From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48663) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1elcUx-0007Ix-Kw for qemu-devel@nongnu.org; Tue, 13 Feb 2018 10:28:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1elcUu-0003Ct-U3 for qemu-devel@nongnu.org; Tue, 13 Feb 2018 10:27:59 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:47368 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1elcUu-0003Cb-Nr for qemu-devel@nongnu.org; Tue, 13 Feb 2018 10:27:56 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5F6B87CBA5 for ; Tue, 13 Feb 2018 15:27:56 +0000 (UTC) Date: Tue, 13 Feb 2018 15:27:53 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180213152753.GR573@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <1518531279-11966-1-git-send-email-thuth@redhat.com> <20180213150911.GG2378@work-vm> <20180213151125.GQ573@redhat.com> <20180213152529.GH2378@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180213152529.GH2378@work-vm> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] io/channel-command: Delay the killing of the child after closing the pipe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: Thomas Huth , qemu-devel@nongnu.org, Juan Quintela , =?utf-8?B?THVrw6HFoQ==?= Doktor , Cornelia Huck On Tue, Feb 13, 2018 at 03:25:30PM +0000, Dr. David Alan Gilbert wrote: > * Daniel P. Berrang=C3=A9 (berrange@redhat.com) wrote: > > On Tue, Feb 13, 2018 at 03:09:12PM +0000, Dr. David Alan Gilbert wrot= e: > > > * Thomas Huth (thuth@redhat.com) wrote: > > > > We are currently facing some migration failure on s390x when runn= ing > > > > certain avocado tests, e.g. when running the test > > > > type_specific.io-github-autotest-qemu.migrate.with_reboot.exec.gz= ip_exec. > > > > This test is using 'migrate -d "exec:nc localhost 5200"' for the = migration. > > > > The problem is detected at the receiving side, where the migratio= n stream > > > > apparently ends too early. However, the cause for the problem is = the > > > > sending side: After writing the migration stream into the pipe to= netcat, > > > > the source QEMU calls qio_channel_command_close() which closes th= e pipe > > > > and immediately (!) kills the child process afterwards. So if the > > > > sending netcat did not read the final bytes from the pipe yet, or > > > > if it did not manage to send out all its buffers yet, it is kille= d > > > > before the whole migration stream is passed to the destination si= de. > > >=20 > > > Thanks for tracking that down! > > >=20 > > > > To ease the situation at least a little bit, we should give the c= hild > > > > process at least some few more time slices before we kill it with > > > > SIGTERM and then with SIGKILL. With this change, the avocado test= now > > > > succeeds here in 10 out of 10 runs. > > > >=20 > > > > Signed-off-by: Thomas Huth > > > > --- > > > > io/channel-command.c | 6 +++--- > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > >=20 > > > > diff --git a/io/channel-command.c b/io/channel-command.c > > > > index 319c5ed..f64db3e 100644 > > > > --- a/io/channel-command.c > > > > +++ b/io/channel-command.c > > > > @@ -177,11 +177,11 @@ static int qio_channel_command_abort(QIOCha= nnelCommand *ioc, > > > > return -1; > > > > } > > > > } else if (ret =3D=3D 0) { > > > > - if (step =3D=3D 0) { > > > > + if (step =3D=3D 4) { > > > > kill(ioc->pid, SIGTERM); > > > > - } else if (step =3D=3D 1) { > > > > + } else if (step =3D=3D 8) { > > > > kill(ioc->pid, SIGKILL); > > > > - } else { > > > > + } else if (step >=3D 9) { > > >=20 > > > Hmm. This seems pretty arbitrary; if I understand correctly you're > > > saying it'll get a SIGTERM after 4 (arbitrary) * 10ms (arbitrary). > > >=20 > > > Who is to say that's enough for a scp or gzip or the like? > >=20 > > We could conceivably implement the qio_channel_shutdown() operation > > for the QIOChannelCommand class. It would merely close the FD to the > > child process, but leave it running. That would give it time to read > > any data still in the pipe from QEMU IIUC. >=20 > Yeh that's better; although when would we call shutdown or close on it? Doesn't QEMU alredy use shutdown() during the right part of migration, or is that only wrt post-copy ? Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|