On 08/22/2017 07:51 AM, Stefan Hajnoczi wrote: > The following scenario leads to an assertion failure in > qio_channel_yield(): > > 1. Request coroutine calls qio_channel_yield() successfully when sending > would block on the socket. It is now yielded. > 2. nbd_read_reply_entry() calls nbd_recv_coroutines_enter_all() because > nbd_receive_reply() failed. > 3. Request coroutine is entered and returns from qio_channel_yield(). > Note that the socket fd handler has not fired yet so > ioc->write_coroutine is still set. > 4. Request coroutine attempts to send the request body with nbd_rwv() > but the socket would still block. qio_channel_yield() is called > again and assert(!ioc->write_coroutine) is hit. > > The problem is that nbd_read_reply_entry() does not distinguish between > request coroutines that are waiting to receive a reply and those that > are not. > > This patch adds a per-request bool receiving flag so > nbd_read_reply_entry() can avoid spurious aio_wake() calls. > > Reported-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
Using the steps in https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg03853.html, I've verified that this avoids the hang that is otherwise present, so I'm adding: Tested-by: Eric Blake <ebl...@redhat.com> -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
signature.asc
Description: OpenPGP digital signature
