Jason Baron [off-list ref] writes:

On 11/19/2015 06:52 PM, Rainer Weikusat wrote:

[...]

quoted

@@ -1590,21 +1718,35 @@ restart:
 			goto out_unlock;
 	}
 
-	if (unix_peer(other) != sk && unix_recvq_full(other)) {
-		if (!timeo) {
+	if (unlikely(unix_peer(other) != sk && unix_recvq_full(other))) {
+		if (timeo) {
+			timeo = unix_wait_for_peer(other, timeo);
+
+			err = sock_intr_errno(timeo);
+			if (signal_pending(current))
+				goto out_free;
+
+			goto restart;
+		}
+
+		if (unix_peer(sk) != other ||
+		    unix_dgram_peer_wake_me(sk, other)) {
 			err = -EAGAIN;
 			goto out_unlock;
 		}

Hi,

So here we are calling unix_dgram_peer_wake_me() without the sk lock the first time
through - right?

Yes. And this is obviously wrong. I spend most of the 'evening time'
(some people would call that 'night time') with testing this and didn't
get to read through it again yet. Thank you for pointing this out. I'll
send an updated patch shortly.