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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 23119C4338F for ; Fri, 30 Jul 2021 02:34:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3DE660F4A for ; Fri, 30 Jul 2021 02:34:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235466AbhG3Cer (ORCPT ); Thu, 29 Jul 2021 22:34:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230200AbhG3Cep (ORCPT ); Thu, 29 Jul 2021 22:34:45 -0400 Received: from mail-pl1-x636.google.com (mail-pl1-x636.google.com [IPv6:2607:f8b0:4864:20::636]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A429C0613C1 for ; Thu, 29 Jul 2021 19:34:41 -0700 (PDT) Received: by mail-pl1-x636.google.com with SMTP id q2so9258084plr.11 for ; Thu, 29 Jul 2021 19:34:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=OrnW4TDngOfmT4k1Ifughwagt8BmS1Mfblfsw7s1vyw=; b=sCBp+WebYpI5Z9F5/Q3Yqxn7z/iABDei+1bGAY6Eb+qvxZnqBq3AoNCMtY7SjlRdCw V0gox9Fyqip/WZUwEbnACYCEwQP9fPDxfzFbSVadNYyenjP4DvwlYI6sfO+0wo9PQO++ DeEOjlwQGzxR7u2teqGXnaffsL1lNMExo9NQlJR00TUC0qx/6sYJopIwQuuBZa+k8aEq f6zX0jjLeZGNF0zhY86tGIVqrkY+g6RKKUOvyPh7eP2Cx+MRJIYvdv8pAkt4cG1OLDE+ nfBed/rDolcbxTZZsQ1QjFY5GQAtGOCGH6OhFu7v/3eWULQji7xUH18UC5PQig+rY30B mG4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=OrnW4TDngOfmT4k1Ifughwagt8BmS1Mfblfsw7s1vyw=; b=cgQBeEucWG4Mu+RWUD8YjpDAGK0K3YA6ufkHIkP1K/LUpX6bFYsbb0Qv9fZNdYvsPd TdSTE3davVxn/6tFlqkjld9YYK/FvxNFDzMQT5EuPGq1n/hONaBx4VJDav/9hXnqKedv ZVTFYnfOK51bhDH4L0j3XwCjbIE+X34zTLMSDXQTj1gsA+B+YUkVu2Y/5ATVQAWOdDlH Zjn13kEBGYEqNnE5SV3VLwg4ykQpIENWa8axBGB3iQbm89Y3jpIOYKo0eRsjP7md/k9t EH6Ckg3Uz/0ewvTuQ+UTP32/ic/jHvSilr1WEmNlA2Ydzlk6FHaZnm6oaf3aIXhLlQIj sAJw== X-Gm-Message-State: AOAM533mP8EBD6ggyimBmkhR42iocPDnUr5Pc6z9QahkjmzIJplvC1oA i94P6NiJJo+RlOiD6LVnEV21JE6++23KImPRg09yAQ== X-Google-Smtp-Source: ABdhPJzmgpl+O4iYQgoT3Ku82TzGbEGeGUtmB2tMZ58JKjkpbyAh74p90jNkObUdqkedLXTRssh5VexSBlLg96Ex/rE= X-Received: by 2002:a62:92d7:0:b029:32c:8c46:9491 with SMTP id o206-20020a6292d70000b029032c8c469491mr280988pfd.2.1627612480527; Thu, 29 Jul 2021 19:34:40 -0700 (PDT) MIME-Version: 1.0 References: <20210729125755.16871-1-linmiaohe@huawei.com> <20210729125755.16871-6-linmiaohe@huawei.com> <29c4bb2a-ceaf-6c8b-c222-38b30460780f@huawei.com> In-Reply-To: <29c4bb2a-ceaf-6c8b-c222-38b30460780f@huawei.com> From: Muchun Song Date: Fri, 30 Jul 2021 10:33:59 +0800 Message-ID: Subject: Re: [External] Re: [PATCH 5/5] mm, memcg: always call __mod_node_page_state() with preempt disabled To: Miaohe Lin Cc: Shakeel Butt , Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Roman Gushchin , Matthew Wilcox , Alex Shi , Wei Yang , Linux MM , LKML , Cgroups Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 30, 2021 at 9:52 AM Miaohe Lin wrote: > > On 2021/7/29 22:39, Shakeel Butt wrote: > > On Thu, Jul 29, 2021 at 5:58 AM Miaohe Lin wrote: > >> > >> We should always ensure __mod_node_page_state() is called with preempt > >> disabled or percpu ops may manipulate the wrong cpu when preempt happened. > >> > >> Fixes: b4e0b68fbd9d ("mm: memcontrol: use obj_cgroup APIs to charge kmem pages") > >> Signed-off-by: Miaohe Lin > >> --- > >> mm/memcontrol.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c > >> index 70a32174e7c4..616d1a72ece3 100644 > >> --- a/mm/memcontrol.c > >> +++ b/mm/memcontrol.c > >> @@ -697,8 +697,8 @@ void __mod_lruvec_page_state(struct page *page, enum node_stat_item idx, > >> memcg = page_memcg(head); > >> /* Untracked pages have no memcg, no lruvec. Update only the node */ > >> if (!memcg) { > >> - rcu_read_unlock(); > >> __mod_node_page_state(pgdat, idx, val); > >> + rcu_read_unlock(); > > > > This rcu is for page_memcg. The preemption and interrupts are disabled > > across __mod_lruvec_page_state(). > > > > I thought it's used to protect __mod_node_page_state(). Looks somewhat confusing for me. > Many thanks for pointing this out! Hi Miaohe, git show b4e0b68fbd9d can help you find out why we add the rcu read lock around it. Thanks. > > >> return; > >> } > >> > >> -- > >> 2.23.0 > >> > > . > > >