Commit e03a9a55 authored Apr 09, 2011 by Peter Zijlstra Committed by Ingo Molnar May 28, 2011

perf: Change close() semantics for group events



In order to always call list_del_event() on the correct cpu if the
event is part of an active context and avoid having to do two IPIs,
change the close() semantics slightly.

The current perf_event_disable() call would disable a whole group if
the event that's being closed is the group leader, whereas the new
code keeps the group siblings enabled.

People should not rely on this behaviour and I don't think they do,
but in case we find they do, the fix is easy and we have to take the
double IPI cost.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Vince Weaver <vweaver1@eecs.utk.edu>
Link: http://lkml.kernel.org/r/20110409192142.038377551@chello.nl


Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent dce5855b

kernel/events/core.c

+1 −7

Original line number	Diff line number	Diff line
		@@ -2920,12 +2920,6 @@ int perf_event_release_kernel(struct perf_event *event)
		{
		struct perf_event_context *ctx = event->ctx;

		/*
		* Remove from the PMU, can't get re-enabled since we got
		* here because the last ref went.
		*/
		perf_event_disable(event);

		WARN_ON_ONCE(ctx->parent_ctx);
		/*
		* There are two ways this annotation is useful:
		@@ -2942,8 +2936,8 @@ int perf_event_release_kernel(struct perf_event *event)
		mutex_lock_nested(&ctx->mutex, SINGLE_DEPTH_NESTING);
		raw_spin_lock_irq(&ctx->lock);
		perf_group_detach(event);
		list_del_event(event, ctx);
		raw_spin_unlock_irq(&ctx->lock);
		perf_remove_from_context(event);
		mutex_unlock(&ctx->mutex);

		free_event(event);

Admin message