On Mon, 25 Feb 2019 10:31:27 -0800, Jakub Kicinski wrote:

+static bool devlink_is_registered(struct devlink *devlink)
+{
+       return list_empty(&devlink->list);
+}

Nevermind, this won't really help the drivers that much, those
registering devlink after netdevs will have to take care of the
potential race by marking the devlink instance as dead in their priv
data structure from the thread doing the devlink_unregister, using
their own locking.