From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40390) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ds67P-0005TG-E3 for qemu-devel@nongnu.org; Wed, 13 Sep 2017 07:46:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ds67L-0001nk-Et for qemu-devel@nongnu.org; Wed, 13 Sep 2017 07:46:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36662) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ds67L-0001ms-5j for qemu-devel@nongnu.org; Wed, 13 Sep 2017 07:46:07 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2D257C0587E3 for ; Wed, 13 Sep 2017 11:46:06 +0000 (UTC) Date: Wed, 13 Sep 2017 12:45:58 +0100 From: "Daniel P. Berrange" Message-ID: <20170913114558.GF3067@redhat.com> Reply-To: "Daniel P. Berrange" References: <20170808162629.32493-1-quintela@redhat.com> <20170808162629.32493-16-quintela@redhat.com> <20170811152949.GU2554@redhat.com> <87r2vadels.fsf@secure.laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87r2vadels.fsf@secure.laptop> Subject: Re: [Qemu-devel] [PATCH v6 15/19] migration: Create thread infrastructure for multifd recv side List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Juan Quintela Cc: qemu-devel@nongnu.org, lvivier@redhat.com, dgilbert@redhat.com, peterx@redhat.com On Wed, Sep 13, 2017 at 01:26:07PM +0200, Juan Quintela wrote: > "Daniel P. Berrange" wrote: > > On Tue, Aug 08, 2017 at 06:26:25PM +0200, Juan Quintela wrote: > >> We make the locking and the transfer of information specific, even if we > >> are still receiving things through the main thread. > >> > >> Signed-off-by: Juan Quintela > >> > >> -- > >> > >> We split when we create the main channel and where we start the main > >> migration thread, so we wait for the creation of the other threads. > >> > >> Use multifd_clear_group(). > >> --- > >> migration/migration.c | 7 ++++--- > >> migration/migration.h | 1 + > >> migration/ram.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++---- > >> migration/socket.c | 2 +- > >> 4 files changed, 57 insertions(+), 8 deletions(-) > > > > > >> diff --git a/migration/socket.c b/migration/socket.c > >> index 5dd6f42..3af9f7c 100644 > >> --- a/migration/socket.c > >> +++ b/migration/socket.c > >> @@ -183,12 +183,12 @@ static gboolean > >> socket_accept_incoming_migration(QIOChannel *ioc, > >> > >> qio_channel_set_name(QIO_CHANNEL(sioc), "migration-socket-incoming"); > >> migration_channel_process_incoming(QIO_CHANNEL(sioc)); > >> - object_unref(OBJECT(sioc)); > > > > AFAICT, migration_channel_process_incoming() acquires its own reference > > on 'sioc', so removing this object_unref means the code is now leaking a > > reference > > Nack. > > I did it and ended with a segmentation fault because reference count was > bad. > > (qemu) > Thread 6 "multifdrecv_0" received signal SIGSEGV, Segmentation fault. > [Switching to Thread 0x7fff9f9ff700 (LWP 10065)] > 0x00005555559c12f8 in type_is_ancestor (type=0xb60f18247c894860, > target_type=0x555556531b30) at /mnt/kvm/qemu/cleanup/qom/object.c:217 > 217 while (type) { > (gdb) bt > #0 0x00005555559c12f8 in type_is_ancestor (type=0xb60f18247c894860, target_type=0x555556531b30) at /mnt/kvm/qemu/cleanup/qom/object.c:217 > #1 0x00005555559c1dbb in object_class_dynamic_cast (class=class@entry=0x7ffff2cb3ce8 , typename=typename@entry=0x555555aa6d91 "qio-channel") > at /mnt/kvm/qemu/cleanup/qom/object.c:691 > #2 0x00005555559c1ed2 in object_class_dynamic_cast_assert (class=0x7ffff2cb3ce8 , typename=typename@entry=0x555555aa6d91 "qio-channel", file=file@entry=0x555555b88208 "/mnt/kvm/qemu/cleanup/io/channel.c", line=line@entry=56, func=func@entry=0x555555b884e0 <__func__.22671> "qio_channel_readv_full") > at /mnt/kvm/qemu/cleanup/qom/object.c:723 > #3 0x0000555555a3d4d7 in qio_channel_readv_full (ioc=0x5555568c5a00, iov=0x7fff900008c0, niov=15, fds=0x0, nfds=0x0, errp=0x7fff9f9fe950) > at /mnt/kvm/qemu/cleanup/io/channel.c:56 > #4 0x0000555555a3ddc2 in qio_channel_readv (errp=0x7fff9f9fe950, niov=, iov=, ioc=0x5555568c5a00) > at /mnt/kvm/qemu/cleanup/io/channel.c:197 > #5 0x0000555555a3ddc2 in qio_channel_readv_all_eof (ioc=0x5555568c5a00, iov=, niov=, errp=errp@entry=0x7fff9f9fe950) > at /mnt/kvm/qemu/cleanup/io/channel.c:106 > #6 0x0000555555a3de79 in qio_channel_readv_all (ioc=, iov=, niov=, errp=errp@entry=0x7fff9f9fe950) > at /mnt/kvm/qemu/cleanup/io/channel.c:142 > #7 0x0000555555794768 in multifd_recv_thread (opaque=0x5555570e5e00) > ---Type to continue, or q to quit---up > at /mnt/kvm/qemu/cleanup/migration/ram.c:722 > #8 0x00007ffff2cc036d in start_thread (arg=0x7fff9f9ff700) > at pthread_create.c:456 > #9 0x00007ffff29f8bbf in clone () > at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97 > (gdb) up > > Removing this unref fixed things, so I think that the accounting is good > (famous last words). No, this is just papering over a bug elsewhere. The multifd_new_channel metohd needs to be acquiring a reference for the multifd_recv_thread to hold onto. 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 :|