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[23.128.96.18]) by mx.google.com with ESMTP id v13si4786780edl.474.2021.06.16.20.09.39; Wed, 16 Jun 2021 20:10:02 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@efficios.com header.s=default header.b=h3aaimjb; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=efficios.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231607AbhFPSKk (ORCPT + 99 others); Wed, 16 Jun 2021 14:10:40 -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