sched: Ensure update_cfs_shares() is called for parents of continuously-running tasks

tip:sched/urgent tip-bot for Peter Zijlstra 1 participant 1 message Jul 31, 2013 Scheduler

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2013-07-31 08:56 UTC #0 lore raw

Commit-ID:  bf0bd948d1682e3996adc093b43021ed391983e6
Gitweb:     http://git.kernel.org/tip/bf0bd948d1682e3996adc093b43021ed391983e6
Author:     Peter Zijlstra <[email protected]>
AuthorDate: Fri, 26 Jul 2013 23:48:42 +0200
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 30 Jul 2013 22:14:37 +0200

sched: Ensure update_cfs_shares() is called for parents of continuously-running tasks

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 <[email protected]>

Signed-off-by Peter Zijlstra <[email protected]>

Reviewed-by Paul Turner <[email protected]>

Link http://lkml.kernel.org/n/[email protected] open here

Cc <[email protected]>

Signed-off-by Ingo Molnar <[email protected]>

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

kernel/sched/fair.c +1 -0

index 98d1355..06db94b 100644
@@ -2032,6 +2032,7 @@ 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
 	/*