Re: [PATCH v3 10/15] qemu_iotests: extent QMP socket timeout when using valgrind

[Emanuele Giuseppe Esposito]

On 13/05/2021 20:47, John Snow wrote:
> On 4/14/21 1:03 PM, Emanuele Giuseppe Esposito wrote:
> > As with gdbserver, valgrind delays the test execution, so
> > the default QMP socket timeout timeout too soon.
> >
> > Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> > ---
> >   python/qemu/machine.py        | 2 +-
> >   tests/qemu-iotests/iotests.py | 4 ++--
> >   2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/python/qemu/machine.py b/python/qemu/machine.py
> > index d6142271c2..dce96e1858 100644
> > --- a/python/qemu/machine.py
> > +++ b/python/qemu/machine.py
> > @@ -410,7 +410,7 @@ def _launch(self) -> None:
> >                                          shell=False,
> >                                          close_fds=False)
> > -        if 'gdbserver' in self._wrapper:
> > +        if 'gdbserver' in self._wrapper or 'valgrind' in self._wrapper:
>
> This approaches me suggesting that we just change __init__ to accept a 
> parameter that lets the caller decide what kind of timeout(s) they find 
> acceptable. They know more about what they're trying to run than we do.
>
> Certainly after launch occurs, the user is free to just grab the qmp 
> object and tinker around with the timeouts, but that does not allow us 
> to change the timeout(s) for accept itself.
>
> D'oh.
>
> (Spilled milk: It was probably a mistake to make the default launch 
> behavior here have a timeout of 15 seconds. That logic likely belongs to 
> the iotests implementation. The default here probably ought to indeed be 
> "wait forever".)
>
> In the here and now ... would it be acceptable to change the launch() 
> method to add a timeout parameter? It's still a little awkward, because 
> conceptually it's a timeout for just QMP and not for the actual duration 
> of the entire launch process.
>
> But, I guess, it's *closer* to the truth.
>
> If you wanted to route it that way, I take back what I said about not 
> wanting to pass around variables to event loop hooks.
>
> If we defined the timeout as something that applies exclusively to the 
> launching process, then it'd be appropriate to route that to the 
> launch-related functions ... and subclasses would have to be adjusted to 
> be made aware that they're expected to operate within those parameters, 
> which is good.
>
> Sorry for my waffling back and forth on this. Let me know what the 
> actual requirements are if you figure out which timeouts you need / 
> don't need and I'll give you some review priority.

Uhm.. I am getting a little bit confused on what to do too :)

So the current plan I have for _qmp_timer is:

- As Max suggested, move it in __init__ and check there for the wrapper 
contents. If we need to block forever (gdb, valgrind), we set it to 
None. Otherwise to 15 seconds. I think setting it always to None is not 
ideal, because if you are testing something that deadlocks (see my 
attempts to remove/add locks in QEMU multiqueue) and the socket is set 
to block forever, you don't know if the test is super slow or it just 
deadlocked.

Well, one can argue that in both cases this is not the expected 
behavior, but I think having an upper bound on each QMP command 
execution would be good.

- pass _qmp_timer directly to self._qmp.accept() in _post launch, 
leaving _launch() intact. I think this makes sense because as you also 
mentioned, changing _post_launch() into taking a parameter requires 
changing also all subclasses and pass values around.

Any opinion on this is very welcome.

Spoiler alert I haven't tested these changes yet, but I am positive that 
there shouldn't be any problem. (Last famous words)

Emanuele


> If you attack this series again, can you please split out the python/* 
> patches into its own little series and CC me?
>
> --js
>
> >               self._qmp_timer = None
> >           self._post_launch()
> > diff --git a/tests/qemu-iotests/iotests.py 
> > b/tests/qemu-iotests/iotests.py
> > index a2e8604674..94597433fa 100644
> > --- a/tests/qemu-iotests/iotests.py
> > +++ b/tests/qemu-iotests/iotests.py
> > @@ -489,7 +489,7 @@ def log(msg: Msg,
> >   class Timeout:
> >       def __init__(self, seconds, errmsg="Timeout"):
> > -        if qemu_gdb:
> > +        if qemu_gdb or qemu_valgrind:
> >               self.seconds = 3000
> >           else:
> >               self.seconds = seconds
> > @@ -700,7 +700,7 @@ def qmp_to_opts(self, obj):
> >           return ','.join(output_list)
> >       def get_qmp_events(self, wait: bool = False) -> List[QMPMessage]:
> > -        if qemu_gdb:
> > +        if qemu_gdb or qemu_valgrind:
> >               wait = 0.0
> >           return super().get_qmp_events(wait=wait)