+static unsigned int unix_datagram_poll(struct file *file, struct socket *sock,
+ poll_table *wait)
+{
+ struct sock *sk = sock->sk, *peer;
+ unsigned int mask;
+
+ poll_wait(file, sk->sk_sleep, wait);
+
+ peer = unix_peer_get(sk);
+ if (peer) {
+ if (peer != sk) {
+ /*
+ * Writability of a connected socket additionally
+ * depends on the state of the receive queue of the
+ * peer.
+ */
+ poll_wait(file, &unix_sk(peer)->peer_wait, wait);
+ } else {
+ sock_put(peer);
+ peer = NULL;
+ }
+ }
+
+ mask = 0;
+
+ /* exceptional events? */
+ if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
+ mask |= POLLERR;
+ if (sk->sk_shutdown & RCV_SHUTDOWN)
+ mask |= POLLRDHUP;
+ if (sk->sk_shutdown == SHUTDOWN_MASK)
+ mask |= POLLHUP;
+
+ /* readable? */
+ if (!skb_queue_empty(&sk->sk_receive_queue) ||
+ (sk->sk_shutdown & RCV_SHUTDOWN))
+ mask |= POLLIN | POLLRDNORM;
+
+ /* Connection-based need to check for termination and startup */
+ if (sk->sk_type == SOCK_SEQPACKET) {
+ if (sk->sk_state == TCP_CLOSE)
+ mask |= POLLHUP;
+ /* connection hasn't started yet? */
+ if (sk->sk_state == TCP_SYN_SENT)
+ return mask;
+ }
+
+ /* writable? */
+ if (unix_writable(sk) && !(peer && unix_recvq_full(peer)))
+ mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
+ else
+ set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
+
+ if (peer)
+ sock_put(peer);
+
+ return mask;
+}