On Wed, 2012-05-30 at 10:36 +0300, Alexandru Copot wrote:

+struct inet_bind_bucket *
+inet4_find_bind_buckets(struct sock *sk,
+			unsigned short port,
+			struct inet_bind_hashbucket **p_bhead,
+			struct inet_bind_hashbucket **p_portaddr_bhead)
+{
+	struct net *net = sock_net(sk);
+	struct inet_hashinfo *hinfo = sk->sk_prot->h.hashinfo;
+	struct inet_bind_bucket *tb = NULL;
+	struct hlist_node *node;
+
+	struct inet_bind_hashbucket *bhead, *portaddr_bhead, *portaddrany_bhead;
+	bhead = &hinfo->bhash[inet_bhashfn(net, port, hinfo->bhash_size)];
+	portaddr_bhead = inet4_portaddr_hashbucket(hinfo, net,
+				sk_rcv_saddr(sk), port);
+	portaddrany_bhead = inet4_portaddr_hashbucket(hinfo, net,
+						INADDR_ANY, port);
+
+	*p_portaddr_bhead = portaddr_bhead;
+	*p_bhead = bhead;
+
+	/*
+	 * prevent dead locks by always taking locks in a fixed order:
+	 * - always take the port-only lock first. This is done because in some
+	 *   other places this is the lock taken, being folllowed in only some
+	 *   cases by the portaddr lock.
+	 * - between portaddr and portaddrany always choose the one with the
+	 *   lower address. Unlock ordering is not important, as long as the
+	 *   locking order is consistent.
+	 * - make sure to not take the same lock twice
+	 */
+	spin_lock(&bhead->lock);
+	if (portaddr_bhead > portaddrany_bhead) {
+		spin_lock(&portaddrany_bhead->lock);
+		spin_lock(&portaddr_bhead->lock);
+	} else if (portaddr_bhead < portaddrany_bhead) {
+		spin_lock(&portaddr_bhead->lock);
+		spin_lock(&portaddrany_bhead->lock);
+	} else {
+		spin_lock(&portaddr_bhead->lock);
+	}
+
+	if (sk_rcv_saddr(sk) != INADDR_ANY) {
+		struct inet_bind_hashbucket *_head;
+
+		_head = portaddr_bhead;
+		if (bhead->count < portaddr_bhead->count) {
+			_head = bhead;
+			inet_bind_bucket_for_each(tb, node, &_head->chain)
+				if ((net_eq(ib_net(tb), net)) &&
+				    (tb->port == port) &&
+				    (tb->ib_addr_ipv4 == sk_rcv_saddr(sk)))
+					goto found;
+		} else {
+			inet_portaddr_bind_bucket_for_each(tb, node, &_head->chain)
+				if ((net_eq(ib_net(tb), net)) &&
+				    (tb->port == port) &&
+				    (tb->ib_addr_ipv4 == sk_rcv_saddr(sk)))
+					goto found;
+		}
+		_head = portaddrany_bhead;
+		if (bhead->count < portaddrany_bhead->count) {
+			_head = bhead;
+			inet_bind_bucket_for_each(tb, node, &_head->chain)
+				if ((ib_net(tb) == net) &&
+				    (tb->port == port) &&
+				    (tb->ib_addr_ipv4 == INADDR_ANY))
+					goto found;
+		} else {
+			inet_portaddr_bind_bucket_for_each(tb, node, &_head->chain)
+				if ((ib_net(tb) == net) &&
+				    (tb->port == port) &&
+				    (tb->ib_addr_ipv4 == INADDR_ANY))
+					goto found;
+		}
+	} else {
+		inet_bind_bucket_for_each(tb, node, &bhead->chain)
+			if ((ib_net(tb) == net) && (tb->port == port))
+				goto found;
+	}
+
+	tb = NULL;
+found:
+	if (portaddr_bhead != portaddrany_bhead)
+		spin_unlock(&portaddrany_bhead->lock);
+
+	/* the other locks remain taken, as the caller
+	 * may want to change the hash tabels */
+	return tb;
+}
+
+

How this is going to work with IPv6 sockets in the middle of the
chains ?

Also, comments are not properly formatted, they should all look like :

	/* the other locks remain taken, as the caller
	 * may want to change the hash tables
	 */

And finally, make sure LOCKDEP is happy with your locking code.