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

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

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
>>> <zhang.zhanghailiang@huawei.com> 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
>>
>
>
> .
>