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Commit e03a9a55 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarPeter 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: default avatarIngo Molnar <mingo@elte.hu>
parent dce5855b

kernel/events/core.c

+1 −7
Original line number Original line 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;

	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);

	WARN_ON_ONCE(ctx->parent_ctx);

	/*

	/*

	 * There are two ways this annotation is useful:

	 * 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);

	mutex_lock_nested(&ctx->mutex, SINGLE_DEPTH_NESTING);

	raw_spin_lock_irq(&ctx->lock);

	raw_spin_lock_irq(&ctx->lock);

	perf_group_detach(event);

	perf_group_detach(event);

	list_del_event(event, ctx);

	raw_spin_unlock_irq(&ctx->lock);

	raw_spin_unlock_irq(&ctx->lock);

	perf_remove_from_context(event);

	mutex_unlock(&ctx->mutex);

	mutex_unlock(&ctx->mutex);





	free_event(event);

	free_event(event);