linux-kernel - [ 07/45] sched: Ensure update_cfs_shares() is called for parents of continuously-running tasks

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Date:	Sun, 18 Aug 2013 13:35:56 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Max Hailperin <max@...tavus.edu>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul Turner <pjt@...gle.com>, Ingo Molnar <mingo@...nel.org>
Subject: [ 07/45] sched: Ensure update_cfs_shares() is called for parents of continuously-running tasks

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@...radead.org>

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@...tavus.edu>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Reviewed-by: Paul Turner <pjt@...gle.com>
Link: http://lkml.kernel.org/n/tip-9545m3apw5d93ubyrotrj31y@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/sched/fair.c |    1 +
 1 file changed, 1 insertion(+)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1984,6 +1984,7 @@ entity_tick(struct cfs_rq *cfs_rq, struc
 	 */
 	update_entity_load_avg(curr, 1);
 	update_cfs_rq_blocked_load(cfs_rq, 1);
+	update_cfs_shares(cfs_rq);
 
 #ifdef CONFIG_SCHED_HRTICK
 	/*


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