From patchwork Fri Jan 18 16:28:40 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [7/8] dataplane: avoid reentrancy during virtio_blk_data_plane_stop() Date: Fri, 18 Jan 2013 06:28:40 -0000 From: Stefan Hajnoczi X-Patchwork-Id: 213678 Message-Id: <1358526521-24300-8-git-send-email-stefanha@redhat.com> To: Cc: Anthony Liguori , Stefan Hajnoczi 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 --- hw/dataplane/virtio-blk.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) 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; }