Re: [Qemu-devel] [PATCH] vhost-user: fix watcher need be removed when vhost-user hotplug

[Marc-André Lureau]

On Wed, May 10, 2017 at 5:55 AM wangyunjian <address@hidden> wrote:

> On Tue, May 9, 2017 at 5:04 PM Yunjian Wang <address@hidden>
> wrote:
>
> > > From: w00273186 <address@hidden>
> > >
> > > "nc" is freed after hotplug vhost-user, but the watcher don't be
> removed.
> > >
> >
> >
> > > The QEMU crash when the watcher access the "nc" on socket disconnect.
> > >
> > >
> > Do you have a reproducer? thanks
> >
>
> reproduce steps:
>
> 1. virsh attach-device vm0 vhost-user.xml
> 2. virsh detach-device vm0 vhost-user.xml
> 3. virsh attach-device vm0 vhost-user.xml
> 4. service openvswitch restart
> 5. repeat step 2~4
>
> The vhost-user xml:
>
>     <interface type='vhostuser'>
>       <mac address='00:01:01:00:10:41'/>
>       <source type='unix' path='/var/run/vhost-user/tap1' mode='client'/>
>       <model type='virtio'/>
>       <driver queues='8'/>
> </interface>
>
> Thanks
>
> >
> > > Call Trace:
> > >     #0  object_get_class (address@hidden) at qom/object.c:751
> > >     #1  0x00007fc031c79f41 in qemu_chr_fe_disconnect (be=<optimized
> out>)
> > > at chardev/char.c:1048
> > >     #2  0x00007fc031bd62e0 in net_vhost_user_watch (chan=<optimized
> out>,
> > > cond=<optimized out>, opaque=<optimized out>) at net/vhost-user.c:191
> > >     #3  0x00007fc02c23e99a in g_main_context_dispatch () from
> > > /lib64/libglib-2.0.so.0
> > >     #4  0x00007fc031ccfc0c in glib_pollfds_poll () at
> util/main-loop.c:213
> > >     #5  os_host_main_loop_wait (timeout=<optimized out>) at
> > > util/main-loop.c:261
> > >     #6  main_loop_wait (address@hidden) at
> > > util/main-loop.c:517
> > >     #7  0x00007fc03193bc87 in main_loop () at vl.c:1899
> > >     #8  main (argc=<optimized out>, argv=<optimized out>,
> envp=<optimized
> > > out>) at vl.c:4719
> > >
> > > Signed-off-by: Yunjian Wang <address@hidden>
> > > ---
> > >  net/vhost-user.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/net/vhost-user.c b/net/vhost-user.c
> > > index 00a0c1c..5cc2178 100644
> > > --- a/net/vhost-user.c
> > > +++ b/net/vhost-user.c
> > > @@ -155,6 +155,10 @@ static void vhost_user_cleanup(NetClientState *nc)
> > >
> > >          qemu_chr_fe_deinit(&s->chr);
> > >          object_unparent(OBJECT(chr));
> > > +        if (s->watch) {
> > > +            g_source_remove(s->watch);
> > > +            s->watch = 0;
> > > +        }
> > >      }
>

This change looks ok, and happens because libvirt calls netdev_del before
the chardev is closed or removed.

I would move the chunk before deinit/unparent though, since that's when the
close happens.

> >
> > >      qemu_purge_queued_packets(nc);
> > > --
> > > 1.8.3.1
> > >
> > >
> > >
> > > --
> > Marc-André Lureau
>
-- 
Marc-André Lureau