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=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 785A6CA9EB9 for ; Sat, 26 Oct 2019 13:34:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 47634206DD for ; Sat, 26 Oct 2019 13:34:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572096885; bh=ujFA00CPmwDhYK78Zmsep9jkd82hTMcP1udgDVX1RKc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Jqg4k4NS/rUzrS4RUFgfLE2SXnTKQIa3agb4iXOqIXgYcMrQRpNq4r3v27jBB+gDF czCrnaAsdhVEPl7/vEvGJNnmoiXnl+TUvhnW2nrhRE+mx02XvK34c7XwGwAI08oFbU bIvzcrsfZJFReYhEhg1u53F7EtO2cIMyaMCWeNTQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728256AbfJZNeo (ORCPT ); Sat, 26 Oct 2019 09:34:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:39198 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727400AbfJZNRg (ORCPT ); Sat, 26 Oct 2019 09:17:36 -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 2A11D222D1; Sat, 26 Oct 2019 13:17:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572095856; bh=ujFA00CPmwDhYK78Zmsep9jkd82hTMcP1udgDVX1RKc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XOjf+NJ7hC5eUo0Q6YiToA5Setzn2dBn0jVdA5cB8/y85Db3O2b21Efey2ecP/JQF QvTfyGOM0mbGkBHyfwgPx17WWh8v0R3opvxQgPaKchxcgSjbFQIi31jVgO26KV6Pty zNndsr6wjlj0iM45kMYAI54QKIQKM2i4oNBjZh2g= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Eric Dumazet , Zhang Yu , Wang Li , Li RongQing , Jason Wang , Jakub Kicinski , Sasha Levin , netdev@vger.kernel.org Subject: [PATCH AUTOSEL 5.3 50/99] tun: remove possible false sharing in tun_flow_update() Date: Sat, 26 Oct 2019 09:15:11 -0400 Message-Id: <20191026131600.2507-50-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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet [ Upstream commit 4ffdd22e49f47db543906d75453a0048a53071ab ] 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 (e->queue_index != queue_index) e->queue_index = queue_index; to : e->queue_index = queue_index; Note that the code using jiffies has no issue, since jiffies has volatile attribute. if (e->updated != jiffies) e->updated = jiffies; Fixes: 83b1bc122cab ("tun: align write-heavy flow entry members to a cache line") Signed-off-by: Eric Dumazet Cc: Zhang Yu Cc: Wang Li Cc: Li RongQing Acked-by: Jason Wang Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/tun.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index aab0be40d4430..dd1d7dc361f1c 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -526,8 +526,8 @@ static void tun_flow_update(struct tun_struct *tun, u32 rxhash, e = tun_flow_find(head, rxhash); if (likely(e)) { /* TODO: keep queueing to old queue until it's empty? */ - if (e->queue_index != queue_index) - e->queue_index = queue_index; + if (READ_ONCE(e->queue_index) != queue_index) + WRITE_ONCE(e->queue_index, queue_index); if (e->updated != jiffies) e->updated = jiffies; sock_rps_record_flow_hash(e->rps_rxhash); -- 2.20.1