Re: [Qemu-devel] vhost-user-test failure

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Hi,

On 09/26/2016 02:13 PM, Eduardo Habkost wrote:
> On Sun, Sep 25, 2016 at 04:55:53PM -0400, Marc-André Lureau wrote:
>> Hi
>>
>> ----- Original Message -----
>>> This time with Marc-André in cc:...
>>>
>>> On 09/23/2016 07:40 PM, Maxime Coquelin wrote:
>>>>
>>>>
>>>> On 09/23/2016 05:41 PM, Michael S. Tsirkin wrote:
>>>>> On Fri, Sep 23, 2016 at 12:36:12PM -0300, Eduardo Habkost wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I hit a weird vhost-user-test failure on travis-ci recently, on a
>>>>>> branch where I didn't touch any vhost-related code. From a quick
>>>>>> look at the code, it looks like the vhost-user code is unhappy to
>>>>>> see a disconnected socket.
>>>>>>
>>>>>> I wasn't able to reproduce it. It seems to be a hard to reproduce
>>>>>> race between vhost-user code and socket reconnection.
>>>>>>
>>>>>> The failure can be seen at:
>>>>>>
>>>>>> https://travis-ci.org/ehabkost/qemu-hacks/jobs/162077239
>>>>>
>>>>> Maxime looked at something similiar. Any idea?
>>>> No, not really.
>>>> Marc-André contributed a lot to these tests, I add him in cc: in case
>>>> he has an idea.
>>>>
>>>> I will have a look in the mean time.
>>>>
>>
>> I am unable to reproduce locally (over 500x iterations), and I
>> have no clue what's going on: the warnings there aren't the
>> problem (that's the main reason why we use the subprocess, to
>> silence those). Do you have a local reproducer or is it only on
>> travis? Afaik, there are no other reports of this test failing,
>> are you sure its not related to changes on your branch?
>
> I don't have a local reproducer, I could only see it once on
> travis-ci. Maybe it is not possible to reproduce it if the
> machine isn't loaded enough to make the right thread/process be
> delayed.

I'm also trying to reproduce it.
Interestingly, launching the test with strace, I reproduce another
problem systematically:
$> strace -o /tmp/vut -ff ./tests/vhost-user-test
/x86_64/vhost-user/read-guest-mem: OK
/x86_64/vhost-user/migrate: Vhost user backend fails to broadcast fake RARP
OK
/x86_64/vhost-user/reconnect: OK

I'll try to load the CPU randomly when executing the test.

Regards,
Maxime