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Commit 7af68335 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched/numa: Avoid selecting oneself as swap target 



Because the whole numa task selection stuff runs with preemption
enabled (its long and expensive) we can end up migrating and selecting
oneself as a swap target. This doesn't really work out well -- we end
up trying to acquire the same lock twice for the swap migrate -- so
avoid this.

Reported-and-Tested-by: default avatarSasha Levin <sasha.levin@oracle.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141110100328.GF29390@twins.programming.kicks-ass.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c123588b

kernel/sched/fair.c

+7 −0
Original line number Diff line number Diff line
@@ -1179,6 +1179,13 @@ static void task_numa_compare(struct task_numa_env *env, 
		cur = NULL;

	raw_spin_unlock_irq(&dst_rq->lock);



	/*

	 * Because we have preemption enabled we can get migrated around and

	 * end try selecting ourselves (current == env->p) as a swap candidate.

	 */

	if (cur == env->p)

		goto unlock;



	/*

	 * "imp" is the fault differential for the source task between the

	 * source and destination node. Calculate the total differential for