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=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 B306EC54E4B for ; Mon, 11 May 2020 21:00:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9E8A9208DB for ; Mon, 11 May 2020 21:00:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732207AbgEKVAh (ORCPT ); Mon, 11 May 2020 17:00:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44182 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1732121AbgEKVAM (ORCPT ); Mon, 11 May 2020 17:00:12 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 26BCBC061A0C; Mon, 11 May 2020 14:00:11 -0700 (PDT) Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jYFWz-00063U-8M; Mon, 11 May 2020 23:00:09 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 58B321C0872; Mon, 11 May 2020 22:59:45 +0200 (CEST) Date: Mon, 11 May 2020 20:59:45 -0000 From: "tip-bot2 for Paul E. McKenney" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/rcu] rcu: Add WRITE_ONCE() to rcu_node ->boost_tasks Cc: "Paul E. McKenney" , x86 , LKML MIME-Version: 1.0 Message-ID: <158923078527.390.9732610515449854619.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the core/rcu branch of tip: Commit-ID: 5822b8126ff01e0baaf7d5168adc4ac8aeae088c Gitweb: https://git.kernel.org/tip/5822b8126ff01e0baaf7d5168adc4ac8aeae088c Author: Paul E. McKenney AuthorDate: Sat, 04 Jan 2020 10:44:41 -08:00 Committer: Paul E. McKenney CommitterDate: Mon, 27 Apr 2020 11:01:16 -07:00 rcu: Add WRITE_ONCE() to rcu_node ->boost_tasks The rcu_node structure's ->boost_tasks 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_plugin.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index ed6bb46..664d0aa 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -505,7 +505,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags) /* Snapshot ->boost_mtx ownership w/rnp->lock held. */ drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; if (&t->rcu_node_entry == rnp->boost_tasks) - rnp->boost_tasks = np; + WRITE_ONCE(rnp->boost_tasks, np); } /* @@ -1082,7 +1082,7 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) rnp->qsmask == 0 && (ULONG_CMP_GE(jiffies, rnp->boost_time) || rcu_state.cbovld))) { if (rnp->exp_tasks == NULL) - rnp->boost_tasks = rnp->gp_tasks; + WRITE_ONCE(rnp->boost_tasks, rnp->gp_tasks); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcu_wake_cond(rnp->boost_kthread_task, READ_ONCE(rnp->boost_kthread_status));