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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 23C25C33CA2 for ; Thu, 9 Jan 2020 14:31:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E679C2072A for ; Thu, 9 Jan 2020 14:31:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E679C2072A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7104F8E0016; Thu, 9 Jan 2020 09:31:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6BFDF8E0001; Thu, 9 Jan 2020 09:31:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5D5D58E0016; Thu, 9 Jan 2020 09:31:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0223.hostedemail.com [216.40.44.223]) by kanga.kvack.org (Postfix) with ESMTP id 46E818E0001 for ; Thu, 9 Jan 2020 09:31:41 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id E3669180AD80F for ; Thu, 9 Jan 2020 14:31:40 +0000 (UTC) X-FDA: 76358334360.07.wire57_2bb45998dc057 X-HE-Tag: wire57_2bb45998dc057 X-Filterd-Recvd-Size: 3846 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Thu, 9 Jan 2020 14:31:40 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 Jan 2020 06:31:38 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,414,1571727600"; d="scan'208";a="254610972" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 09 Jan 2020 06:31:37 -0800 From: Wei Yang To: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org Cc: 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, Wei Yang Subject: [Patch v2] mm: thp: grab the lock before manipulation defer list Date: Thu, 9 Jan 2020 22:30:54 +0800 Message-Id: <20200109143054.13203-1-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 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: 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 --- 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