Re: [PATCH v4 6/7] blk-mq: fix freeze queue race

From: Christoph Hellwig
Date: Tue Sep 29 2015 - 02:56:06 EST

On Mon, Sep 28, 2015 at 10:48:39AM -0400, Tejun Heo wrote:
> Ah, you're right. I was thinking that percpu_ref_switch_to_percpu()
> being called after blk_mq_freeze_queue_start() would be buggy and thus
> the above can't be enough but that is safe as long as the calls are
> properly synchronized. Hmmm... maybe we should add synchronization to
> those operations from percpu_ref side.

I think that would be very useful, as most users of the code will
have similar issues.
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