On Thu, Apr 13, 2017 at 03:39:59PM +0100, Stefan Hajnoczi wrote: > 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. >
Without the fix, iothreads are not usable in 2.9.0, because a running block job can create a deadlock by a guest-initiated reboot. I think losing the ability to use iothreads is enough reason to warrant a fix (especially if an -rc5 may happen anyway). -Jeff
