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Date: Thu, 17 Mar 2016 08:39:06 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 0/4] Tweaks around virtio-blk start/stop
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, tubo@linux.vnet.ibm.com, "Michael S. Tsirkin" <mst@redhat.com>, qemu-devel@nongnu.org, Christian Borntraeger <borntraeger@de.ibm.com>, Stefan Hajnoczi <stefanha@redhat.com>, cornelia.huck@de.ibm.com

On Wed, 03/16 14:45, Paolo Bonzini wrote:
> 
> 
> On 16/03/2016 14:38, Christian Borntraeger wrote:
> > > If you just remove the calls to virtio_queue_host_notifier_read, here
> > > and in virtio_queue_aio_set_host_notifier_fd_handler, does it work
> > > (keeping patches 2-4 in)?
> > 
> > With these changes and patch 2-4 it does no longer locks up. 
> > I keep it running some hour to check if a crash happens.
> > 
> > Tu Bo, your setup is currently better suited for reproducing. Can you also check?
> 
> Great, I'll prepare a patch to virtio then sketching the solution that
> Conny agreed with.
> 
> While Fam and I agreed that patch 1 is not required, I'm not sure if the
> mutex is necessary in the end.

If we can fix this from the virtio_queue_host_notifier_read side, the mutex/BH
are not necessary; but OTOH the mutex does catch such bugs, so maybe it's good
to have it. I'm not sure about the BH.

And on a hindsight I realize we don't want patches 2-3 too. Actually the
begin/end pair won't work as expected because of the blk_set_aio_context.

Let's hold on this series.

> 
> So if Tu Bo can check without the virtio_queue_host_notifier_read calls,
> and both with/without Fam's patches, it would be great.

Tu Bo, only with/withoug patch 4, if you want to check. Sorry for the noise.

Thanks,
Fam