Commit 74c3337c authored Oct 15, 2010 by Peter Zijlstra Committed by Ingo Molnar Oct 18, 2010

perf: Fix group moving



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>

parent e360adbe

kernel/perf_event.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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)