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 23083C35242 for ; Fri, 14 Feb 2020 23:57:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EFEE5222C4 for ; Fri, 14 Feb 2020 23:57:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724642; bh=kkWVvzcfYyb6s78K6hN+gaYRTSKBYtihy3ywc/PWw0I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lyUVi+sZIkRGv2z6tG00r/35wHLC1Dl+gVS/FxsrAvaN9tIWSs3Bp16T/P54vhrnr Il9n+eSFTP0tA90BBBjCi27H9PBeuP7LQNY92Q0Yr//rNZX1QDL+Ohs80Z9mtbwITV k9+4Nr/SRPVDwUabZ1FKq7I4w53mkJv1r84JcvOY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728080AbgBNX5V (ORCPT ); Fri, 14 Feb 2020 18:57:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:37180 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728202AbgBNX5U (ORCPT ); Fri, 14 Feb 2020 18:57:20 -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 AD0012072D; Fri, 14 Feb 2020 23:57:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724640; bh=kkWVvzcfYyb6s78K6hN+gaYRTSKBYtihy3ywc/PWw0I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eWLuvl+84o+an7+qt+WDrebPj8KayftX7SorxGevPy685saazQGtkr3lEsh60Xi9Y W9vVX2noUO8yStBcG+v4Gyr5NMyqyS6pabjj57WlALznGSZZpmlffESBiJ8IJ/t6iJ g9bnZc/jgLLoO/CmqfnyiWR3HA0g0hNTzq3Mh77E= 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 19/30] rcu: Add WRITE_ONCE() to rcu_state ->gp_start Date: Fri, 14 Feb 2020 15:55:56 -0800 Message-Id: <20200214235607.13749-19-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200214235536.GA13364@paulmck-ThinkPad-P72> References: <20200214235536.GA13364@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 rcu_state structure's ->gp_start field is read locklessly, so this commit adds the WRITE_ONCE() to an update in order to provide proper documentation and READ_ONCE()/WRITE_ONCE() pairing. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_stall.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 3275f27..56df88e 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -102,7 +102,7 @@ static void record_gp_stall_check_time(void) unsigned long j = jiffies; unsigned long j1; - rcu_state.gp_start = j; + WRITE_ONCE(rcu_state.gp_start, j); j1 = rcu_jiffies_till_stall_check(); /* Record ->gp_start before ->jiffies_stall. */ smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */ -- 2.9.5