[ 3.8.y.z extended stable ] Patch "sched: Ensure update_cfs_shares() is called for parents of" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    sched: Ensure update_cfs_shares() is called for parents of

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 14cf5a97696e32c6be6681a7b4818aee683a3182 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz at infradead.org>
Date: Fri, 26 Jul 2013 23:48:42 +0200
Subject: sched: Ensure update_cfs_shares() is called for parents of
 continuously-running tasks

commit bf0bd948d1682e3996adc093b43021ed391983e6 upstream.

We typically update a task_group's shares within the dequeue/enqueue
path.  However, continuously running tasks sharing a CPU are not
subject to these updates as they are only put/picked.  Unfortunately,
when we reverted f269ae046 (in 17bc14b7), we lost the augmenting
periodic update that was supposed to account for this; resulting in a
potential loss of fairness.

To fix this, re-introduce the explicit update in
update_cfs_rq_blocked_load() [called via entity_tick()].

Reported-by: Max Hailperin <max at gustavus.edu>
Signed-off-by: Peter Zijlstra <peterz at infradead.org>
Reviewed-by: Paul Turner <pjt at google.com>
Link: http://lkml.kernel.org/n/tip-9545m3apw5d93ubyrotrj31y@git.kernel.org
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 kernel/sched/fair.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 81fa536..7d0374f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1964,6 +1964,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 	 */
 	update_entity_load_avg(curr, 1);
 	update_cfs_rq_blocked_load(cfs_rq, 1);
+	update_cfs_shares(cfs_rq);

 #ifdef CONFIG_SCHED_HRTICK
 	/*
--
1.8.1.2