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 5D676C35242 for ; Fri, 14 Feb 2020 23:56:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 35279206B6 for ; Fri, 14 Feb 2020 23:56:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724590; bh=kwoRjwghjouGORVQT28JH43vJOyFgoRNW5ZaMzKqNck=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=cZPysaTRgoJWpW9J2ug44MK+LzoLSH04I3TtTXUbaAxbliKx9UBELeqWfvAQNIGHN V7sELzNl9kLOhAwlRH3QKktfgrY42kMpYkg/F9WJk0BMk/LZX6BhXLDQI0nXeYJ9Qd rRBtRBryUHLuL7Lfg5GTo4dTKjSfcPzhBHqm7GzE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728009AbgBNX43 (ORCPT ); Fri, 14 Feb 2020 18:56:29 -0500 Received: from mail.kernel.org ([198.145.29.99]:36254 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727959AbgBNX42 (ORCPT ); Fri, 14 Feb 2020 18:56:28 -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 29C3924650; Fri, 14 Feb 2020 23:56:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724588; bh=kwoRjwghjouGORVQT28JH43vJOyFgoRNW5ZaMzKqNck=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nJEbCip6ux14xv4+i8P9JHP4+p1FfxlAkMvhuMsGILswrsKiQPOxxoM1IgIGgmwyc bMxHMT2uEC9uNRgpJC3yVyRvMJy7ReJDqIgrySGAaiUNCiyBzCk48xDINTeaTkg3MG MIPrA9Beh1lj/sVSLyx5HAFaDEesEfOdu+xRjP/U= 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 05/30] rcu: Add WRITE_ONCE() to rcu_node ->qsmask update Date: Fri, 14 Feb 2020 15:55:42 -0800 Message-Id: <20200214235607.13749-5-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_node structure's ->qsmask 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.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d91c915..bb57c24 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1881,7 +1881,7 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp, WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */ WARN_ON_ONCE(!rcu_is_leaf_node(rnp) && rcu_preempt_blocked_readers_cgp(rnp)); - rnp->qsmask &= ~mask; + WRITE_ONCE(rnp->qsmask, rnp->qsmask & ~mask); trace_rcu_quiescent_state_report(rcu_state.name, rnp->gp_seq, mask, rnp->qsmask, rnp->level, rnp->grplo, rnp->grphi, -- 2.9.5