ndisc: Update neigh->updated with write lock.

index 7c34c01..1341f68 100644
@@ -499,22 +499,26 @@ static void rt6_probe(struct rt6_info *rt)
 	 * to no more than one per minute.
 	 */
 	neigh = rt ? rt->n : NULL;
-	if (!neigh || (neigh->nud_state & NUD_VALID))
+	if (!neigh)
+		return;
+	write_lock_bh(&neigh->lock);
+	if (neigh->nud_state & NUD_VALID) {
+		write_unlock_bh(&neigh->lock);
 		return;
-	read_lock_bh(&neigh->lock);
+	}
 	if (!(neigh->nud_state & NUD_VALID) &&
 	    time_after(jiffies, neigh->updated + rt->rt6i_idev->cnf.rtr_probe_interval)) {
 		struct in6_addr mcaddr;
 		struct in6_addr *target;
 
 		neigh->updated = jiffies;
-		read_unlock_bh(&neigh->lock);
+		write_unlock_bh(&neigh->lock);
 
 		target = (struct in6_addr *)&neigh->primary_key;
 		addrconf_addr_solict_mult(target, &mcaddr);
 		ndisc_send_ns(rt->dst.dev, NULL, target, &mcaddr, NULL);
 	} else {
-		read_unlock_bh(&neigh->lock);
+		write_unlock_bh(&neigh->lock);
 	}
 }
 #else