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SubjectRe: [PATCH v2 1/1] percpu-refcount: do not forget to rcu_barrier() just before freeing
On Wed, Aug 10, 2016 at 09:55:39PM +0200, Roman Pen wrote:
> percpu issues some RCU callbacks to synchronize its state, so before
> freeing we have to wait all those callbacks to finish.
>
> E.g. the following simple sequence on stack causes nasty crash:
>
> struct percpu_ref ref;
>
> percpu_ref_init(&ref, release, 0, GFP_KERNEL);
> percpu_ref_kill(&ref);
> percpu_ref_exit(&ref);

Hmmm... that's just an illegal sequence of operations. You can't exit
a ref which hasn't completed killing yet (the kill callback hasn't
been called).

Thanks.

--
tejun

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