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Commit 53d3bc77 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

Revert "sched/fair: Fix fairness issue on migration" 



Mike reported that this recent commit:

  3a47d512 ("sched/fair: Fix fairness issue on migration")

... broke interactivity and the signal starvation test.

We have a proper fix series in the works but ran out of time for
v4.6, so revert the commit.

Reported-by: default avatarMike Galbraith <efault@gmx.de>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c5114626

kernel/sched/fair.c

+6 −14
Original line number Diff line number Diff line
@@ -3188,25 +3188,17 @@ static inline void check_schedstat_required(void) 
static void

enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)

{

	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING);

	bool curr = cfs_rq->curr == se;



	/*

	 * If we're the current task, we must renormalise before calling

	 * update_curr().

	 * Update the normalized vruntime before updating min_vruntime

	 * through calling update_curr().

	 */

	if (renorm && curr)

	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))

		se->vruntime += cfs_rq->min_vruntime;



	update_curr(cfs_rq);



	/*

	 * Otherwise, renormalise after, such that we're placed at the current

	 * moment in time, instead of some random moment in the past.

	 * Update run-time statistics of the 'current'.

	 */

	if (renorm && !curr)

		se->vruntime += cfs_rq->min_vruntime;



	update_curr(cfs_rq);

	enqueue_entity_load_avg(cfs_rq, se);

	account_entity_enqueue(cfs_rq, se);

	update_cfs_shares(cfs_rq);
@@ -3222,7 +3214,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 
		update_stats_enqueue(cfs_rq, se);

		check_spread(cfs_rq, se);

	}

	if (!curr)

	if (se != cfs_rq->curr)

		__enqueue_entity(cfs_rq, se);

	se->on_rq = 1;