linux-kernel - [tip:sched/core] sched: Don't update shares twice on on

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Message-ID: <tip-9598c82dcacadc3b9daa8170613fd054c6124d30@git.kernel.org>
Date:	Thu, 21 Jul 2011 18:28:25 GMT
From:	tip-bot for Paul Turner <pjt@...gle.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, pjt@...gle.com, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:sched/core] sched: Don't update shares twice on on_rq parent

Commit-ID:  9598c82dcacadc3b9daa8170613fd054c6124d30
Gitweb:     http://git.kernel.org/tip/9598c82dcacadc3b9daa8170613fd054c6124d30
Author:     Paul Turner <pjt@...gle.com>
AuthorDate: Wed, 6 Jul 2011 22:30:37 -0700
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 21 Jul 2011 18:01:44 +0200

sched: Don't update shares twice on on_rq parent

In dequeue_task_fair() we bail on dequeue when we encounter a parenting entity
with additional weight.  However, we perform a double shares update on this
entity as we continue the shares update traversal from this point, despite
dequeue_entity() having already updated its queuing cfs_rq.
Avoid this by starting from the parent when we resume.

Signed-off-by: Paul Turner <pjt@...gle.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/20110707053059.797714697@google.com
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched_fair.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index f88720b..6cdff84 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1370,6 +1370,9 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 			 */
 			if (task_sleep && parent_entity(se))
 				set_next_buddy(parent_entity(se));
+
+			/* avoid re-evaluating load for this entity */
+			se = parent_entity(se);
 			break;
 		}
 		flags |= DEQUEUE_SLEEP;
--
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