2.6.38-stable review patch. If anyone has any objections, please let us know.
------------------ From: Peter Zijlstra <[email protected]> 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 <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Cc: Oleg Nesterov <[email protected]> LKML-Reference: <1301520405.4859.213.camel@twins> Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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); _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
