Commit-ID: 94d5d1b2d891f1fd5205f978246b7864d998b25c
Gitweb: http://git.kernel.org/tip/94d5d1b2d891f1fd5205f978246b7864d998b25c
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Thu, 13 Aug 2009 16:14:42 +0200
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 13 Aug 2009 16:17:15 +0200
perf_counter: Report the cloning task as parent on perf_counter_fork()
A bug in (9f498cc: perf_counter: Full task tracing) makes
profiling multi-threaded apps it go belly up.
[ output as: (PID:TID):(PPID:PTID) ]
# ./perf report -D | grep FORK
0x4b0 [0x18]: PERF_EVENT_FORK: (3237:3237):(3236:3236)
0xa10 [0x18]: PERF_EVENT_FORK: (3237:3238):(3236:3236)
0xa70 [0x18]: PERF_EVENT_FORK: (3237:3239):(3236:3236)
0xad0 [0x18]: PERF_EVENT_FORK: (3237:3240):(3236:3236)
0xb18 [0x18]: PERF_EVENT_FORK: (3237:3241):(3236:3236)
Shows us that the test (27d028d perf report: Update for the new
FORK/EXIT events) in builtin-report.c:
/*
* A thread clone will have the same PID for both
* parent and child.
*/
if (thread == parent)
return 0;
Will clearly fail.
The problem is that perf_counter_fork() reports the actual
parent, instead of the cloning thread.
Fixing that (with the below patch), yields:
# ./perf report -D | grep FORK
0x4c8 [0x18]: PERF_EVENT_FORK: (1590:1590):(1589:1589)
0xbd8 [0x18]: PERF_EVENT_FORK: (1590:1591):(1590:1590)
0xc80 [0x18]: PERF_EVENT_FORK: (1590:1592):(1590:1590)
0x3338 [0x18]: PERF_EVENT_FORK: (1590:1593):(1590:1590)
0x66b0 [0x18]: PERF_EVENT_FORK: (1590:1594):(1590:1590)
Which both makes more sense and doesn't confuse perf report
anymore.
Reported-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: paulus@xxxxxxxxx
Cc: Anton Blanchard <anton@xxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
LKML-Reference: <1250172882.5241.62.camel@twins>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/perf_counter.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 3f841be..534e20d 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3028,10 +3028,10 @@ static void perf_counter_task_output(struct perf_counter *counter,
return;
task_event->event.pid = perf_counter_pid(counter, task);
- task_event->event.ppid = perf_counter_pid(counter, task->real_parent);
+ task_event->event.ppid = perf_counter_pid(counter, current);
task_event->event.tid = perf_counter_tid(counter, task);
- task_event->event.ptid = perf_counter_tid(counter, task->real_parent);
+ task_event->event.ptid = perf_counter_tid(counter, current);
perf_output_put(&handle, task_event->event);
perf_output_end(&handle);
--
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