x25: remove the BKL

This replaces all instances of lock_kernel in x25
with lock_sock, taking care to release the socket
lock around sleeping functions (sock_alloc_send_skb
and skb_recv_datagram). It is not clear whether
this is a correct solution, but it seem to be what
other protocols do in the same situation.

Includes a fix suggested by Eric Dumazet.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David S. Miller <davem@davemloft.net>
Tested-by: Andrew Hendry <andrew.hendry@gmail.com>
Cc: linux-x25@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: Eric Dumazet <eric.dumazet@gmail.com>

net/x25/x25_out.c

diff --git a/net/x25/x25_out.c b/net/x25/x25_out.c
index d00649f..0144271 100644
--- a/net/x25/x25_out.c
+++ b/net/x25/x25_out.c
@@ -68,8 +68,11 @@
 		frontlen = skb_headroom(skb);
 
 		while (skb->len > 0) {
-			if ((skbn = sock_alloc_send_skb(sk, frontlen + max_len,
-							noblock, &err)) == NULL){
+			release_sock(sk);
+			skbn = sock_alloc_send_skb(sk, frontlen + max_len,
+						   noblock, &err);
+			lock_sock(sk);
+			if (!skbn) {
 				if (err == -EWOULDBLOCK && noblock){
 					kfree_skb(skb);
 					return sent;