bonding: Fix netconsole to not deadlock on rmmod

Netconsole calls netpoll_cleanup on receipt of a NETDEVICE_UNREGISTER event.
The notifier subsystem calls these event handlers with rtnl_lock held, which
netpoll_cleanup also takes, resulting in deadlock.  Fix this by calling the
__netpoll_cleanup interior function instead, and fixing up the additional
pointers.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netconsole.c

@@ -678,7 +678,14 @@ static int netconsole_netdev_event(struct notifier_block *this,
 				strlcpy(nt->np.dev_name, dev->name, IFNAMSIZ);
 				break;
 			case NETDEV_UNREGISTER:
-				netpoll_cleanup(&nt->np);
+				/*
+				 * rtnl_lock already held
+				 */
+				if (nt->np.dev) {
+					__netpoll_cleanup(&nt->np);
+					dev_put(nt->np.dev);
+					nt->np.dev = NULL;
+				}
 				/* Fall through */
 			case NETDEV_GOING_DOWN:
 			case NETDEV_BONDING_DESLAVE: