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Re: [Qemu-devel] [PATCH] thread-pool: Notify AIO context upon completion

From: Fam Zheng
Subject: Re: [Qemu-devel] [PATCH] thread-pool: Notify AIO context upon completion
Date: Thu, 2 Jul 2015 15:17:40 +0800
User-agent: Mutt/1.5.23 (2014-03-12)

On Thu, 07/02 09:11, Paolo Bonzini wrote:
> On 02/07/2015 08:33, Fam Zheng wrote:
> > bdrv_flush() uses a loop like
> > 
> >     while (rwco.ret == NOT_DONE) {
> >         aio_poll(aio_context, true);
> >     }
> > 
> > to wait for thread pool, which may not get notified about the scheduled
> > BH right away, if there is no new event that wakes up a blocking
> > qemu_poll_ns().
> That translates to "the dispatching optimization does not work". :)  I
> do not think that is the problem.

I must be missing something. I see a hang locally with some AioContext patches
I'm testing, and this does fix it.

I traced that qemu_bh_schedule does call aio_notify and event_notifier_set, so
it's curious. Still looking.


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