[RFC][PATCH 00/10] tracing: Add triggers to trace_marker writes

[RFC][PATCH 00/10] tracing: Add triggers to trace_marker writes

[Steven Rostedt]

A few people have asked for this in the past, and I finally got around
to implementing it. What this does is to allow writes into trace_marker
to initiate a trigger.

The trace_marker event is described in:

 tracefs/events/ftrace/print

Thus the trigger file is added there:

 tracefs/events/ftrace/print/trigger

As there's already a "hist" file there, everything appears to work
just like any other trigger to an event. See the last patch for
documentation on how to use the triggers to a trace_marker write.

By the way, the patch:

  tracing: Prevent further users of zero size static arrays in trace events

May prevent your kernel from building if you include Xen. You will need
to add this patch to make it work.

 http://lkml.kernel.org/r/20180509144605.5a220327@gandalf.local.home

-- Steve


Steven Rostedt (VMware) (10):
      tracing: Do not reference event data in post call triggers
      tracing: Add __find_event_file() to find event files without restrictions
      tracing: Have event_trace_init() called by trace_init_tracefs()
      tracing: Add brackets in ftrace event dynamic arrays
      tracing: Do not show filter file for ftrace internal events
      tracing: Add trigger file for trace_markers tracefs/ftrace/print
      tracing: Have zero size length in filter logic be full string
      tracing: Prevent further users of zero size static arrays in trace events
      tracing: Allow histogram triggers to access ftrace internal events
      tracing: Document trace_marker triggers

----
 Documentation/trace/events.rst      |   6 +-
 Documentation/trace/ftrace.rst      |   5 +
 Documentation/trace/histogram.txt   | 546 +++++++++++++++++++++++++++++++++++-
 include/linux/trace_events.h        |   3 +-
 include/trace/trace_events.h        |   1 +
 kernel/trace/trace.c                |  19 ++
 kernel/trace/trace.h                |   9 +-
 kernel/trace/trace_entries.h        |   6 +-
 kernel/trace/trace_events.c         |  36 ++-
 kernel/trace/trace_events_filter.c  |  23 +-
 kernel/trace/trace_events_hist.c    |   2 +-
 kernel/trace/trace_events_trigger.c |   6 +-
 kernel/trace/trace_export.c         |   9 +-
 13 files changed, 634 insertions(+), 37 deletions(-)

[RFC][PATCH 01/10] tracing: Do not reference event data in post call triggers

[Steven Rostedt]

[-- Attachment #1: 0001-tracing-Do-not-reference-event-data-in-post-call-tri.patch --]
[-- Type: text/plain, Size: 3553 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Trace event triggers can be called before or after the event has been
committed. If it has been called after the commit, there's a possibility
that the event no longer exists. Currently, the two post callers is the
trigger to disable tracing (traceoff) and the one that will record a stack
dump (stacktrace). Neither of them reference the trace event entry record,
as that would lead to a race condition that could pass in corrupted data.

To prevent any other users of the post data triggers from using the trace
event record, pass in NULL to the post call trigger functions for the event
record, as they should never need to use them in the first place.

This does not fix any bug, but prevents bugs from happening by new post call
trigger users.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/linux/trace_events.h        | 3 +--
 kernel/trace/trace.h                | 4 ++--
 kernel/trace/trace_events_trigger.c | 6 ++----
 3 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 2bde3eff564c..d1c442d9bd85 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -435,8 +435,7 @@ 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);
+			 enum event_trigger_type tt);
 
 bool trace_event_ignore_this_pid(struct trace_event_file *trace_file);
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 6fb46a06c9dc..24b666891eaf 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1334,7 +1334,7 @@ event_trigger_unlock_commit(struct trace_event_file *file,
 		trace_buffer_unlock_commit(file->tr, buffer, event, irq_flags, pc);
 
 	if (tt)
-		event_triggers_post_call(file, tt, entry, event);
+		event_triggers_post_call(file, tt);
 }
 
 /**
@@ -1367,7 +1367,7 @@ event_trigger_unlock_commit_regs(struct trace_event_file *file,
 						irq_flags, pc, regs);
 
 	if (tt)
-		event_triggers_post_call(file, tt, entry, event);
+		event_triggers_post_call(file, tt);
 }
 
 #define FILTER_PRED_INVALID	((unsigned short)-1)
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index d251cabcf69a..cc4148bfc01a 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -97,7 +97,6 @@ EXPORT_SYMBOL_GPL(event_triggers_call);
  * event_triggers_post_call - Call 'post_triggers' for a trace event
  * @file: The trace_event_file associated with the event
  * @tt: enum event_trigger_type containing a set bit for each trigger to invoke
- * @rec: The trace entry for the event
  *
  * For each trigger associated with an event, invoke the trigger
  * function registered with the associated trigger command, if the
@@ -108,8 +107,7 @@ EXPORT_SYMBOL_GPL(event_triggers_call);
  */
 void
 event_triggers_post_call(struct trace_event_file *file,
-			 enum event_trigger_type tt,
-			 void *rec, struct ring_buffer_event *event)
+			 enum event_trigger_type tt)
 {
 	struct event_trigger_data *data;
 
@@ -117,7 +115,7 @@ event_triggers_post_call(struct trace_event_file *file,
 		if (data->paused)
 			continue;
 		if (data->cmd_ops->trigger_type & tt)
-			data->ops->func(data, rec, event);
+			data->ops->func(data, NULL, NULL);
 	}
 }
 EXPORT_SYMBOL_GPL(event_triggers_post_call);
-- 
2.17.0

[RFC][PATCH 02/10] tracing: Add __find_event_file() to find event files without restrictions

[Steven Rostedt]

[-- Attachment #1: 0002-tracing-Add-__find_event_file-to-find-event-files-wi.patch --]
[-- Type: text/plain, Size: 2943 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

By adding the function __find_event_file() that can search for files without
restrictions, such as if the event associated with the file has a reg
function, or if it has the "ignore" flag set, the files that are associated
to ftrace internal events (like trace_marker and function events) can be
found and used.

find_event_file() still returns a "filtered" file, as most callers need a
valid trace event file. One created by the trace_events.h macros and not one
created for parsing ftrace specific events.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.h        |  3 +++
 kernel/trace/trace_events.c | 22 +++++++++++++++++-----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 24b666891eaf..8ecca43d6aea 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1454,6 +1454,9 @@ extern void trace_event_enable_tgid_record(bool enable);
 extern int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr);
 extern int event_trace_del_tracer(struct trace_array *tr);
 
+extern struct trace_event_file *__find_event_file(struct trace_array *tr,
+						  const char *system,
+						  const char *event);
 extern struct trace_event_file *find_event_file(struct trace_array *tr,
 						const char *system,
 						const char *event);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 05c7172c6667..caf76355f0a3 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2473,8 +2473,9 @@ __trace_add_event_dirs(struct trace_array *tr)
 	}
 }
 
+/* Returns any file that matches the system and event */
 struct trace_event_file *
-find_event_file(struct trace_array *tr, const char *system,  const char *event)
+__find_event_file(struct trace_array *tr, const char *system, const char *event)
 {
 	struct trace_event_file *file;
 	struct trace_event_call *call;
@@ -2485,10 +2486,7 @@ find_event_file(struct trace_array *tr, const char *system,  const char *event)
 		call = file->event_call;
 		name = trace_event_name(call);
 
-		if (!name || !call->class || !call->class->reg)
-			continue;
-
-		if (call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)
+		if (!name || !call->class)
 			continue;
 
 		if (strcmp(event, name) == 0 &&
@@ -2498,6 +2496,20 @@ find_event_file(struct trace_array *tr, const char *system,  const char *event)
 	return NULL;
 }
 
+/* Returns valid trace event files that match system and event */
+struct trace_event_file *
+find_event_file(struct trace_array *tr, const char *system, const char *event)
+{
+	struct trace_event_file *file;
+
+	file = __find_event_file(tr, system, event);
+	if (!file || !file->event_call->class->reg ||
+	    file->event_call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)
+		return NULL;
+
+	return file;
+}
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 /* Avoid typos */
-- 
2.17.0

[RFC][PATCH 03/10] tracing: Have event_trace_init() called by trace_init_tracefs()

[Steven Rostedt]

[-- Attachment #1: 0003-tracing-Have-event_trace_init-called-by-trace_init_t.patch --]
[-- Type: text/plain, Size: 2231 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Instead of having both trace_init_tracefs() and event_trace_init() be called
by fs_initcall() routines, have event_trace_init() called directly by
trace_init_tracefs(). This will guarantee order of how the events are
created with respect to the rest of the ftrace infrastructure. This is
needed to be able to assoctiate event files with ftrace internal events,
such as the trace_marker.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c        | 2 ++
 kernel/trace/trace.h        | 1 +
 kernel/trace/trace_events.c | 4 +---
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 414d7210b2ec..e0d6ffb76985 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8111,6 +8111,8 @@ static __init int tracer_init_tracefs(void)
 	if (IS_ERR(d_tracer))
 		return 0;
 
+	event_trace_init();
+
 	init_tracer_tracefs(&global_trace, d_tracer);
 	ftrace_init_tracefs_toplevel(&global_trace, d_tracer);
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8ecca43d6aea..2414fd72dedd 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1451,6 +1451,7 @@ trace_find_event_field(struct trace_event_call *call, char *name);
 extern void trace_event_enable_cmd_record(bool enable);
 extern void trace_event_enable_tgid_record(bool enable);
 
+extern int event_trace_init(void);
 extern int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr);
 extern int event_trace_del_tracer(struct trace_array *tr);
 
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index caf76355f0a3..5b647904a65b 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3144,7 +3144,7 @@ static __init int event_trace_enable_again(void)
 
 early_initcall(event_trace_enable_again);
 
-static __init int event_trace_init(void)
+__init int event_trace_init(void)
 {
 	struct trace_array *tr;
 	struct dentry *d_tracer;
@@ -3189,8 +3189,6 @@ void __init trace_event_init(void)
 	event_trace_enable();
 }
 
-fs_initcall(event_trace_init);
-
 #ifdef CONFIG_FTRACE_STARTUP_TEST
 
 static DEFINE_SPINLOCK(test_spinlock);
-- 
2.17.0

[RFC][PATCH 04/10] tracing: Add brackets in ftrace event dynamic arrays

[Steven Rostedt]

[-- Attachment #1: 0004-tracing-Add-brackets-in-ftrace-event-dynamic-arrays.patch --]
[-- Type: text/plain, Size: 1121 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

The dynamic arrays defined for ftrace internal events, such as the buf field
for trace_marker (ftrace/print) did not have brackets which makes the filter
code not accept it as a string. This is not currently an issues because the
filter code doesn't do anything for these events, but they will in the
future, and this needs to be fixed for when it does.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace_export.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
index 548e62eb5c46..d842f1eadfe5 100644
--- a/kernel/trace/trace_export.c
+++ b/kernel/trace/trace_export.c
@@ -117,7 +117,7 @@ static void __always_unused ____ftrace_check_##name(void)		\
 
 #undef __dynamic_array
 #define __dynamic_array(type, item)					\
-	ret = trace_define_field(event_call, #type, #item,		\
+	ret = trace_define_field(event_call, #type "[]", #item,  \
 				 offsetof(typeof(field), item),		\
 				 0, is_signed_type(type), filter_type);\
 	if (ret)							\
-- 
2.17.0

[RFC][PATCH 05/10] tracing: Do not show filter file for ftrace internal events

[Steven Rostedt]

[-- Attachment #1: 0005-tracing-Do-not-show-filter-file-for-ftrace-internal-.patch --]
[-- Type: text/plain, Size: 1394 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

The filter file in the ftrace internal events, like in
/sys/kernel/tracing/events/ftrace/function/filter is not attached to any
functionality. Do not create them as they are meaningless.

In the future, if an ftrace internal event gets filter functionality, then
it will need to create it directly.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace_events.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 5b647904a65b..14ff4ff3caab 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2007,16 +2007,18 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file)
 			return -1;
 		}
 	}
-	trace_create_file("filter", 0644, file->dir, file,
-			  &ftrace_event_filter_fops);
 
 	/*
 	 * Only event directories that can be enabled should have
-	 * triggers.
+	 * triggers or filters.
 	 */
-	if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
+	if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)) {
+		trace_create_file("filter", 0644, file->dir, file,
+				  &ftrace_event_filter_fops);
+
 		trace_create_file("trigger", 0644, file->dir, file,
 				  &event_trigger_fops);
+	}
 
 #ifdef CONFIG_HIST_TRIGGERS
 	trace_create_file("hist", 0444, file->dir, file,
-- 
2.17.0

[RFC][PATCH 06/10] tracing: Add trigger file for trace_markers tracefs/ftrace/print

[Steven Rostedt]

[-- Attachment #1: 0006-tracing-Add-trigger-file-for-trace_markers-tracefs-f.patch --]
[-- Type: text/plain, Size: 4138 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Allow writing to the trace_markers file initiate triggers defined in
tracefs/ftrace/print/trigger file. This will allow of user space to trigger
the same type of triggers (including histograms) that the trace events use.

Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Karim Yaghmour <karim.yaghmour@opersys.com>
Cc: Brendan Gregg <bgregg@netflix.com>
Suggested-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c         | 17 +++++++++++++++++
 kernel/trace/trace.h         |  1 +
 kernel/trace/trace_entries.h |  6 ++++--
 kernel/trace/trace_export.c  |  7 +++++++
 4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e0d6ffb76985..f11b89fa5049 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6074,6 +6074,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 {
 	struct trace_array *tr = filp->private_data;
 	struct ring_buffer_event *event;
+	enum event_trigger_type tt = ETT_NONE;
 	struct ring_buffer *buffer;
 	struct print_entry *entry;
 	unsigned long irq_flags;
@@ -6122,6 +6123,12 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 		written = cnt;
 	len = cnt;
 
+	if (tr->trace_marker_file && !list_empty(&tr->trace_marker_file->triggers)) {
+		/* do not add \n before testing triggers, but add \0 */
+		entry->buf[cnt] = '\0';
+		tt = event_triggers_call(tr->trace_marker_file, entry, event);
+	}
+
 	if (entry->buf[cnt - 1] != '\n') {
 		entry->buf[cnt] = '\n';
 		entry->buf[cnt + 1] = '\0';
@@ -6130,6 +6137,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 
 	__buffer_unlock_commit(buffer, event);
 
+	if (tt)
+		event_triggers_post_call(tr->trace_marker_file, tt);
+
 	if (written > 0)
 		*fpos += written;
 
@@ -7896,6 +7906,7 @@ static __init void create_trace_instances(struct dentry *d_tracer)
 static void
 init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
 {
+	struct trace_event_file *file;
 	int cpu;
 
 	trace_create_file("available_tracers", 0444, d_tracer,
@@ -7928,6 +7939,12 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
 	trace_create_file("trace_marker", 0220, d_tracer,
 			  tr, &tracing_mark_fops);
 
+	file = __find_event_file(tr, "ftrace", "print");
+	if (file && file->dir)
+		trace_create_file("trigger", 0644, file->dir, file,
+				  &event_trigger_fops);
+	tr->trace_marker_file = file;
+
 	trace_create_file("trace_marker_raw", 0220, d_tracer,
 			  tr, &tracing_mark_raw_fops);
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 2414fd72dedd..c7fa58d31a84 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -259,6 +259,7 @@ struct trace_array {
 	struct trace_options	*topts;
 	struct list_head	systems;
 	struct list_head	events;
+	struct trace_event_file *trace_marker_file;
 	cpumask_var_t		tracing_cpumask; /* only trace on set CPUs */
 	int			ref;
 #ifdef CONFIG_FUNCTION_TRACER
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index e3a658bac10f..de3fce14cd00 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -230,7 +230,7 @@ FTRACE_ENTRY(bprint, bprint_entry,
 	FILTER_OTHER
 );
 
-FTRACE_ENTRY(print, print_entry,
+FTRACE_ENTRY_REG(print, print_entry,
 
 	TRACE_PRINT,
 
@@ -242,7 +242,9 @@ FTRACE_ENTRY(print, print_entry,
 	F_printk("%ps: %s",
 		 (void *)__entry->ip, __entry->buf),
 
-	FILTER_OTHER
+	FILTER_OTHER,
+
+	 ftrace_event_register
 );
 
 FTRACE_ENTRY(raw_data, raw_data_entry,
diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
index d842f1eadfe5..45630a76ed3a 100644
--- a/kernel/trace/trace_export.c
+++ b/kernel/trace/trace_export.c
@@ -14,6 +14,13 @@
 
 #include "trace_output.h"
 
+/* Stub function for events with triggers */
+static int ftrace_event_register(struct trace_event_call *call,
+				 enum trace_reg type, void *data)
+{
+	return 0;
+}
+
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM	ftrace
 
-- 
2.17.0

[RFC][PATCH 07/10] tracing: Have zero size length in filter logic be full string

[Steven Rostedt]

[-- Attachment #1: 0007-tracing-Have-zero-size-length-in-filter-logic-be-ful.patch --]
[-- Type: text/plain, Size: 1996 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

As strings in trace events may not have a nul terminating character, the
filter string compares use the defined string length for the field for the
compares.

The trace_marker records data slightly different than do normal events. It's
size is zero, meaning that the string is the rest of the array, and that the
string also ends with '\0'.

If the size is zero, assume that the string is nul terminated and read the
string in question as is.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace_events_filter.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 7d306b74230f..675392b9edd2 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -750,31 +750,32 @@ static int filter_pred_none(struct filter_pred *pred, void *event)
  *
  * Note:
  * - @str might not be NULL-terminated if it's of type DYN_STRING
- *   or STATIC_STRING
+ *   or STATIC_STRING, unless @len is zero.
  */
 
 static int regex_match_full(char *str, struct regex *r, int len)
 {
-	if (strncmp(str, r->pattern, len) == 0)
-		return 1;
-	return 0;
+	/* len means str is dynamic and ends with '\0' */
+	if (!len)
+		return strcmp(str, r->pattern) == 0;
+
+	return strncmp(str, r->pattern, len) == 0;
 }
 
 static int regex_match_front(char *str, struct regex *r, int len)
 {
-	if (len < r->len)
+	if (len && len < r->len)
 		return 0;
 
-	if (strncmp(str, r->pattern, r->len) == 0)
-		return 1;
-	return 0;
+	return strncmp(str, r->pattern, len) == 0;
 }
 
 static int regex_match_middle(char *str, struct regex *r, int len)
 {
-	if (strnstr(str, r->pattern, len))
-		return 1;
-	return 0;
+	if (!len)
+		return strstr(str, r->pattern) != NULL;
+
+	return strnstr(str, r->pattern, len) != NULL;
 }
 
 static int regex_match_end(char *str, struct regex *r, int len)
-- 
2.17.0

[RFC][PATCH 08/10] tracing: Prevent further users of zero size static arrays in trace events

[Steven Rostedt]

[-- Attachment #1: 0008-tracing-Prevent-further-users-of-zero-size-static-ar.patch --]
[-- Type: text/plain, Size: 1111 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

A zero size static array has special meaning in the ftrace infrastructure.
Trace events are for recording data in the trace buffers that is normally
difficult to obtain via probes or function tracing. There is no reason for
any trace event to declare a zero size static array.

If one does, BUILD_BUG_ON() will trigger and prevent the kernel from
compiling.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/trace/trace_events.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
index bfda803b0a09..4ecdfe2e3580 100644
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -422,6 +422,7 @@ static struct trace_event_functions trace_event_type_funcs_##call = {	\
 	do {								\
 		char *type_str = #type"["__stringify(len)"]";		\
 		BUILD_BUG_ON(len > MAX_FILTER_STR_VAL);			\
+		BUILD_BUG_ON(len <= 0);					\
 		ret = trace_define_field(event_call, type_str, #item,	\
 				 offsetof(typeof(field), item),		\
 				 sizeof(field.item),			\
-- 
2.17.0

[RFC][PATCH 09/10] tracing: Allow histogram triggers to access ftrace internal events

[Steven Rostedt]

[-- Attachment #1: 0009-tracing-Allow-histogram-triggers-to-access-ftrace-in.patch --]
[-- Type: text/plain, Size: 948 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Now that trace_marker can have triggers, including a histogram triggers, the
onmatch() and onmax() access the trace event. To do so, the search routine
to find the event file needs to use the raw __find_event_file() that does
not filter out ftrace events.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 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 b9061ed59bbd..046c716a6536 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -2865,7 +2865,7 @@ static struct trace_event_file *event_file(struct trace_array *tr,
 {
 	struct trace_event_file *file;
 
-	file = find_event_file(tr, system, event_name);
+	file = __find_event_file(tr, system, event_name);
 	if (!file)
 		return ERR_PTR(-EINVAL);
 
-- 
2.17.0

[RFC][PATCH 10/10] tracing: Document trace_marker triggers

[Steven Rostedt]

[-- Attachment #1: 0010-tracing-Document-trace_marker-triggers.patch --]
[-- Type: text/plain, Size: 35563 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Add documentation and an example on how to use trace_marker triggers.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 Documentation/trace/events.rst    |   6 +-
 Documentation/trace/ftrace.rst    |   5 +
 Documentation/trace/histogram.txt | 546 +++++++++++++++++++++++++++++-
 3 files changed, 555 insertions(+), 2 deletions(-)

diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst
index a5ea2cb0082b..1afae55dc55c 100644
--- a/Documentation/trace/events.rst
+++ b/Documentation/trace/events.rst
@@ -338,10 +338,14 @@ used for conditionally invoking triggers.
 
 The syntax for event triggers is roughly based on the syntax for
 set_ftrace_filter 'ftrace filter commands' (see the 'Filter commands'
-section of Documentation/trace/ftrace.txt), but there are major
+section of Documentation/trace/ftrace.rst), but there are major
 differences and the implementation isn't currently tied to it in any
 way, so beware about making generalizations between the two.
 
+Note: Writing into trace_marker (See Documentation/trace/ftrace.rst)
+     can also enable triggers that are written into
+     /sys/kernel/tracing/events/ftrace/print/trigger
+
 6.1 Expression syntax
 ---------------------
 
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index 67d9c38e95eb..aad4776c0f5d 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -507,6 +507,11 @@ of ftrace. Here is a list of some of the key files:
 
 		trace_fd = open("trace_marker", WR_ONLY);
 
+	Note: Writing into the trace_marker file can also initiate triggers
+	      that are written into /sys/kernel/tracing/events/ftrace/print/trigger
+	      See "Event triggers" in Documentation/trace/events.rst and an
+              example in Documentation/trace/histogram.rst (Section 3.)
+
   trace_marker_raw:
 
 	This is similar to trace_marker above, but is meant for for binary data
diff --git a/Documentation/trace/histogram.txt b/Documentation/trace/histogram.txt
index 6e05510afc28..8c871f0c0e33 100644
--- a/Documentation/trace/histogram.txt
+++ b/Documentation/trace/histogram.txt
@@ -1604,7 +1604,6 @@
         Entries: 7
         Dropped: 0
 
-
 2.2 Inter-event hist triggers
 -----------------------------
 
@@ -1993,3 +1992,548 @@ hist trigger specification.
           Hits: 12970
           Entries: 2
           Dropped: 0
+
+3. User space creating a trigger
+--------------------------------
+
+Writing into /sys/kernel/tracing/trace_marker writes into the ftrace
+ring buffer. This can also act like an event, by writing into the trigger
+file located in /sys/kernel/tracing/events/ftrace/print/
+
+Modifying cyclictest to write into the trace_marker file before it sleeps
+and after it wakes up, something like this:
+
+static void traceputs(char *str)
+{
+	/* tracemark_fd is the trace_marker file descripto */
+	if (tracemark_fd < 0)
+		return;
+	/* write the tracemark message */
+	write(tracemark_fd, str, strlen(str));
+}
+
+And later add something like:
+
+	traceputs("start");
+	clock_nanosleep(...);
+	traceputs("end");
+
+We can make a histogram from this:
+
+ # cd /sys/kernel/tracing
+ # echo 'latency u64 lat' > synthetic_events
+ # echo 'hist:keys=common_pid:ts0=common_timestamp.usecs if buf == "start"' > events/ftrace/print/trigger
+ # echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(ftrace.print).latency($lat) if buf == "end"' >> events/ftrace/print/trigger
+ # echo 'hist:keys=lat,common_pid:sort=lat' > events/synthetic/latency/trigger
+
+The above created a synthetic event called "latency" and two histograms
+against the trace_marker, one gets triggered when "start" is written into the
+trace_marker file and the other when "end" is written. If the pids match, then
+it will call the "latency" synthetic event with the calculated latency as its
+parameter. Finally, a histogram is added to the latency synthetic event to
+record the calculated latency along with the pid.
+
+Now running cyclictest with:
+
+ # ./cyclictest -p80 -d0 -i250 -n -a -t --tracemark -b 1000
+
+ -p80  : run threads at priority 80
+ -d0   : have all threads run at the same interval
+ -i250 : start the interval at 250 microseconds (all threads will do this)
+ -n    : sleep with nanosleep
+ -a    : affine all threads to a separate CPU
+ -t    : one thread per available CPU
+ --tracemark : enable trace mark writing
+ -b 1000 : stop if any latency is greater than 1000 microseconds
+
+Note, the -b 1000 is used just to make --tracemark available.
+
+The we can see the histogram created by this with:
+
+ # cat events/synthetic/latency/hist
+# event histogram
+#
+# trigger info: hist:keys=lat,common_pid:vals=hitcount:sort=lat:size=2048 [active]
+#
+
+{ lat:        107, common_pid:       2039 } hitcount:          1
+{ lat:        122, common_pid:       2041 } hitcount:          1
+{ lat:        166, common_pid:       2039 } hitcount:          1
+{ lat:        174, common_pid:       2039 } hitcount:          1
+{ lat:        194, common_pid:       2041 } hitcount:          1
+{ lat:        196, common_pid:       2036 } hitcount:          1
+{ lat:        197, common_pid:       2038 } hitcount:          1
+{ lat:        198, common_pid:       2039 } hitcount:          1
+{ lat:        199, common_pid:       2039 } hitcount:          1
+{ lat:        200, common_pid:       2041 } hitcount:          1
+{ lat:        201, common_pid:       2039 } hitcount:          2
+{ lat:        202, common_pid:       2038 } hitcount:          1
+{ lat:        202, common_pid:       2043 } hitcount:          1
+{ lat:        203, common_pid:       2039 } hitcount:          1
+{ lat:        203, common_pid:       2036 } hitcount:          1
+{ lat:        203, common_pid:       2041 } hitcount:          1
+{ lat:        206, common_pid:       2038 } hitcount:          2
+{ lat:        207, common_pid:       2039 } hitcount:          1
+{ lat:        207, common_pid:       2036 } hitcount:          1
+{ lat:        208, common_pid:       2040 } hitcount:          1
+{ lat:        209, common_pid:       2043 } hitcount:          1
+{ lat:        210, common_pid:       2039 } hitcount:          1
+{ lat:        211, common_pid:       2039 } hitcount:          4
+{ lat:        212, common_pid:       2043 } hitcount:          1
+{ lat:        212, common_pid:       2039 } hitcount:          2
+{ lat:        213, common_pid:       2039 } hitcount:          1
+{ lat:        214, common_pid:       2038 } hitcount:          1
+{ lat:        214, common_pid:       2039 } hitcount:          2
+{ lat:        214, common_pid:       2042 } hitcount:          1
+{ lat:        215, common_pid:       2039 } hitcount:          1
+{ lat:        217, common_pid:       2036 } hitcount:          1
+{ lat:        217, common_pid:       2040 } hitcount:          1
+{ lat:        217, common_pid:       2039 } hitcount:          1
+{ lat:        218, common_pid:       2039 } hitcount:          6
+{ lat:        219, common_pid:       2039 } hitcount:          9
+{ lat:        220, common_pid:       2039 } hitcount:         11
+{ lat:        221, common_pid:       2039 } hitcount:          5
+{ lat:        221, common_pid:       2042 } hitcount:          1
+{ lat:        222, common_pid:       2039 } hitcount:          7
+{ lat:        223, common_pid:       2036 } hitcount:          1
+{ lat:        223, common_pid:       2039 } hitcount:          3
+{ lat:        224, common_pid:       2039 } hitcount:          4
+{ lat:        224, common_pid:       2037 } hitcount:          1
+{ lat:        224, common_pid:       2036 } hitcount:          2
+{ lat:        225, common_pid:       2039 } hitcount:          5
+{ lat:        225, common_pid:       2042 } hitcount:          1
+{ lat:        226, common_pid:       2039 } hitcount:          7
+{ lat:        226, common_pid:       2036 } hitcount:          4
+{ lat:        227, common_pid:       2039 } hitcount:          6
+{ lat:        227, common_pid:       2036 } hitcount:         12
+{ lat:        227, common_pid:       2043 } hitcount:          1
+{ lat:        228, common_pid:       2039 } hitcount:          7
+{ lat:        228, common_pid:       2036 } hitcount:         14
+{ lat:        229, common_pid:       2039 } hitcount:          9
+{ lat:        229, common_pid:       2036 } hitcount:          8
+{ lat:        229, common_pid:       2038 } hitcount:          1
+{ lat:        230, common_pid:       2039 } hitcount:         11
+{ lat:        230, common_pid:       2036 } hitcount:          6
+{ lat:        230, common_pid:       2043 } hitcount:          1
+{ lat:        230, common_pid:       2042 } hitcount:          2
+{ lat:        231, common_pid:       2041 } hitcount:          1
+{ lat:        231, common_pid:       2036 } hitcount:          6
+{ lat:        231, common_pid:       2043 } hitcount:          1
+{ lat:        231, common_pid:       2039 } hitcount:          8
+{ lat:        232, common_pid:       2037 } hitcount:          1
+{ lat:        232, common_pid:       2039 } hitcount:          6
+{ lat:        232, common_pid:       2040 } hitcount:          2
+{ lat:        232, common_pid:       2036 } hitcount:          5
+{ lat:        232, common_pid:       2043 } hitcount:          1
+{ lat:        233, common_pid:       2036 } hitcount:          5
+{ lat:        233, common_pid:       2039 } hitcount:         11
+{ lat:        234, common_pid:       2039 } hitcount:          4
+{ lat:        234, common_pid:       2038 } hitcount:          2
+{ lat:        234, common_pid:       2043 } hitcount:          2
+{ lat:        234, common_pid:       2036 } hitcount:         11
+{ lat:        234, common_pid:       2040 } hitcount:          1
+{ lat:        235, common_pid:       2037 } hitcount:          2
+{ lat:        235, common_pid:       2036 } hitcount:          8
+{ lat:        235, common_pid:       2043 } hitcount:          2
+{ lat:        235, common_pid:       2039 } hitcount:          5
+{ lat:        235, common_pid:       2042 } hitcount:          2
+{ lat:        235, common_pid:       2040 } hitcount:          4
+{ lat:        235, common_pid:       2041 } hitcount:          1
+{ lat:        236, common_pid:       2036 } hitcount:          7
+{ lat:        236, common_pid:       2037 } hitcount:          1
+{ lat:        236, common_pid:       2041 } hitcount:          5
+{ lat:        236, common_pid:       2039 } hitcount:          3
+{ lat:        236, common_pid:       2043 } hitcount:          9
+{ lat:        236, common_pid:       2040 } hitcount:          7
+{ lat:        237, common_pid:       2037 } hitcount:          1
+{ lat:        237, common_pid:       2040 } hitcount:          1
+{ lat:        237, common_pid:       2036 } hitcount:          9
+{ lat:        237, common_pid:       2039 } hitcount:          3
+{ lat:        237, common_pid:       2043 } hitcount:          8
+{ lat:        237, common_pid:       2042 } hitcount:          2
+{ lat:        237, common_pid:       2041 } hitcount:          2
+{ lat:        238, common_pid:       2043 } hitcount:         10
+{ lat:        238, common_pid:       2040 } hitcount:          1
+{ lat:        238, common_pid:       2037 } hitcount:          9
+{ lat:        238, common_pid:       2038 } hitcount:          1
+{ lat:        238, common_pid:       2039 } hitcount:          1
+{ lat:        238, common_pid:       2042 } hitcount:          3
+{ lat:        238, common_pid:       2036 } hitcount:          7
+{ lat:        239, common_pid:       2041 } hitcount:          1
+{ lat:        239, common_pid:       2043 } hitcount:         11
+{ lat:        239, common_pid:       2037 } hitcount:         11
+{ lat:        239, common_pid:       2038 } hitcount:          6
+{ lat:        239, common_pid:       2036 } hitcount:          7
+{ lat:        239, common_pid:       2040 } hitcount:          1
+{ lat:        239, common_pid:       2042 } hitcount:          9
+{ lat:        240, common_pid:       2037 } hitcount:         29
+{ lat:        240, common_pid:       2043 } hitcount:         15
+{ lat:        240, common_pid:       2040 } hitcount:         44
+{ lat:        240, common_pid:       2039 } hitcount:          1
+{ lat:        240, common_pid:       2041 } hitcount:          2
+{ lat:        240, common_pid:       2038 } hitcount:          1
+{ lat:        240, common_pid:       2036 } hitcount:         10
+{ lat:        240, common_pid:       2042 } hitcount:         13
+{ lat:        241, common_pid:       2036 } hitcount:         21
+{ lat:        241, common_pid:       2041 } hitcount:         36
+{ lat:        241, common_pid:       2037 } hitcount:         34
+{ lat:        241, common_pid:       2042 } hitcount:         14
+{ lat:        241, common_pid:       2040 } hitcount:         94
+{ lat:        241, common_pid:       2039 } hitcount:         12
+{ lat:        241, common_pid:       2038 } hitcount:          2
+{ lat:        241, common_pid:       2043 } hitcount:         28
+{ lat:        242, common_pid:       2040 } hitcount:        109
+{ lat:        242, common_pid:       2041 } hitcount:        506
+{ lat:        242, common_pid:       2039 } hitcount:        155
+{ lat:        242, common_pid:       2042 } hitcount:         21
+{ lat:        242, common_pid:       2037 } hitcount:         52
+{ lat:        242, common_pid:       2043 } hitcount:         21
+{ lat:        242, common_pid:       2036 } hitcount:         16
+{ lat:        242, common_pid:       2038 } hitcount:        156
+{ lat:        243, common_pid:       2037 } hitcount:         46
+{ lat:        243, common_pid:       2039 } hitcount:         40
+{ lat:        243, common_pid:       2042 } hitcount:        119
+{ lat:        243, common_pid:       2041 } hitcount:        611
+{ lat:        243, common_pid:       2036 } hitcount:         69
+{ lat:        243, common_pid:       2038 } hitcount:        784
+{ lat:        243, common_pid:       2040 } hitcount:        323
+{ lat:        243, common_pid:       2043 } hitcount:         14
+{ lat:        244, common_pid:       2043 } hitcount:         35
+{ lat:        244, common_pid:       2042 } hitcount:        305
+{ lat:        244, common_pid:       2039 } hitcount:          8
+{ lat:        244, common_pid:       2040 } hitcount:       4515
+{ lat:        244, common_pid:       2038 } hitcount:        371
+{ lat:        244, common_pid:       2037 } hitcount:         31
+{ lat:        244, common_pid:       2036 } hitcount:        114
+{ lat:        244, common_pid:       2041 } hitcount:       3396
+{ lat:        245, common_pid:       2036 } hitcount:        700
+{ lat:        245, common_pid:       2041 } hitcount:       2772
+{ lat:        245, common_pid:       2037 } hitcount:        268
+{ lat:        245, common_pid:       2039 } hitcount:        472
+{ lat:        245, common_pid:       2038 } hitcount:       2758
+{ lat:        245, common_pid:       2042 } hitcount:       3833
+{ lat:        245, common_pid:       2040 } hitcount:       3105
+{ lat:        245, common_pid:       2043 } hitcount:        645
+{ lat:        246, common_pid:       2038 } hitcount:       3451
+{ lat:        246, common_pid:       2041 } hitcount:        142
+{ lat:        246, common_pid:       2037 } hitcount:       5101
+{ lat:        246, common_pid:       2040 } hitcount:         68
+{ lat:        246, common_pid:       2043 } hitcount:       5099
+{ lat:        246, common_pid:       2039 } hitcount:       5608
+{ lat:        246, common_pid:       2042 } hitcount:       3723
+{ lat:        246, common_pid:       2036 } hitcount:       4738
+{ lat:        247, common_pid:       2042 } hitcount:        312
+{ lat:        247, common_pid:       2043 } hitcount:       2385
+{ lat:        247, common_pid:       2041 } hitcount:        452
+{ lat:        247, common_pid:       2038 } hitcount:        792
+{ lat:        247, common_pid:       2040 } hitcount:         78
+{ lat:        247, common_pid:       2036 } hitcount:       2375
+{ lat:        247, common_pid:       2039 } hitcount:       1834
+{ lat:        247, common_pid:       2037 } hitcount:       2655
+{ lat:        248, common_pid:       2037 } hitcount:         36
+{ lat:        248, common_pid:       2042 } hitcount:         11
+{ lat:        248, common_pid:       2038 } hitcount:        122
+{ lat:        248, common_pid:       2036 } hitcount:        135
+{ lat:        248, common_pid:       2039 } hitcount:         26
+{ lat:        248, common_pid:       2041 } hitcount:        503
+{ lat:        248, common_pid:       2043 } hitcount:         66
+{ lat:        248, common_pid:       2040 } hitcount:         46
+{ lat:        249, common_pid:       2037 } hitcount:         29
+{ lat:        249, common_pid:       2038 } hitcount:          1
+{ lat:        249, common_pid:       2043 } hitcount:         29
+{ lat:        249, common_pid:       2039 } hitcount:          8
+{ lat:        249, common_pid:       2042 } hitcount:         56
+{ lat:        249, common_pid:       2040 } hitcount:         27
+{ lat:        249, common_pid:       2041 } hitcount:         11
+{ lat:        249, common_pid:       2036 } hitcount:         27
+{ lat:        250, common_pid:       2038 } hitcount:          1
+{ lat:        250, common_pid:       2036 } hitcount:         30
+{ lat:        250, common_pid:       2040 } hitcount:         19
+{ lat:        250, common_pid:       2043 } hitcount:         22
+{ lat:        250, common_pid:       2042 } hitcount:         20
+{ lat:        250, common_pid:       2041 } hitcount:          1
+{ lat:        250, common_pid:       2039 } hitcount:          6
+{ lat:        250, common_pid:       2037 } hitcount:         48
+{ lat:        251, common_pid:       2037 } hitcount:         43
+{ lat:        251, common_pid:       2039 } hitcount:          1
+{ lat:        251, common_pid:       2036 } hitcount:         12
+{ lat:        251, common_pid:       2042 } hitcount:          2
+{ lat:        251, common_pid:       2041 } hitcount:          1
+{ lat:        251, common_pid:       2043 } hitcount:         15
+{ lat:        251, common_pid:       2040 } hitcount:          3
+{ lat:        252, common_pid:       2040 } hitcount:          1
+{ lat:        252, common_pid:       2036 } hitcount:         12
+{ lat:        252, common_pid:       2037 } hitcount:         21
+{ lat:        252, common_pid:       2043 } hitcount:         14
+{ lat:        253, common_pid:       2037 } hitcount:         21
+{ lat:        253, common_pid:       2039 } hitcount:          2
+{ lat:        253, common_pid:       2036 } hitcount:          9
+{ lat:        253, common_pid:       2043 } hitcount:          6
+{ lat:        253, common_pid:       2040 } hitcount:          1
+{ lat:        254, common_pid:       2036 } hitcount:          8
+{ lat:        254, common_pid:       2043 } hitcount:          3
+{ lat:        254, common_pid:       2041 } hitcount:          1
+{ lat:        254, common_pid:       2042 } hitcount:          1
+{ lat:        254, common_pid:       2039 } hitcount:          1
+{ lat:        254, common_pid:       2037 } hitcount:         12
+{ lat:        255, common_pid:       2043 } hitcount:          1
+{ lat:        255, common_pid:       2037 } hitcount:          2
+{ lat:        255, common_pid:       2036 } hitcount:          2
+{ lat:        255, common_pid:       2039 } hitcount:          8
+{ lat:        256, common_pid:       2043 } hitcount:          1
+{ lat:        256, common_pid:       2036 } hitcount:          4
+{ lat:        256, common_pid:       2039 } hitcount:          6
+{ lat:        257, common_pid:       2039 } hitcount:          5
+{ lat:        257, common_pid:       2036 } hitcount:          4
+{ lat:        258, common_pid:       2039 } hitcount:          5
+{ lat:        258, common_pid:       2036 } hitcount:          2
+{ lat:        259, common_pid:       2036 } hitcount:          7
+{ lat:        259, common_pid:       2039 } hitcount:          7
+{ lat:        260, common_pid:       2036 } hitcount:          8
+{ lat:        260, common_pid:       2039 } hitcount:          6
+{ lat:        261, common_pid:       2036 } hitcount:          5
+{ lat:        261, common_pid:       2039 } hitcount:          7
+{ lat:        262, common_pid:       2039 } hitcount:          5
+{ lat:        262, common_pid:       2036 } hitcount:          5
+{ lat:        263, common_pid:       2039 } hitcount:          7
+{ lat:        263, common_pid:       2036 } hitcount:          7
+{ lat:        264, common_pid:       2039 } hitcount:          9
+{ lat:        264, common_pid:       2036 } hitcount:          9
+{ lat:        265, common_pid:       2036 } hitcount:          5
+{ lat:        265, common_pid:       2039 } hitcount:          1
+{ lat:        266, common_pid:       2036 } hitcount:          1
+{ lat:        266, common_pid:       2039 } hitcount:          3
+{ lat:        267, common_pid:       2036 } hitcount:          1
+{ lat:        267, common_pid:       2039 } hitcount:          3
+{ lat:        268, common_pid:       2036 } hitcount:          1
+{ lat:        268, common_pid:       2039 } hitcount:          6
+{ lat:        269, common_pid:       2036 } hitcount:          1
+{ lat:        269, common_pid:       2043 } hitcount:          1
+{ lat:        269, common_pid:       2039 } hitcount:          2
+{ lat:        270, common_pid:       2040 } hitcount:          1
+{ lat:        270, common_pid:       2039 } hitcount:          6
+{ lat:        271, common_pid:       2041 } hitcount:          1
+{ lat:        271, common_pid:       2039 } hitcount:          5
+{ lat:        272, common_pid:       2039 } hitcount:         10
+{ lat:        273, common_pid:       2039 } hitcount:          8
+{ lat:        274, common_pid:       2039 } hitcount:          2
+{ lat:        275, common_pid:       2039 } hitcount:          1
+{ lat:        276, common_pid:       2039 } hitcount:          2
+{ lat:        276, common_pid:       2037 } hitcount:          1
+{ lat:        276, common_pid:       2038 } hitcount:          1
+{ lat:        277, common_pid:       2039 } hitcount:          1
+{ lat:        277, common_pid:       2042 } hitcount:          1
+{ lat:        278, common_pid:       2039 } hitcount:          1
+{ lat:        279, common_pid:       2039 } hitcount:          4
+{ lat:        279, common_pid:       2043 } hitcount:          1
+{ lat:        280, common_pid:       2039 } hitcount:          3
+{ lat:        283, common_pid:       2036 } hitcount:          2
+{ lat:        284, common_pid:       2039 } hitcount:          1
+{ lat:        284, common_pid:       2043 } hitcount:          1
+{ lat:        288, common_pid:       2039 } hitcount:          1
+{ lat:        289, common_pid:       2039 } hitcount:          1
+{ lat:        300, common_pid:       2039 } hitcount:          1
+{ lat:        384, common_pid:       2039 } hitcount:          1
+
+Totals:
+    Hits: 67625
+    Entries: 278
+    Dropped: 0
+
+Note, the writes are around the sleep, so ideally they will all be of 250
+microseconds. If you are wondering how there are several that are under
+250 microseconds, that is because the way cyclictest works, is if one
+iteration comes in late, the next one will set the timer to wake up less that
+250. That is, if an iteration came in 50 microseconds late, the next wake up
+will be at 200 microseconds.
+
+But this could easily be done in userspace. To make this even more
+interesting, we can mix the histogram between events that happened in the
+kernel with trace_marker.
+
+ # cd /sys/kernel/tracing
+ # echo 'latency u64 lat' > synthetic_events
+ # echo 'hist:keys=pid:ts0=common_timestamp.usecs' > events/sched/sched_waking/trigger
+ # echo '!hist:keys=common_pid:vals=hitcount:lat=common_timestamp.usecs-$ts0:sort=hitcount:size=2048:clock=global:onmatch(sched.sched_switch).latency($lat) if buf == "end"' > events/ftrace/print/trigger
+ # echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_waking).latency($lat) if buf == "end"' > events/ftrace/print/trigger
+ # echo 'hist:keys=lat,common_pid:sort=lat' > events/synthetic/latency/trigger
+
+The difference this time is that instead of using the trace_marker to start
+the latency, the sched_waking event is used, matching the common_pid for the
+trace_marker write with the pid that is being worken by sched_waking.
+
+After running cyclictest again with the same parameters, we now have:
+
+ # cat events/synthetic/latency/hist
+# event histogram
+#
+# trigger info: hist:keys=lat,common_pid:vals=hitcount:sort=lat:size=2048 [active]
+#
+
+{ lat:          7, common_pid:       2302 } hitcount:        640
+{ lat:          7, common_pid:       2299 } hitcount:         42
+{ lat:          7, common_pid:       2303 } hitcount:         18
+{ lat:          7, common_pid:       2305 } hitcount:        166
+{ lat:          7, common_pid:       2306 } hitcount:          1
+{ lat:          7, common_pid:       2301 } hitcount:         91
+{ lat:          7, common_pid:       2300 } hitcount:         17
+{ lat:          8, common_pid:       2303 } hitcount:       8296
+{ lat:          8, common_pid:       2304 } hitcount:       6864
+{ lat:          8, common_pid:       2305 } hitcount:       9464
+{ lat:          8, common_pid:       2301 } hitcount:       9213
+{ lat:          8, common_pid:       2306 } hitcount:       6246
+{ lat:          8, common_pid:       2302 } hitcount:       8797
+{ lat:          8, common_pid:       2299 } hitcount:       8771
+{ lat:          8, common_pid:       2300 } hitcount:       8119
+{ lat:          9, common_pid:       2305 } hitcount:       1519
+{ lat:          9, common_pid:       2299 } hitcount:       2346
+{ lat:          9, common_pid:       2303 } hitcount:       2841
+{ lat:          9, common_pid:       2301 } hitcount:       1846
+{ lat:          9, common_pid:       2304 } hitcount:       3861
+{ lat:          9, common_pid:       2302 } hitcount:       1210
+{ lat:          9, common_pid:       2300 } hitcount:       2762
+{ lat:          9, common_pid:       2306 } hitcount:       4247
+{ lat:         10, common_pid:       2299 } hitcount:         16
+{ lat:         10, common_pid:       2306 } hitcount:        333
+{ lat:         10, common_pid:       2303 } hitcount:         16
+{ lat:         10, common_pid:       2304 } hitcount:        168
+{ lat:         10, common_pid:       2302 } hitcount:        240
+{ lat:         10, common_pid:       2301 } hitcount:         28
+{ lat:         10, common_pid:       2300 } hitcount:         95
+{ lat:         10, common_pid:       2305 } hitcount:         18
+{ lat:         11, common_pid:       2303 } hitcount:          5
+{ lat:         11, common_pid:       2305 } hitcount:          8
+{ lat:         11, common_pid:       2306 } hitcount:        221
+{ lat:         11, common_pid:       2302 } hitcount:         76
+{ lat:         11, common_pid:       2304 } hitcount:         26
+{ lat:         11, common_pid:       2300 } hitcount:        125
+{ lat:         11, common_pid:       2299 } hitcount:          2
+{ lat:         12, common_pid:       2305 } hitcount:          3
+{ lat:         12, common_pid:       2300 } hitcount:          6
+{ lat:         12, common_pid:       2306 } hitcount:         90
+{ lat:         12, common_pid:       2302 } hitcount:          4
+{ lat:         12, common_pid:       2303 } hitcount:          1
+{ lat:         12, common_pid:       2304 } hitcount:        122
+{ lat:         13, common_pid:       2300 } hitcount:         12
+{ lat:         13, common_pid:       2301 } hitcount:          1
+{ lat:         13, common_pid:       2306 } hitcount:         32
+{ lat:         13, common_pid:       2302 } hitcount:          5
+{ lat:         13, common_pid:       2305 } hitcount:          1
+{ lat:         13, common_pid:       2303 } hitcount:          1
+{ lat:         13, common_pid:       2304 } hitcount:         61
+{ lat:         14, common_pid:       2303 } hitcount:          4
+{ lat:         14, common_pid:       2306 } hitcount:          5
+{ lat:         14, common_pid:       2305 } hitcount:          4
+{ lat:         14, common_pid:       2304 } hitcount:         62
+{ lat:         14, common_pid:       2302 } hitcount:         19
+{ lat:         14, common_pid:       2300 } hitcount:         33
+{ lat:         14, common_pid:       2299 } hitcount:          1
+{ lat:         14, common_pid:       2301 } hitcount:          4
+{ lat:         15, common_pid:       2305 } hitcount:          1
+{ lat:         15, common_pid:       2302 } hitcount:         25
+{ lat:         15, common_pid:       2300 } hitcount:         11
+{ lat:         15, common_pid:       2299 } hitcount:          5
+{ lat:         15, common_pid:       2301 } hitcount:          1
+{ lat:         15, common_pid:       2304 } hitcount:          8
+{ lat:         15, common_pid:       2303 } hitcount:          1
+{ lat:         15, common_pid:       2306 } hitcount:          6
+{ lat:         16, common_pid:       2302 } hitcount:         31
+{ lat:         16, common_pid:       2306 } hitcount:          3
+{ lat:         16, common_pid:       2300 } hitcount:          5
+{ lat:         17, common_pid:       2302 } hitcount:          6
+{ lat:         17, common_pid:       2303 } hitcount:          1
+{ lat:         18, common_pid:       2304 } hitcount:          1
+{ lat:         18, common_pid:       2302 } hitcount:          8
+{ lat:         18, common_pid:       2299 } hitcount:          1
+{ lat:         18, common_pid:       2301 } hitcount:          1
+{ lat:         19, common_pid:       2303 } hitcount:          4
+{ lat:         19, common_pid:       2304 } hitcount:          5
+{ lat:         19, common_pid:       2302 } hitcount:          4
+{ lat:         19, common_pid:       2299 } hitcount:          3
+{ lat:         19, common_pid:       2306 } hitcount:          1
+{ lat:         19, common_pid:       2300 } hitcount:          4
+{ lat:         19, common_pid:       2305 } hitcount:          5
+{ lat:         20, common_pid:       2299 } hitcount:          2
+{ lat:         20, common_pid:       2302 } hitcount:          3
+{ lat:         20, common_pid:       2305 } hitcount:          1
+{ lat:         20, common_pid:       2300 } hitcount:          2
+{ lat:         20, common_pid:       2301 } hitcount:          2
+{ lat:         20, common_pid:       2303 } hitcount:          3
+{ lat:         21, common_pid:       2305 } hitcount:          1
+{ lat:         21, common_pid:       2299 } hitcount:          5
+{ lat:         21, common_pid:       2303 } hitcount:          4
+{ lat:         21, common_pid:       2302 } hitcount:          7
+{ lat:         21, common_pid:       2300 } hitcount:          1
+{ lat:         21, common_pid:       2301 } hitcount:          5
+{ lat:         21, common_pid:       2304 } hitcount:          2
+{ lat:         22, common_pid:       2302 } hitcount:          5
+{ lat:         22, common_pid:       2303 } hitcount:          1
+{ lat:         22, common_pid:       2306 } hitcount:          3
+{ lat:         22, common_pid:       2301 } hitcount:          2
+{ lat:         22, common_pid:       2300 } hitcount:          1
+{ lat:         22, common_pid:       2299 } hitcount:          1
+{ lat:         22, common_pid:       2305 } hitcount:          1
+{ lat:         22, common_pid:       2304 } hitcount:          1
+{ lat:         23, common_pid:       2299 } hitcount:          1
+{ lat:         23, common_pid:       2306 } hitcount:          2
+{ lat:         23, common_pid:       2302 } hitcount:          6
+{ lat:         24, common_pid:       2302 } hitcount:          3
+{ lat:         24, common_pid:       2300 } hitcount:          1
+{ lat:         24, common_pid:       2306 } hitcount:          2
+{ lat:         24, common_pid:       2305 } hitcount:          1
+{ lat:         24, common_pid:       2299 } hitcount:          1
+{ lat:         25, common_pid:       2300 } hitcount:          1
+{ lat:         25, common_pid:       2302 } hitcount:          4
+{ lat:         26, common_pid:       2302 } hitcount:          2
+{ lat:         27, common_pid:       2305 } hitcount:          1
+{ lat:         27, common_pid:       2300 } hitcount:          1
+{ lat:         27, common_pid:       2302 } hitcount:          3
+{ lat:         28, common_pid:       2306 } hitcount:          1
+{ lat:         28, common_pid:       2302 } hitcount:          4
+{ lat:         29, common_pid:       2302 } hitcount:          1
+{ lat:         29, common_pid:       2300 } hitcount:          2
+{ lat:         29, common_pid:       2306 } hitcount:          1
+{ lat:         29, common_pid:       2304 } hitcount:          1
+{ lat:         30, common_pid:       2302 } hitcount:          4
+{ lat:         31, common_pid:       2302 } hitcount:          6
+{ lat:         32, common_pid:       2302 } hitcount:          1
+{ lat:         33, common_pid:       2299 } hitcount:          1
+{ lat:         33, common_pid:       2302 } hitcount:          3
+{ lat:         34, common_pid:       2302 } hitcount:          2
+{ lat:         35, common_pid:       2302 } hitcount:          1
+{ lat:         35, common_pid:       2304 } hitcount:          1
+{ lat:         36, common_pid:       2302 } hitcount:          4
+{ lat:         37, common_pid:       2302 } hitcount:          6
+{ lat:         38, common_pid:       2302 } hitcount:          2
+{ lat:         39, common_pid:       2302 } hitcount:          2
+{ lat:         39, common_pid:       2304 } hitcount:          1
+{ lat:         40, common_pid:       2304 } hitcount:          2
+{ lat:         40, common_pid:       2302 } hitcount:          5
+{ lat:         41, common_pid:       2304 } hitcount:          1
+{ lat:         41, common_pid:       2302 } hitcount:          8
+{ lat:         42, common_pid:       2302 } hitcount:          6
+{ lat:         42, common_pid:       2304 } hitcount:          1
+{ lat:         43, common_pid:       2302 } hitcount:          3
+{ lat:         43, common_pid:       2304 } hitcount:          4
+{ lat:         44, common_pid:       2302 } hitcount:          6
+{ lat:         45, common_pid:       2302 } hitcount:          5
+{ lat:         46, common_pid:       2302 } hitcount:          5
+{ lat:         47, common_pid:       2302 } hitcount:          7
+{ lat:         48, common_pid:       2301 } hitcount:          1
+{ lat:         48, common_pid:       2302 } hitcount:          9
+{ lat:         49, common_pid:       2302 } hitcount:          3
+{ lat:         50, common_pid:       2302 } hitcount:          1
+{ lat:         50, common_pid:       2301 } hitcount:          1
+{ lat:         51, common_pid:       2302 } hitcount:          2
+{ lat:         51, common_pid:       2301 } hitcount:          1
+{ lat:         61, common_pid:       2302 } hitcount:          1
+{ lat:        110, common_pid:       2302 } hitcount:          1
+
+Totals:
+    Hits: 89565
+    Entries: 158
+    Dropped: 0
+
+This doesn't tell us any information about how late cyclictest may have
+worken up, but it does show us a nice histogram of how long it took from
+the time that cyclictest was worken to the time it made it into user space.
-- 
2.17.0

Re: [RFC][PATCH 01/10] tracing: Do not reference event data in post call triggers

[Masami Hiramatsu]

On Fri, 11 May 2018 15:49:28 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> 
> Trace event triggers can be called before or after the event has been
> committed. If it has been called after the commit, there's a possibility
> that the event no longer exists. Currently, the two post callers is the
> trigger to disable tracing (traceoff) and the one that will record a stack
> dump (stacktrace). Neither of them reference the trace event entry record,
> as that would lead to a race condition that could pass in corrupted data.
> 
> To prevent any other users of the post data triggers from using the trace
> event record, pass in NULL to the post call trigger functions for the event
> record, as they should never need to use them in the first place.
> 
> This does not fix any bug, but prevents bugs from happening by new post call
> trigger users.
> 

OK, so after commit the event record, the event handler should not access it.

Looks good to me.

Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>

Thanks,


> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
>  include/linux/trace_events.h        | 3 +--
>  kernel/trace/trace.h                | 4 ++--
>  kernel/trace/trace_events_trigger.c | 6 ++----
>  3 files changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index 2bde3eff564c..d1c442d9bd85 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -435,8 +435,7 @@ 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);
> +			 enum event_trigger_type tt);
>  
>  bool trace_event_ignore_this_pid(struct trace_event_file *trace_file);
>  
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 6fb46a06c9dc..24b666891eaf 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -1334,7 +1334,7 @@ event_trigger_unlock_commit(struct trace_event_file *file,
>  		trace_buffer_unlock_commit(file->tr, buffer, event, irq_flags, pc);
>  
>  	if (tt)
> -		event_triggers_post_call(file, tt, entry, event);
> +		event_triggers_post_call(file, tt);
>  }
>  
>  /**
> @@ -1367,7 +1367,7 @@ event_trigger_unlock_commit_regs(struct trace_event_file *file,
>  						irq_flags, pc, regs);
>  
>  	if (tt)
> -		event_triggers_post_call(file, tt, entry, event);
> +		event_triggers_post_call(file, tt);
>  }
>  
>  #define FILTER_PRED_INVALID	((unsigned short)-1)
> diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
> index d251cabcf69a..cc4148bfc01a 100644
> --- a/kernel/trace/trace_events_trigger.c
> +++ b/kernel/trace/trace_events_trigger.c
> @@ -97,7 +97,6 @@ EXPORT_SYMBOL_GPL(event_triggers_call);
>   * event_triggers_post_call - Call 'post_triggers' for a trace event
>   * @file: The trace_event_file associated with the event
>   * @tt: enum event_trigger_type containing a set bit for each trigger to invoke
> - * @rec: The trace entry for the event
>   *
>   * For each trigger associated with an event, invoke the trigger
>   * function registered with the associated trigger command, if the
> @@ -108,8 +107,7 @@ EXPORT_SYMBOL_GPL(event_triggers_call);
>   */
>  void
>  event_triggers_post_call(struct trace_event_file *file,
> -			 enum event_trigger_type tt,
> -			 void *rec, struct ring_buffer_event *event)
> +			 enum event_trigger_type tt)
>  {
>  	struct event_trigger_data *data;
>  
> @@ -117,7 +115,7 @@ event_triggers_post_call(struct trace_event_file *file,
>  		if (data->paused)
>  			continue;
>  		if (data->cmd_ops->trigger_type & tt)
> -			data->ops->func(data, rec, event);
> +			data->ops->func(data, NULL, NULL);
>  	}
>  }
>  EXPORT_SYMBOL_GPL(event_triggers_post_call);
> -- 
> 2.17.0
> 
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [RFC][PATCH 07/10] tracing: Have zero size length in filter logic be full string

[Masami Hiramatsu]

On Fri, 11 May 2018 15:49:34 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> 
> As strings in trace events may not have a nul terminating character, the
> filter string compares use the defined string length for the field for the
> compares.
> 
> The trace_marker records data slightly different than do normal events. It's
> size is zero, meaning that the string is the rest of the array, and that the
> string also ends with '\0'.
> 
> If the size is zero, assume that the string is nul terminated and read the
> string in question as is.
> 
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
>  kernel/trace/trace_events_filter.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index 7d306b74230f..675392b9edd2 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -750,31 +750,32 @@ static int filter_pred_none(struct filter_pred *pred, void *event)
>   *
>   * Note:
>   * - @str might not be NULL-terminated if it's of type DYN_STRING
> - *   or STATIC_STRING
> + *   or STATIC_STRING, unless @len is zero.
>   */
>  
>  static int regex_match_full(char *str, struct regex *r, int len)
>  {
> -	if (strncmp(str, r->pattern, len) == 0)
> -		return 1;
> -	return 0;
> +	/* len means str is dynamic and ends with '\0' */
           ^^^
          !len (or len == 0)?

Thank you,




-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [RFC][PATCH 07/10] tracing: Have zero size length in filter logic be full string

[Steven Rostedt]

On Sat, 12 May 2018 21:40:29 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:


> >  static int regex_match_full(char *str, struct regex *r, int len)
> >  {
> > -	if (strncmp(str, r->pattern, len) == 0)
> > -		return 1;
> > -	return 0;
> > +	/* len means str is dynamic and ends with '\0' */  
>            ^^^
>           !len (or len == 0)?
> 
> Thank you,
> 

Yes, agreed. Thanks for the review!

-- Steve

Re: [RFC][PATCH 07/10] tracing: Have zero size length in filter logic be full string

[Yann Ylavic]

On Fri, May 11, 2018 at 9:49 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
[]
>
>  static int regex_match_front(char *str, struct regex *r, int len)
>  {
> -       if (len < r->len)
> +       if (len && len < r->len)
>                 return 0;
>
> -       if (strncmp(str, r->pattern, r->len) == 0)
> -               return 1;
> -       return 0;
> +       return strncmp(str, r->pattern, len) == 0;

strncmp(..., r->len) still?

>  }

Regards,
Yann.

Re: [RFC][PATCH 07/10] tracing: Have zero size length in filter logic be full string

[Namhyung Kim]

Hi,

On Sat, May 12, 2018 at 08:32:18PM +0200, Yann Ylavic wrote:
> On Fri, May 11, 2018 at 9:49 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> []
> >
> >  static int regex_match_front(char *str, struct regex *r, int len)
> >  {
> > -       if (len < r->len)
> > +       if (len && len < r->len)
> >                 return 0;
> >
> > -       if (strncmp(str, r->pattern, r->len) == 0)
> > -               return 1;
> > -       return 0;
> > +       return strncmp(str, r->pattern, len) == 0;
> 
> strncmp(..., r->len) still?

Yep, I think so.  Otherwise it'll always return true when len is 0.

Thanks,
Namhyung

Re: [RFC][PATCH 06/10] tracing: Add trigger file for trace_markers tracefs/ftrace/print

[Namhyung Kim]

On Fri, May 11, 2018 at 03:49:33PM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> 
> Allow writing to the trace_markers file initiate triggers defined in
> tracefs/ftrace/print/trigger file. This will allow of user space to trigger
> the same type of triggers (including histograms) that the trace events use.
> 
> Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
> Cc: Clark Williams <williams@redhat.com>
> Cc: Karim Yaghmour <karim.yaghmour@opersys.com>
> Cc: Brendan Gregg <bgregg@netflix.com>
> Suggested-by: Joel Fernandes <joelaf@google.com>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---

[SNIP]
> diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> index e3a658bac10f..de3fce14cd00 100644
> --- a/kernel/trace/trace_entries.h
> +++ b/kernel/trace/trace_entries.h
> @@ -230,7 +230,7 @@ FTRACE_ENTRY(bprint, bprint_entry,
>  	FILTER_OTHER
>  );
>  
> -FTRACE_ENTRY(print, print_entry,
> +FTRACE_ENTRY_REG(print, print_entry,
>  
>  	TRACE_PRINT,
>  
> @@ -242,7 +242,9 @@ FTRACE_ENTRY(print, print_entry,
>  	F_printk("%ps: %s",
>  		 (void *)__entry->ip, __entry->buf),
>  
> -	FILTER_OTHER
> +	FILTER_OTHER,
> +
> +	 ftrace_event_register

I wonder this is still needed since you added __find_event_file()
which ignores the reg field.  Maybe I'm missing something..

Anyway it looks whitespace damaged.

Thanks,
Namhyung


>  );
>  
>  FTRACE_ENTRY(raw_data, raw_data_entry,
> diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
> index d842f1eadfe5..45630a76ed3a 100644
> --- a/kernel/trace/trace_export.c
> +++ b/kernel/trace/trace_export.c
> @@ -14,6 +14,13 @@
>  
>  #include "trace_output.h"
>  
> +/* Stub function for events with triggers */
> +static int ftrace_event_register(struct trace_event_call *call,
> +				 enum trace_reg type, void *data)
> +{
> +	return 0;
> +}
> +
>  #undef TRACE_SYSTEM
>  #define TRACE_SYSTEM	ftrace
>  
> -- 
> 2.17.0
> 
> 

Re: [RFC][PATCH 07/10] tracing: Have zero size length in filter logic be full string

[Steven Rostedt]

On Sat, 12 May 2018 20:32:18 +0200
Yann Ylavic <ylavic.dev@gmail.com> wrote:

> On Fri, May 11, 2018 at 9:49 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> []
> >
> >  static int regex_match_front(char *str, struct regex *r, int len)
> >  {
> > -       if (len < r->len)
> > +       if (len && len < r->len)
> >                 return 0;
> >
> > -       if (strncmp(str, r->pattern, r->len) == 0)
> > -               return 1;
> > -       return 0;
> > +       return strncmp(str, r->pattern, len) == 0;  
> 
> strncmp(..., r->len) still?
> 
> >  }  

Ouch! Yes! I have no idea how I did that :-/

Thanks for pointing that out.

-- Steve

Re: [RFC][PATCH 06/10] tracing: Add trigger file for trace_markers tracefs/ftrace/print

[Steven Rostedt]

On Mon, 14 May 2018 12:13:22 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> On Fri, May 11, 2018 at 03:49:33PM -0400, Steven Rostedt wrote:
> > From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> > 
> > Allow writing to the trace_markers file initiate triggers defined in
> > tracefs/ftrace/print/trigger file. This will allow of user space to trigger
> > the same type of triggers (including histograms) that the trace events use.
> > 
> > Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
> > Cc: Clark Williams <williams@redhat.com>
> > Cc: Karim Yaghmour <karim.yaghmour@opersys.com>
> > Cc: Brendan Gregg <bgregg@netflix.com>
> > Suggested-by: Joel Fernandes <joelaf@google.com>
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > ---  
> 
> [SNIP]
> > diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> > index e3a658bac10f..de3fce14cd00 100644
> > --- a/kernel/trace/trace_entries.h
> > +++ b/kernel/trace/trace_entries.h
> > @@ -230,7 +230,7 @@ FTRACE_ENTRY(bprint, bprint_entry,
> >  	FILTER_OTHER
> >  );
> >  
> > -FTRACE_ENTRY(print, print_entry,
> > +FTRACE_ENTRY_REG(print, print_entry,
> >  
> >  	TRACE_PRINT,
> >  
> > @@ -242,7 +242,9 @@ FTRACE_ENTRY(print, print_entry,
> >  	F_printk("%ps: %s",
> >  		 (void *)__entry->ip, __entry->buf),
> >  
> > -	FILTER_OTHER
> > +	FILTER_OTHER,
> > +
> > +	 ftrace_event_register  
> 
> I wonder this is still needed since you added __find_event_file()
> which ignores the reg field.  Maybe I'm missing something..

No, that's not the reason for it. The reason is due to the
event_trigger_callback() function. I'll update the changelog to specify
this.

We have something like:

 # echo snapshot > events/ftrace/print/trigger

Which will do:

  event_trigger_write() {
    event_trigger_regex_write() {
      trigger_process_regex() {
        for p in trigger_commands {
          p->func(); /* trigger_snapshot_cmd->func */
            event_trigger_callback() {
              cmd_ops->reg() /* register_trigger() */ {
                trace_event_trigger_enable_disable() {
                  trace_event_enable_disable() {
                    call->class->reg();

Without this patch, we jump to NULL and BOOM!
                

> 
> Anyway it looks whitespace damaged.
>

Thanks, I'll fix it up.

-- Steve

Re: [RFC][PATCH 06/10] tracing: Add trigger file for trace_markers tracefs/ftrace/print

[Namhyung Kim]

Hi Steve,

On Mon, May 14, 2018 at 11:04:36AM -0400, Steven Rostedt wrote:
> On Mon, 14 May 2018 12:13:22 +0900
> Namhyung Kim <namhyung@kernel.org> wrote:
> 
> > On Fri, May 11, 2018 at 03:49:33PM -0400, Steven Rostedt wrote:
> > > From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> > > 
> > > Allow writing to the trace_markers file initiate triggers defined in
> > > tracefs/ftrace/print/trigger file. This will allow of user space to trigger
> > > the same type of triggers (including histograms) that the trace events use.
> > > 
> > > Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
> > > Cc: Clark Williams <williams@redhat.com>
> > > Cc: Karim Yaghmour <karim.yaghmour@opersys.com>
> > > Cc: Brendan Gregg <bgregg@netflix.com>
> > > Suggested-by: Joel Fernandes <joelaf@google.com>
> > > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > > ---  
> > 
> > [SNIP]
> > > diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> > > index e3a658bac10f..de3fce14cd00 100644
> > > --- a/kernel/trace/trace_entries.h
> > > +++ b/kernel/trace/trace_entries.h
> > > @@ -230,7 +230,7 @@ FTRACE_ENTRY(bprint, bprint_entry,
> > >  	FILTER_OTHER
> > >  );
> > >  
> > > -FTRACE_ENTRY(print, print_entry,
> > > +FTRACE_ENTRY_REG(print, print_entry,
> > >  
> > >  	TRACE_PRINT,
> > >  
> > > @@ -242,7 +242,9 @@ FTRACE_ENTRY(print, print_entry,
> > >  	F_printk("%ps: %s",
> > >  		 (void *)__entry->ip, __entry->buf),
> > >  
> > > -	FILTER_OTHER
> > > +	FILTER_OTHER,
> > > +
> > > +	 ftrace_event_register  
> > 
> > I wonder this is still needed since you added __find_event_file()
> > which ignores the reg field.  Maybe I'm missing something..
> 
> No, that's not the reason for it. The reason is due to the
> event_trigger_callback() function. I'll update the changelog to specify
> this.
> 
> We have something like:
> 
>  # echo snapshot > events/ftrace/print/trigger
> 
> Which will do:
> 
>   event_trigger_write() {
>     event_trigger_regex_write() {
>       trigger_process_regex() {
>         for p in trigger_commands {
>           p->func(); /* trigger_snapshot_cmd->func */
>             event_trigger_callback() {
>               cmd_ops->reg() /* register_trigger() */ {
>                 trace_event_trigger_enable_disable() {
>                   trace_event_enable_disable() {
>                     call->class->reg();
> 
> Without this patch, we jump to NULL and BOOM!

Thanks for the explanation.  I wonder we can skip calling
trace_event_enable_disable() for events which have the
TRACE_EVENT_FL_IGNORE_ENABLE flag.

Thanks,
Namhyung

Re: [RFC][PATCH 06/10] tracing: Add trigger file for trace_markers tracefs/ftrace/print

[Steven Rostedt]

On Wed, 16 May 2018 16:49:04 +0900
Namhyung Kim <namhyung@kernel.org> wrote:


> > Which will do:
> > 
> >   event_trigger_write() {
> >     event_trigger_regex_write() {
> >       trigger_process_regex() {
> >         for p in trigger_commands {
> >           p->func(); /* trigger_snapshot_cmd->func */
> >             event_trigger_callback() {
> >               cmd_ops->reg() /* register_trigger() */ {
> >                 trace_event_trigger_enable_disable() {
> >                   trace_event_enable_disable() {
> >                     call->class->reg();
> > 
> > Without this patch, we jump to NULL and BOOM!  
> 
> Thanks for the explanation.  I wonder we can skip calling
> trace_event_enable_disable() for events which have the
> TRACE_EVENT_FL_IGNORE_ENABLE flag.

Sounds like something we can do in the future. I rather have do the
minimal now as it will have the least side effects, and it's already
getting late in the current rc series. I'm looking to get this into the
next merge window.

But after that, changing it this way would be a nice clean up.

-- Steve