[tip:sched/core] sched: Don't update shares twice on on_rq parent

[tip-bot for Paul Turner <pjt@google.com>]

Commit-ID:  9598c82dcacadc3b9daa8170613fd054c6124d30
Gitweb:     http://git.kernel.org/tip/9598c82dcacadc3b9daa8170613fd054c6124d30
Author:     Paul Turner <pjt@google.com>
AuthorDate: Wed, 6 Jul 2011 22:30:37 -0700
Committer:  Ingo Molnar <mingo@elte.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@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110707053059.797714697@google.com
Signed-off-by: Ingo Molnar <mingo@elte.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;