vhost: fix lock on device readiness notification

The vhost notifies the application of device readiness via
vhost_user_notify_queue_state(), but calling this function
is not protected by the lock. This patch is to make this
function call lock protected.

Fixes: d0fcc38 ("vhost: improve device readiness notifications")
Cc: stable@dpdk.org

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

lib/vhost/vhost_user.c

@@ -2995,9 +2995,6 @@ vhost_user_msg_handler(int vid, int fd)
 		}
 	}
 
-	if (unlock_required)
-		vhost_user_unlock_all_queue_pairs(dev);
-
 	/* If message was not handled at this stage, treat it as an error */
 	if (!handled) {
 		VHOST_LOG_CONFIG(ERR,
@@ -3032,6 +3029,8 @@ vhost_user_msg_handler(int vid, int fd)
 		}
 	}
 
+	if (unlock_required)
+		vhost_user_unlock_all_queue_pairs(dev);
 
 	if (!virtio_is_ready(dev))
 		goto out;