Re: [PATCH] tests/avocado/reverse_debugging: Disable the ppc64 tests by default

[Daniel P . Berrangé]

On Thu, Nov 16, 2023 at 11:15:25AM +1000, Nicholas Piggin wrote:
> On Thu Nov 16, 2023 at 3:22 AM AEST, Daniel P. Berrangé wrote:
> > On Wed, Nov 15, 2023 at 01:14:53PM +0000, Daniel P. Berrangé wrote:
> > > On Wed, Nov 15, 2023 at 07:23:01AM +0100, Thomas Huth wrote:
> > > > On 15/11/2023 02.15, Nicholas Piggin wrote:
> > > > > On Wed Nov 15, 2023 at 4:29 AM AEST, Thomas Huth wrote:
> > > > > > On 14/11/2023 17.37, Philippe Mathieu-Daudé wrote:
> > > > > > > On 14/11/23 17:31, Thomas Huth wrote:
> > > > > > > > The tests seem currently to be broken. Disable them by default
> > > > > > > > until someone fixes them.
> > > > > > > > 
> > > > > > > > Signed-off-by: Thomas Huth <thuth@redhat.com>
> > > > > > > > ---
> > > > > > > >    tests/avocado/reverse_debugging.py | 7 ++++---
> > > > > > > >    1 file changed, 4 insertions(+), 3 deletions(-)
> > > > > > > 
> > > > > > > Similarly, I suspect 
> > > > > > > https://gitlab.com/qemu-project/qemu/-/issues/1961
> > > > > > > which has a fix ready:
> > > > > > > https://lore.kernel.org/qemu-devel/20231110170831.185001-1-richard.henderson@linaro.org/
> > > > > > > 
> > > > > > > Maybe wait the fix gets in first?
> > > > > > 
> > > > > > No, I applied Richard's patch, but the problem persists. Does this 
> > > > > > test
> > > > > > still work for you?
> > > > > 
> > > > > I bisected it to 1d4796cd008373 ("python/machine: use socketpair() for
> > > > > console connections"),
> > > > 
> > > > Maybe John (who wrote that commit) can help?
> > > 
> > > I find it hard to believe this commit is a direct root cause of the
> > > problem since all it does is change the QEMU startup sequence so that
> > > instead of QEMU listening for a monitor connection, it is given a
> > > pre-opened monitor connection.
> > > 
> > > At the very most that should affect the startup timing a little.
> > > 
> > > I notice all the reverse debugging tests have a skip on gitlab
> > > with a comment:
> > > 
> > >     # unidentified gitlab timeout problem
> > > 
> > > this makes be suspicious that John's patch has merely made this
> > > (henceforth undiagnosed) timeout more likely to ocurr.
> >
> > After an absolutely horrendous hours long debugging session I think
> > I figured out the problem. The QEMU process is blocking in
> >
> >     qemu_chr_write_buffer
> >
> > spinning in the loop on EAGAIN.
> 
> Great work.
> 
> Why does this make the gdb socket give an empty response? Something
> just times out?

There's no empty response - avocado is sending SIGTERM to the
test because no response ever arrived after 10 seconds 

> > @@ -357,6 +360,10 @@ def _pre_launch(self) -> None:
> >  
> >          if self._console_set:
> >              self._cons_sock_pair = socket.socketpair()
> > +            self._cons_sock_pair[0].setsockopt(socket.SOL_SOCKET, 
> > socket.SO_SNDBUF, 1024*1024);
> > +            self._cons_sock_pair[0].setsockopt(socket.SOL_SOCKET, 
> > socket.SO_RCVBUF, 1024*1024);
> > +            self._cons_sock_pair[1].setsockopt(socket.SOL_SOCKET, 
> > socket.SO_SNDBUF, 1024*1024);
> > +            self._cons_sock_pair[1].setsockopt(socket.SOL_SOCKET, 
> > socket.SO_RCVBUF, 1024*1024);
> >              os.set_inheritable(self._cons_sock_pair[0].fileno(), True)
> >  
> >          # NOTE: Make sure any opened resources are *definitely* freed in
> 
> So perhaps ppc64 fails just because it prints more to the console in early
> boot than other targets?

Yes, that's exactly it - the ppc firmware is very verbose, so is enough
to tip it over the limit.

> > The Machine class doesn't know if anything will ever use the console,
> > so as is the change is unsafe.
> >
> > The original goal of John's change was to guarantee we capture early
> > boot messages as some test need that.  
> >
> > I think we need to be able to have a flag to say whether the caller needs
> > an "early console" facility, and only use the pre-opened FD passing for
> > that case. Tests we need early console will have to ask for that guarantee
> > explicitly.
> 
> The below patch makes this test work. Maybe as a quick fix it is
> better than disabling the test.
> 
> I guess we still have a problem if a test invokes vm.launch()
> directly without subsequently waiting for a console pattern or
> doing something with the console as you say. Your suggesstion is
> add something like vm.launch(console=True) ? 
> 
> Thanks,
> Nick
> ---
> 
> diff --git a/tests/avocado/reverse_debugging.py 
> b/tests/avocado/reverse_debugging.py
> index fc47874eda..128d85bc0e 100644
> --- a/tests/avocado/reverse_debugging.py
> +++ b/tests/avocado/reverse_debugging.py
> @@ -12,6 +12,7 @@
>  
>  from avocado import skipIf
>  from avocado_qemu import BUILD_DIR
> +from avocado.utils import datadrainer
>  from avocado.utils import gdb
>  from avocado.utils import process
>  from avocado.utils.network.ports import find_free_port
> @@ -52,6 +53,10 @@ def run_vm(self, record, shift, args, replay_path, 
> image_path, port):
>          if args:
>              vm.add_args(*args)
>          vm.launch()
> +        console_drainer = datadrainer.LineLogger(vm.console_socket.fileno(),
> +                                    logger=self.log.getChild('console'),
> +                                    stop_check=(lambda : not 
> vm.is_running()))
> +        console_drainer.start()
>          return vm
>  
>      @staticmethod

Yes, thus should do the trick.

With regards,
Daniel
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