tcp: tcp_prequeue() can use keyed wakeups

We can avoid waking up tasks not interested in receive notifications,
using wake_up_interruptible_poll() instead of wake_up_interruptible()
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -908,7 +908,8 @@ static inline int tcp_prequeue(struct sock *sk, struct sk_buff *skb)
 
 		tp->ucopy.memory = 0;
 	} else if (skb_queue_len(&tp->ucopy.prequeue) == 1) {
-		wake_up_interruptible(sk->sk_sleep);
+		wake_up_interruptible_poll(sk->sk_sleep,
+					   POLLIN | POLLRDNORM | POLLRDBAND);
 		if (!inet_csk_ack_scheduled(sk))
 			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 						  (3 * TCP_RTO_MIN) / 4,