rcu: convert uses of rcu_assign_pointer(x, NULL) to RCU_INIT_POINTER

When assigning a NULL value to an RCU protected pointer, no barrier
is needed. The rcu_assign_pointer, used to handle that but will soon
change to not handle the special case.

Convert all rcu_assign_pointer of NULL value.

//smpl
@@ expression P; @@

- rcu_assign_pointer(P, NULL)
+ RCU_INIT_POINTER(P, NULL)

// </smpl>

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_tunnel.c

@@ -218,8 +218,8 @@ ip6_tnl_link(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
 {
 	struct ip6_tnl __rcu **tp = ip6_tnl_bucket(ip6n, &t->parms);
 
-	rcu_assign_pointer(t->next , rtnl_dereference(*tp));
-	rcu_assign_pointer(*tp, t);
+	RCU_INIT_POINTER(t->next , rtnl_dereference(*tp));
+	RCU_INIT_POINTER(*tp, t);
 }
 
 /**
@@ -237,7 +237,7 @@ ip6_tnl_unlink(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
 	     (iter = rtnl_dereference(*tp)) != NULL;
 	     tp = &iter->next) {
 		if (t == iter) {
-			rcu_assign_pointer(*tp, t->next);
+			RCU_INIT_POINTER(*tp, t->next);
 			break;
 		}
 	}
@@ -350,7 +350,7 @@ ip6_tnl_dev_uninit(struct net_device *dev)
 	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
 
 	if (dev == ip6n->fb_tnl_dev)
-		rcu_assign_pointer(ip6n->tnls_wc[0], NULL);
+		RCU_INIT_POINTER(ip6n->tnls_wc[0], NULL);
 	else
 		ip6_tnl_unlink(ip6n, t);
 	ip6_tnl_dst_reset(t);
@@ -1440,7 +1440,7 @@ static int __net_init ip6_fb_tnl_dev_init(struct net_device *dev)
 
 	t->parms.proto = IPPROTO_IPV6;
 	dev_hold(dev);
-	rcu_assign_pointer(ip6n->tnls_wc[0], t);
+	RCU_INIT_POINTER(ip6n->tnls_wc[0], t);
 	return 0;
 }