[dm-devel] [PATCH 8/9] dm: Fix two race conditions related to stopping and starting queues
Mike Snitzer
snitzer at redhat.com
Thu Sep 1 21:17:18 UTC 2016
On Thu, Sep 01 2016 at 4:52pm -0400,
Bart Van Assche <bart.vanassche at sandisk.com> wrote:
> On 09/01/2016 01:48 PM, Mike Snitzer wrote:
> >Yeah, I since fixed that. Doesn't change the fact that your use of
> >blk_mq_freeze_queue() causes the 100% cpu usage.
>
> Hello Mike,
>
> Sorry but that doesn't make sense to me. blk_mq_freeze_queue()
> either returns quickly or waits. It cannot cause 100% CPU usage.
> Something else must be going on. If you can make the code available
> that you used in your test I will have a look at it.
The suspend is hanging due the blk_mq_freeze_queue() -- and in turn the
resume (after reinstating paths) never happens. So no paths are
available. IO just keeps getting requeued, hence the 100% usage.
The root of the problem is that the suspend isn't completing though.
I've moved your work out to my private devel branch, see:
http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=devel
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