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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 279A3C48BE5 for ; Wed, 16 Jun 2021 18:08:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C318613DB for ; Wed, 16 Jun 2021 18:08:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231613AbhFPSKl (ORCPT ); Wed, 16 Jun 2021 14:10:41 -0400 Received: from mail.efficios.com ([167.114.26.124]:57400 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231604AbhFPSKi (ORCPT ); Wed, 16 Jun 2021 14:10:38 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 2974B34A6DD; Wed, 16 Jun 2021 14:08:32 -0400 (EDT) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id tBhqg2yREHVV; Wed, 16 Jun 2021 14:08:31 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id D82DF34AACE; Wed, 16 Jun 2021 14:08:31 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com D82DF34AACE DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1623866911; bh=XHjzwm+Qk6dV84haijn1vWryMlunqNQUoDh0KBzrHXY=; h=Date:From:To:Message-ID:MIME-Version; b=h3aaimjb9J8elYZlzXSS44DCxezgoi7MHnYcKywxf5D+bK6D23HAVmH6gUKr/49fi lJoLgwcIqohW8UP93te3Czbqn/KX7a0uwS1/hAceMp0Ch/EkC8TfW99V3qsgLBKv3d xM8E+bUqDwUPAwnurygDvFN1usVQR0F0BnASMWUg5qFtWL/JyFMTqFKAsoyjwtt+ow zkpCM67CGcx/m6l3bROv0Yl4qpqAUUV45FX4GNNL+MWZMWTIvVNaT8/X1+wFlNY2WF 42ZUVsMFeIBSoX7j46gAD9jIeTJij8FoRI47lhdZFrLqKcZdv6tYwkqoc+OvtDhbV9 lG712ceuu1Xmg== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id c-3lUd37Ru1R; Wed, 16 Jun 2021 14:08:31 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id CB6B634A8D5; Wed, 16 Jun 2021 14:08:31 -0400 (EDT) Date: Wed, 16 Jun 2021 14:08:31 -0400 (EDT) From: Mathieu Desnoyers To: Andy Lutomirski Cc: x86 , Dave Hansen , linux-kernel , linux-mm , Andrew Morton , Nicholas Piggin , Peter Zijlstra Message-ID: <987970694.9105.1623866911729.JavaMail.zimbra@efficios.com> In-Reply-To: <74ace142f48db7d0e71b05b5ace72bfe8e0a2652.1623813516.git.luto@kernel.org> References: <74ace142f48db7d0e71b05b5ace72bfe8e0a2652.1623813516.git.luto@kernel.org> Subject: Re: [PATCH 5/8] membarrier, kthread: Use _ONCE accessors for task->mm MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_4018 (ZimbraWebClient - FF89 (Linux)/8.8.15_GA_4026) Thread-Topic: membarrier, kthread: Use _ONCE accessors for task->mm Thread-Index: jSWeuglZnPsonKah7Uz3PhyqbxusGQ== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Jun 15, 2021, at 11:21 PM, Andy Lutomirski luto@kernel.org wrote: > membarrier reads cpu_rq(remote cpu)->curr->mm without locking. Use > READ_ONCE() and WRITE_ONCE() to remove the data races. I notice that kernel/exit.c:exit_mm() also has: current->mm = NULL; I suspect you may want to add a WRITE_ONCE() there as well ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com