Re: [PATCH] tests/acceptance: test hot(un)plug of ccw devices

[Philippe Mathieu-Daudé]

On 12/3/20 7:14 PM, Thomas Huth wrote:
> On 03/12/2020 19.11, Philippe Mathieu-Daudé wrote:
>> On 12/3/20 6:22 PM, Thomas Huth wrote:
>>> On 03/12/2020 16.39, Cornelia Huck wrote:
>>>> Hotplug a virtio-net-ccw device, and then hotunplug it again.
>>>
>>> Good idea! ... is it also possible with a pci device?
>>>
>>>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
>>>> ---
>> ...
>>>> +        exec_command_and_wait_for_pattern(self, 'dmesg | tail -n 1', 
>>>> 'CRW')
>>>
>>> That looks like it could be a little bit racy ... what if the kernel outputs
>>> another log message by chance, so that tail -n 1 reports that instead.
>>>
>>> I think it would be better to clear the dmesg log ("dmesg -c") before
>>> plugging, and then look at all the new output of "dmesg" without using
>>> "tail" afterwards.
>>
>> "dmesg --follow"?
> 
> Then you'd need to send control-c afterwards to stop it? ... not sure
> whether that's such a better solution...

Oh indeed, I missed there is further interaction.

Thanks,

Phil.