ip6tnl: Optimize multiple unregistration

Speedup module unloading by factorizing synchronize_rcu() calls
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_tunnel.c

@@ -1393,14 +1393,19 @@ static void ip6_tnl_destroy_tunnels(struct ip6_tnl_net *ip6n)
 {
 	int h;
 	struct ip6_tnl *t;
+	LIST_HEAD(list);
 
 	for (h = 0; h < HASH_SIZE; h++) {
-		while ((t = ip6n->tnls_r_l[h]) != NULL)
-			unregister_netdevice(t->dev);
+		t = ip6n->tnls_r_l[h];
+		while (t != NULL) {
+			unregister_netdevice_queue(t->dev, &list);
+			t = t->next;
+		}
 	}
 
 	t = ip6n->tnls_wc[0];
-	unregister_netdevice(t->dev);
+	unregister_netdevice_queue(t->dev, &list);
+	unregister_netdevice_many(&list);
 }
 
 static int ip6_tnl_init_net(struct net *net)