On 03/23/2016 10:08 AM, Paolo Bonzini wrote: > > > On 23/03/2016 09:10, Cornelia Huck wrote: >>> - /* Kick right away to begin processing requests already in vring */ >>> - event_notifier_set(virtio_queue_get_host_notifier(s->vq)); >>> + vblk->dataplane_started = true; >>> >>> - /* Get this show started by hooking up our callbacks */ >>> + /* Get this show started by hooking up our callbacks. */ >>> aio_context_acquire(s->ctx); >>> virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, true, true); >>> aio_context_release(s->ctx); >>> + atomic_dec(&s->starting); >>> + >>> + /* Kick right away to begin processing requests already in vring */ >>> + event_notifier_set(virtio_queue_get_host_notifier(s->vq)); >> >> I'm wondering whether moving this event_notifier_set() masks something? >> IOW, may we run into trouble if the event notifier is set from some >> other path before the callbacks are set up properly? > > The reentrancy check should catch that... But: > > 1) the patch really makes no difference, your fix is enough for me
Tu Bo, can you test with master + Cornelias 6 refactoring patches and nothing on top? > 2) vblk->dataplane_started becomes true before the callbacks are set; > that should be enough. > > 3) this matches what I tested, but it would of course be better if the > assertions on s->starting suffice > >>> - if (!vblk->dataplane_started || s->stopping) { >>> + if (!vblk->dataplane_started) { >> >> No fear of reentrancy here? > > No, because this is only invoked from reset, hence only from the CPU > thread and only under the BQL. > > On start, reentrancy happens between iothread (running outside BQL) and > a CPU thread (running within BQL). > > Paolo > >>> return; >>> } >>> >>> @@ -255,7 +251,7 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) >>> vblk->dataplane_started = false; >>> return; >>> } >>> - s->stopping = true; >>> + >>> trace_virtio_blk_data_plane_stop(s); >>> >>> aio_context_acquire(s->ctx); >>> @@ -274,5 +270,4 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) >>> k->set_guest_notifiers(qbus->parent, 1, false); >>> >>> vblk->dataplane_started = false; >>> - s->stopping = false; >>> } >>> >> >