sched, net: socket wakeups are sync

'sync' wakeups are a hint towards the scheduler that (certain)
networking related wakeups likely create coupling between tasks.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

net/core/sock.c

@@ -1621,7 +1621,7 @@ static void sock_def_readable(struct sock *sk, int len)
 {
 	read_lock(&sk->sk_callback_lock);
 	if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
-		wake_up_interruptible(sk->sk_sleep);
+		wake_up_interruptible_sync(sk->sk_sleep);
 	sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
 	read_unlock(&sk->sk_callback_lock);
 }
@@ -1635,7 +1635,7 @@ static void sock_def_write_space(struct sock *sk)
 	 */
 	if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf) {
 		if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
-			wake_up_interruptible(sk->sk_sleep);
+			wake_up_interruptible_sync(sk->sk_sleep);
 
 		/* Should agree with poll, otherwise some programs break */
 		if (sock_writeable(sk))