netlink: wake up netlink listeners sooner (v2)

This patch changes it to yield sooner at halfway instead. Still not a cure-all
for listener overrun if listner is slow, but works much reliably.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/af_netlink.c

@@ -959,7 +959,7 @@ static int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb)
 		skb_set_owner_r(skb, sk);
 		skb_queue_tail(&sk->sk_receive_queue, skb);
 		sk->sk_data_ready(sk, skb->len);
-		return atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf;
+		return atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1);
 	}
 	return -1;
 }