Commit 77b75f4d authored Nov 26, 2015 by Rainer Weikusat Committed by David S. Miller Dec 01, 2015

unix: use wq_has_sleeper in unix_dgram_recvmsg

The current unix_dgram_recvmsg does a wake up for every received
datagram. This seems wasteful as only SOCK_DGRAM client sockets in an
n:1 association with a server socket will ever wait because of the
associated condition. The patch below changes the function such that the
wake up only happens if wq_has_sleeper indicates that someone actually
wants to be notified. Testing with SOCK_SEQPACKET and SOCK_DGRAM socket
seems to confirm that this is an improvment.

Signed-Off-By: Rainer Weikusat <rweikusat@mobileactivedefense.com>

Signed-off-by: David S. Miller <davem@davemloft.net>

parent 75c4a57c

net/unix/af_unix.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -1914,8 +1914,10 @@ static int unix_dgram_recvmsg(struct socket sock, struct msghdr msg,
		goto out_unlock;
		}

		if (wq_has_sleeper(&u->peer_wait))
		wake_up_interruptible_sync_poll(&u->peer_wait,
		POLLOUT \| POLLWRNORM \| POLLWRBAND);
		POLLOUT \| POLLWRNORM \|
		POLLWRBAND);

		if (msg->msg_name)
		unix_copy_addr(msg, skb->sk);

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