Commit 1e876231 authored May 17, 2011 by Peter Zijlstra Committed by Ingo Molnar May 28, 2011

sched: Fix ->min_vruntime calculation in dequeue_entity()



Dima Zavin <dima@android.com> reported:

"After pulling the thread off the run-queue during a cgroup change,
the cfs_rq.min_vruntime gets recalculated. The dequeued thread's vruntime
then gets normalized to this new value. This can then lead to the thread
getting an unfair boost in the new group if the vruntime of the next
task in the old run-queue was way further ahead."

Reported-by: Dima Zavin <dima@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Recalls-having-tested-once-upon-a-time-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1305674470-23727-1-git-send-email-john.stultz@linaro.org


Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent d6aa8f85

kernel/sched_fair.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -1076,8 +1076,6 @@ dequeue_entity(struct cfs_rq cfs_rq, struct sched_entity se, int flags)
		se->on_rq = 0;
		update_cfs_load(cfs_rq, 0);
		account_entity_dequeue(cfs_rq, se);
		update_min_vruntime(cfs_rq);
		update_cfs_shares(cfs_rq);

		/*
		* Normalize the entity after updating the min_vruntime because the
		@@ -1086,6 +1084,9 @@ dequeue_entity(struct cfs_rq cfs_rq, struct sched_entity se, int flags)
		*/
		if (!(flags & DEQUEUE_SLEEP))
		se->vruntime -= cfs_rq->min_vruntime;

		update_min_vruntime(cfs_rq);
		update_cfs_shares(cfs_rq);
		}

		/*

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