Re: [PATCH v4 6/7] blk-mq: fix freeze queue race
From: Tejun Heo
Date: Tue Sep 29 2015 - 17:50:22 EST
On Tue, Sep 29, 2015 at 11:03:46AM -0400, Tejun Heo wrote:
> On Tue, Sep 29, 2015 at 09:01:31AM -0600, Jens Axboe wrote:
> > I think that would be very useful, it seems sort of half-assed if the caller
> > side has to provide serialization for that.
> Yeah, the thing is init/exit are usually caller synchronized but
> percpu_rwsem's kill/reinit are more of mode-switching operations which
> can be performed concurrently during operation so I think the right
> thing to do here is making it synchronize itself. Will spin a patch.
Unfortunately, the required changes on percpu_ref side ended up
somewhat invasive and don't seem fit for -stable backport. I think
it'd be a good idea to apply Akinobu's patch for now and then revert
it later when the percpu_ref changes hit mainline.
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