Re: [Qemu-devel] [PATCH v9 0/6] monitor: enable OOB by default

[Peter Xu <peterx@redhat.com>]

On Wed, Oct 10, 2018 at 03:27:34PM -0500, Eric Blake wrote:
> On 10/10/18 2:26 PM, Eric Blake wrote:
> 
> > 
> > On the other hand, when I'm trying to use a qemu binary with these
> > patches applied, libvirt is hanging when trying to probe the
> > capabilities of the binary, waiting for a response to
> > "qmp_capabilities". I'll try and bisect which patch is causing the
> > problem, and figure out why it is happening for libvirt and not running
> > by hand (perhaps is it a tty vs. Unix socket thing?)
> 
> Bisect didn't help much; it landed on:
> 
>     monitor: remove "x-oob", turn oob on by default
> 
> as the cause of libvirt hanging. I didn't have time to investigate further,
> other than the command line that is hanging:
> 
> /home/eblake/qemu/x86_64-softmmu/qemu-system-x86_64 -S -no-user-config
> -nodefaults -nographic -machine none,accel=kvm:tcg -qmp
> unix:/var/lib/libvirt/qemu/capabilities.monitor.sock,server,nowait -pidfile
> /var/lib/libvirt/qemu/capabilities.pidfile -daemonize
> 
> And I suspect it is the -daemonize that is causing the hang I'm seeing when
> run by libvirt.
> 
> > Based-on: <20180828191048.29806-1-armbru@redhat.com>
> > Based-on: <20180901111716.1675-1-armbru@redhat.com>
> > 
> > (this series is based on Markus's monitor-next tree)
> 
> 
> Am I missing any prerequisite patches? Markus' monitor-next tree is
> currently a subset of git master (merge efd1d522).

Sorry for the confusion. I should have removed these lines from the
old cover letter.

It's very possible the daemonize thing, actually Wolfgang Bumiller has
posted patches to fix this up (it's not the problem of this series,
but it just exposed this to libvirt by the series since it only
happens when oob and daemonize are both enabled).  The fixes are:

  [PATCH v2 0/2] delay monitor iothread creation

Since it cannot be applied cleanly onto this series, I resolved the
conflicts and pushed a tree here in case you wanna try with these two
extra patches applied:

  https://github.com/xzpeter/qemu/tree/test-oob

Please feel free to test with libvirt again with that.

Thanks for playing with the tree and further investigation!  I will
also mention this in the next version of cover letter (if there is one).

Regards,

-- 
Peter Xu