linux-kernel - [tip:sched/core] sched: Check the right ->nr_running in yield_task

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Message-ID: <tip-725e7580aaf98e9f7b22b8ccfc640ad0c09e2b08@git.kernel.org>
Date:	Thu, 3 Feb 2011 14:11:32 GMT
From:	tip-bot for Rik van Riel <riel@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, riel@...hat.com, hpa@...or.com,
	mingo@...hat.com, a.p.zijlstra@...llo.nl, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:sched/core] sched: Check the right ->nr_running in yield_task_fair()

Commit-ID:  725e7580aaf98e9f7b22b8ccfc640ad0c09e2b08
Gitweb:     http://git.kernel.org/tip/725e7580aaf98e9f7b22b8ccfc640ad0c09e2b08
Author:     Rik van Riel <riel@...hat.com>
AuthorDate: Tue, 1 Feb 2011 09:47:15 -0500
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 3 Feb 2011 14:20:32 +0100

sched: Check the right ->nr_running in yield_task_fair()

With CONFIG_FAIR_GROUP_SCHED, each task_group has its own cfs_rq.
Yielding to a task from another cfs_rq may be worthwhile, since
a process calling yield typically cannot use the CPU right now.

Therefor, we want to check the per-cpu nr_running, not the
cgroup local one.

Signed-off-by: Rik van Riel <riel@...hat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <20110201094715.798c4f86@...uminas.surriel.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched_fair.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 55040f3..4de9905 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1331,7 +1331,7 @@ static void yield_task_fair(struct rq *rq)
 	/*
 	 * Are we the only task in the tree?
 	 */
-	if (unlikely(cfs_rq->nr_running == 1))
+	if (unlikely(rq->nr_running == 1))
 		return;
 
 	clear_buddies(cfs_rq, se);
--
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