Messages in this thread |  | | Date | Mon, 10 Nov 2014 17:01:48 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v4] sched/numa: fix unsafe get_task_struct() in task_numa_assign() |
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On Mon, Nov 10, 2014 at 10:48:28AM -0500, Sasha Levin wrote: > On 11/10/2014 05:03 AM, Peter Zijlstra wrote: > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -1268,6 +1268,13 @@ static void task_numa_compare(struct tas > > 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; > > This is too late though, because currently the lockup happens couple of lines > above that at: > > raw_spin_lock_irq(&dst_rq->lock); <=== here > cur = dst_rq->curr; > > Which got me a bit stuck trying to use your old patch since we can't access '->curr' > without locking dst_rq, but locking dst_rq is causing a lockup.
confused... how can we lock up there. We should not be holding _any_ lock there.
That a different problem that the originally reported one.
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