| Message ID | 1358266778-14621-1-git-send-email-stefanha@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Jan 15, 2013 at 05:19:38PM +0100, Stefan Hajnoczi wrote: > When dataplane is stopping, the s->vdev->binding->set_host_notifier(..., > false) call can invoke the virtqueue handler if an ioeventfd > notification is pending. This causes hw/virtio-blk.c to invoke > virtio_blk_data_plane_start() before virtio_blk_data_plane_stop() > returns! > > The result is that we try to restart dataplane while trying to stop it > and the following assertion is raised: > > msix_set_mask_notifier: Assertion `!dev->msix_mask_notifier' failed. > > Although the code was intended to prevent this scenario, the s->started > boolean isn't enough. Add s->stopping so that we can postpone clearing > s->started until we've completely stopped dataplane. > > This way, virtqueue handler calls during virtio_blk_data_plane_stop() > are ignored. When dataplane is legitimately started again later we > already self-kick ourselves to resume processing. > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > hw/dataplane/virtio-blk.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) Applied to my block tree: https://github.com/stefanha/qemu/commits/block Stefan
diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c index 4b26faa..3f2da22 100644 --- a/hw/dataplane/virtio-blk.c +++ b/hw/dataplane/virtio-blk.c @@ -40,6 +40,7 @@ typedef struct { struct VirtIOBlockDataPlane { bool started; + bool stopping; QEMUBH *start_bh; QemuThread thread; @@ -357,7 +358,7 @@ static void *data_plane_thread(void *opaque) do { event_poll(&s->event_poll); - } while (s->started || s->num_reqs > 0); + } while (!s->stopping || s->num_reqs > 0); return NULL; } @@ -486,10 +487,10 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s) void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) { - if (!s->started) { + if (!s->started || s->stopping) { return; } - s->started = false; + s->stopping = true; trace_virtio_blk_data_plane_stop(s); /* Stop thread or cancel pending thread creation BH */ @@ -511,4 +512,6 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, 1, false); vring_teardown(&s->vring); + s->started = false; + s->stopping = false; }
When dataplane is stopping, the s->vdev->binding->set_host_notifier(..., false) call can invoke the virtqueue handler if an ioeventfd notification is pending. This causes hw/virtio-blk.c to invoke virtio_blk_data_plane_start() before virtio_blk_data_plane_stop() returns! The result is that we try to restart dataplane while trying to stop it and the following assertion is raised: msix_set_mask_notifier: Assertion `!dev->msix_mask_notifier' failed. Although the code was intended to prevent this scenario, the s->started boolean isn't enough. Add s->stopping so that we can postpone clearing s->started until we've completely stopped dataplane. This way, virtqueue handler calls during virtio_blk_data_plane_stop() are ignored. When dataplane is legitimately started again later we already self-kick ourselves to resume processing. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- hw/dataplane/virtio-blk.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)