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 BDF30C35242 for ; Fri, 14 Feb 2020 23:56:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91C8C2081E for ; Fri, 14 Feb 2020 23:56:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724608; bh=YJsKqtq5hgtJjA3M1Egg6/HLjFJpeqz3ZuMIDCW7JrM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=klu+WyWxHfwwh06jAYffFUz2d+wyufZx76LLYfr50BPZUsEqA2/HxfXGAWR0bi4Fg UDsMn4/sE6hHp8sYXchQ0JnSIJgijlh476JghuQ0ZND8nzCMhJgi/wwxTsTNwcP7pH hwqKAh9/V8KLcrcoHRNDLg54Gx+QP93tgV1i2INs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727998AbgBNX4s (ORCPT ); Fri, 14 Feb 2020 18:56:48 -0500 Received: from mail.kernel.org ([198.145.29.99]:36592 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727959AbgBNX4r (ORCPT ); Fri, 14 Feb 2020 18:56:47 -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 87BBD2467E; Fri, 14 Feb 2020 23:56:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724606; bh=YJsKqtq5hgtJjA3M1Egg6/HLjFJpeqz3ZuMIDCW7JrM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wdiPAqx6p49VpCnPfC6hRdpN6AZlt0pblNL8FqBA305vSh7B8D5Wuo302nmv6FM0Z THBOWT25H2xBXsvmIU1VHvcYMweZuWutLekYjleqfkcEpFsLi7lMAC/wuzNxvCmFRN 4gYjEzAmd4WIvFxjqhFxo85BLxBp1WCWnbkvLOG4= 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" , Ingo Molnar , Will Deacon Subject: [PATCH tip/core/rcu 10/30] locking/rtmutex: rcu: Add WRITE_ONCE() to rt_mutex ->owner Date: Fri, 14 Feb 2020 15:55:47 -0800 Message-Id: <20200214235607.13749-10-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 rt_mutex structure's ->owner 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 Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon --- kernel/locking/rtmutex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 851bbb1..c9f090d 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -57,7 +57,7 @@ rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner) if (rt_mutex_has_waiters(lock)) val |= RT_MUTEX_HAS_WAITERS; - lock->owner = (struct task_struct *)val; + WRITE_ONCE(lock->owner, (struct task_struct *)val); } static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) -- 2.9.5