This is a note to let you know that I've just added the patch titled
perf: Fix task context scheduling
to the 2.6.38-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-fix-task-context-scheduling.patch
and it can be found in the queue-2.6.38 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From ab711fe08297de1485fff0a366e6db8828cafd6a Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <[email protected]>
Date: Thu, 31 Mar 2011 10:29:26 +0200
Subject: perf: Fix task context scheduling
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);
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.38/perf-fix-task-context-scheduling.patch
_______________________________________________
stable mailing list
[email protected]
http://linux.kernel.org/mailman/listinfo/stable
