linux-kernel - [tip:perf/core] perf: Change close() semantics for group events

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Date:	Sat, 28 May 2011 16:41:49 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, vweaver1@...s.utk.edu,
	mingo@...e.hu
Subject: [tip:perf/core] perf: Change close() semantics for group events

Commit-ID:  e03a9a55b4e45377af9ca3d464135f9ea280b8f8
Gitweb:     http://git.kernel.org/tip/e03a9a55b4e45377af9ca3d464135f9ea280b8f8
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Sat, 9 Apr 2011 21:17:47 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Sat, 28 May 2011 18:01:21 +0200

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@...llo.nl>
Cc: Vince Weaver <vweaver1@...s.utk.edu>
Link: http://lkml.kernel.org/r/20110409192142.038377551@chello.nl
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/events/core.c |    8 +-------
 1 files changed, 1 insertions(+), 7 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 802f3b2..c378062 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -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);
--
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