From: Jason Baron <jbaron@akamai.com>
Date: Wed, 25 Jan 2017 02:49:41 +0000 (-0500)
Subject: tcp: correct memory barrier usage in tcp_check_space()
X-Git-Tag: v4.14-rc1~1628^2~15
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=56d806222ace4c3aeae516cd7a855340fb2839d8;p=platform%2Fkernel%2Flinux-rpi3.git

tcp: correct memory barrier usage in tcp_check_space()

sock_reset_flag() maps to __clear_bit() not the atomic version clear_bit().
Thus, we need smp_mb(), smp_mb__after_atomic() is not sufficient.

Fixes: 3c7151275c0c ("tcp: add memory barriers to write space paths")
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6c79075..41dcbd5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5078,7 +5078,7 @@ static void tcp_check_space(struct sock *sk)
 	if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
 		sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
 		/* pairs with tcp_poll() */
-		smp_mb__after_atomic();
+		smp_mb();
 		if (sk->sk_socket &&
 		    test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
 			tcp_new_space(sk);