathological data set.

Add an extra param to tracing_map_sort_entries() and use it to display
the value in the hist trigger output.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 14 ++++++++------
 kernel/trace/tracing_map.c       | 12 +++++++++---
 kernel/trace/tracing_map.h       |  3 ++-
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 53a0634..ab94e2a 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -4011,7 +4011,8 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
 }
 
 static int print_entries(struct seq_file *m,
-			 struct hist_trigger_data *hist_data)
+			 struct hist_trigger_data *hist_data,
+			 unsigned int *n_dups)
 {
 	struct tracing_map_sort_entry **sort_entries = NULL;
 	struct tracing_map *map = hist_data->map;
@@ -4019,7 +4020,7 @@ static int print_entries(struct seq_file *m,
 
 	n_entries = tracing_map_sort_entries(map, hist_data->sort_keys,
 					     hist_data->n_sort_keys,
-					     &sort_entries);
+					     &sort_entries, n_dups);
 	if (n_entries < 0)
 		return n_entries;
 
@@ -4038,6 +4039,7 @@ static void hist_trigger_show(struct seq_file *m,
 {
 	struct hist_trigger_data *hist_data;
 	int n_entries, ret = 0;
+	unsigned int n_dups;
 
 	if (n > 0)
 		seq_puts(m, "\n\n");
@@ -4047,15 +4049,15 @@ static void hist_trigger_show(struct seq_file *m,
 	seq_puts(m, "#\n\n");
 
 	hist_data = data->private_data;
-	n_entries = print_entries(m, hist_data);
+	n_entries = print_entries(m, hist_data, &n_dups);
 	if (n_entries < 0) {
 		ret = n_entries;
 		n_entries = 0;
 	}
 
-	seq_printf(m, "\nTotals:\n    Hits: %llu\n    Entries: %u\n    Dropped: %llu\n",
-		   (u64)atomic64_read(&hist_data->map->hits),
-		   n_entries, (u64)atomic64_read(&hist_data->map->drops));
+	seq_printf(m, "\nTotals:\n    Hits: %llu\n    Entries: %u\n    Dropped: %llu\n    Duplicates: %u\n",
+		   (u64)atomic64_read(&hist_data->map->hits), n_entries,
+		   (u64)atomic64_read(&hist_data->map->drops), n_dups);
 }
 
 static int hist_show(struct seq_file *m, void *v)
diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
index f987069..9ed04b6 100644
--- a/kernel/trace/tracing_map.c
+++ b/kernel/trace/tracing_map.c
@@ -1084,6 +1084,7 @@ static void sort_secondary(struct tracing_map *map,
  * @map: The tracing_map
  * @sort_key: The sort key to use for sorting
  * @sort_entries: outval: pointer to allocated and sorted array of entries
+ * @n_dups: outval: pointer to variable receiving a count of duplicates found
  *
  * tracing_map_sort_entries() sorts the current set of entries in the
  * map and returns the list of tracing_map_sort_entries containing
@@ -1100,13 +1101,16 @@ static void sort_secondary(struct tracing_map *map,
  * The client should not hold on to the returned array but should use
  * it and call tracing_map_destroy_sort_entries() when done.
  *
- * Return: the number of sort_entries in the struct tracing_map_sort_entry
- * array, negative on error
+ * Return: the number of sort_entries in the struct
+ * tracing_map_sort_entry array, negative on error.  If n_dups is
+ * non-NULL, it will receive the number of duplicate entries found
+ * (and merged) during the sort.
  */
 int tracing_map_sort_entries(struct tracing_map *map,
 			     struct tracing_map_sort_key *sort_keys,
 			     unsigned int n_sort_keys,
-			     struct tracing_map_sort_entry ***sort_entries)
+			     struct tracing_map_sort_entry ***sort_entries,
+			     unsigned int *n_dups)
 {
 	int (*cmp_entries_fn)(const struct tracing_map_sort_entry **,
 			      const struct tracing_map_sort_entry **);
@@ -1147,6 +1151,8 @@ int tracing_map_sort_entries(struct tracing_map *map,
 	if (ret < 0)
 		goto free;
 	n_entries -= ret;
+	if (n_dups)
+		*n_dups = ret;
 
 	if (is_key(map, sort_keys[0].field_idx))
 		cmp_entries_fn = cmp_entries_key;
diff --git a/kernel/trace/tracing_map.h b/kernel/trace/tracing_map.h
index 303bc4f..a44cc0c 100644
--- a/kernel/trace/tracing_map.h
+++ b/kernel/trace/tracing_map.h
@@ -286,7 +286,8 @@ extern void tracing_map_set_field_descr(struct tracing_map *map,
 tracing_map_sort_entries(struct tracing_map *map,
 			 struct tracing_map_sort_key *sort_keys,
 			 unsigned int n_sort_keys,
-			 struct tracing_map_sort_entry ***sort_entries);
+			 struct tracing_map_sort_entry ***sort_entries,
+			 unsigned int *n_dups);
 
 extern void
 tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries,
-- 
1.9.3

[PATCH 27/32] tracing: Add cpu field for hist triggers

[Tom Zanussi]

A common key to use in a histogram is the cpuid - add a new cpu
'synthetic' field for that purpose.  This field is named cpu rather
than $cpu or $common_cpu because 'cpu' already exists as a special
filter field and it makes more sense to match that rather than add
another name for the same thing.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 Documentation/trace/events.txt   | 18 ++++++++++++++++++
 kernel/trace/trace_events_hist.c | 30 +++++++++++++++++++++++++++---
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index 2cc08d4..9717688 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -668,6 +668,24 @@ The following commands are supported:
   The examples below provide a more concrete illustration of the
   concepts and typical usage patterns discussed above.
 
+  'synthetic' event fields
+  ------------------------
+
+  There are a number of 'synthetic fields' available for use as keys
+  or values in a hist trigger.  These look like and behave as if they
+  were event fields, but aren't actually part of the event's field
+  definition or format file.  They are however available for any
+  event, and can be used anywhere an actual event field could be.
+  'Synthetic' field names are always prefixed with a '$' character to
+  indicate that they're not normal fields (with the exception of
+  'cpu', for compatibility with existing filter usage):
+
+    $common_timestamp      u64 - timestamp (from ring buffer) associated
+                                 with the event, in nanoseconds.  May be
+				 modified by .usecs to have timestamps
+				 interpreted as microseconds.
+    cpu                    int - the cpu on which the event occurred.
+
 
 6.2 'hist' trigger examples
 ---------------------------
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index ab94e2a..904a635 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -224,6 +224,7 @@ enum hist_field_flags {
 	HIST_FIELD_FL_VAR_ONLY		= 8192,
 	HIST_FIELD_FL_EXPR		= 16384,
 	HIST_FIELD_FL_VAR_REF		= 32768,
+	HIST_FIELD_FL_CPU		= 65536,
 };
 
 struct hist_trigger_attrs {
@@ -1081,6 +1082,16 @@ static u64 hist_field_timestamp(struct hist_field *hist_field,
 	return ts;
 }
 
+static u64 hist_field_cpu(struct hist_field *hist_field,
+			  struct tracing_map_elt *elt,
+			  struct ring_buffer_event *rbe,
+			  void *event)
+{
+	int cpu = raw_smp_processor_id();
+
+	return cpu;
+}
+
 static struct hist_field *check_var_ref(struct hist_field *hist_field,
 					struct hist_trigger_data *var_data,
 					unsigned int var_idx)
@@ -1407,6 +1418,8 @@ static const char *hist_field_name(struct hist_field *field,
 		field_name = hist_field_name(field->operands[0], ++level);
 	else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
 		field_name = "$common_timestamp";
+	else if (field->flags & HIST_FIELD_FL_CPU)
+		field_name = "cpu";
 	else if (field->flags & HIST_FIELD_FL_EXPR ||
 		 field->flags & HIST_FIELD_FL_VAR_REF)
 		field_name = field->name;
@@ -1848,6 +1861,15 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 		goto out;
 	}
 
+	if (flags & HIST_FIELD_FL_CPU) {
+		hist_field->fn = hist_field_cpu;
+		hist_field->size = sizeof(int);
+		hist_field->type = kstrdup("int", GFP_KERNEL);
+		if (!hist_field->type)
+			goto free;
+		goto out;
+	}
+
 	if (WARN_ON_ONCE(!field))
 		goto out;
 
@@ -1980,7 +2002,9 @@ static struct hist_field *parse_var_ref(char *system, char *event_name,
 		hist_data->enable_timestamps = true;
 		if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
 			hist_data->attrs->ts_in_usecs = true;
-	} else {
+	} else if (strcmp(field_name, "cpu") == 0)
+		*flags |= HIST_FIELD_FL_CPU;
+	else {
 		field = trace_find_event_field(file->event_call, field_name);
 		if (!field)
 			return ERR_PTR(-EINVAL);
@@ -3019,7 +3043,6 @@ static int onmatch_create(struct hist_trigger_data *hist_data,
 				goto out;
 			}
 		}
-
 		if (param[0] == '$')
 			hist_field = onmatch_find_var(hist_data, data, system,
 						      event_name, param);
@@ -3034,7 +3057,6 @@ static int onmatch_create(struct hist_trigger_data *hist_data,
 			ret = -EINVAL;
 			goto out;
 		}
-
 		if (check_synth_field(event, hist_field, field_pos) == 0) {
 			var_ref = create_var_ref(hist_field);
 			if (!var_ref) {
@@ -4128,6 +4150,8 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
 
 	if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP)
 		seq_puts(m, "$common_timestamp");
+	else if (hist_field->flags & HIST_FIELD_FL_CPU)
+		seq_puts(m, "cpu");
 	else if (field_name)
 		seq_printf(m, "%s", field_name);
 
-- 
1.9.3

[PATCH 28/32] tracing: Add hist trigger support for variable reference aliases

[Tom Zanussi]

Add support for alias=$somevar where alias can be used as
onmatch($alias).

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 46 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 43 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 904a635..799b95e 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -225,6 +225,7 @@ enum hist_field_flags {
 	HIST_FIELD_FL_EXPR		= 16384,
 	HIST_FIELD_FL_VAR_REF		= 32768,
 	HIST_FIELD_FL_CPU		= 65536,
+	HIST_FIELD_FL_ALIAS		= 131072,
 };
 
 struct hist_trigger_attrs {
@@ -1414,7 +1415,8 @@ static const char *hist_field_name(struct hist_field *field,
 
 	if (field->field)
 		field_name = field->field->name;
-	else if (field->flags & HIST_FIELD_FL_LOG2)
+	else if (field->flags & HIST_FIELD_FL_LOG2 ||
+		 field->flags & HIST_FIELD_FL_ALIAS)
 		field_name = hist_field_name(field->operands[0], ++level);
 	else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
 		field_name = "$common_timestamp";
@@ -1819,7 +1821,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 
 	hist_field->hist_data = hist_data;
 
-	if (flags & HIST_FIELD_FL_EXPR)
+	if (flags & HIST_FIELD_FL_EXPR || flags & HIST_FIELD_FL_ALIAS)
 		goto out; /* caller will populate */
 
 	if (flags & HIST_FIELD_FL_VAR_REF) {
@@ -2013,6 +2015,34 @@ static struct hist_field *parse_var_ref(char *system, char *event_name,
 	return field;
 }
 
+static struct hist_field *create_alias(struct hist_trigger_data *hist_data,
+				       struct hist_field *var_ref,
+				       char *var_name)
+{
+	struct hist_field *alias = NULL;
+	unsigned long flags = HIST_FIELD_FL_ALIAS | HIST_FIELD_FL_VAR |
+		HIST_FIELD_FL_VAR_ONLY;
+
+	alias = create_hist_field(hist_data, NULL, flags, var_name);
+	if (!alias)
+		return NULL;
+
+	alias->fn = var_ref->fn;
+	alias->operands[0] = var_ref;
+	alias->var.idx = var_ref->var.idx;
+	alias->var.hist_data = var_ref->hist_data;
+	alias->size = var_ref->size;
+	alias->is_signed = var_ref->is_signed;
+	alias->type = kstrdup(var_ref->type, GFP_KERNEL);
+	if (!alias->type) {
+		kfree(alias->type);
+		destroy_hist_field(alias, 0);
+		return NULL;
+	}
+
+	return alias;
+}
+
 struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
 			      struct trace_event_file *file, char *str,
 			      unsigned long *flags, char *var_name)
@@ -2036,6 +2066,13 @@ struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
 	if (hist_field) {
 		hist_data->var_refs[hist_data->n_var_refs] = hist_field;
 		hist_field->var_ref_idx = hist_data->n_var_refs++;
+		if (var_name) {
+			hist_field = create_alias(hist_data, hist_field, var_name);
+			if (!hist_field) {
+				ret = -ENOMEM;
+				goto out;
+			}
+		}
 		return hist_field;
 	}
 
@@ -4152,8 +4189,11 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
 		seq_puts(m, "$common_timestamp");
 	else if (hist_field->flags & HIST_FIELD_FL_CPU)
 		seq_puts(m, "cpu");
-	else if (field_name)
+	else if (field_name) {
+		if (hist_field->flags & HIST_FIELD_FL_ALIAS)
+			seq_putc(m, '$');
 		seq_printf(m, "%s", field_name);
+	}
 
 	if (hist_field->flags) {
 		const char *flags_str = get_hist_field_flags(hist_field);
-- 
1.9.3

[PATCH 29/32] tracing: Add 'last error' error facility for hist triggers

[Tom Zanussi]

With the addition of variables and actions, it's become necessary to
provide more detailed error information to users about syntax errors.

Add a 'last error' facility accessible via the erroring event's 'hist'
file.  Reading the hist file after an error will display more detailed
information about what went wrong, if information is available.  This
extended error information will be available until the next hist
trigger command for that event.

  # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
  echo: write error: Invalid argument

  # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist

  ERROR: Couldn't yyy: zzz
  Last command: xxx

Also add specific error messages for variable and action errors.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 Documentation/trace/events.txt   |  19 ++++
 kernel/trace/trace_events_hist.c | 181 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 188 insertions(+), 12 deletions(-)

diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index 9717688..f271d87 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -686,6 +686,25 @@ The following commands are supported:
 				 interpreted as microseconds.
     cpu                    int - the cpu on which the event occurred.
 
+  Extended error information
+  --------------------------
+
+  For some error conditions encountered when invoking a hist trigger
+  command, extended error information is available via the
+  corresponding event's 'hist' file.  Reading the hist file after an
+  error will display more detailed information about what went wrong,
+  if information is available.  This extended error information will
+  be available until the next hist trigger command for that event.
+
+  If available for a given error condition, the extended error
+  information and usage takes the following form:
+
+    # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
+    echo: write error: Invalid argument
+
+    # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
+    ERROR: Couldn't yyy: zzz
+      Last command: xxx
 
 6.2 'hist' trigger examples
 ---------------------------
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 799b95e..06049f8 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -288,6 +288,7 @@ struct hist_trigger_data {
 	struct field_var		*max_vars[SYNTH_FIELDS_MAX];
 	unsigned int			n_max_vars;
 	unsigned int			n_max_var_str;
+	char				*last_err;
 };
 
 struct synth_field {
@@ -332,6 +333,83 @@ struct action_data {
 	struct hist_field	*onmax_var;
 };
 
+
+static char *hist_err_str;
+static char *last_hist_cmd;
+
+static int hist_err_alloc(void)
+{
+	int ret = 0;
+
+	last_hist_cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
+	hist_err_str = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
+	if (!last_hist_cmd || !hist_err_str)
+		ret = -ENOMEM;
+
+	return ret;
+}
+
+static void last_cmd_set(char *str)
+{
+	if (!last_hist_cmd || !str)
+		return;
+
+	if (strlen(last_hist_cmd) > MAX_FILTER_STR_VAL - 1)
+		return;
+
+	strcpy(last_hist_cmd, str);
+}
+
+static void hist_err(char *str, char *var)
+{
+	int maxlen = MAX_FILTER_STR_VAL - 1;
+
+	if (strlen(hist_err_str))
+		return;
+
+	if (!hist_err_str || !str)
+		return;
+
+	if (!var)
+		var = "";
+
+	if (strlen(hist_err_str) + strlen(str) + strlen(var) > maxlen)
+		return;
+
+	strcat(hist_err_str, str);
+	strcat(hist_err_str, var);
+}
+
+static void hist_err_event(char *str, char *system, char *event, char *var)
+{
+	char err[MAX_FILTER_STR_VAL];
+
+	if (system && var)
+		sprintf(err, "%s.%s.%s", system, event, var);
+	else if (system)
+		sprintf(err, "%s.%s", system, event);
+	else
+		strcpy(err, var);
+
+	hist_err(str, err);
+}
+
+static void hist_err_clear(void)
+{
+	if (!hist_err_str)
+		return;
+
+	hist_err_str[0] = '\0';
+}
+
+static bool have_hist_err(void)
+{
+	if (hist_err_str && strlen(hist_err_str))
+		return true;
+
+	return false;
+}
+
 static LIST_HEAD(synth_event_list);
 static DEFINE_MUTEX(synth_event_mutex);
 
@@ -1954,12 +2032,21 @@ static struct hist_field *create_var_ref(struct hist_field *var_field)
 	return ref_field;
 }
 
+static bool is_common_field(char *var_name)
+{
+	if (strncmp(var_name, "$common_timestamp", strlen("$common_timestamp")) == 0)
+		return true;
+
+	return false;
+}
+
 static struct hist_field *parse_var_ref(char *system, char *event_name,
 					char *var_name)
 {
 	struct hist_field *var_field = NULL, *ref_field = NULL;
 
-	if (!var_name || strlen(var_name) < 2 || var_name[0] != '$')
+	if (!var_name || strlen(var_name) < 2 || var_name[0] != '$' ||
+	    is_common_field(var_name))
 		return NULL;
 
 	var_name++;
@@ -1968,6 +2055,10 @@ static struct hist_field *parse_var_ref(char *system, char *event_name,
 	if (var_field)
 		ref_field = create_var_ref(var_field);
 
+	if (!ref_field)
+		hist_err_event("Couldn't find variable: $",
+			       system, event_name, var_name);
+
 	return ref_field;
 }
 
@@ -2426,8 +2517,11 @@ static struct trace_event_file *event_file(char *system, char *event_name)
 	char *cmd;
 	int ret;
 
-	if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX)
+	if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX) {
+		hist_err_event("onmatch: Too many field variables defined: ",
+			       system, event_name, field_name);
 		return ERR_PTR(-EINVAL);
+	}
 
 	tr = top_trace_array();
 	if (!tr)
@@ -2435,13 +2529,18 @@ static struct trace_event_file *event_file(char *system, char *event_name)
 
 	file = event_file(system, event_name);
 	if (IS_ERR(file)) {
+		hist_err_event("onmatch: Event file not found: ",
+			       system, event_name, field_name);
 		ret = PTR_ERR(file);
 		return ERR_PTR(ret);
 	}
 
 	hist_data = find_compatible_hist(target_hist_data, file);
-	if (!hist_data)
+	if (!hist_data) {
+		hist_err_event("onmatch: Matching event histogram not found: ",
+			       system, event_name, field_name);
 		return ERR_PTR(-EINVAL);
+	}
 
 	var_hist = kzalloc(sizeof(*var_hist), GFP_KERNEL);
 	if (!var_hist)
@@ -2489,6 +2588,8 @@ static struct trace_event_file *event_file(char *system, char *event_name)
 		kfree(cmd);
 		kfree(var_hist->cmd);
 		kfree(var_hist);
+		hist_err_event("onmatch: Couldn't create histogram for field: ",
+			       system, event_name, field_name);
 		return ERR_PTR(ret);
 	}
 
@@ -2500,6 +2601,8 @@ static struct trace_event_file *event_file(char *system, char *event_name)
 		kfree(cmd);
 		kfree(var_hist->cmd);
 		kfree(var_hist);
+		hist_err_event("onmatch: Couldn't find synthetic variable: ",
+			       system, event_name, field_name);
 		return ERR_PTR(-EINVAL);
 	}
 
@@ -2636,18 +2739,21 @@ static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
 	int ret = 0;
 
 	if (hist_data->n_field_vars >= SYNTH_FIELDS_MAX) {
+		hist_err("Too many field variables defined: ", field_name);
 		ret = -EINVAL;
 		goto err;
 	}
 
 	val = parse_atom(hist_data, file, field_name, &flags, NULL);
 	if (IS_ERR(val)) {
+		hist_err("Couldn't parse field variable: ", field_name);
 		ret = PTR_ERR(val);
 		goto err;
 	}
 
 	var = create_var(hist_data, file, field_name, val->size, val->type);
 	if (IS_ERR(var)) {
+		hist_err("Couldn't create or find variable: ", field_name);
 		kfree(val);
 		ret = PTR_ERR(var);
 		goto err;
@@ -2772,14 +2878,18 @@ static int onmax_create(struct hist_trigger_data *hist_data,
 	int ret = 0;
 
 	onmax_var_str = data->onmax_var_str;
-	if (onmax_var_str[0] != '$')
+	if (onmax_var_str[0] != '$') {
+		hist_err("onmax: For onmax(x), x must be a variable: ", onmax_var_str);
 		return -EINVAL;
+	}
 	onmax_var_str++;
 
 	event_name = trace_event_name(call);
 	var_field = find_target_event_var(hist_data, NULL, NULL, onmax_var_str);
-	if (!var_field)
+	if (!var_field) {
+		hist_err("onmax: Couldn't find onmax variable: ", onmax_var_str);
 		return -EINVAL;
+	}
 
 	flags = HIST_FIELD_FL_VAR_REF;
 	ref_field = create_hist_field(hist_data, NULL, flags, NULL);
@@ -2803,6 +2913,7 @@ static int onmax_create(struct hist_trigger_data *hist_data,
 	data->max_var_ref_idx = var_ref_idx;
 	max_var = create_var(hist_data, file, "max", sizeof(u64), "u64");
 	if (IS_ERR(max_var)) {
+		hist_err("onmax: Couldn't create onmax variable: ", "max");
 		ret = PTR_ERR(max_var);
 		goto out;
 	}
@@ -2815,6 +2926,7 @@ static int onmax_create(struct hist_trigger_data *hist_data,
 
 		field_var = create_target_field_var(hist_data, NULL, NULL, param);
 		if (IS_ERR(field_var)) {
+			hist_err("onmax: Couldn't create field variable: ", param);
 			ret = PTR_ERR(field_var);
 			kfree(param);
 			goto out;
@@ -2847,6 +2959,7 @@ static int parse_action_params(char *params, struct action_data *data)
 
 		param = strstrip(param);
 		if (strlen(param) < 2) {
+			hist_err("Invalid action param: ", param);
 			ret = -EINVAL;
 			goto out;
 		}
@@ -3004,6 +3117,9 @@ static int check_synth_field(struct synth_event *event,
 		hist_field = find_event_var(system, event, var);
 	}
 
+	if (!hist_field)
+		hist_err_event("onmatch: Couldn't find onmatch param: $", system, event, var);
+
 	return hist_field;
 }
 
@@ -3055,6 +3171,7 @@ static int onmatch_create(struct hist_trigger_data *hist_data,
 
 	event = find_synth_event(data->synth_event_name);
 	if (!event) {
+		hist_err("onmatch: Couldn't find synthetic event: ", data->synth_event_name);
 		ret = -EINVAL;
 		goto out;
 	}
@@ -3094,6 +3211,7 @@ static int onmatch_create(struct hist_trigger_data *hist_data,
 			ret = -EINVAL;
 			goto out;
 		}
+
 		if (check_synth_field(event, hist_field, field_pos) == 0) {
 			var_ref = create_var_ref(hist_field);
 			if (!var_ref) {
@@ -3108,12 +3226,15 @@ static int onmatch_create(struct hist_trigger_data *hist_data,
 			continue;
 		}
 
+		hist_err_event("onmatch: Param type doesn't match synthetic event field type: ",
+			       system, event_name, param);
 		kfree(p);
 		ret = -EINVAL;
 		goto out;
 	}
 
 	if (field_pos != event->n_fields) {
+		hist_err("onmatch: Param count doesn't match synthetic event field count: ", event->name);
 		ret = -EINVAL;
 		goto out;
 	}
@@ -3141,31 +3262,44 @@ static struct action_data *onmatch_parse(char *str)
 		return ERR_PTR(-ENOMEM);
 
 	match_event = strsep(&str, ")");
-	if (!match_event || !str)
+	if (!match_event || !str) {
+		hist_err("onmatch: Missing closing paren: ", match_event);
 		goto free;
+	}
 
 	match_event_system = strsep(&match_event, ".");
-	if (!match_event)
+	if (!match_event) {
+		hist_err("onmatch: Missing subsystem for match event: ", match_event_system);
 		goto free;
+	}
 
-	if (IS_ERR(event_file(match_event_system, match_event)))
+	if (IS_ERR(event_file(match_event_system, match_event))) {
+		hist_err_event("onmatch: Invalid subsystem or event name: ",
+			       match_event_system, match_event, NULL);
 		goto free;
+	}
 
 	data->match_event = kstrdup(match_event, GFP_KERNEL);
 	data->match_event_system = kstrdup(match_event_system, GFP_KERNEL);
 
 	strsep(&str, ".");
-	if (!str)
+	if (!str) {
+		hist_err("onmatch: Missing . after onmatch(): ", str);
 		goto free;
+	}
 
 	synth_event_name = strsep(&str, "(");
-	if (!synth_event_name || !str)
+	if (!synth_event_name || !str) {
+		hist_err("onmatch: Missing opening paramlist paren: ", synth_event_name);
 		goto free;
+	}
 	data->synth_event_name = kstrdup(synth_event_name, GFP_KERNEL);
 
 	params = strsep(&str, ")");
-	if (!params || !str || (str && strlen(str)))
+	if (!params || !str || (str && strlen(str))) {
+		hist_err("onmatch: Missing closing paramlist paren: ", params);
 		goto free;
+	}
 
 	ret = parse_action_params(params, data);
 	if (ret)
@@ -3217,6 +3351,7 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 	if (field_str && var_name) {
 		if (find_var(file, var_name) &&
 		    !hist_data->remove) {
+			hist_err("Variable already defined: ", var_name);
 			ret = -EINVAL;
 			goto out;
 		}
@@ -3224,6 +3359,7 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 		flags |= HIST_FIELD_FL_VAR;
 		hist_data->n_vars++;
 		if (hist_data->n_vars > TRACING_MAP_VARS_MAX) {
+			hist_err("Too many variables defined: ", var_name);
 			ret = -EINVAL;
 			goto out;
 		}
@@ -3234,6 +3370,7 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 		field_str = var_name;
 		var_name = NULL;
 	} else {
+		hist_err("Malformed assignment: ", var_name);
 		ret = -EINVAL;
 		goto out;
 	}
@@ -3248,6 +3385,7 @@ static int create_val_field(struct hist_trigger_data *hist_data,
 		hist_field = parse_atom(hist_data, file, field_str,
 					&flags, var_name);
 		if (IS_ERR(hist_field)) {
+			hist_err("Unable to parse atom: ", field_str);
 			ret = PTR_ERR(hist_field);
 			goto out;
 		}
@@ -4138,6 +4276,11 @@ static int hist_show(struct seq_file *m, void *v)
 			hist_trigger_show(m, data, n++);
 	}
 
+	if (have_hist_err()) {
+		seq_printf(m, "\nERROR: %s\n", hist_err_str);
+		seq_printf(m, "  Last command: %s\n", last_hist_cmd);
+	}
+
  out_unlock:
 	mutex_unlock(&event_mutex);
 
@@ -4509,6 +4652,7 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
 		if (named_data) {
 			if (!hist_trigger_match(data, named_data, named_data,
 						true)) {
+				hist_err("Named hist trigger doesn't match existing named trigger (includes variables): ", hist_data->attrs->name);
 				ret = -EINVAL;
 				goto out;
 			}
@@ -4528,13 +4672,16 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
 				test->paused = false;
 			else if (hist_data->attrs->clear)
 				hist_clear(test);
-			else
+			else {
+				hist_err("Hist trigger already exists", NULL);
 				ret = -EEXIST;
+			}
 			goto out;
 		}
 	}
  new:
 	if (hist_data->attrs->cont || hist_data->attrs->clear) {
+		hist_err("Can't clear or continue a nonexistent hist trigger", NULL);
 		ret = -ENOENT;
 		goto out;
 	}
@@ -4701,6 +4848,11 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	char *trigger, *p;
 	int ret = 0;
 
+	if (glob && strlen(glob)) {
+		last_cmd_set(param);
+		hist_err_clear();
+	}
+
 	if (!param)
 		return -EINVAL;
 
@@ -4804,6 +4956,9 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	/* Just return zero, not the number of registered triggers */
 	ret = 0;
  out:
+	if (ret == 0)
+		hist_err_clear();
+
 	return ret;
  out_unreg:
 	cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
@@ -5002,6 +5157,8 @@ static __init int trace_events_hist_init(void)
 		goto err;
 	}
 
+	hist_err_alloc();
+
 	return err;
  err:
 	pr_warn("Could not create tracefs 'synthetic_events' entry\n");
-- 
1.9.3

Re: [PATCH 29/32] tracing: Add 'last error' error facility for hist triggers

[Namhyung Kim]

On Mon, Jun 26, 2017 at 05:49:30PM -0500, Tom Zanussi wrote:
> With the addition of variables and actions, it's become necessary to
> provide more detailed error information to users about syntax errors.
> 
> Add a 'last error' facility accessible via the erroring event's 'hist'
> file.  Reading the hist file after an error will display more detailed
> information about what went wrong, if information is available.  This
> extended error information will be available until the next hist
> trigger command for that event.
> 
>   # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
>   echo: write error: Invalid argument
> 
>   # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
> 
>   ERROR: Couldn't yyy: zzz
>   Last command: xxx
> 
> Also add specific error messages for variable and action errors.
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>  Documentation/trace/events.txt   |  19 ++++
>  kernel/trace/trace_events_hist.c | 181 ++++++++++++++++++++++++++++++++++++---
>  2 files changed, 188 insertions(+), 12 deletions(-)
> 
> diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
> index 9717688..f271d87 100644
> --- a/Documentation/trace/events.txt
> +++ b/Documentation/trace/events.txt
> @@ -686,6 +686,25 @@ The following commands are supported:
>  				 interpreted as microseconds.
>      cpu                    int - the cpu on which the event occurred.
>  
> +  Extended error information
> +  --------------------------
> +
> +  For some error conditions encountered when invoking a hist trigger
> +  command, extended error information is available via the
> +  corresponding event's 'hist' file.  Reading the hist file after an
> +  error will display more detailed information about what went wrong,
> +  if information is available.  This extended error information will
> +  be available until the next hist trigger command for that event.
> +
> +  If available for a given error condition, the extended error
> +  information and usage takes the following form:
> +
> +    # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
> +    echo: write error: Invalid argument
> +
> +    # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
> +    ERROR: Couldn't yyy: zzz
> +      Last command: xxx
>  
>  6.2 'hist' trigger examples
>  ---------------------------
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 799b95e..06049f8 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -288,6 +288,7 @@ struct hist_trigger_data {
>  	struct field_var		*max_vars[SYNTH_FIELDS_MAX];
>  	unsigned int			n_max_vars;
>  	unsigned int			n_max_var_str;
> +	char				*last_err;

I couldn't find where it's used.

>  };
>  
>  struct synth_field {
> @@ -332,6 +333,83 @@ struct action_data {
>  	struct hist_field	*onmax_var;
>  };
>  
> +
> +static char *hist_err_str;
> +static char *last_hist_cmd;
> +
> +static int hist_err_alloc(void)
> +{
> +	int ret = 0;
> +
> +	last_hist_cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> +	hist_err_str = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> +	if (!last_hist_cmd || !hist_err_str)
> +		ret = -ENOMEM;

This makes me uncomfortable..

> +
> +	return ret;
> +}
> +
> +static void last_cmd_set(char *str)
> +{
> +	if (!last_hist_cmd || !str)
> +		return;
> +
> +	if (strlen(last_hist_cmd) > MAX_FILTER_STR_VAL - 1)
> +		return;

Hmm.. why does it check 'last_hist_cmd' rather than 'str'?

> +
> +	strcpy(last_hist_cmd, str);
> +}
> +
> +static void hist_err(char *str, char *var)
> +{
> +	int maxlen = MAX_FILTER_STR_VAL - 1;
> +
> +	if (strlen(hist_err_str))
> +		return;

Shouldn't it move to after the NULL check below?

Thanks,
Namhyung


> +
> +	if (!hist_err_str || !str)
> +		return;
> +
> +	if (!var)
> +		var = "";
> +
> +	if (strlen(hist_err_str) + strlen(str) + strlen(var) > maxlen)
> +		return;
> +
> +	strcat(hist_err_str, str);
> +	strcat(hist_err_str, var);
> +}
> +
> +static void hist_err_event(char *str, char *system, char *event, char *var)
> +{
> +	char err[MAX_FILTER_STR_VAL];
> +
> +	if (system && var)
> +		sprintf(err, "%s.%s.%s", system, event, var);
> +	else if (system)
> +		sprintf(err, "%s.%s", system, event);
> +	else
> +		strcpy(err, var);
> +
> +	hist_err(str, err);
> +}
> +
> +static void hist_err_clear(void)
> +{
> +	if (!hist_err_str)
> +		return;
> +
> +	hist_err_str[0] = '\0';
> +}
> +
> +static bool have_hist_err(void)
> +{
> +	if (hist_err_str && strlen(hist_err_str))
> +		return true;
> +
> +	return false;
> +}

Re: [PATCH 29/32] tracing: Add 'last error' error facility for hist triggers

[Tom Zanussi]

Hi Namhyung,

On Wed, 2017-07-26 at 13:39 +0900, Namhyung Kim wrote:
> On Mon, Jun 26, 2017 at 05:49:30PM -0500, Tom Zanussi wrote:
> > With the addition of variables and actions, it's become necessary to
> > provide more detailed error information to users about syntax errors.
> > 
> > Add a 'last error' facility accessible via the erroring event's 'hist'
> > file.  Reading the hist file after an error will display more detailed
> > information about what went wrong, if information is available.  This
> > extended error information will be available until the next hist
> > trigger command for that event.
> > 
> >   # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
> >   echo: write error: Invalid argument
> > 
> >   # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
> > 
> >   ERROR: Couldn't yyy: zzz
> >   Last command: xxx
> > 
> > Also add specific error messages for variable and action errors.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
> >  Documentation/trace/events.txt   |  19 ++++
> >  kernel/trace/trace_events_hist.c | 181 ++++++++++++++++++++++++++++++++++++---
> >  2 files changed, 188 insertions(+), 12 deletions(-)
> > 
> > diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
> > index 9717688..f271d87 100644
> > --- a/Documentation/trace/events.txt
> > +++ b/Documentation/trace/events.txt
> > @@ -686,6 +686,25 @@ The following commands are supported:
> >  				 interpreted as microseconds.
> >      cpu                    int - the cpu on which the event occurred.
> >  
> > +  Extended error information
> > +  --------------------------
> > +
> > +  For some error conditions encountered when invoking a hist trigger
> > +  command, extended error information is available via the
> > +  corresponding event's 'hist' file.  Reading the hist file after an
> > +  error will display more detailed information about what went wrong,
> > +  if information is available.  This extended error information will
> > +  be available until the next hist trigger command for that event.
> > +
> > +  If available for a given error condition, the extended error
> > +  information and usage takes the following form:
> > +
> > +    # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
> > +    echo: write error: Invalid argument
> > +
> > +    # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
> > +    ERROR: Couldn't yyy: zzz
> > +      Last command: xxx
> >  
> >  6.2 'hist' trigger examples
> >  ---------------------------
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index 799b95e..06049f8 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> > @@ -288,6 +288,7 @@ struct hist_trigger_data {
> >  	struct field_var		*max_vars[SYNTH_FIELDS_MAX];
> >  	unsigned int			n_max_vars;
> >  	unsigned int			n_max_var_str;
> > +	char				*last_err;
> 
> I couldn't find where it's used.
> 

It's not, will remove.

> >  };
> >  
> >  struct synth_field {
> > @@ -332,6 +333,83 @@ struct action_data {
> >  	struct hist_field	*onmax_var;
> >  };
> >  
> > +
> > +static char *hist_err_str;
> > +static char *last_hist_cmd;
> > +
> > +static int hist_err_alloc(void)
> > +{
> > +	int ret = 0;
> > +
> > +	last_hist_cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> > +	hist_err_str = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> > +	if (!last_hist_cmd || !hist_err_str)
> > +		ret = -ENOMEM;
> 
> This makes me uncomfortable..
> 
> > +
> > +	return ret;
> > +}
> > +
> > +static void last_cmd_set(char *str)
> > +{
> > +	if (!last_hist_cmd || !str)
> > +		return;
> > +
> > +	if (strlen(last_hist_cmd) > MAX_FILTER_STR_VAL - 1)
> > +		return;
> 
> Hmm.. why does it check 'last_hist_cmd' rather than 'str'?
> 
> > +
> > +	strcpy(last_hist_cmd, str);
> > +}
> > +
> > +static void hist_err(char *str, char *var)
> > +{
> > +	int maxlen = MAX_FILTER_STR_VAL - 1;
> > +
> > +	if (strlen(hist_err_str))
> > +		return;
> 
> Shouldn't it move to after the NULL check below?
> 

Yes, will fix this and the others above.

Thanks,

Tom

[PATCH 30/32] tracing: Add inter-event hist trigger Documentation

[Tom Zanussi]

Add background and details on inter-event hist triggers, including
hist variables, synthetic events, and actions.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 Documentation/trace/events.txt | 376 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 376 insertions(+)

diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index f271d87..888907c 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -571,6 +571,7 @@ The following commands are supported:
 	.sym-offset display an address as a symbol and offset
 	.syscall    display a syscall id as a system call name
 	.execname   display a common_pid as a program name
+	.usecs      display a $common_timestamp in microseconds
 
   Note that in general the semantics of a given field aren't
   interpreted when applying a modifier to it, but there are some
@@ -2101,3 +2102,378 @@ The following commands are supported:
         Hits: 489
         Entries: 7
         Dropped: 0
+
+6.3 Inter-event hist triggers
+-----------------------------
+
+Inter-event hist triggers are hist triggers that combine values from
+one or more other events and create a histogram using that data.  Data
+from an inter-event histogram can in turn become the source for
+further combined histograms, thus providing a chain of related
+histograms, which is important for some applications.
+
+The most important example of an inter-event quantity that can be used
+in this manner is latency, which is simply a difference in timestamps
+between two events (although trace events don't have an externally
+visible timestamp field, the inter-event hist trigger support adds a
+pseudo-field to all events named '$common_timestamp' which can be used
+as if it were an actual event field).  Although latency is the most
+important inter-event quantity, note that because the support is
+completely general across the trace event subsystem, any event field
+can be used in an inter-event quantity.
+
+An example of a histogram that combines data from other histograms
+into a useful chain would be a 'wakeupswitch latency' histogram that
+combines a 'wakeup latency' histogram and a 'switch latency'
+histogram.
+
+Normally, a hist trigger specification consists of a (possibly
+compound) key along with one or more numeric values, which are
+continually updated sums associated with that key.  A histogram
+specification in this case consists of individual key and value
+specifications that refer to trace event fields associated with a
+single event type.
+
+The inter-event hist trigger extension allows fields from multiple
+events to be referenced and combined into a multi-event histogram
+specification.  In support of this overall goal, a few enabling
+features have been added to the hist trigger support:
+
+  - In order to compute an inter-event quantity, a value from one
+    event needs to saved and then referenced from another event.  This
+    requires the introduction of support for histogram 'variables'.
+
+  - The computation of inter-event quantities and their combination
+    require some minimal amount of support for applying simple
+    expressions to variables (+ and -).
+
+  - A histogram consisting of inter-event quantities isn't logically a
+    histogram on either event (so having the 'hist' file for either
+    event host the histogram output doesn't really make sense).  To
+    address the idea that the histogram is associated with a
+    combination of events, support is added allowing the creation of
+    'synthetic' events that are events derived from other events.
+    These synthetic events are full-fledged events just like any other
+    and can be used as such, as for instance to create the
+    'combination' histograms mentioned previously.
+
+  - A set of 'actions' can be associated with histogram entries -
+    these can be used to generate the previously mentioned synthetic
+    events, but can also be used for other purposes, such as for
+    example saving context when a 'max' latency has been hit.
+
+  - Trace events don't have a 'timestamp' associated with them, but
+    there is an implicit timestamp saved along with an event in the
+    underlying ftrace ring buffer.  This timestamp is now exposed as a
+    a synthetic field named '$common_timestamp' which can be used in
+    histograms as if it were any other event field.  Note that it has
+    a '$' prefixed to it - this is meant to indicate that it isn't an
+    actual field in the trace format but rather is a synthesized value
+    that nonetheless can be used as if it were an actual field.  By
+    default it is in units of nanoseconds; appending '.usecs' to a
+    common_timestamp field changes the units to microseconds.
+
+These features are decribed in more detail in the following sections.
+
+6.3.1 Histogram Variables
+-------------------------
+
+Variables are simply named locations used for saving and retrieving
+values between matching events.  A 'matching' event is defined as an
+event that has a matching key - if a variable is saved for a histogram
+entry corresponding to that key, any subsequent event with a matching
+key can access that variable.
+
+A variable's value is normally available to any subsequent event until
+it is set to something else by a subsequent event.  The one exception
+to that rule is that any variable used in an expression is essentially
+'read-once' - once it's used by an expression in a subsequent event,
+it's reset to its 'unset' state, which means it can't be used again
+unless it's set again.  This ensures not only that an event doesn't
+use an uninitialized variable in a calculation, but that that variable
+is used only once and not for any unrelated subsequent match.
+
+The basic syntax for saving a variable is to simply prefix a unique
+variable name not corresponding to any keyword along with an '=' sign
+to any event field.
+
+Either keys or values can be saved and retrieved in this way.  This
+creates a variable named 'ts0' for a histogram entry with the key
+'next_pid':
+
+  # echo 'hist:keys=next_pid:vals=ts0=$common_timestamp ... >> event/trigger
+
+The ts0 variable can be accessed by any subsequent event having the
+same pid as 'next_pid'.
+
+Variable references are formed by prepending the variable name with
+the '$' sign.  Thus for example, the ts0 variable above would be
+referenced as '$ts0' in subsequent expressions.
+
+Because 'vals=' is used, the $common_timestamp variable value above
+will also be summed as a normal histogram value would (though for a
+timestamp it makes little sense).
+
+The below shows that a key value can also be saved in the same way:
+
+  # echo 'hist:key=timer_pid=common_pid ...' >> event/trigger
+
+If a variable isn't a key variable or prefixed with 'vals=', the
+associated event field will be saved in a variable but won't be summed
+as a value:
+
+  # echo 'hist:keys=next_pid:ts1=$common_timestamp ... >> event/trigger
+
+Multiple variables can be assigned at the same time.  The below would
+result in both ts0 and b being created as variables, with both
+common_timestamp and field1 additionally being summed as values:
+
+  # echo 'hist:keys=pid:vals=ts0=$common_timestamp,b=field1 ... >> event/trigger
+
+Any number of variables not bound to a 'vals=' prefix can also be
+assigned by simply separating them with colons.  Below is the same
+thing but without the values being summed in the histogram:
+
+  # echo 'hist:keys=pid:ts0=$common_timestamp:b=field1 ... >> event/trigger
+
+Variables set as above can be referenced and used in expressions on
+another event.
+
+For example, here's how a latency can be calculated:
+
+  # echo 'hist:keys=pid,prio:ts0=$common_timestamp ... >> event1/trigger
+  # echo 'hist:keys=next_pid:wakeup_lat=$common_timestamp-$ts0 ... >> event2/trigger
+
+In the first line above, the event's timetamp is saved into the
+variable ts0.  In the next line, ts0 is subtracted from the second
+event's timestamp to produce the latency, which is then assigned into
+yet another variable, 'wakeup_lat'.  The hist trigger below in turn
+makes use of the wakeup_lat variable to compute a combined latency
+using the same key and variable from yet another event:
+
+  # echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ... >> event3/trigger
+
+6.3.2 Synthetic Events
+----------------------
+
+Synthetic events are user-defined events generated from hist trigger
+variables or fields associated with one or more other events.  Their
+purpose is to provide a mechanism for displaying data spanning
+multiple events consistent with the existing and already familiar
+usage for normal events.
+
+To define a synthetic event, the user writes a simple specification
+consisting of the name of the new event along with one or more
+variables and their types, which can be any valid field type,
+separated by semicolons, to the tracing/synthetic_events file.
+
+For instance, the following creates a new event named 'wakeup_latency'
+with 3 fields: lat, pid, and prio.  Each of those fields is simply a
+variable reference to a variable on another event:
+
+  # echo 'wakeup_latency \
+          u64 lat; \
+          pid_t pid; \
+	  int prio' >> \
+	  /sys/kernel/debug/tracing/synthetic_events
+
+Reading the tracing/synthetic_events file lists all the currently
+defined synthetic events, in this case the event defined above:
+
+  # cat /sys/kernel/debug/tracing/synthetic_events
+    wakeup_latency u64 lat; pid_t pid; int prio
+
+An existing synthetic event definition can be removed by prepending
+the command that defined it with a '!':
+
+  # echo '!wakeup_latency u64 lat pid_t pid int prio' >> \
+    /sys/kernel/debug/tracing/synthetic_events
+
+At this point, there isn't yet an actual 'wakeup_latency' event
+instantiated in the event subsytem - for this to happen, a 'hist
+trigger action' needs to be instantiated and bound to actual fields
+and variables defined on other events (see Section 6.3.3 below).
+
+Once that is done, an event instance is created, and a histogram can
+be defined using it:
+
+  # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \
+        /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
+
+The new event is created under the tracing/events/synthetic/ directory
+and looks and behaves just like any other event:
+
+  # ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency
+        enable  filter  format  hist  id  trigger
+
+Like any other event, once a histogram is enabled for the event, the
+output can be displayed by reading the event's 'hist' file.
+
+6.3.3 Hist trigger 'actions'
+----------------------------
+
+A hist trigger 'action' is a function that's executed whenever a
+histogram entry is added or updated.
+
+The default 'action' if no special function is explicity specified is
+as it always has been, to simply update the set of values associated
+with an entry.  Some applications, however, may want to perform
+additional actions at that point, such as generate another event, or
+compare and save a maximum.
+
+The following additional actions are available.  To specify an action
+for a given event, simply specify the action between colons in the
+hist trigger specification.
+
+  - onmatch(matching.event).<synthetic_event_name>(param list)
+
+    The 'onmatch(matching.event).<synthetic_event_name>(params)' hist
+    trigger action is invoked whenever an event matches and the
+    histogram entry would be added or updated.  It causes the named
+    synthetic event to be generated with the values given in the
+    'param list'.  The result is the generation of a synthetic event
+    that consists of the values contained in those variables at the
+    time the invoking event was hit.
+
+    The 'param list' consists of one or more parameters which may be
+    either variables or fields defined on either the 'matching.event'
+    or the target event.  The variables or fields specified in the
+    param list may be either fully-qualified or unqualified.  If a
+    variable is specified as unqualified, it must be unique between
+    the two events.  A field name used as a param can be unqualified
+    if it refers to the target event, but must be fully qualified if
+    it refers to the matching event.  A fully-qualified name is of the
+    form 'system.event_name.$var_name' or 'system.event_name.field'.
+
+    The 'matching.event' specification is simply the fully qualified
+    event name of the event that matches the target event for the
+    onmatch() functionality, in the form 'system.event_name'.
+
+    Finally, the number and type of variables/fields in the 'param
+    list' must match the number and types of the fields in the
+    synthetic event being generated.
+
+    As an example the below defines a simple synthetic event and uses
+    a variable defined on the sched_wakeup_new event as a parameter
+    when invoking the synthetic event.  Here we define the synthetic
+    event:
+
+    # echo 'wakeup_new_test pid_t pid' >> \
+           /sys/kernel/debug/tracing/synthetic_events
+
+    # cat /sys/kernel/debug/tracing/synthetic_events
+          wakeup_new_test pid_t pid
+
+    The following hist trigger both defines the missing testpid
+    variable and specifies an onmatch() action that generates a
+    wakeup_new_test synthetic event whenever a sched_wakeup_new event
+    occurs, which because of the 'if comm == "cyclictest"' filter only
+    happens when the executable is cyclictest:
+
+    # echo 'hist:keys=testpid=pid:onmatch(sched.sched_wakeup_new).\
+            wakeup_new_test($testpid) if comm=="cyclictest"' >> \
+            /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
+
+    Creating and displaying a histogram based on those events is now
+    just a matter of using the fields and new synthetic event in the
+    tracing/events/synthetic directory, as usual:
+
+    # echo 'hist:keys=pid:sort=pid' >> \
+           /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger
+
+    Running 'cyclictest' should cause wakeup_new events to generate
+    wakeup_new_test synthetic events which should result in histogram
+    output in the wakeup_new_test event's hist file:
+
+    # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/hist
+
+    A more typical usage would be to use two events to calculate a
+    latency.  The following example uses a set of hist triggers to
+    produce a 'wakeup_latency' histogram:
+
+    First, we define a 'wakeup_latency' synthetic event:
+
+    # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \
+            /sys/kernel/debug/tracing/synthetic_events
+
+    Next, we specify that whenever we see a sched_wakeup event for a
+    cyclictest thread, save the timestamp in a 'ts0' variable:
+
+    # echo 'hist:keys=saved_pid=pid:ts0=$common_timestamp.usecs \
+            if comm=="cyclictest"' >> \
+	    /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
+
+    Then, when the corresponding thread is actually scheduled onto the
+    CPU by a sched_switch event, calculate the latency and use that
+    along with another variable and an event field to generate a
+    wakeup_latency synthetic event:
+
+    # echo 'hist:keys=next_pid:wakeup_lat=$common_timestamp.usecs-$ts0:\
+            onmatch(sched.sched_wakeup).wakeup_latency($wakeup_lat,\
+	            $saved_pid,next_prio) if next_comm=="cyclictest"' >> \
+	    /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
+
+    We also need to create a histogram on the wakeup_latency synthetic
+    event in order to aggregate the generated synthetic event data:
+
+    # echo 'hist:keys=pid,prio,lat:sort=pid,lat' >> \
+            /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
+
+    Finally, once we've run cyclictest to actually generate some
+    events, we can see the output by looking at the wakeup_latency
+    synthetic event's hist file:
+
+    # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist
+
+  - onmax(var).save(field,...)
+
+    The 'onmax(var).save(field,...)' hist trigger action is invoked
+    whenever the value of 'var' associated with a histogram entry
+    exceeds the current maximum contained in that variable.
+
+    The end result is that the trace event fields specified as the
+    onmax.save() params will be saved if 'var' exceeds the current
+    maximum for that hist trigger entry.  This allows context from the
+    event that exhibited the new maximum to be saved for later
+    reference.  When the histogram is displayed, additional fields
+    displaying the saved values will be printed.
+
+    As an example the below defines a couple of hist triggers, one for
+    sched_wakeup and another for sched_switch, keyed on pid.  Whenever
+    a sched_wakeup occurs, the timestamp is saved in the entry
+    corresponding to the current pid, and when the scheduler switches
+    back to that pid, the timestamp difference is calculated.  If the
+    resulting latency, stored in wakeup_lat, exceeds the current
+    maximum latency, the values specified in the save() fields are
+    recoreded:
+
+    # echo 'hist:keys=pid:ts0=$common_timestamp.usecs \
+            if comm=="cyclictest"' >> \
+            /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
+
+    # echo 'hist:keys=next_pid:\
+            wakeup_lat=$common_timestamp.usecs-$ts0:\
+            onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm) \
+            if next_comm=="cyclictest"' >> \
+            /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
+
+    When the histogram is displayed, the max value and the saved
+    values corresponding to the max are displayed following the rest
+    of the fields:
+
+    # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
+      { next_pid:       2255 } hitcount:        239
+        common_timestamp-ts0:          0
+        max:         27
+	next_comm: cyclictest
+        prev_pid:          0  prev_prio:        120  prev_comm: swapper/1
+
+      { next_pid:       2256 } hitcount:       2355
+        common_timestamp-ts0: 0
+        max:         49  next_comm: cyclictest
+        prev_pid:          0  prev_prio:        120  prev_comm: swapper/0
+
+      Totals:
+          Hits: 12970
+          Entries: 2
+          Dropped: 0
-- 
1.9.3

[PATCH 31/32] tracing: Make tracing_set_clock() non-static

[Tom Zanussi]

Allow tracing code outside of trace.c to access tracing_set_clock().

Some applications may require a particular clock in order to function
properly, such as latency calculations.

Also, add an accessor returning the current clock string.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace.c | 2 +-
 kernel/trace/trace.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ec84822..5e86fb0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6007,7 +6007,7 @@ static int tracing_clock_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static int tracing_set_clock(struct trace_array *tr, const char *clockstr)
+int tracing_set_clock(struct trace_array *tr, const char *clockstr)
 {
 	int i;
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 7dc13fa..6ee9952 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -282,6 +282,7 @@ enum {
 extern void trace_array_put(struct trace_array *tr);
 
 extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
+extern int tracing_set_clock(struct trace_array *tr, const char *clockstr);
 
 extern bool trace_clock_in_ns(struct trace_array *tr);
 
-- 
1.9.3

[PATCH 32/32] tracing: Add a clock attribute for hist triggers

[Tom Zanussi]

The default clock if timestamps are used in a histogram is "global".
If timestamps aren't used, the clock is irrelevant.

Use the "clock=" param only if you want to override the default
"global" clock for a histogram with timestamps.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 Documentation/trace/events.txt   |  9 +++++++++
 kernel/trace/trace_events_hist.c | 34 +++++++++++++++++++++++++++++++---
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index 888907c..20e4fd4 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -2173,6 +2173,15 @@ features have been added to the hist trigger support:
     default it is in units of nanoseconds; appending '.usecs' to a
     common_timestamp field changes the units to microseconds.
 
+A note on inter-event timestamps: If $common_timestamp is used in a
+histogram, the trace buffer is automatically switched over to using
+absolute timestamps and the "global" trace clock, in order to avoid
+bogus timestamp differences with other clocks that aren't coherent
+across CPUs.  This can be overriden by specifying one of the other
+trace clocks instead, using the "clock=XXX" hist trigger attribute,
+where XXX is any of the clocks listed in the tracing/trace_clock
+pseudo-file.
+
 These features are decribed in more detail in the following sections.
 
 6.3.1 Histogram Variables
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 06049f8..af508a3 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -233,6 +233,7 @@ struct hist_trigger_attrs {
 	char		*vals_str;
 	char		*sort_key_str;
 	char		*name;
+	char		*clock;
 	bool		pause;
 	bool		cont;
 	bool		clear;
@@ -1586,6 +1587,7 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 	kfree(attrs->sort_key_str);
 	kfree(attrs->keys_str);
 	kfree(attrs->vals_str);
+	kfree(attrs->clock);
 	kfree(attrs);
 }
 
@@ -1625,7 +1627,16 @@ static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
 		attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
 	else if (strncmp(str, "name=", strlen("name=")) == 0)
 		attrs->name = kstrdup(str, GFP_KERNEL);
-	else if (strncmp(str, "size=", strlen("size=")) == 0) {
+	else if (strncmp(str, "clock=", strlen("clock=")) == 0) {
+		strsep(&str, "=");
+		if (!str) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		str = strstrip(str);
+		attrs->clock = kstrdup(str, GFP_KERNEL);
+	} else if (strncmp(str, "size=", strlen("size=")) == 0) {
 		int map_bits = parse_map_size(str);
 
 		if (map_bits < 0) {
@@ -1688,6 +1699,12 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
 		goto free;
 	}
 
+	if (!attrs->clock) {
+		attrs->clock = kstrdup("global", GFP_KERNEL);
+		if (!attrs->clock)
+			goto free;
+	}
+
 	return attrs;
  free:
 	destroy_hist_trigger_attrs(attrs);
@@ -4437,6 +4454,8 @@ static int event_hist_trigger_print(struct seq_file *m,
 			seq_puts(m, ".descending");
 	}
 	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
+	if (hist_data->enable_timestamps)
+		seq_printf(m, ":clock=%s", hist_data->attrs->clock);
 
 	print_actions_spec(m, hist_data);
 
@@ -4702,10 +4721,19 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
 			goto out;
 	}
 
-	ret++;
+	if (hist_data->enable_timestamps) {
+		char *clock = hist_data->attrs->clock;
+
+		ret = tracing_set_clock(file->tr, hist_data->attrs->clock);
+		if (ret) {
+			hist_err("Couldn't set trace_clock: ", clock);
+			goto out;
+		}
 
-	if (hist_data->enable_timestamps)
 		tracing_set_time_stamp_abs(file->tr, true);
+	}
+
+	ret++;
  out:
 	return ret;
 }
-- 
1.9.3

Re: [PATCH 00/32] tracing: Inter-event (e.g. latency) support

[Steven Rostedt]

On Mon, 26 Jun 2017 17:49:00 -0500
Tom Zanussi <tom.zanussi@linux.intel.com> wrote:

> This patchset adds support for 'inter-event' quantities to the trace
> event subsystem.  The most important example of inter-event quantities
> are latencies, or the time differences between two events.
>

Hi Tom,

Thanks for sending this out. I'm going to try to find some time this
week to take a look at it. It's quite a lot to go over. I don't think
it will be ready for this merge window, as I don't like rushing things
like this, and we are already at rc7. But I want to get this in by 4.14.

-- Steve

Re: [PATCH 00/32] tracing: Inter-event (e.g. latency) support

[Masami Hiramatsu]

Hi Tom,

On Mon, 26 Jun 2017 17:49:01 -0500
Tom Zanussi <tom.zanussi@linux.intel.com> wrote:

> This patchset adds support for 'inter-event' quantities to the trace
> event subsystem.  The most important example of inter-event quantities
> are latencies, or the time differences between two events.
> 

Thank you for your great work!
I'm playing this and found some issues.

(1) new event format
----
# echo "wakeup_latency u64 lat; pid_t pid; int prio" > synthetic_events 
# cat /sys/kernel/debug/tracing # cat events/synthetic/wakeup_latency/format 
name: wakeup_latency
ID: 972
format:
	field:unsigned short common_type;	offset:0;	size:2;	signed:0;
	field:unsigned char common_flags;	offset:2;	size:1;	signed:0;
	field:unsigned char common_preempt_count;	offset:3;	size:1;signed:0;
	field:int common_pid;	offset:4;	size:4;	signed:1;

	field:u64 lat;	offset:16;	size:8;	signed:0;
	field:pid_t pid;	offset:24;	size:4;	signed:1;
	field:int prio;	offset:32;	size:4;	signed:1;

print fmt: "lat: 0x%08lx, pid: 0x%08lx, prio: 0x%08lx", ((u64)(REC->lat)), ((u64)(REC->pid)), ((u64)(REC->prio))
----
Here, IMO, this format would be better "lat=0x%08lx pid=0x%08lx prio=0x%08lx" so that perf-script can parse it correctly.

(2) lockdep found a dead lock case
When I added a histogram trigger, it happened.
----
# echo 'hist:keys=pid:ts0=$common_timestamp.usecs' >>  /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
[33967.672485] 
[33967.673117] ======================================================
[33967.673117] WARNING: possible circular locking dependency detected
[33967.673117] 4.12.0-rc5+ #1 Not tainted
[33967.673117] ------------------------------------------------------
[33967.673117] bash/708 is trying to acquire lock:
[33967.673117]  (trace_types_lock){+.+.+.}, at: [<ffffffff811307e6>] tracing_set_clock+0x66/0xe0
[33967.673117] 
[33967.673117] but task is already holding lock:
[33967.673117]  (trigger_cmd_mutex){+.+.+.}, at: [<ffffffff81144264>] event_trigger_write+0xb4/0x1a0
[33967.673117] 
[33967.673117] which lock already depends on the new lock.
[33967.673117] 
[33967.673117] 
[33967.673117] the existing dependency chain (in reverse order) is:
[33967.673117] 
[33967.673117] -> #2 (trigger_cmd_mutex){+.+.+.}:
[33967.673117]        lock_acquire+0xe3/0x1d0
[33967.673117]        __mutex_lock+0x81/0x950
[33967.673117]        mutex_lock_nested+0x1b/0x20
[33967.673117]        event_trigger_write+0xb4/0x1a0
[33967.673117]        __vfs_write+0x28/0x120
[33967.673117]        vfs_write+0xc7/0x1b0
[33967.673117]        SyS_write+0x49/0xa0
[33967.673117]        entry_SYSCALL_64_fastpath+0x1f/0xbe
[33967.673117] 
[33967.673117] -> #1 (event_mutex){+.+.+.}:
[33967.673117]        lock_acquire+0xe3/0x1d0
[33967.673117]        __mutex_lock+0x81/0x950
[33967.673117]        mutex_lock_nested+0x1b/0x20
[33967.673117]        trace_add_event_call+0x28/0xc0
[33967.673117]        create_synth_event+0x40a/0x880
[33967.673117]        trace_run_command+0x54/0x60
[33967.673117]        trace_parse_run_command+0xc4/0x160
[33967.673117]        synth_events_write+0x10/0x20
[33967.673117]        __vfs_write+0x28/0x120
[33967.673117]        vfs_write+0xc7/0x1b0
[33967.673117]        SyS_write+0x49/0xa0
[33967.673117]        entry_SYSCALL_64_fastpath+0x1f/0xbe
[33967.673117] 
[33967.673117] -> #0 (trace_types_lock){+.+.+.}:
[33967.673117]        __lock_acquire+0x1026/0x11d0
[33967.673117]        lock_acquire+0xe3/0x1d0
[33967.673117]        __mutex_lock+0x81/0x950
[33967.673117]        mutex_lock_nested+0x1b/0x20
[33967.673117]        tracing_set_clock+0x66/0xe0
[33967.673117]        hist_register_trigger+0x209/0x2a0
[33967.673117]        event_hist_trigger_func+0xc6b/0x2610
[33967.673117]        event_trigger_write+0xfa/0x1a0
[33967.673117]        __vfs_write+0x28/0x120
[33967.673117]        vfs_write+0xc7/0x1b0
[33967.673117]        SyS_write+0x49/0xa0
[33967.673117]        entry_SYSCALL_64_fastpath+0x1f/0xbe
[33967.673117] 
[33967.673117] other info that might help us debug this:
[33967.673117] 
[33967.673117] Chain exists of:
[33967.673117]   trace_types_lock --> event_mutex --> trigger_cmd_mutex
[33967.673117] 
[33967.673117]  Possible unsafe locking scenario:
[33967.673117] 
[33967.673117]        CPU0                    CPU1
[33967.673117]        ----                    ----
[33967.673117]   lock(trigger_cmd_mutex);
[33967.673117]                                lock(event_mutex);
[33967.673117]                                lock(trigger_cmd_mutex);
[33967.673117]   lock(trace_types_lock);
[33967.673117] 
[33967.673117]  *** DEADLOCK ***
[33967.673117] 
[33967.673117] 3 locks held by bash/708:
[33967.673117]  #0:  (sb_writers#8){.+.+.+}, at: [<ffffffff811ef42f>] vfs_write+0x18f/0x1b0
[33967.673117]  #1:  (event_mutex){+.+.+.}, at: [<ffffffff8114421c>] event_trigger_write+0x6c/0x1a0
[33967.673117]  #2:  (trigger_cmd_mutex){+.+.+.}, at: [<ffffffff81144264>] event_trigger_write+0xb4/0x1a0
[33967.673117] 
[33967.673117] stack backtrace:
[33967.673117] CPU: 4 PID: 708 Comm: bash Not tainted 4.12.0-rc5+ #1
[33967.673117] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
[33967.673117] Call Trace:
[33967.673117]  dump_stack+0x86/0xcf
[33967.673117]  print_circular_bug+0x1be/0x210
[33967.673117]  __lock_acquire+0x1026/0x11d0
[33967.673117]  lock_acquire+0xe3/0x1d0
[33967.673117]  ? lock_acquire+0xe3/0x1d0
[33967.673117]  ? tracing_set_clock+0x66/0xe0
[33967.673117]  ? tracing_set_clock+0x66/0xe0
[33967.673117]  __mutex_lock+0x81/0x950
[33967.673117]  ? tracing_set_clock+0x66/0xe0
[33967.673117]  ? rcu_read_lock_sched_held+0x4a/0x80
[33967.673117]  ? tracing_set_clock+0x66/0xe0
[33967.673117]  mutex_lock_nested+0x1b/0x20
[33967.673117]  ? mutex_lock_nested+0x1b/0x20
[33967.673117]  tracing_set_clock+0x66/0xe0
[33967.673117]  hist_register_trigger+0x209/0x2a0
[33967.673117]  event_hist_trigger_func+0xc6b/0x2610
[33967.673117]  ? event_trigger_write+0xb4/0x1a0
[33967.673117]  ? __mutex_lock+0x81/0x950
[33967.673117]  ? event_trigger_write+0xb4/0x1a0
[33967.673117]  ? event_trigger_write+0xb4/0x1a0
[33967.673117]  event_trigger_write+0xfa/0x1a0
[33967.673117]  __vfs_write+0x28/0x120
[33967.673117]  ? rcu_read_lock_sched_held+0x4a/0x80
[33967.673117]  ? rcu_sync_lockdep_assert+0x2f/0x60
[33967.673117]  ? __sb_start_write+0xe7/0x1e0
[33967.673117]  ? vfs_write+0x18f/0x1b0
[33967.673117]  vfs_write+0xc7/0x1b0
[33967.673117]  SyS_write+0x49/0xa0
[33967.673117]  entry_SYSCALL_64_fastpath+0x1f/0xbe
[33967.673117] RIP: 0033:0x4bb040
[33967.673117] RSP: 002b:00007ffd79e44288 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[33967.673117] RAX: ffffffffffffffda RBX: 0000000002829220 RCX: 00000000004bb040
[33967.673117] RDX: 000000000000002a RSI: 00000000028288f0 RDI: 0000000000000001
[33967.673117] RBP: 0000000002828000 R08: fefefefefefefeff R09: ff8772626471ff72
[33967.673117] R10: 00000000028288f0 R11: 0000000000000246 R12: 0000000002827f90
[33967.673117] R13: 0000000000000003 R14: 0000000000000001 R15: 0000000000000071
----

Anyway I just started to run this series, I'll also try to check other
features.

Thank you!


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH 00/32] tracing: Inter-event (e.g. latency) support

[Tom Zanussi]

Hi Masami,

On Wed, 2017-06-28 at 23:21 +0900, Masami Hiramatsu wrote:
> Hi Tom,
> 
> On Mon, 26 Jun 2017 17:49:01 -0500
> Tom Zanussi <tom.zanussi@linux.intel.com> wrote:
> 
> > This patchset adds support for 'inter-event' quantities to the trace
> > event subsystem.  The most important example of inter-event quantities
> > are latencies, or the time differences between two events.
> > 
> 
> Thank you for your great work!
> I'm playing this and found some issues.
> 
> (1) new event format
> ----
> # echo "wakeup_latency u64 lat; pid_t pid; int prio" > synthetic_events 
> # cat /sys/kernel/debug/tracing # cat events/synthetic/wakeup_latency/format 
> name: wakeup_latency
> ID: 972
> format:
> 	field:unsigned short common_type;	offset:0;	size:2;	signed:0;
> 	field:unsigned char common_flags;	offset:2;	size:1;	signed:0;
> 	field:unsigned char common_preempt_count;	offset:3;	size:1;signed:0;
> 	field:int common_pid;	offset:4;	size:4;	signed:1;
> 
> 	field:u64 lat;	offset:16;	size:8;	signed:0;
> 	field:pid_t pid;	offset:24;	size:4;	signed:1;
> 	field:int prio;	offset:32;	size:4;	signed:1;
> 
> print fmt: "lat: 0x%08lx, pid: 0x%08lx, prio: 0x%08lx", ((u64)(REC->lat)), ((u64)(REC->pid)), ((u64)(REC->prio))
> ----
> Here, IMO, this format would be better "lat=0x%08lx pid=0x%08lx prio=0x%08lx" so that perf-script can parse it correctly.
> 

OK, will change it.

> (2) lockdep found a dead lock case
> When I added a histogram trigger, it happened.
> ----
> # echo 'hist:keys=pid:ts0=$common_timestamp.usecs' >>  /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
> [33967.672485] 
> [33967.673117] ======================================================
> [33967.673117] WARNING: possible circular locking dependency detected
> [33967.673117] 4.12.0-rc5+ #1 Not tainted
> [33967.673117] ------------------------------------------------------

Yeah, will fix this and anything else similar, thanks for pointing it
out.

Tom

Re: [PATCH 00/32] tracing: Inter-event (e.g. latency) support

[Joel Fernandes (Google)]

Hi Tom,
Nice series and nice ELC talk as well. Thanks.

On Mon, Jun 26, 2017 at 3:49 PM, Tom Zanussi
<tom.zanussi@linux.intel.com> wrote:
> This patchset adds support for 'inter-event' quantities to the trace
> event subsystem.  The most important example of inter-event quantities
> are latencies, or the time differences between two events.

I tried your patches out and they are working fine for me. I will test
them out more.

I think for the wakeup latency in your examples, its better / more
accurate to use sched_waking instead of sched_wakeup tracepoint? [1]

Also, one other comment I had is, it would be nice to suppress the
output of individual trace events that are part of the synthetic event
into the trace buffer. Otherwise I feel the value of it is slightly
diminished - because one can simply post-process the individual
non-synthetic trace events themselves to get wake up latencies which
the synthetic events is trying to calculate in the first place.
Inorder to conserve space, if a user doesn't care about individual
events, and just the synthetic events then the individual ones
shouldn't be written to the trace buffer IMO.

-Joel

[1] commit fbd705a0c6184580d0e2fbcbd47a37b6e5822511 (sched: Introduce
the 'trace_sched_waking' tracepoint)

Re: [PATCH 00/32] tracing: Inter-event (e.g. latency) support

[Tom Zanussi]

Hi Joel,

Sorry for the delayed reply, was out for the holidays..

On Sat, 2017-07-01 at 00:01 -0700, Joel Fernandes (Google) wrote:
> Hi Tom,
> Nice series and nice ELC talk as well. Thanks.
> 
> On Mon, Jun 26, 2017 at 3:49 PM, Tom Zanussi
> <tom.zanussi@linux.intel.com> wrote:
> > This patchset adds support for 'inter-event' quantities to the trace
> > event subsystem.  The most important example of inter-event quantities
> > are latencies, or the time differences between two events.
> 
> I tried your patches out and they are working fine for me. I will test
> them out more.
> 
> I think for the wakeup latency in your examples, its better / more
> accurate to use sched_waking instead of sched_wakeup tracepoint? [1]
> 

Yeah, makes sense - thanks for pointing it out.

> Also, one other comment I had is, it would be nice to suppress the
> output of individual trace events that are part of the synthetic event
> into the trace buffer. Otherwise I feel the value of it is slightly
> diminished - because one can simply post-process the individual
> non-synthetic trace events themselves to get wake up latencies which
> the synthetic events is trying to calculate in the first place.
> Inorder to conserve space, if a user doesn't care about individual
> events, and just the synthetic events then the individual ones
> shouldn't be written to the trace buffer IMO.
> 

Yes, you're right, this is also something I need to fix.  I added a flag
to avoid discards, but this has the effect of, well, avoiding discards,
so unwanted events appear in the trace buffer.  Also, regardless, any
trigger that exists simply to provide input to a synthetic event should
be filtered out, regardless of the enable state.  I'll have to think
about a better way do handle all this...

Thanks,

Tom

> -Joel
> 
> [1] commit fbd705a0c6184580d0e2fbcbd47a37b6e5822511 (sched: Introduce
> the 'trace_sched_waking' tracepoint)

Re: [PATCH 00/32] tracing: Inter-event (e.g. latency) support

[Sebastian Andrzej Siewior]

On 2017-06-26 17:49:00 [-0500], Tom Zanussi wrote:
> This patchset adds support for 'inter-event' quantities to the trace
> event subsystem.  The most important example of inter-event quantities
> are latencies, or the time differences between two events.
…

I took this series and pushed into my v4.11 RT tree and removed the
"old" latency hist patches I had there.
Please keep me in CC if you post new versions of this series.

Sebastian

Re: [PATCH 00/32] tracing: Inter-event (e.g. latency) support

[Tom Zanussi]

Hi Sebastian,

On Tue, 2017-07-04 at 18:12 +0200, Sebastian Andrzej Siewior wrote:
> On 2017-06-26 17:49:00 [-0500], Tom Zanussi wrote:
> > This patchset adds support for 'inter-event' quantities to the trace
> > event subsystem.  The most important example of inter-event quantities
> > are latencies, or the time differences between two events.
> …
> 
> I took this series and pushed into my v4.11 RT tree and removed the
> "old" latency hist patches I had there.

That's great, thanks!

> Please keep me in CC if you post new versions of this series.
> 

I will, and will have a new version coming soon. ;-)

Tom

> Sebastian