Re: [PATCH] tests/acceptance: Fix race conditions in s390x tests & skip fedora on gitlab-CI

["Alex Bennée" <alex.bennee@linaro.org>]

Cornelia Huck <cohuck@redhat.com> writes:

> On Fri,  8 Jan 2021 19:56:45 +0100
> Thomas Huth <thuth@redhat.com> wrote:
>
>> There was a race condition in the first test where there was already the
>> "crw" output in the dmesg, but the "0.0.4711" entry has not been created
>> in the /sys fs yet. Fix it by waiting until it is there.
>> 
>> The second test has even more problems on gitlab-CI. Even after adding some
>> more synchronization points (that wait for some messages in the "dmesg"
>> output to make sure that the modules got loaded correctly), there are still
>> occasionally some hangs in this test when it is running in the gitlab-CI.
>> So far I was unable to reproduce these hangs locally on my computer, so
>> this issue might take a while to debug. Thus disable the 2nd test in the
>> gitlab-CI until the problems are better understood and fixed.
>> 
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>  tests/acceptance/machine_s390_ccw_virtio.py | 14 ++++++++++++--
>>  1 file changed, 12 insertions(+), 2 deletions(-)
>> 
>> diff --git a/tests/acceptance/machine_s390_ccw_virtio.py b/tests/acceptance/machine_s390_ccw_virtio.py
>> index eccf26b262..4028c99afc 100644
>> --- a/tests/acceptance/machine_s390_ccw_virtio.py
>> +++ b/tests/acceptance/machine_s390_ccw_virtio.py
>> @@ -12,6 +12,7 @@
>>  import os
>>  import tempfile
>>  
>> +from avocado import skipIf
>>  from avocado_qemu import Test
>>  from avocado_qemu import exec_command_and_wait_for_pattern
>>  from avocado_qemu import wait_for_console_pattern
>> @@ -133,8 +134,10 @@ class S390CCWVirtioMachine(Test):
>>          self.vm.command('device_add', driver='virtio-net-ccw',
>>                          devno='fe.0.4711', id='net_4711')
>>          self.wait_for_crw_reports()
>> -        exec_command_and_wait_for_pattern(self, 'ls /sys/bus/ccw/devices/',
>> -                                          '0.0.4711')
>> +        exec_command_and_wait_for_pattern(self, 'for i in 1 2 3 4 5 6 7 ; do '
>> +                    'if [ -e /sys/bus/ccw/devices/*4711 ]; then break; fi ;'
>> +                    'sleep 1 ; done ; ls /sys/bus/ccw/devices/',
>> +                    '0.0.4711')
>
> I'm wondering whether we should introduce a generic helper function for
> "execute command repeatedly, if the expected result did not yet show
> up", or "wait for a file/directory to exist". It's probably not
> uncommon for a desired outcome to arrive asynchronously, and having a
> function for waiting/retrying could be handy.

We don't really want to encourage fragile shell scripts in the guest so
something that makes it easy to encode these loops in python. Currently
the _console_interaction helper fails the test if failure_message is
seen so I guess we need a slightly more liberal interaction which
accepts a command can fail so we can write something like:

  while True:
      if exec_command_and_check(self, "stat -t /sys/bus/ccw/devices/0.0.4711",
                                "/sys/bus/ccw/devices/0.0.4711"):
          break

?

>
>>          # and detach it again
>>          self.clear_guest_dmesg()
>>          self.vm.command('device_del', id='net_4711')


-- 
Alex Bennée