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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,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 A57ABC35242 for ; Sat, 15 Feb 2020 00:41:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 75281206CC for ; Sat, 15 Feb 2020 00:41:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581727314; bh=8Kxm3zyAZ3fmYD0WfbKmxTzytBdFkh6lWSPKacF2s0k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=kgH83/lOisExqOJJusLJ+doTQRHdyPn03CG2ruIEo049ivR2Vw7Sqd1rU3nu7xZ+j ruia1FaPiK9caGNVD3Lj3ziWro8d/fOQHwgvWBLmqZWHbgHiw5LGsPLjVcnTCGhyPR RF4FTj7btZkD7JAs0ipSlxXea+wmT6yVUGbizm2U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727880AbgBOAly (ORCPT ); Fri, 14 Feb 2020 19:41:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:48770 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725924AbgBOAlx (ORCPT ); Fri, 14 Feb 2020 19:41:53 -0500 Received: from paulmck-ThinkPad-P72.c.hoisthospitality.com (unknown [62.84.152.189]) (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 2305A222C4; Sat, 15 Feb 2020 00:41:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581727313; bh=8Kxm3zyAZ3fmYD0WfbKmxTzytBdFkh6lWSPKacF2s0k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=x/PDvtCIpq7PWjm7ixuyovbCCGsSAnJGJX/pftT6d7bJ2Xo6zyCm1xifW9MfN/k4/ LK9UAbduoISJy3JNjIEW9rGCi4Lnox2rrsQ2zkJ+898UT42rCVOy/3wLk3m4mdR7XE P63TmHc32Chm2Ugg//FNKzrTimXcl8JYQ+J+JeyE= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 13/18] rcutorture: Add READ_ONCE() to rcu_torture_count and rcu_torture_batch Date: Fri, 14 Feb 2020 16:41:20 -0800 Message-Id: <20200215004125.16953-7-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200215003634.GA16227@paulmck-ThinkPad-P72> References: <20200215003634.GA16227@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" The rcutorture rcu_torture_count and rcu_torture_batch per-CPU variables are read locklessly, so this commit adds the READ_ONCE() to a load in order to avoid various types of compiler vandalism^Woptimization. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely and due to this being rcutorture. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 124160a..0b9ce9a 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1413,8 +1413,8 @@ rcu_torture_stats_print(void) for_each_possible_cpu(cpu) { for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { - pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i]; - batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i]; + pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]); + batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]); } } for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) { -- 2.9.5