net: wan: lapbether.c: Use built-in RCU list checking

The only callers of the function lapbeth_get_x25_dev()
are lapbeth_rcv() and lapbeth_device_event().

lapbeth_rcv() uses rcu_read_lock() whereas lapbeth_device_event()
is called with RTNL held (As mentioned in the comments).

Therefore, pass lockdep_rtnl_is_held() as cond argument in
list_for_each_entry_rcu();
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/lapbether.c

@@ -64,7 +64,7 @@ static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
 {
 	struct lapbethdev *lapbeth;
 
-	list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node) {
+	list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node, lockdep_rtnl_is_held()) {
 		if (lapbeth->ethdev == dev) 
 			return lapbeth;
 	}