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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 B0B82C4338F for ; Fri, 13 Aug 2021 16:58:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id DB44260F51 for ; Fri, 13 Aug 2021 16:58:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org DB44260F51 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 54AF08D0005; Fri, 13 Aug 2021 12:58:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4FB278D0001; Fri, 13 Aug 2021 12:58:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4103F8D0005; Fri, 13 Aug 2021 12:58:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0048.hostedemail.com [216.40.44.48]) by kanga.kvack.org (Postfix) with ESMTP id 29E688D0001 for ; Fri, 13 Aug 2021 12:58:31 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 78296181A88E4 for ; Fri, 13 Aug 2021 16:58:30 +0000 (UTC) X-FDA: 78470665980.13.26405DE Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf25.hostedemail.com (Postfix) with ESMTP id 03DF1B00019A for ; Fri, 13 Aug 2021 16:58:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=0UI+t+Lwy1Rr6qFJnN0v7oi7YR7udzcEaq8kOV0xM7I=; b=QrHC9t1fVlZkV1fcJKwUPBPd/F 9s2kmq3nnHEMQ1OXzRUu5fr4XVWugcdRwRxgLxNivhi0zmM7iO4TuB9zRn7pcKzLOWYNPiBV+k7lC 0c5Zg22lsQrcWdL4lpGruck+dHjwAM7ORwXkEnp609DDPJZ8cyuTZPUD4BLnmPBV86eMvdA4irGK0 xgzMkX82QHXS+Oumfp55N6mj8B1DxhtjvpHDvKPySs/e/t+MYFaU/Df5VegeUj7obBMsDPskMqcfp FKWn6xuqnCxlkzfCAvJvUbjYwmRL2DRNvrr1EBorWe4679HSfVCP5qHBJuWk5JFSbBM3Nurx+hNnj 7YxiLE9w==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mEaVC-00FtDZ-5e; Fri, 13 Aug 2021 16:57:57 +0000 Date: Fri, 13 Aug 2021 17:57:50 +0100 From: Matthew Wilcox To: yanghui Cc: akpm@linux-foundation.org, linux-mm@kvack.org, songmuchun@bytedance.com Subject: Re: [PATCH] mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task Message-ID: References: <20210813164053.51481-1-yanghui.def@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210813164053.51481-1-yanghui.def@bytedance.com> X-Rspamd-Queue-Id: 03DF1B00019A Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=QrHC9t1f; dmarc=none; spf=none (imf25.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Rspamd-Server: rspam04 X-Stat-Signature: xgd7kechjpj3ihtz3urqpz937x6rt9tj X-HE-Tag: 1628873909-544767 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, Aug 14, 2021 at 12:40:53AM +0800, yanghui wrote: > +++ b/mm/mempolicy.c > @@ -193,7 +193,7 @@ static int mpol_new_interleave(struct mempolicy *pol, const nodemask_t *nodes) > { > if (nodes_empty(*nodes)) > return -EINVAL; > - pol->nodes = *nodes; > + WRITE_ONCE(pol->nodes, *nodes); typedef struct { DECLARE_BITMAP(bits, MAX_NUMNODES); } nodemask_t; If MAX_NUMNODES is large enough, is WRITE_ONCE going to work? It could be 128 bits, and few architectures have an atomic 128-bit store instruction.