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perf: Fix group moving

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Matt found we trigger the WARN_ON_ONCE() in perf_group_attach() when we take
the move_group path in perf_event_open().

Since we cannot de-construct the group (we rely on it to move the events), we
have to simply ignore the double attach. The group state is context invariant
and doesn't need changing.

Reported-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1287135757.29097.1368.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-10-15 11:40:29 +02:00 committed by Ingo Molnar
parent e360adbe29
commit 74c3337c2f
1 changed files with 6 additions and 1 deletions
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7
kernel/perf_event.c
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@ -315,7 +315,12 @@ static void perf_group_attach(struct perf_event *event)
{
struct perf_event *group_leader = event->group_leader;
WARN_ON_ONCE(event->attach_state & PERF_ATTACH_GROUP);
/*
* We can have double attach due to group movement in perf_event_open.
*/
if (event->attach_state & PERF_ATTACH_GROUP)
return;
event->attach_state |= PERF_ATTACH_GROUP;
if (group_leader == event)