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Date: Thu, 2 Jul 2015 15:17:40 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] thread-pool: Notify AIO context upon
	completion
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, borntraeger@de.ibm.com, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

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.

Fam