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=-15.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 0A50DCA9EB9 for ; Sat, 26 Oct 2019 13:20:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C4A90214DA for ; Sat, 26 Oct 2019 13:20:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572096034; bh=K0atXUxpG9WhD5XI8JOI5g1VkCdz/TVL+kT1pKqe/Qk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=iqIRHADr27O4XMF/vqF6ojXJ7UhJ5vr8gtUGPrPQXPWlxedcszS614EgfrEu+kyOc wfpOrz9rUKdrkX9rAyKsH2y6uWmH0oocgcznVNMlCpPi59xp9uNfMsAauWdZL+U5eU sND0C6CfVH3IAYIEP7y9ugAcPW6KbDF5Ev4+Q0tQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727379AbfJZNUc (ORCPT ); Sat, 26 Oct 2019 09:20:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:42128 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726964AbfJZNUV (ORCPT ); Sat, 26 Oct 2019 09:20:21 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 39D67206DD; Sat, 26 Oct 2019 13:20:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572096020; bh=K0atXUxpG9WhD5XI8JOI5g1VkCdz/TVL+kT1pKqe/Qk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JkhPCydNFxhLfuMZS6dAEiNyF/MMbHuBbqL43qwodhmxaZ/QvGLvfOPVQRtyg1S7i 98xP8LB6xSjZ+KbTlAkuwUZnFi+ifzjG59fpVnvL8eO79q86c2uM7GdH2m/9cc+DXw xeE6oT4KdnVseRDJi9URK+cK+h1KHu40P7+iuq0M= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Eric Dumazet , Jakub Kicinski , Sasha Levin , netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 34/59] net: avoid possible false sharing in sk_leave_memory_pressure() Date: Sat, 26 Oct 2019 09:18:45 -0400 Message-Id: <20191026131910.3435-34-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191026131910.3435-1-sashal@kernel.org> References: <20191026131910.3435-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 f881eea1c4a47..fa38a2d3cb106 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