From: Rik van Riel <riel@redhat.com>
Date: Tue, 1 Feb 2011 14:47:15 +0000 (-0500)
Subject: sched: Check the right ->nr_running in yield_task_fair()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=725e7580aaf98e9f7b22b8ccfc640ad0c09e2b08;p=linux-beck.git

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@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110201094715.798c4f86@annuminas.surriel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 55040f3938d8..4de9905228c4 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);