From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D82C9C2D0DB for ; Fri, 24 Jan 2020 11:34:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A0E5722527 for ; Fri, 24 Jan 2020 11:34:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579865692; bh=W2BbV80fV5kcpEqWWvIsJPKoZwQoUK2B7KmrxaYr6+g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=IukgrdFpLQMVx7FiXNs5A0bW40dUKAC95gXdvxR8Pnf/DRlxT8Y1i3Bw8KWhKGnQH SuJXZES5h5HQ5Z+5dNY0sqRfwnJ5auf1980Hb7EIosOzE7X32bKFsgUZfEXnRiV1Nb Za4gMcRoA+TGtKVrh80jMEQVUiNzmK028FSHyM4M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404578AbgAXLev (ORCPT ); Fri, 24 Jan 2020 06:34:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:54732 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404554AbgAXLer (ORCPT ); Fri, 24 Jan 2020 06:34:47 -0500 Received: from localhost (ip-213-127-102-57.ip.prioritytelecom.net [213.127.102.57]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3B8D1214AF; Fri, 24 Jan 2020 11:34:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579865687; bh=W2BbV80fV5kcpEqWWvIsJPKoZwQoUK2B7KmrxaYr6+g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CH/kY4ncBRM26DCEy/Qgm/Rw9V3ZOVmgxGNifz3B37gCJSgIpUSd1jpp4IZNrz11U IK49omo9md3H6fHt6plBoxJe5XQZ/13nfsZ6SQe6UzoKAzT7jehTThnaSJIjA+2LnW KesJjiLg/XBko6iwKke/x34cXmwpZP/zXo61G1ug= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 4.19 599/639] net: avoid possible false sharing in sk_leave_memory_pressure() Date: Fri, 24 Jan 2020 10:32:49 +0100 Message-Id: <20200124093204.391643194@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200124093047.008739095@linuxfoundation.org> References: <20200124093047.008739095@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet [ Upstream commit 503978aca46124cd714703e180b9c8292ba50ba7 ] As mentioned in https://github.com/google/ktsan/wiki/READ_ONCE-and-WRITE_ONCE#it-may-improve-performance a C compiler can legally transform : if (memory_pressure && *memory_pressure) *memory_pressure = 0; to : if (memory_pressure) *memory_pressure = 0; Fixes: 0604475119de ("tcp: add TCPMemoryPressuresChrono counter") Fixes: 180d8cd942ce ("foundations of per-cgroup memory pressure controlling.") Fixes: 3ab224be6d69 ("[NET] CORE: Introducing new memory accounting interface.") Signed-off-by: Eric Dumazet Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/core/sock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/core/sock.c b/net/core/sock.c index bbde5f6a7dc91..b9ec14f2c729a 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2179,8 +2179,8 @@ static void sk_leave_memory_pressure(struct sock *sk) } else { unsigned long *memory_pressure = sk->sk_prot->memory_pressure; - if (memory_pressure && *memory_pressure) - *memory_pressure = 0; + if (memory_pressure && READ_ONCE(*memory_pressure)) + WRITE_ONCE(*memory_pressure, 0); } } -- 2.20.1