linux-kernel - [PATCH 2/2 v2] optimize for perf_event_init

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Message-ID: <4ABC5AF9.6060808@cn.fujitsu.com>
Date:	Fri, 25 Sep 2009 13:54:01 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/2 v2] optimize for perf_event_init_task()

We can traverse ctx->group_list to get all group leader, it should be safe
since we hold ctx->mutex

Changlog v1->v2:
- remove WARN_ON_ONCE() as Peter Zijlstra's suggestion

Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
---
 kernel/perf_event.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 2a15cd6..0276fb4 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4767,9 +4767,7 @@ int perf_event_init_task(struct task_struct *child)
 	 * We dont have to disable NMIs - we are only looking at
 	 * the list, not manipulating it:
 	 */
-	list_for_each_entry_rcu(event, &parent_ctx->event_list, event_entry) {
-		if (event != event->group_leader)
-			continue;
+	list_for_each_entry(event, &parent_ctx->group_list, group_entry) {
 
 		if (!event->attr.inherit) {
 			inherited_all = 0;
-- 
1.6.1.2


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