[Qemu-devel] [PATCH] virtio-blk: assert on starting/stopping

["Michael S. Tsirkin" <mst@redhat.com>]

Reentrancy cannot happen while the BQL is being held,
so we should never enter this condition.

Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

This is a replacement for [PATCH 9/9] virtio: remove starting/stopping
checks Christian, could you please give it a spin with debug enabled?
Since you reported above Paolo's patch triggers segfaults, I expect this
one to trigger assertions as well, which should give us more info on
the root cause.

 hw/block/dataplane/virtio-blk.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index fd06726..04e0e0d 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -203,10 +203,12 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
     int r;
 
-    if (vblk->dataplane_started || s->starting) {
+    if (vblk->dataplane_started) {
         return;
     }
 
+    assert(!s->starting);
+
     s->starting = true;
     s->vq = virtio_get_queue(s->vdev, 0);
 
@@ -257,10 +259,12 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
 
-    if (!vblk->dataplane_started || s->stopping) {
+    if (!vblk->dataplane_started) {
         return;
     }
 
+    assert(!s->stopping);
+
     /* Better luck next time. */
     if (vblk->dataplane_disabled) {
         vblk->dataplane_disabled = false;
-- 
MST