From ab711fe08297de1485fff0a366e6db8828cafd6a Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 31 Mar 2011 10:29:26 +0200 Subject: [PATCH] perf: Fix task context scheduling 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 Signed-off-by: Peter Zijlstra Cc: Oleg Nesterov Cc: # .37+ LKML-Reference: <1301520405.4859.213.camel@twins> Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 311b4dc785a..04d75a8a20e 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1086,7 +1086,7 @@ void perf_event_task_sched_out(struct task_struct *task, struct task_struct *nex { perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 1, NULL, 0); - COND_STMT(&perf_sched_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); -- 2.11.4.GIT