Commit 7af68335 authored Nov 10, 2014 by Peter Zijlstra Committed by Ingo Molnar Nov 16, 2014

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: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter 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: Ingo 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

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