[TIPC]: Optimize wakeup logic when socket has no waiting processes

This patch adds a simple test so TIPC doesn't try waking up processes
waiting on a socket if there are none waiting.
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Per Liden <per.liden@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/socket.c

@@ -1208,6 +1208,7 @@ static u32 dispatch(struct tipc_port *tport, struct sk_buff *buf)
 	atomic_inc(&tipc_queue_size);
 	skb_queue_tail(&sock->sk->sk_receive_queue, buf);
 
+	if (waitqueue_active(sock->sk->sk_sleep))
 		wake_up_interruptible(sock->sk->sk_sleep);
 	return TIPC_OK;
 }
@@ -1223,6 +1224,7 @@ static void wakeupdispatch(struct tipc_port *tport)
 {
 	struct tipc_sock *tsock = (struct tipc_sock *)tport->usr_handle;
 
+	if (waitqueue_active(tsock->sk.sk_sleep))
 		wake_up_interruptible(tsock->sk.sk_sleep);
 }