diff options
authorPeter Zijlstra <peterz@infradead.org>2009-08-13 16:14:42 +0200
committerIngo Molnar <mingo@elte.hu>2009-08-13 16:17:15 +0200
commit94d5d1b2d891f1fd5205f978246b7864d998b25c (patch)
parent970892a9031a5dc7217bd394fb9d89fa75a4a7bc (diff)
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@cs.helsinki.fi> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: paulus@samba.org Cc: Anton Blanchard <anton@samba.org> Cc: Arjan van de Ven <arjan@infradead.org> LKML-Reference: <1250172882.5241.62.camel@twins> Signed-off-by: Ingo Molnar <mingo@elte.hu>
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 3f841beefc7..534e20d14d6 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,
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);