On Wed, Feb 02, 2022 at 12:49:36PM +0100, Fabian Ebner wrote: > Am 27.09.21 um 23:55 schrieb Eric Blake: > > From: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> > > > > OK, that's a big rewrite of the logic. > > > > Pre-patch we have an always running coroutine - connection_co. It does > > reply receiving and reconnecting. And it leads to a lot of difficult > > and unobvious code around drained sections and context switch. We also > > abuse bs->in_flight counter which is increased for connection_co and > > temporary decreased in points where we want to allow drained section to > > begin. One of these place is in another file: in nbd_read_eof() in > > nbd/client.c. > > > > We also cancel reconnect and requests waiting for reconnect on drained > > begin which is not correct. And this patch fixes that. > > > > Let's finally drop this always running coroutine and go another way: > > do both reconnect and receiving in request coroutines. > > > > Hi, > > while updating our stack to 6.2, one of our live-migration tests stopped > working (backtrace is below) and bisecting led me to this patch. > > The VM has a single qcow2 disk (converting to raw doesn't make a > difference) and the issue only appears when using iothread (for both > virtio-scsi-pci and virtio-block-pci). > > Reverting 1af7737871fb3b66036f5e520acb0a98fc2605f7 (which lives on top) > and 4ddb5d2fde6f22b2cf65f314107e890a7ca14fcf (the commit corresponding > to this patch) in v6.2.0 makes the migration work again. > > Backtrace: > > Thread 1 (Thread 0x7f9d93458fc0 (LWP 56711) "kvm"): > #0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50 > #1 0x00007f9d9d6bc537 in __GI_abort () at abort.c:79 > #2 0x00007f9d9d6bc40f in __assert_fail_base (fmt=0x7f9d9d825128 > "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0x5579153763f8 > "qemu_get_current_aio_context() == qemu_coroutine_get_aio_context(co)", > file=0x5579153764f9 "../io/channel.c", line=483, function=<optimized > out>) at assert.c:92
Given that this assertion is about which aio context is set, I wonder if the conversation at https://lists.gnu.org/archive/html/qemu-devel/2022-02/msg00096.html is relevant; if so, Vladimir may already be working on the patch. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
