Re: boot stall regression due to blk-mq: use percpu_ref for mq usage count

Tejun Heo
2014-09-23T06:01:41Z

On Tue, Sep 23, 2014 at 07:59:24AM +0200, Christoph Hellwig wrote:
> "[PATCHSET percpu/for-3.18] percpu_ref: implement switch_to_atomic/percpu()"
>
> looks way to big for 3.17, and the regression was introduced in the 3.17
> merge window. I'm not sure what was broken before, but it defintively
> survived a lot of testing.

Do we even care about fixing it for 3.17? scsi-mq isn't enabled by
default even for 3.18. The open-coded percpu ref thing was subtly
broken there. It'd be difficult to trigger but I'm fairly sure it'd
crap out in the wild once in a blue moon.

Thanks.

--
tejun