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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D42A2C25B4E for ; Fri, 20 Jan 2023 14:58:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231239AbjATO66 (ORCPT ); Fri, 20 Jan 2023 09:58:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230113AbjATO65 (ORCPT ); Fri, 20 Jan 2023 09:58:57 -0500 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D34141B72; Fri, 20 Jan 2023 06:58:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1674226736; x=1705762736; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=gBOkIamQG9QHF/G+o/K7jdNTIqklSm7vqXdeE00im04=; b=mKUXBmlskJvFvotzlt/RmAf/zPmcbzAgksE51uLigMaSTbIgtyxjr6M9 GeJjHzVcF2Iz2d6H7fw2CdDnhz1ZPuFiIN5Mozx6Fxg7bS2NIszLUdIZN w4AvrP2FVpx3taGNUATqMlXjB79toy7RXf29FMNSXF/qQ3GDMKHJ1SEv/ S3gPOB0Z9X8N5D3FgGvIswgU9rlWhCP425aZI9Olhn8LXC93XiwpeGEka DvUYv5BHzcT/PQp7GExVRH6WShAVRgvW/TCYIR6LnX9ZUDEWqxO2e7WN9 N7GgFbG++xDZyh+csLGL9/yUATD8LsKN8guJZLhK01ybq1/2tLOaQMJpA A==; X-IronPort-AV: E=McAfee;i="6500,9779,10595"; a="352849378" X-IronPort-AV: E=Sophos;i="5.97,232,1669104000"; d="scan'208";a="352849378" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jan 2023 06:58:21 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10595"; a="638175957" X-IronPort-AV: E=Sophos;i="5.97,232,1669104000"; d="scan'208";a="638175957" Received: from avandeve-mobl.amr.corp.intel.com (HELO [10.209.102.161]) ([10.209.102.161]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jan 2023 06:58:21 -0800 Message-ID: <562c883b-b2c3-3a27-f045-97e7e3281e0b@linux.intel.com> Date: Fri, 20 Jan 2023 06:58:20 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH] Fix data race in mark_rt_mutex_waiters Content-Language: en-US To: Hernan Ponce de Leon , peterz@infradead.org, mingo@redhat.com, will@kernel.org, longman@redhat.com, boqun.feng@gmail.com, akpm@osdl.org, tglx@linutronix.de, joel@joelfernandes.org, paulmck@kernel.org, stern@rowland.harvard.edu, diogo.behrens@huawei.com, jonas.oberhauser@huawei.com Cc: linux-kernel@vger.kernel.org, Hernan Ponce de Leon , stable@vger.kernel.org References: <20230120135525.25561-1-hernan.poncedeleon@huaweicloud.com> From: Arjan van de Ven In-Reply-To: <20230120135525.25561-1-hernan.poncedeleon@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/20/2023 5:55 AM, Hernan Ponce de Leon wrote: > From: Hernan Ponce de Leon > > 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 010cf4e6d0b8..7ed9472edd48 100644 > --- a/kernel/locking/rtmutex.c > +++ b/kernel/locking/rtmutex.c > @@ -235,7 +235,7 @@ static __always_inline void mark_rt_mutex_waiters(struct rt_mutex_base *lock) > unsigned long owner, *p = (unsigned long *) &lock->owner; > > do { > - owner = *p; > + owner = READ_ONCE(*p); > } while (cmpxchg_relaxed(p, owner, I don't see how this makes any difference at all. *p can be read a dozen times and it's fine; cmpxchg has barrier semantics for compilers afaics