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,URIBL_BLOCKED, 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 BA95BCA9EB9 for ; Sat, 26 Oct 2019 13:34:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8DF682070B for ; Sat, 26 Oct 2019 13:34:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572096867; bh=qqvNnOjqCOD1FypEMsgnyT4VFPIZF5ZQH7kISA2LnS8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=bxMtyW7BbdDNnc4mn5B6s5yCLHmH5yXGPit7Z3AzZysXS7S9T8wJja1+AnlHHQerk PR7CVbjppJC17sclDT+Pj/AJS/ED5/0d9zsQqGuSTAouXwBET149eWtbBLgV/2uQUY Y7ceqfxLM0FRFnSqaYOUFR88OYuVb68klXYcMxN0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727437AbfJZNRl (ORCPT ); Sat, 26 Oct 2019 09:17:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:39236 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727430AbfJZNRj (ORCPT ); Sat, 26 Oct 2019 09:17:39 -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 C0699222BE; Sat, 26 Oct 2019 13:17:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572095858; bh=qqvNnOjqCOD1FypEMsgnyT4VFPIZF5ZQH7kISA2LnS8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Krj6lR9dVs9d7WbbPv3Ilr2e2Y9XMm+0XKnktvYD5oaLMtRDF1X2ryCL7KU8se5Y2 yrrMiWLsynddnx2nZgMEVo0lNNZgumJO0o8Pn+hfOfNRoQCv8qdMa4XUeIn3NVL9Zg y+FDFFQf1JT8us0Ln+eE6S++rQAHLO/AM9D2GbXc= 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 5.3 51/99] net: avoid possible false sharing in sk_leave_memory_pressure() Date: Sat, 26 Oct 2019 09:15:12 -0400 Message-Id: <20191026131600.2507-51-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191026131600.2507-1-sashal@kernel.org> References: <20191026131600.2507-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@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 3aa93af51d48d..650873f5b9ce2 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2331,8 +2331,8 @@ 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