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=-18.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_IN_DEF_DKIM_WL 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 3D902C433ED for ; Tue, 13 Apr 2021 14:17:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 859E2613B2 for ; Tue, 13 Apr 2021 14:17:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 859E2613B2 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 15D2B6B0036; Tue, 13 Apr 2021 10:17:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 10C136B006E; Tue, 13 Apr 2021 10:17:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EEFAC6B0070; Tue, 13 Apr 2021 10:17:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0110.hostedemail.com [216.40.44.110]) by kanga.kvack.org (Postfix) with ESMTP id D46626B0036 for ; Tue, 13 Apr 2021 10:17:13 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 8F0E21176A1 for ; Tue, 13 Apr 2021 14:17:13 +0000 (UTC) X-FDA: 78027545946.29.22F243A Received: from mail-lf1-f41.google.com (mail-lf1-f41.google.com [209.85.167.41]) by imf30.hostedemail.com (Postfix) with ESMTP id 5FB1AE00012A for ; Tue, 13 Apr 2021 14:17:03 +0000 (UTC) Received: by mail-lf1-f41.google.com with SMTP id x13so17511003lfr.2 for ; Tue, 13 Apr 2021 07:17:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=cZ6kidUHRj7ZJtI2NPkmgGxB5X5ZhGWZ4M1kxQQ4MYE=; b=BbdoH85aPSywvPs8poem3KXLPuVQZ0Kud5h/cKfVLSvTpb3s3WRCjKaOnzd7UiQ0yq 4lA/nQdnm3zKkexJFCHsP8B/J5xwoqKyvfvcAaqxC9Ghrwk7DfHu5Cwy+dDZsN7on+ww UZYSmg69HMoOxDD2sujKtzM1tl72CX+LfmA482OIMXPEx9ZfaDCNcfmDQHGXu4seq4Z9 5MJLRToL1Bxvp7riJ4qerWQwAFlDWg0LwOppAtmUM/JdKapyoDW1zmI18gbeHiBYZVq9 iIvfcN8Ura4CX2Y4SgtdZV0b2q9ADUWn5FUULh2bUhR+aZD1vQbsw7TH3+2WZyKXbUKc 4fcA== 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=cZ6kidUHRj7ZJtI2NPkmgGxB5X5ZhGWZ4M1kxQQ4MYE=; b=iNVIlbUdHjY9rTGNs9uFmvUbLVSlWhk47GqRnSNTxqMwQaSc+el7LYo/5dtUmvDa/s F5mT++n1jd1TPe57VSC6PSr+L6DIn9V1ic3jHx7z0Un16ANrvLZzdsTXKwKam312HaH7 OCeExii2nFjqdn3QM8D1Ca1VKywCZjj+uym4Zz2A1kWIalOUuEI+V5FB9zTqePj67/QE 6rIa1lCD5JDN8qCTR0jRUQ2ZSxCgPWTh3ooU/AAiN8Snc1SDL1UVLVgE3qdckqoZrftC pUrY+ihGTqzTVaelfsVtGxWMo/f1ryZgg6Z5RgClmXwaEtwHnx95GN2QOwzPhrXyMi1r 5BRQ== X-Gm-Message-State: AOAM533Aju0z2xs1eXGhn5j43gqISO7H9Obeb9iPokfxC/8XgSXaXO9h 1rc+8QRFt4D0XrdUC9CepXedSE2WJ31+6IiE8jdcOA== X-Google-Smtp-Source: ABdhPJxUo28t6OhONsKty8BOllgQA7NRCoDBCUDBTN+rZWjQ8O6BwzZERctqfq+bNN0cfipLBWKK93kZVz6RjRMm398= X-Received: by 2002:a05:6512:3703:: with SMTP id z3mr22508451lfr.358.1618323431274; Tue, 13 Apr 2021 07:17:11 -0700 (PDT) MIME-Version: 1.0 References: <20210413065153.63431-1-songmuchun@bytedance.com> <20210413065153.63431-6-songmuchun@bytedance.com> In-Reply-To: <20210413065153.63431-6-songmuchun@bytedance.com> From: Shakeel Butt Date: Tue, 13 Apr 2021 07:16:58 -0700 Message-ID: Subject: Re: [PATCH 5/7] mm: memcontrol: simplify the logic of objcg pinning memcg To: Muchun Song Cc: Roman Gushchin , Johannes Weiner , Michal Hocko , Andrew Morton , Vladimir Davydov , LKML , Linux MM , Xiongchun duan , fam.zheng@bytedance.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5FB1AE00012A X-Stat-Signature: hnp1jeo6gejafpuaostt394bqxfymqen Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf30; identity=mailfrom; envelope-from=""; helo=mail-lf1-f41.google.com; client-ip=209.85.167.41 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618323423-871789 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 Mon, Apr 12, 2021 at 11:58 PM Muchun Song wrote: > > The obj_cgroup_release() and memcg_reparent_objcgs() are serialized by > the css_set_lock. We do not need to care about objcg->memcg being > released in the process of obj_cgroup_release(). So there is no need > to pin memcg before releasing objcg. Remove those pinning logic to > simplfy the code. > > There are only two places that modifies the objcg->memcg. One is the > initialization to objcg->memcg in the memcg_online_kmem(), another > is objcgs reparenting in the memcg_reparent_objcgs(). It is also > impossible for the two to run in parallel. So xchg() is unnecessary > and it is enough to use WRITE_ONCE(). > > Signed-off-by: Muchun Song > Acked-by: Johannes Weiner Reviewed-by: Shakeel Butt