Re: [Qemu-devel] [PATCH] libqtest: fail if child coredumps

[Thomas Huth <thuth@redhat.com>]

On 24.05.2018 17:00, Michael S. Tsirkin wrote:
> On Thu, May 24, 2018 at 04:45:31PM +0200, Thomas Huth wrote:
>> On 24.05.2018 16:30, Michael S. Tsirkin wrote:
>>> Right now tests report OK status if QEMU crashes during cleanup.
>>> Let's catch that case and fail the test.
>>>
>>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>>> ---
>>>  tests/libqtest.c | 9 ++++++++-
>>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/tests/libqtest.c b/tests/libqtest.c
>>> index 43fb97e..f869854 100644
>>> --- a/tests/libqtest.c
>>> +++ b/tests/libqtest.c
>>> @@ -103,8 +103,15 @@ static int socket_accept(int sock)
>>>  static void kill_qemu(QTestState *s)
>>>  {
>>>      if (s->qemu_pid != -1) {
>>> +        int wstatus = 0;
>>> +        pid_t pid;
>>> +
>>>          kill(s->qemu_pid, SIGTERM);
>>> -        waitpid(s->qemu_pid, NULL, 0);
>>> +        pid = waitpid(s->qemu_pid, &wstatus, 0);
>>> +
>>> +        if (pid == s->qemu_pid && WIFSIGNALED(wstatus)) {
>>> +            assert(!WCOREDUMP(wstatus));
>>> +        }
>>>      }
>>>  }
>>
>> That's basically a good idea ... but I've already seen yet another issue
>> in the past already: QEMU sometimes simply hangs in an endless loop
>> during clean up and never terminates. I think we should detect that
>> situation, too. So instead of killing QEMU at the end of the testing, I think we should
>> rather try to terminate it with the QMP "quit" command. If QEMU does not
>> terminate with an exit code of 0, then the test should be flagged a
>> failed (and only if QEMU did not terminate at all, it should be killed
>> with SIGKILL).
>>
>>  Thomas
> 
> Fine but can we agree to do this as a patch on top? And do you have
> the time to implement this?

Fine for me if we do that later. And no, I currently don't have time to
work on this (but I've got it on my TODO list somewhere, so I hope I
won't forget about it later...).

> I'm seeing patches that cause crash on cleanup, it's not a theoretical
> problem for me, so I'd like this one to go in first.

Ok, so here are the two problems that I remember:

1)

git checkout 17bd9597be45b96ae00716b0ae01a4d11bbee1ab~1
make -j4 subdir-nios2-softmmu
nios2-softmmu/qemu-system-nios2 -monitor stdio

==> You can neither "quit" from the HMP prompt, nor kill QEMU with
SIGTERM, you've got to use SIGKILL instead.

Ok, libqtest likely would not have reported success in this case, too,
we just did not notice since there is no libqtest in place that tests
the nios2 machine in TCG mode. Anyway, it would be nice if qtest would
properly detect the situation and report an error instead of just
hanging in waitpid().

2)

git checkout b39b61e410022f96ceb53d4381d25cba5126ac44~1
make -j4 subdir-ppc-softmmu
ppc-softmmu/qemu-system-ppc -M 40p -monitor stdio

===> QEMU asserts here with both, HMP "quit" and SIGTERM. This was the
problem where libqtest did not report an error though it should have
reported one. So QEMU was not hanging in an endless loop here, but core
dumped ... Sorry, I apparently mixed this up in my mind with the first
case. That means we should be fine here with your patch.

 Thomas