Re: [Qemu-block] [Qemu-devel] Regression from 2.8: stuck in bdrv_drain()

[Stefan Hajnoczi]

On Thu, Apr 13, 2017 at 01:45:55PM +0800, Paolo Bonzini wrote:
> 
> 
> On 13/04/2017 09:11, Jeff Cody wrote:
> >> It didn't make it into 2.9-rc4 because of limited time. :(
> >>
> >> Looks like there is no -rc5, we'll have to document this as a known issue.
> >> Users should "block-job-complete/cancel" as soon as possible to avoid such 
> >> a
> >> hang.
> >
> > I'd argue for including a fix for 2.9, since this is both a regression, and
> > a hard lock without possible recovery short of restarting the QEMU process.
> 
> It is a bit of a corner case (and jobs on I/O thread are relatively rare
> too), so maybe it's not worth delaying 2.9.  It has been delayed already
> quite a bit.  Another reason I think I prefer to wait is to ensure that
> we have an entry in qemu-iotests to avoid the future regression.

I also think this does not require delaying the release:

1. It needs to be marked as a known issue in the release notes.
2. Let's roll the 2.9.1 stable release within a month of 2.9.0.

If both conditions are met then very few end users will be exposed to
the problem.  I hope libvirt will create IOThreads by default soon but
for the time being it is not a widely used configuration.

Stefan

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