On Thu, Jan 24, 2019 at 09:11:15AM +0000, Dr. David Alan Gilbert wrote:
> * Jason Wang (jasow...@redhat.com) wrote:
> >
> > On 2019/1/24 上午3:53, Dr. David Alan Gilbert wrote:
> > > * Jason Wang (jasow...@redhat.com) wrote:
> > > > On 2019/1/22 上午2:56, Peter Maydell wrote:
> > > > > On Thu, 17 Jan 2019 at 09:46, Jason Wang<jasow...@redhat.com> wrote:
> > > > > > On 2019/1/15 上午12:33, Zhang Chen wrote:
> > > > > > > On Sat, Jan 12, 2019 at 12:15 AM Dr. David Alan Gilbert
> > > > > > > <dgilb...@redhat.com <mailto:dgilb...@redhat.com>> wrote:
> > > > > > >
> > > > > > > * Peter Maydell (peter.mayd...@linaro.org
> > > > > > > <mailto:peter.mayd...@linaro.org>) wrote:
> > > > > > > > Recently I've noticed that test-filter-mirror has been
> > > > > > > hanging
> > > > > > > > intermittently, typically when run on some other TCG
> > > > > > > architecture.
> > > > > > > > In the instance I've just looked at, this was with s390x
> > > > > > > guest on
> > > > > > > > x86-64 host, though I've also seen it on other host archs
> > > > > > > and
> > > > > > > > perhaps with other guests.
> > > > > > >
> > > > > > > Watch out to see if you really do see it for other guests;
> > > > > > > it carefully avoids using virtio-net to avoid vhost; but on
> > > > > > > s390x it
> > > > > > > uses virtio-net-ccw - could that hit the vhost it was
> > > > > > > trying to avoid?
> > > > > > >
> > > > > > > > Below is a backtrace, though it seems to be pretty
> > > > > > > unhelpful.
> > > > > > > > Anybody got any theories ? Does the mirror test rely on
> > > > > > > dirty
> > > > > > > > memory bitmaps like the migration test (which also hangs
> > > > > > > > occasionally with TCG due to some bug I'm sure we've
> > > > > > > investigated
> > > > > > > > in the past) ?
> > > > > > >
> > > > > > > I don't think it relies on the CPU at all.
> > > > > > > I have no idea about this currently, but Jason and I designed
> > > > > > > the
> > > > > > > test case.
> > > > > > > Add Jason: Have any comments about this ?
> > > > > > I can't reproduce this locally with s390x-softmmu. It looks to me
> > > > > > the
> > > > > > test should be independent to any kinds of emulation. It should pass
> > > > > > when mainloop work.
> > > > > I've just seen a hang with ppc64 guest on s390x host, so it is
> > > > > indeed not specific to s390x guest (and so not specific to
> > > > > virtio-net either, since the ppc64 guest setup uses e1000).
> > > > >
> > > > > thanks
> > > > > -- PMM
> > > > Finally reproduced locally after hundreds (sometimes thousands) times of
> > > > running.
> > > >
> > > > Bisection points to OOB monitor[1].
> > > >
> > > > It looks to me after OOB is used unconditionally we lose a barrier to
> > > > make
> > > > sure socket is connected before sending packets in
> > > > test-filter-mirror.c. Is
> > > > there any other similar and simple thing that we could do to kick the
> > > > mainloop?
> > > Do you mean the:
> > >
> > > /* send a qmp command to guarantee that 'connected' is setting to
> > > true. */
> > > qmp_discard_response(qts, "{ 'execute' : 'query-status'}");
> >
> >
> > Yes.
> >
> >
> > >
> > > why was that ever sufficient to know the socket was ready?
> >
> >
> > It was suggested by Fam, I don't remember the details. Can we make sure all
> > pending events has been processed (UNIX socket was set to connected) after
> > query-status is returned with an non OOB monitor?
>
> I'm not sure - it doesn't sound like a 'query-status' should ensure
> anything else.
> How about something like a 'query-chardev' - can that tell you what you
> need and loop until it's ready?
Yeah it sounds hacky to use "query status" to make sure a specific
chardev is connected even before the OOB...
I saw that currently the chardev requires "nowait":
qts = qtest_initf(
"-netdev socket,id=qtest-bn0,fd=%d "
"-device %s,netdev=qtest-bn0,id=qtest-e0 "
"-chardev socket,id=mirror0,path=%s,server,nowait "
"-object
filter-mirror,id=qtest-f0,netdev=qtest-bn0,queue=tx,outdev=mirror0 "
, send_sock[1], devstr, sock_path);
Could it work without "nowait"? Would that make sure QEMU will wait
until connection established before going on?
Regards,
--
Peter Xu
