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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 982BDC282DD for ; Thu, 9 Jan 2020 18:58:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 605E220721 for ; Thu, 9 Jan 2020 18:58:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 605E220721 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 007878E0008; Thu, 9 Jan 2020 13:58:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EF9018E0005; Thu, 9 Jan 2020 13:58:49 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DBFF98E0008; Thu, 9 Jan 2020 13:58:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0206.hostedemail.com [216.40.44.206]) by kanga.kvack.org (Postfix) with ESMTP id C39028E0005 for ; Thu, 9 Jan 2020 13:58:49 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 5753982499A8 for ; Thu, 9 Jan 2020 18:58:49 +0000 (UTC) X-FDA: 76359007578.08.eye95_2fd769691fb61 X-HE-Tag: eye95_2fd769691fb61 X-Filterd-Recvd-Size: 5385 Received: from mail-wm1-f68.google.com (mail-wm1-f68.google.com [209.85.128.68]) by imf40.hostedemail.com (Postfix) with ESMTP for ; Thu, 9 Jan 2020 18:58:48 +0000 (UTC) Received: by mail-wm1-f68.google.com with SMTP id p17so4048725wmb.0 for ; Thu, 09 Jan 2020 10:58:48 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=MLlNWsBXrOryBNtAajsP6p+tnqNK4xK0vs1yNExUT74=; b=mc+4F4dTDiTjBV2TiEZ0X+eYx9Oauvf+hUi9Bd+fr5l52LUVZfJcz+eYRPZHGmynxE Ff0k8bQKYkVtL7uKO/cMxcSKzmiH0S3Vk15avwYmKpzGpSNgUDunmAiVd/tI/wOIVbO7 nISszMLRoAa45S8Tt27U0ZnToRGObuQyG2H3+uzTsjzG+SigyNeWdlACu5aPfZ7LIQxa fOUA+E3QfcvhuRv6bvcBLcvhdbzryafwQn2edF3K0rr2twvwQdJjCToWJphX6GxfsJw5 DU+PPR5S1PjflmRnMAhUIYPTGJ95vjIS9zOnQQUBzWH+97ZkbckAoq1dWhnniypJ9+GY DcjQ== X-Gm-Message-State: APjAAAW4BIgKst14WFwlFAL+EVhAnXVhR5tuulIONb82TJ7hTGI/luWD KrSL3vej32pmRENgYcyt888= X-Google-Smtp-Source: APXvYqxJvw5/CUhjdAN8kmCIJe1AG6KRvRw2pvb/+xrKwKH1l+cWQxudUwXlSn+EWHzV35YjdU4xBA== X-Received: by 2002:a7b:cd0a:: with SMTP id f10mr6730175wmj.56.1578596327589; Thu, 09 Jan 2020 10:58:47 -0800 (PST) Received: from localhost (ip-37-188-146-105.eurotel.cz. [37.188.146.105]) by smtp.gmail.com with ESMTPSA id q19sm3631897wmc.12.2020.01.09.10.58.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2020 10:58:46 -0800 (PST) Date: Thu, 9 Jan 2020 19:58:44 +0100 From: Michal Hocko To: Wei Yang Cc: hannes@cmpxchg.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com, yang.shi@linux.alibaba.com, alexander.duyck@gmail.com, rientjes@google.com Subject: Re: [Patch v2] mm: thp: grab the lock before manipulation defer list Message-ID: <20200109185844.GW4951@dhcp22.suse.cz> References: <20200109143054.13203-1-richardw.yang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200109143054.13203-1-richardw.yang@linux.intel.com> User-Agent: Mutt/1.12.2 (2019-09-21) 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 Thu 09-01-20 22:30:54, Wei Yang wrote: > As all the other places, we grab the lock before manipulate the defer list. > Current implementation may face a race condition. > > For example, the potential race would be: > > CPU1 CPU2 > mem_cgroup_move_account split_huge_page_to_list > !list_empty > lock > !list_empty > list_del > unlock > lock > # !list_empty might not hold anymore > list_del_init > unlock > > When this sequence happens, the list_del_init() in > mem_cgroup_move_account() would crash if CONFIG_DEBUG_LIST since the > page is already been removed by list_del in split_huge_page_to_list(). > > Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") > > Signed-off-by: Wei Yang > Acked-by: David Rientjes Thanks a lot for the changelog approvements! Acked-by: Michal Hocko > > --- > v2: > * move check on compound outside suggested by Alexander > * an example of the race condition, suggested by Michal > --- > mm/memcontrol.c | 18 +++++++++++------- > 1 file changed, 11 insertions(+), 7 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index bc01423277c5..1492eefe4f3c 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5368,10 +5368,12 @@ static int mem_cgroup_move_account(struct page *page, > } > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > - if (compound && !list_empty(page_deferred_list(page))) { > + if (compound) { > spin_lock(&from->deferred_split_queue.split_queue_lock); > - list_del_init(page_deferred_list(page)); > - from->deferred_split_queue.split_queue_len--; > + if (!list_empty(page_deferred_list(page))) { > + list_del_init(page_deferred_list(page)); > + from->deferred_split_queue.split_queue_len--; > + } > spin_unlock(&from->deferred_split_queue.split_queue_lock); > } > #endif > @@ -5385,11 +5387,13 @@ static int mem_cgroup_move_account(struct page *page, > page->mem_cgroup = to; > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > - if (compound && list_empty(page_deferred_list(page))) { > + if (compound) { > spin_lock(&to->deferred_split_queue.split_queue_lock); > - list_add_tail(page_deferred_list(page), > - &to->deferred_split_queue.split_queue); > - to->deferred_split_queue.split_queue_len++; > + if (list_empty(page_deferred_list(page))) { > + list_add_tail(page_deferred_list(page), > + &to->deferred_split_queue.split_queue); > + to->deferred_split_queue.split_queue_len++; > + } > spin_unlock(&to->deferred_split_queue.split_queue_lock); > } > #endif > -- > 2.17.1 -- Michal Hocko SUSE Labs