* [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings
@ 2017-06-30 17:17 Michael Sartain
2017-06-30 21:50 ` Steven Rostedt
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Michael Sartain @ 2017-06-30 17:17 UTC (permalink / raw)
To: linux-kernel; +Cc: Joel Fernandes, Steven Rostedt, Ingo Molnar
Export the cached pid / tgid mappings to userspace. This allows user
apps to translate the pids from a trace to their respective thread
group.
Example saved_tgids file with pid / tgid values separated by ' ':
# cat saved_tgids
1048 1048
1047 1047
7 7
1049 1047
1054 1047
1053 1047
[ Impact: let userspace apps reading binary buffer know tgid's ]
Signed-off-by: Michael Sartain <mikesart@fastmail.com>
---
kernel/trace/trace.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 59 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 68c214b..ca84c97 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4692,6 +4692,7 @@ static const struct file_operations tracing_readme_fops = {
static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
{
unsigned int *ptr = v;
+ long tgid_check = (long) m->private;
if (*pos || m->count)
ptr++;
@@ -4702,6 +4703,8 @@ static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
ptr++) {
if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
continue;
+ if (tgid_check && !trace_find_tgid(*ptr))
+ continue;
return ptr;
}
@@ -4713,6 +4716,10 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
{
void *v;
loff_t l = 0;
+ long tgid_check = (long) m->private;
+
+ if (tgid_check && !tgid_map)
+ return NULL;
preempt_disable();
arch_spin_lock(&trace_cmdline_lock);
@@ -4743,6 +4750,14 @@ static int saved_cmdlines_show(struct seq_file *m, void *v)
return 0;
}
+static int saved_tgids_show(struct seq_file *m, void *v)
+{
+ unsigned int *pid = v;
+
+ seq_printf(m, "%d %d\n", *pid, trace_find_tgid(*pid));
+ return 0;
+}
+
static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
.start = saved_cmdlines_start,
.next = saved_cmdlines_next,
@@ -4750,12 +4765,45 @@ static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
.show = saved_cmdlines_show,
};
+static const struct seq_operations tracing_saved_tgids_seq_ops = {
+ .start = saved_cmdlines_start,
+ .next = saved_cmdlines_next,
+ .stop = saved_cmdlines_stop,
+ .show = saved_tgids_show,
+};
+
static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp)
{
+ int ret;
+
+ if (tracing_disabled)
+ return -ENODEV;
+
+ ret = seq_open(filp, &tracing_saved_cmdlines_seq_ops);
+ if (!ret) {
+ struct seq_file *m = filp->private_data;
+
+ m->private = (void *) 0; /* Do not check for valid tgids */
+ }
+
+ return ret;
+}
+
+static int tracing_saved_tgids_open(struct inode *inode, struct file *filp)
+{
+ int ret;
+
if (tracing_disabled)
return -ENODEV;
- return seq_open(filp, &tracing_saved_cmdlines_seq_ops);
+ ret = seq_open(filp, &tracing_saved_tgids_seq_ops);
+ if (!ret) {
+ struct seq_file *m = filp->private_data;
+
+ m->private = (void *) 1; /* Check for valid tgids */
+ }
+
+ return ret;
}
static const struct file_operations tracing_saved_cmdlines_fops = {
@@ -4765,6 +4813,13 @@ static const struct file_operations tracing_saved_cmdlines_fops = {
.release = seq_release,
};
+static const struct file_operations tracing_saved_tgids_fops = {
+ .open = tracing_saved_tgids_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
static ssize_t
tracing_saved_cmdlines_size_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
@@ -7933,6 +7988,9 @@ static __init int tracer_init_tracefs(void)
trace_create_file("saved_cmdlines_size", 0644, d_tracer,
NULL, &tracing_saved_cmdlines_size_fops);
+ trace_create_file("saved_tgids", 0444, d_tracer,
+ NULL, &tracing_saved_tgids_fops);
+
trace_eval_init();
trace_create_eval_file(d_tracer);
--
2.11.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings
2017-06-30 17:17 [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings Michael Sartain
@ 2017-06-30 21:50 ` Steven Rostedt
2017-06-30 23:37 ` Joel Fernandes
2017-07-01 0:32 ` Michael Sartain
2017-07-02 1:47 ` kbuild test robot
2017-07-02 2:03 ` kbuild test robot
2 siblings, 2 replies; 6+ messages in thread
From: Steven Rostedt @ 2017-06-30 21:50 UTC (permalink / raw)
To: Michael Sartain; +Cc: linux-kernel, Joel Fernandes, Ingo Molnar
On Fri, 30 Jun 2017 11:17:50 -0600
Michael Sartain <mikesart@fastmail.com> wrote:
> Export the cached pid / tgid mappings to userspace. This allows user
> apps to translate the pids from a trace to their respective thread
> group.
>
> Example saved_tgids file with pid / tgid values separated by ' ':
>
> # cat saved_tgids
> 1048 1048
> 1047 1047
> 7 7
> 1049 1047
> 1054 1047
> 1053 1047
>
> [ Impact: let userspace apps reading binary buffer know tgid's ]
Impact line? Linus put a kibosh on this a while ago...
https://lkml.org/lkml/2009/4/15/296
Although, I will admit that this line is actually useful. Just remove
the brackets.
>
> Signed-off-by: Michael Sartain <mikesart@fastmail.com>
> ---
> kernel/trace/trace.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 59 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 68c214b..ca84c97 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -4692,6 +4692,7 @@ static const struct file_operations tracing_readme_fops = {
> static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
> {
> unsigned int *ptr = v;
> + long tgid_check = (long) m->private;
I really don't like the subtle use of having m->private != NULL mean
this is for tgid listing.
In fact, I don't see the purpose of reusing the seq code. The cmdlines
and tgid map are quite different. Just create its own functions. I
don't see the benefit of trying to reuse this except for making the
code more complex.
-- Steve
>
> if (*pos || m->count)
> ptr++;
> @@ -4702,6 +4703,8 @@ static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
> ptr++) {
> if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
> continue;
> + if (tgid_check && !trace_find_tgid(*ptr))
> + continue;
>
> return ptr;
> }
> @@ -4713,6 +4716,10 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
> {
> void *v;
> loff_t l = 0;
> + long tgid_check = (long) m->private;
> +
> + if (tgid_check && !tgid_map)
> + return NULL;
>
> preempt_disable();
> arch_spin_lock(&trace_cmdline_lock);
> @@ -4743,6 +4750,14 @@ static int saved_cmdlines_show(struct seq_file *m, void *v)
> return 0;
> }
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings
2017-06-30 21:50 ` Steven Rostedt
@ 2017-06-30 23:37 ` Joel Fernandes
2017-07-01 0:32 ` Michael Sartain
1 sibling, 0 replies; 6+ messages in thread
From: Joel Fernandes @ 2017-06-30 23:37 UTC (permalink / raw)
To: Steven Rostedt; +Cc: Michael Sartain, LKML, Ingo Molnar
On Fri, Jun 30, 2017 at 2:50 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Fri, 30 Jun 2017 11:17:50 -0600
[..]
>>
>> Signed-off-by: Michael Sartain <mikesart@fastmail.com>
>> ---
>> kernel/trace/trace.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 59 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index 68c214b..ca84c97 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -4692,6 +4692,7 @@ static const struct file_operations tracing_readme_fops = {
>> static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
>> {
>> unsigned int *ptr = v;
>> + long tgid_check = (long) m->private;
>
> I really don't like the subtle use of having m->private != NULL mean
> this is for tgid listing.
>
> In fact, I don't see the purpose of reusing the seq code. The cmdlines
> and tgid map are quite different. Just create its own functions. I
> don't see the benefit of trying to reuse this except for making the
> code more complex.
I agree with Steven, this patch should be rewritten to use separate
functions and not reuse the other ones as its otherwise really
confusing and not good design.
Thanks,
Joel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings
2017-06-30 21:50 ` Steven Rostedt
2017-06-30 23:37 ` Joel Fernandes
@ 2017-07-01 0:32 ` Michael Sartain
1 sibling, 0 replies; 6+ messages in thread
From: Michael Sartain @ 2017-07-01 0:32 UTC (permalink / raw)
To: Steven Rostedt; +Cc: linux-kernel, Joel Fernandes, Ingo Molnar
On Fri, Jun 30, 2017 at 05:50:57PM -0400, Steven Rostedt wrote:
> On Fri, 30 Jun 2017 11:17:50 -0600
> Michael Sartain <mikesart@fastmail.com> wrote:
>
> > Export the cached pid / tgid mappings to userspace. This allows user
> > apps to translate the pids from a trace to their respective thread
> > group.
> >
> > Example saved_tgids file with pid / tgid values separated by ' ':
> >
> > # cat saved_tgids
> > 1048 1048
> > 1047 1047
> > 7 7
> > 1049 1047
> > 1054 1047
> > 1053 1047
> >
> > [ Impact: let userspace apps reading binary buffer know tgid's ]
>
> Impact line? Linus put a kibosh on this a while ago...
>
> https://lkml.org/lkml/2009/4/15/296
>
> Although, I will admit that this line is actually useful. Just remove
> the brackets.
Ah, thank you. I saw it used in the previous cmdline patch and used it
as a reference.
> > Signed-off-by: Michael Sartain <mikesart@fastmail.com>
> > ---
> > kernel/trace/trace.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 59 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 68c214b..ca84c97 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -4692,6 +4692,7 @@ static const struct file_operations tracing_readme_fops = {
> > static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
> > {
> > unsigned int *ptr = v;
> > + long tgid_check = (long) m->private;
>
> I really don't like the subtle use of having m->private != NULL mean
> this is for tgid listing.
>
> In fact, I don't see the purpose of reusing the seq code. The cmdlines
> and tgid map are quite different. Just create its own functions. I
> don't see the benefit of trying to reuse this except for making the
> code more complex.
Will do. Joel was also kind enough to send me feedback about RFCs and
merge windows, etc. so I apologize - wasn't trying to get anything by
anyone, just that this is my first real patch and I've obviously got a
lot to learn here. Thank you for the comments. I'll fix and resubmit
next week.
-Mike
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings
2017-06-30 17:17 [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings Michael Sartain
2017-06-30 21:50 ` Steven Rostedt
@ 2017-07-02 1:47 ` kbuild test robot
2017-07-02 2:03 ` kbuild test robot
2 siblings, 0 replies; 6+ messages in thread
From: kbuild test robot @ 2017-07-02 1:47 UTC (permalink / raw)
To: Michael Sartain
Cc: kbuild-all, linux-kernel, Joel Fernandes, Steven Rostedt, Ingo Molnar
[-- Attachment #1: Type: text/plain, Size: 2227 bytes --]
Hi Michael,
[auto build test ERROR on trace/for-next]
[also build test ERROR on next-20170630]
[cannot apply to tip/perf/core linus/master v4.12-rc7]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Michael-Sartain/tracing-Add-saved_tgids-file-to-show-cached-pid-to-tgid-mappings/20170702-092448
base: https://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git for-next
config: i386-randconfig-x070-07010433 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
All errors (new ones prefixed by >>):
kernel//trace/trace.c: In function 'saved_cmdlines_next':
>> kernel//trace/trace.c:4612:22: error: implicit declaration of function 'trace_find_tgid' [-Werror=implicit-function-declaration]
if (tgid_check && !trace_find_tgid(*ptr))
^~~~~~~~~~~~~~~
kernel//trace/trace.c: In function 'saved_cmdlines_start':
>> kernel//trace/trace.c:4627:21: error: 'tgid_map' undeclared (first use in this function)
if (tgid_check && !tgid_map)
^~~~~~~~
kernel//trace/trace.c:4627:21: note: each undeclared identifier is reported only once for each function it appears in
cc1: some warnings being treated as errors
vim +/trace_find_tgid +4612 kernel//trace/trace.c
4606 (*pos)++;
4607
4608 for (; ptr < &savedcmd->map_cmdline_to_pid[savedcmd->cmdline_num];
4609 ptr++) {
4610 if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
4611 continue;
> 4612 if (tgid_check && !trace_find_tgid(*ptr))
4613 continue;
4614
4615 return ptr;
4616 }
4617
4618 return NULL;
4619 }
4620
4621 static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
4622 {
4623 void *v;
4624 loff_t l = 0;
4625 long tgid_check = (long) m->private;
4626
> 4627 if (tgid_check && !tgid_map)
4628 return NULL;
4629
4630 preempt_disable();
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 26667 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings
2017-06-30 17:17 [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings Michael Sartain
2017-06-30 21:50 ` Steven Rostedt
2017-07-02 1:47 ` kbuild test robot
@ 2017-07-02 2:03 ` kbuild test robot
2 siblings, 0 replies; 6+ messages in thread
From: kbuild test robot @ 2017-07-02 2:03 UTC (permalink / raw)
To: Michael Sartain
Cc: kbuild-all, linux-kernel, Joel Fernandes, Steven Rostedt, Ingo Molnar
[-- Attachment #1: Type: text/plain, Size: 3634 bytes --]
Hi Michael,
[auto build test WARNING on trace/for-next]
[also build test WARNING on next-20170630]
[cannot apply to tip/perf/core linus/master v4.12-rc7]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Michael-Sartain/tracing-Add-saved_tgids-file-to-show-cached-pid-to-tgid-mappings/20170702-092448
base: https://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git for-next
config: i386-randconfig-x072-07010433 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
All warnings (new ones prefixed by >>):
In file included from include/uapi/linux/stddef.h:1:0,
from include/linux/stddef.h:4,
from include/uapi/linux/posix_types.h:4,
from include/uapi/linux/types.h:13,
from include/linux/types.h:5,
from include/linux/mm_types_task.h:10,
from include/linux/mm_types.h:4,
from include/linux/kmemcheck.h:4,
from include/linux/ring_buffer.h:4,
from kernel/trace/trace.c:14:
kernel/trace/trace.c: In function 'saved_cmdlines_next':
kernel/trace/trace.c:4612:22: error: implicit declaration of function 'trace_find_tgid' [-Werror=implicit-function-declaration]
if (tgid_check && !trace_find_tgid(*ptr))
^
include/linux/compiler.h:160:30: note: in definition of macro '__trace_if'
if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
^~~~
>> kernel/trace/trace.c:4612:3: note: in expansion of macro 'if'
if (tgid_check && !trace_find_tgid(*ptr))
^~
kernel/trace/trace.c: In function 'saved_cmdlines_start':
kernel/trace/trace.c:4627:21: error: 'tgid_map' undeclared (first use in this function)
if (tgid_check && !tgid_map)
^
include/linux/compiler.h:160:30: note: in definition of macro '__trace_if'
if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
^~~~
kernel/trace/trace.c:4627:2: note: in expansion of macro 'if'
if (tgid_check && !tgid_map)
^~
kernel/trace/trace.c:4627:21: note: each undeclared identifier is reported only once for each function it appears in
if (tgid_check && !tgid_map)
^
include/linux/compiler.h:160:30: note: in definition of macro '__trace_if'
if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
^~~~
kernel/trace/trace.c:4627:2: note: in expansion of macro 'if'
if (tgid_check && !tgid_map)
^~
cc1: some warnings being treated as errors
vim +/if +4612 kernel/trace/trace.c
4596 };
4597
4598 static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
4599 {
4600 unsigned int *ptr = v;
4601 long tgid_check = (long) m->private;
4602
4603 if (*pos || m->count)
4604 ptr++;
4605
4606 (*pos)++;
4607
4608 for (; ptr < &savedcmd->map_cmdline_to_pid[savedcmd->cmdline_num];
4609 ptr++) {
4610 if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
4611 continue;
> 4612 if (tgid_check && !trace_find_tgid(*ptr))
4613 continue;
4614
4615 return ptr;
4616 }
4617
4618 return NULL;
4619 }
4620
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 30480 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
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2017-06-30 17:17 [PATCH] tracing: Add saved_tgids file to show cached pid to tgid mappings Michael Sartain
2017-06-30 21:50 ` Steven Rostedt
2017-06-30 23:37 ` Joel Fernandes
2017-07-01 0:32 ` Michael Sartain
2017-07-02 1:47 ` kbuild test robot
2017-07-02 2:03 ` kbuild test robot
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