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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 3099CC00523 for ; Fri, 3 Jan 2020 23:39:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 065F721835 for ; Fri, 3 Jan 2020 23:39:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726508AbgACXj0 (ORCPT ); Fri, 3 Jan 2020 18:39:26 -0500 Received: from mga06.intel.com ([134.134.136.31]:46435 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726232AbgACXjZ (ORCPT ); Fri, 3 Jan 2020 18:39:25 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Jan 2020 15:39:25 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,392,1571727600"; d="scan'208";a="252740373" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 03 Jan 2020 15:39:23 -0800 Date: Sat, 4 Jan 2020 07:39:25 +0800 From: Wei Yang To: David Rientjes Cc: Wei Yang , hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yang.shi@linux.alibaba.com Subject: Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list Message-ID: <20200103233925.GA3678@richard> Reply-To: Wei Yang References: <20200103143407.1089-1-richardw.yang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 03, 2020 at 11:29:06AM -0800, David Rientjes wrote: >On Fri, 3 Jan 2020, Wei Yang wrote: > >> As all the other places, we grab the lock before manipulate the defer list. >> Current implementation may face a race condition. >> >> Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") >> >> Signed-off-by: Wei Yang >> >> --- >> I notice the difference during code reading and just confused about the >> difference. No specific test is done since limited knowledge about cgroup. >> >> Maybe I miss something important? > >The check for !list_empty(page_deferred_list(page)) must certainly be >serialized with doing list_del_init(page_deferred_list(page)). > Hi David Would you mind giving more information? You mean list_empty and list_del_init is atomic? -- Wei Yang Help you, Help me