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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: 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>
This commit is contained in:
Peter Zijlstra 2014-11-10 10:54:35 +01:00 committed by Ingo Molnar
parent c123588b3b
commit 7af683350c
1 changed files with 7 additions and 0 deletions
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7
kernel/sched/fair.c
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@ -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