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From: Jason Baron <jbaron@akamai.com>
To: eric.dumazet@gmail.com, davem@davemloft.net
Cc: netdev@vger.kernel.org
Subject: [PATCH v2 net-next 1/2] tcp: replace smp_mb__after_atomic() with smp_mb() in tcp_poll()
Date: Wed, 22 Jun 2016 11:32:50 -0400	[thread overview]
Message-ID: <ac8b2dae8215afe2027e1a581f712a435bd91d06.1466608332.git.jbaron@akamai.com> (raw)
In-Reply-To: <cover.1466608332.git.jbaron@akamai.com>
In-Reply-To: <cover.1466608332.git.jbaron@akamai.com>

From: Jason Baron <jbaron@akamai.com>

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

Fixes: 3c7151275c0c ("tcp: add memory barriers to write space paths")
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Jason Baron <jbaron@akamai.com>
---
 net/ipv4/tcp_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 94d4aff97523..3ba526ecdeb9 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4987,7 +4987,7 @@ 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);
-- 
2.6.1

  reply	other threads:[~2016-06-22 15:35 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-22 15:32 [PATCH v2 net-next 0/2] tcp: reduce cpu usage when SO_SNDBUF is set Jason Baron
2016-06-22 15:32 ` Jason Baron [this message]
2016-06-22 15:32 ` [PATCH v2 net-next 2/2] " Jason Baron
2016-06-22 17:34   ` Eric Dumazet
2016-06-22 18:18     ` Jason Baron
2016-06-22 18:43       ` Eric Dumazet
2016-06-22 18:51         ` Eric Dumazet
2016-06-22 19:20           ` Jason Baron
2016-06-22 20:15             ` Eric Dumazet

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