Re: [Qemu-devel] [vhost-user BUG ?] QEMU process segfault when shutdown or reboot with vhost-user

[zhanghailiang]

On 2015/11/4 11:19, Jason Wang wrote:
> On 11/04/2015 10:24 AM, zhanghailiang wrote:
> > On 2015/11/3 22:54, Marc-André Lureau wrote:
> > > Hi
> > >
> > > On Tue, Nov 3, 2015 at 2:01 PM, zhanghailiang
> > > <address@hidden> wrote:
> > > > The corresponding codes where gdb reports error are: (We have added
> > > > some
> > > > codes in net.c)
> > >
> > > Can you reproduce with unmodified qemu? Could you give instructions
> > > to do so?
> >
> > OK, i will try to do it. There is nothing special, we run iperf tool
> > in VM,
> > and then shutdown or reboot it. There is change you can catch segfault.
> >
> > > > ssize_t qemu_deliver_packet(NetClientState *sender,
> > > >                               unsigned flags,
> > > >                               const uint8_t *data,
> > > >                               size_t size,
> > > >                               void *opaque)
> > > > {
> > > >       NetClientState *nc = opaque;
> > > >       ssize_t ret;
> > > >
> > > >       if (nc->link_down) {
> > > >           return size;
> > > >       }
> > > >
> > > >       if (nc->receive_disabled) {
> > > >           return 0;
> > > >       }
> > > >
> > > >       if (flags & QEMU_NET_PACKET_FLAG_RAW && nc->info->receive_raw) {
> > > >           ret = nc->info->receive_raw(nc, data, size);
> > > >       } else {
> > > >           ret = nc->info->receive(nc, data, size);   ----> Here is
> > > > 510 line
> > > >       }
> > > >
> > > > I'm not quite familiar with vhost-user, but for vhost-user, these two
> > > > callback functions seem to be always NULL,
> > > > Why we can come here ?
> > >
> > > You should not come here, vhost-user has nc->receive_disabled (it
> > > changes in 2.5)
> >
> > I have looked at the newest codes, i think we can still have chance to
> > come here, since we will change nc->receive_disable to false
> > temporarily in
> > qemu_flush_or_purge_queued_packets(), there is no difference between
> > 2.3 and 2.5
> > for this.
> > Besides, is it possible for !QTAILQ_EMPTY(&queue->packets) to be true
> > in qemu_net_queue_flush() for vhost-user ?
>
> The only thing I can image is self announcing. Are you trying to do
> migration? 2.5 only support sending rarp through this.

Hmm, it's not triggered by migration, For qemu-2.5, IMHO, it doesn't have such 
problem,
since the callback function 'receive' is not NULL. It is vhost_user_receive().

> And it's better to have a breakpoint to see why a packet was queued for
> vhost-user. The stack trace may also help in this case.
OK, i'm trying to reproduce it.

Thanks,
zhanghailiang

> > i will try to reproduce it by using newest qemu.
> >
> > Thanks,
> > zhanghailiang
>
>
> .