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

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, May 24, 2018 at 05:46:05PM +0200, Thomas Huth wrote:
> 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().

That's a tall order, it assumes we can define a reasonable
time during which QEMU should exit.

> 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