Re: [PATCH 1/3] tests/avocado: reverse_debugging drain console to prevent hang

[Ani Sinha]

> On 16-Nov-2023, at 6:56 PM, Ani Sinha <anisinha@redhat.com> wrote:
> 
> 
> 
>> On 16-Nov-2023, at 5:23 PM, Nicholas Piggin <npiggin@gmail.com> wrote:
>> 
>> Like replay_linux.py, reverse_debugging.py starts the vm with console
>> set but does not interact with it (e.g., with wait_for_console_pattern).
>> In this situation, the console should have a drainer attached so the
>> socket does not fill. replay_linux.py has a drainer, but it is missing
>> from reverse_debugging.py.
>> 
>> Per analysis in Link: this can cause the console socket/pipe to fill and
>> QEMU get stuck in qemu_chr_write_buffer, leading to strange test case
>> failures (ppc64 fails because it prints a lot to console in early bios).
>> Attaching a drainer prevents this.
>> 
>> Note, this commit does not fix bugs introduced by the commits referenced
>> in the first two Fixes: tags, but together those commits conspire to
>> irritate the problem and cause test case failure, which this commit
>> fixes.
>> 
>> Link: ZVT-bY9YOr69QTPX@redhat.com/">https://lore.kernel.org/qemu-devel/ZVT-bY9YOr69QTPX@redhat.com/
>> Fixes: 1d4796cd0083 ("python/machine: use socketpair() for console 
>> connections")
>> Fixes: 761a13b23946 ("tests/avocado: ppc64 reverse debugging tests for 
>> pseries and powernv")
>> Fixes: be52eca30978 ("tests/acceptance: add reverse debugging test")
>> Tested-by: Thomas Huth <thuth@redhat.com>
>> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> 
> Reviewed-by: Ani Sinha <anisinha@redhat.com <mailto:anisinha@redhat.com>>

This bs started happening recently once I upgraded my OS. Sorry about that.

Reviewed-by: Ani Sinha <anisinha@redhat.com <mailto:anisinha@redhat.com>>


> 
>> ---
>> tests/avocado/reverse_debugging.py | 5 +++++
>> 1 file changed, 5 insertions(+)
>> 
>> 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
>> -- 
>> 2.42.0