AF_UNIX: Fix poll blocking problem when reading from a stream socket

poll() call may be blocked by concurrent reading from the same stream
socket.

Signed-off-by: Alexey Moiseytsev <himeraster@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/unix/af_unix.c

@@ -1957,6 +1957,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 			if ((UNIXCB(skb).pid  != siocb->scm->pid) ||
 			    (UNIXCB(skb).cred != siocb->scm->cred)) {
 				skb_queue_head(&sk->sk_receive_queue, skb);
+				sk->sk_data_ready(sk, skb->len);
 				break;
 			}
 		} else {
@@ -1974,6 +1975,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 		chunk = min_t(unsigned int, skb->len, size);
 		if (memcpy_toiovec(msg->msg_iov, skb->data, chunk)) {
 			skb_queue_head(&sk->sk_receive_queue, skb);
+			sk->sk_data_ready(sk, skb->len);
 			if (copied == 0)
 				copied = -EFAULT;
 			break;
@@ -1991,6 +1993,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 			/* put the skb back if we didn't use it up.. */
 			if (skb->len) {
 				skb_queue_head(&sk->sk_receive_queue, skb);
+				sk->sk_data_ready(sk, skb->len);
 				break;
 			}
 
@@ -2006,6 +2009,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 			/* put message back and return */
 			skb_queue_head(&sk->sk_receive_queue, skb);
+			sk->sk_data_ready(sk, skb->len);
 			break;
 		}
 	} while (size);