[PATCH 3.16 137/178] virtio_console: fix uninitialized variable use

[Ben Hutchings]

3.16.46-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

commit 2055997f983c6db7b5c3940ce5f8f822657d5bc3 upstream.

We try to disable callbacks on c_ivq even without multiport
even though that vq is not initialized in this configuration.

Fixes: c743d09dbd01 ("virtio: console: Disable callbacks for virtqueues at start of S4 freeze")
Suggested-by: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/char/virtio_console.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -2180,14 +2180,16 @@ static int virtcons_freeze(struct virtio
 
 	vdev->config->reset(vdev);
 
-	virtqueue_disable_cb(portdev->c_ivq);
+	if (use_multiport(portdev))
+		virtqueue_disable_cb(portdev->c_ivq);
 	cancel_work_sync(&portdev->control_work);
 	cancel_work_sync(&portdev->config_work);
 	/*
 	 * Once more: if control_work_handler() was running, it would
 	 * enable the cb as the last step.
 	 */
-	virtqueue_disable_cb(portdev->c_ivq);
+	if (use_multiport(portdev))
+		virtqueue_disable_cb(portdev->c_ivq);
 	remove_controlq_data(portdev);
 
 	list_for_each_entry(port, &portdev->ports, list) {