path: root/Documentation
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authorLinus Torvalds <>2015-11-06 13:30:20 -0800
committerLinus Torvalds <>2015-11-06 13:30:20 -0800
commit22402cd0af685c1a5d067c87db3051db7fff7709 (patch)
tree4f06ef31f643be28f3d4c92821df36b8ff321d9b /Documentation
parent7c623cac4939fb36916c029609dd22e3dec0a014 (diff)
parentd227c3ae4e94e5eb11dd780a811f59e1a7b74ccd (diff)
Merge tag 'trace-v4.4' of git://
Pull tracking updates from Steven Rostedt: "Most of the changes are clean ups and small fixes. Some of them have stable tags to them. I searched through my INBOX just as the merge window opened and found lots of patches to pull. I ran them through all my tests and they were in linux-next for a few days. Features added this release: ---------------------------- - Module globbing. You can now filter function tracing to several modules. # echo '*:mod:*snd*' > set_ftrace_filter (Dmitry Safonov) - Tracer specific options are now visible even when the tracer is not active. It was rather annoying that you can only see and modify tracer options after enabling the tracer. Now they are in the options/ directory even when the tracer is not active. Although they are still only visible when the tracer is active in the trace_options file. - Trace options are now per instance (although some of the tracer specific options are global) - New tracefs file: set_event_pid. If any pid is added to this file, then all events in the instance will filter out events that are not part of this pid. sched_switch and sched_wakeup events handle next and the wakee pids" * tag 'trace-v4.4' of git:// (68 commits) tracefs: Fix refcount imbalance in start_creating() tracing: Put back comma for empty fields in boot string parsing tracing: Apply tracer specific options from kernel command line. tracing: Add some documentation about set_event_pid ring_buffer: Remove unneeded smp_wmb() before wakeup of reader benchmark tracing: Allow dumping traces without tracking trace started cpus ring_buffer: Fix more races when terminating the producer in the benchmark ring_buffer: Do no not complete benchmark reader too early tracing: Remove redundant TP_ARGS redefining tracing: Rename max_stack_lock to stack_trace_max_lock tracing: Allow arch-specific stack tracer recordmcount: arm64: Replace the ignored mcount call into nop recordmcount: Fix endianness handling bug for nop_mcount tracepoints: Fix documentation of RCU lockdep checks tracing: ftrace_event_is_function() can return boolean tracing: is_legal_op() can return boolean ring-buffer: rb_event_is_commit() can return boolean ring-buffer: rb_per_cpu_empty() can return boolean ring_buffer: ring_buffer_empty{cpu}() can return boolean ring-buffer: rb_is_reader_page() can return boolean ...
Diffstat (limited to 'Documentation')
2 files changed, 41 insertions, 0 deletions
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index 75d25a1d6e42..c010be8c85d7 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -288,6 +288,24 @@ prev_pid == 0
# cat sched_wakeup/filter
common_pid == 0
+5.4 PID filtering
+The set_event_pid file in the same directory as the top events directory
+exists, will filter all events from tracing any task that does not have the
+PID listed in the set_event_pid file.
+# cd /sys/kernel/debug/tracing
+# echo $$ > set_event_pid
+# echo 1 > events/enabled
+Will only trace events for the current task.
+To add more PIDs without losing the PIDs already included, use '>>'.
+# echo 123 244 1 >> set_event_pid
6. Event triggers
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index ef621d34ba5b..f52f297cb406 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -204,6 +204,12 @@ of ftrace. Here is a list of some of the key files:
Have the function tracer only trace a single thread.
+ set_event_pid:
+ Have the events only trace a task with a PID listed in this file.
+ Note, sched_switch and sched_wake_up will also trace events
+ listed in this file.
Set a "trigger" function where tracing should start
@@ -2437,6 +2443,23 @@ The following commands are supported:
echo '!writeback*:mod:ext3' >> set_ftrace_filter
+ Mod command supports module globbing. Disable tracing for all
+ functions except a specific module:
+ echo '!*:mod:!ext3' >> set_ftrace_filter
+ Disable tracing for all modules, but still trace kernel:
+ echo '!*:mod:*' >> set_ftrace_filter
+ Enable filter only for kernel:
+ echo '*write*:mod:!*' >> set_ftrace_filter
+ Enable filter for module globbing:
+ echo '*write*:mod:*snd*' >> set_ftrace_filter
- traceon/traceoff
These commands turn tracing on and off when the specified
functions are hit. The parameter determines how many times the