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authorStefan Hajnoczi <stefanha@redhat.com>2013-01-15 17:19:38 +0100
committerStefan Hajnoczi <stefanha@redhat.com>2013-01-18 16:57:59 +0100
commitcd7fdfe59f4f965665dcd9868fe3764f5256d6aa (patch)
tree97246f6d8e0ecd72c84726d1fc7d0951273e4284
parent3249dbe661ba6ef108ecde97c54b4a4104d719c3 (diff)
downloadqemu-arm-cd7fdfe59f4f965665dcd9868fe3764f5256d6aa.tar.gz
dataplane: avoid reentrancy during virtio_blk_data_plane_stop()
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>
-rw-r--r--hw/dataplane/virtio-blk.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c
index 4b26faa6c2..3f2da22669 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;
}