Re: [PATCH v2] tests/acceptance: test hot(un)plug of ccw devices

[Thomas Huth <thuth@redhat.com>]

On 04/12/2020 13.14, Cornelia Huck wrote:
> Hotplug a virtio-net-ccw device, and then hotunplug it again.
> 
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
> 
> v1->v2:
> - switch device id
> - clear out dmesg before looking for CRW messages
> 
> ---
>  tests/acceptance/machine_s390_ccw_virtio.py | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/tests/acceptance/machine_s390_ccw_virtio.py b/tests/acceptance/machine_s390_ccw_virtio.py
> index 53b8484f8f9c..83c00190621b 100644
> --- a/tests/acceptance/machine_s390_ccw_virtio.py
> +++ b/tests/acceptance/machine_s390_ccw_virtio.py
> @@ -97,3 +97,19 @@ class S390CCWVirtioMachine(Test):
>          exec_command_and_wait_for_pattern(self,
>                                            'cat /sys/bus/pci/devices/000a\:00\:00.0/function_id',
>                                            '0x0000000c')
> +        # add another device
> +        exec_command_and_wait_for_pattern(self, 'dmesg -c', ' ')
> +        self.vm.command('device_add', driver='virtio-net-ccw',
> +                        devno='fe.0.4711', id='net_4711')
> +        exec_command_and_wait_for_pattern(self, 'dmesg', 'CRW')

Looking at this twice, I'm a little bit afraid that this could be racy -
what if the kernel decides to emit the line with the "CRW" just after we
executed the dmesg command? I'd maybe use something like this instead:

exec_command_and_wait_for_pattern(self,
 'while ! dmesg -c | grep CRW ; do sleep 1 ; done', '~ #')

> +        exec_command_and_wait_for_pattern(self, 'ls /sys/bus/ccw/devices/',
> +                                          '0.0.4711')
> +        # and detach it again
> +        exec_command_and_wait_for_pattern(self, 'dmesg -c', ' ')

If adapt my above change, you could also get rid of this dmesg -c here
(since it's done in the while loop already)

> +        self.vm.command('device_del', id='net_4711')
> +        self.vm.event_wait(name='DEVICE_DELETED',
> +                           match={'data': {'device': 'net_4711'}})
> +        exec_command_and_wait_for_pattern(self, 'dmesg', 'CRW')

dito

> +        exec_command_and_wait_for_pattern(self,
> +                                          'ls /sys/bus/ccw/devices/0.0.4711',
> +                                          'No such file or directory')

With my suggestion applied:

Reviewed-by: Thomas Huth <thuth@redhat.com>