From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43094) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1elcF3-0001KS-RJ for qemu-devel@nongnu.org; Tue, 13 Feb 2018 10:11:35 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1elcF0-0008WD-Fe for qemu-devel@nongnu.org; Tue, 13 Feb 2018 10:11:33 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:53434 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 1elcF0-0008Vt-Ax for qemu-devel@nongnu.org; Tue, 13 Feb 2018 10:11:30 -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 F31A740FB645 for ; Tue, 13 Feb 2018 15:11:29 +0000 (UTC) Date: Tue, 13 Feb 2018 15:11:25 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180213151125.GQ573@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <1518531279-11966-1-git-send-email-thuth@redhat.com> <20180213150911.GG2378@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180213150911.GG2378@work-vm> 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 03:09:12PM +0000, Dr. David Alan Gilbert wrote: > * Thomas Huth (thuth@redhat.com) wrote: > > We are currently facing some migration failure on s390x when running > > certain avocado tests, e.g. when running the test > > type_specific.io-github-autotest-qemu.migrate.with_reboot.exec.gzip_exec. > > This test is using 'migrate -d "exec:nc localhost 5200"' for the migration. > > The problem is detected at the receiving side, where the migration 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 the 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 killed > > before the whole migration stream is passed to the destination side. > > Thanks for tracking that down! > > > To ease the situation at least a little bit, we should give the child > > 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. > > > > Signed-off-by: Thomas Huth > > --- > > io/channel-command.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > 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(QIOChannelCommand *ioc, > > return -1; > > } > > } else if (ret == 0) { > > - if (step == 0) { > > + if (step == 4) { > > kill(ioc->pid, SIGTERM); > > - } else if (step == 1) { > > + } else if (step == 8) { > > kill(ioc->pid, SIGKILL); > > - } else { > > + } else if (step >= 9) { > > Hmm. This seems pretty arbitrary; if I understand correctly you're > saying it'll get a SIGTERM after 4 (arbitrary) * 10ms (arbitrary). > > Who is to say that's enough for a scp or gzip or the like? 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. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|