ipip: 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/ipv4/ipip.c

@@ -754,16 +754,19 @@ static struct xfrm_tunnel ipip_handler = {
 static const char banner[] __initconst =
 	KERN_INFO "IPv4 over IPv4 tunneling driver\n";
 
-static void ipip_destroy_tunnels(struct ipip_net *ipn)
+static void ipip_destroy_tunnels(struct ipip_net *ipn, struct list_head *head)
 {
 	int prio;
 
 	for (prio = 1; prio < 4; prio++) {
 		int h;
 		for (h = 0; h < HASH_SIZE; h++) {
-			struct ip_tunnel *t;
-			while ((t = ipn->tunnels[prio][h]) != NULL)
-				unregister_netdevice(t->dev);
+			struct ip_tunnel *t = ipn->tunnels[prio][h];
+
+			while (t != NULL) {
+				unregister_netdevice_queue(t->dev, head);
+				t = t->next;
+			}
 		}
 	}
 }
@@ -816,11 +819,13 @@ err_alloc:
 static void ipip_exit_net(struct net *net)
 {
 	struct ipip_net *ipn;
+	LIST_HEAD(list);
 
 	ipn = net_generic(net, ipip_net_id);
 	rtnl_lock();
-	ipip_destroy_tunnels(ipn);
-	unregister_netdevice(ipn->fb_tunnel_dev);
+	ipip_destroy_tunnels(ipn, &list);
+	unregister_netdevice_queue(ipn->fb_tunnel_dev, &list);
+	unregister_netdevice_many(&list);
 	rtnl_unlock();
 	kfree(ipn);
 }