Messages in this thread Patch in this message | | | Date | Tue, 19 Apr 2011 13:08:26 -0700 | From | Greg KH <> | Subject | [17/70] perf: Fix task context scheduling |
| |
2.6.38-stable review patch. If anyone has any objections, please let us know.
------------------
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
commit ab711fe08297de1485fff0a366e6db8828cafd6a upstream.
Jiri reported:
| | - once an event is created by sys_perf_event_open, task context | is created and it stays even if the event is closed, until the | task is finished ... thats what I see in code and I assume it's | correct | | - when the task opens event, perf_sched_events jump label is | incremented and following callbacks are started from scheduler | | __perf_event_task_sched_in | __perf_event_task_sched_out | | These callback *in/out set/unset cpuctx->task_ctx value to the | task context. | | - close is called on event on CPU 0: | - the task is scheduled on CPU 0 | - __perf_event_task_sched_in is called | - cpuctx->task_ctx is set | - perf_sched_events jump label is decremented and == 0 | - __perf_event_task_sched_out is not called | - cpuctx->task_ctx on CPU 0 stays set | | - exit is called on CPU 1: | - the task is scheduled on CPU 1 | - perf_event_exit_task is called | - task_ctx_sched_out unsets cpuctx->task_ctx on CPU 1 | - put_ctx destroys the context | | - another call of perf_rotate_context on CPU 0 will use invalid | task_ctx pointer, and eventualy panic. |
Cure this the simplest possibly way by partially reverting the jump_label optimization for the sched_out case.
Reported-and-tested-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> LKML-Reference: <1301520405.4859.213.camel@twins> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- include/linux/perf_event.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1052,7 +1052,7 @@ void perf_event_task_sched_out(struct ta { perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 1, NULL, 0); - COND_STMT(&perf_task_events, __perf_event_task_sched_out(task, next)); + __perf_event_task_sched_out(task, next); } extern void perf_event_mmap(struct vm_area_struct *vma);
| |