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Date: Thu, 24 Mar 2016 10:31:00 +0100
From: Cornelia Huck <cornelia.huck@de.ibm.com>
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Subject: Re: [Qemu-devel] [Qemu-block] [PATCH 4/4] virtio-blk: Clean up
 start/stop with mutex and BH
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To: qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>, qemu-block@nongnu.org, Christian Borntraeger <borntraeger@de.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, "Michael S. Tsirkin" <mst@redhat.com>, tu bo <tubo@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

On Thu, 24 Mar 2016 09:47:56 +0100
Cornelia Huck <cornelia.huck@de.ibm.com> wrote:

> On Thu, 24 Mar 2016 09:32:30 +0100
> Cornelia Huck <cornelia.huck@de.ibm.com> wrote:
> 
> > I'll re-send my patches with some added interface doc in patch 1. Stay
> > tuned.
> 
> Grr. Unfortunately, this fails for _me_ now (-EEXIST after reboot).
> Debugging.

Good news is that I think I understand what happens. Bad news is that
we can scratch all of the previous testing :(

My patchset had a typo (check for !disabled instead of disabled). After
I fixed that, the second assignment of the ioeventfd started failing
(that's what changed when I started passing assign in stop_ioeventfd)
with -EEXIST as the previous ioeventfd is of course still assigned.

What we actually want is to keep the ioeventfd assigned, not add a new
one. But we still want adding a new ioeventfd to fail in case of
collisions.

I think we need to track whether we already assigned an ioeventfd and
don't re-register in that case. I'll try to cook something up.