Patch "tcp: make challenge acks faster" has been added to the 3.14-stable tree

Patch "tcp: make challenge acks faster" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    tcp: make challenge acks faster

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp_acks_speedup.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Aug 17 10:00:14 CEST 2016
Date: Wed, 17 Aug 2016 10:00:14 +0200
To: Greg KH <gregkh@linuxfoundation.org>
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: tcp: make challenge acks faster

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

When backporting upstream commit 75ff39ccc1bd ("tcp: make challenge acks
less predictable") I negelected to use the correct ACCESS* type macros.
This fixes that up to hopefully speed things up a bit more.

Thanks to Chas Wiliams for the 3.10 backport which reminded me of this.

Cc: Yue Cao <ycao009@ucr.edu>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Chas Williams <ciwillia@brocade.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/ipv4/tcp_input.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3299,12 +3299,12 @@ static void tcp_send_challenge_ack(struc
 		u32 half = (sysctl_tcp_challenge_ack_limit + 1) >> 1;
 
 		challenge_timestamp = now;
-		challenge_count = half +
+		ACCESS_ONCE(challenge_count) = half +
 				  prandom_u32_max(sysctl_tcp_challenge_ack_limit);
 	}
-	count = challenge_count;
+	count = ACCESS_ONCE(challenge_count);
 	if (count > 0) {
-		challenge_count = count - 1;
+		ACCESS_ONCE(challenge_count) = count - 1;
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK);
 		tcp_send_ack(sk);
 	}


Patches currently in stable-queue which might be from gregkh@linuxfoundation.org are

queue-3.14/tcp_acks_speedup.patch