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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 ACE89C433B4 for ; Thu, 13 May 2021 00:58:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6FA1561108 for ; Thu, 13 May 2021 00:58:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235914AbhEMA7t (ORCPT ); Wed, 12 May 2021 20:59:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232453AbhEMA7f (ORCPT ); Wed, 12 May 2021 20:59:35 -0400 Received: from mail-ed1-x52f.google.com (mail-ed1-x52f.google.com [IPv6:2a00:1450:4864:20::52f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4CD0BC061574 for ; Wed, 12 May 2021 17:58:26 -0700 (PDT) Received: by mail-ed1-x52f.google.com with SMTP id n25so29193137edr.5 for ; Wed, 12 May 2021 17:58:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=SAkFgMmSDBXWFgXDmF2oLvN6riN4KtH7cvTnFetkyEQ=; b=s6kvF/PEuBEHlhVlNGKgmD9IlAE9BIkGL87m8ZrGkif5ql4HQSsG+dV3zHluDFJUMT 5VLuGXyNfkif1KWHltToEaWlzAbECHERtijpqQdWOdrnT+7VapH5MMq3e8vtslEwAEko zqsdHmdNlCB3J0GO1uJpFegDSu4cGcemvT08gFP72tW8ptshuGLtaK67nbzko4cyD1zl uAM1kVeumpnvWvZ5HYoxv9mCYHlVHZDQ29GfSLk2uZUf02QbrER0W9uNXWaZ6Gh5mIj3 4SITj5AWz+dECsgrvP1sUSTHY9yg9tzCZtfF3NlX0LJn/Eg0W3FCvSYod4Sm2X0ZvzDf aX+g== 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:content-transfer-encoding; bh=SAkFgMmSDBXWFgXDmF2oLvN6riN4KtH7cvTnFetkyEQ=; b=GJsx70FS3Wzm+JHMLa3n5P3UH34EVO0qebm4l8obYd9aJiT3bF88fAfzi72VijN70Z /jh1Oz5Wa2GjcKtTeBdarAMNIQUxLVOtC51b5k+V8AXzE6Cv9RSrfjhem4znRkHlGVVj I0yPRmnjgkiFiftyDZUO6P3yqGWZpKrvAu7haQAo/90MoS4qbe3Da3tdwttTpXaK+lNv 08ZAM8qj+ukPTiGo+7Yl0sDTJXT28rGAazEs0oab55St31nNdePYBhaMzi/v690yp5mu SJRP5huWFjnwZvAaNJqZ7uw9pWb/UmEcsadnB/3k4RWVj3JRfTcnvLNuuvfbvgikQxpz ZI/A== X-Gm-Message-State: AOAM531h5cYSbRx4luKeT4eYgLaNO7rt4Q8Z7Qllm77P77NeiziauMW+ Z0v8L5m09oM+JsiyIHzdOGebK7fxcLSAqPk7QKI= X-Google-Smtp-Source: ABdhPJz0pGvYY6oiZfoyOXeRbLauc3nsXbEBPV8qDGP+JGGnx0Z0jCpRgQ/8iYGeYBv7UBRVXBYv2HpOOSeNAqohyt8= X-Received: by 2002:a05:6402:234b:: with SMTP id r11mr46747517eda.137.1620867505040; Wed, 12 May 2021 17:58:25 -0700 (PDT) MIME-Version: 1.0 References: <921e53f3-4b13-aab8-4a9e-e83ff15371e4@nec.com> <701b3c80-b6f0-dcb3-7f3d-da6b74dfc1db@nec.com> In-Reply-To: <701b3c80-b6f0-dcb3-7f3d-da6b74dfc1db@nec.com> From: Yang Shi Date: Wed, 12 May 2021 17:58:13 -0700 Message-ID: Subject: Re: [REGRESSION v5.13-rc1] NULL dereference in do_shrink_slab() To: =?UTF-8?B?Tk9NVVJBIEpVTklDSEko6YeO5p2RIOa3s+S4gCk=?= Cc: Shakeel Butt , Tejun Heo , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "vbabka@suse.cz" , "ktkhai@virtuozzo.com" , "guro@fb.com" , "david@fromorbit.com" , "hannes@cmpxchg.org" , "mhocko@suse.com" , "akpm@linux-foundation.org" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 12, 2021 at 5:10 PM NOMURA JUNICHI(=E9=87=8E=E6=9D=91=E3=80=80= =E6=B7=B3=E4=B8=80) wrote: > > On 2021/05/13 1:31, Yang Shi wrote: > > On Wed, May 12, 2021 at 5:36 AM Shakeel Butt wrot= e: > >> > >> +Tejun Heo > >> > >> On Wed, May 12, 2021 at 3:48 AM NOMURA JUNICHI(=E9=87=8E=E6=9D=91=E3= =80=80=E6=B7=B3=E4=B8=80) > >> wrote: > >>> With the commit 476b30a0949a, if a memcg-aware shrinker is registered= before > >>> cgroup_init(), shrinker->nr_deferred is NULL. However xchg_nr_deferr= ed() > >>> tries to use it as memcg is turned off via "cgroup_disable=3Dmemory". > >>> > >>> Any thoughts? > > > > Thanks for the report. > > > >> > >> Is there a way to find the call chain of "memcg-aware shrinker is > >> registered before cgroup_init()"? > > > > Other than adding some printk in prealloc_memcg_shrinker() then > > checking out the output of dmesg I didn't think of a better way. Not > > sure if we have something like early trace. > > This is the first registration of memcg-aware shrinker: > > [ 1.933693] Call Trace: > [ 1.934694] sget_fc+0x20d/0x2f0 > [ 1.935693] ? compare_single+0x10/0x10 > [ 1.936693] ? shmem_create+0x30/0x30 > [ 1.937693] vfs_get_super+0x3e/0x100 > [ 1.938693] get_tree_nodev+0x16/0x20 > [ 1.939693] shmem_get_tree+0x15/0x20 > [ 1.940693] vfs_get_tree+0x2a/0xc0 > [ 1.941693] fc_mount+0x12/0x40 > [ 1.942693] vfs_kern_mount.part.43+0x61/0xa0 > [ 1.943693] kern_mount+0x24/0x40 > [ 1.944693] shmem_init+0x5c/0xc8 > [ 1.945693] mnt_init+0x12f/0x24a > [ 1.946693] ? __percpu_counter_init+0x8f/0xb0 > [ 1.947693] vfs_caches_init+0xce/0xda > [ 1.948693] start_kernel+0x479/0x4e3 > [ 1.949693] x86_64_start_reservations+0x24/0x26 > [ 1.950693] x86_64_start_kernel+0x8a/0x8d > [ 1.951693] secondary_startup_64_no_verify+0xc2/0xcb > > That is done after command line parsing but before cgroup_init. Thanks for sharing the log. I was not aware that shmem is initialized and mounted so early. > > >> Irrespective I think we can revert a3e72739b7a7e ("cgroup: fix too > >> early usage of static_branch_disable()") as 6041186a3258 ("init: > >> initialize jump labels before command line option parsing") has moved > >> the initialization of jump labels before command line parsing. > > > > Seems make sense to me. If some memcg aware shrinker is registered > > before cgroup_init(), the mem_cgroup_disabled() check in > > prealloc_memcg_shrinker() would return false negative. And I don't > > think any shrinker could be registered before parsing boot > > commandline. > > Thank you. Shakeel 's patch works for me: > > [PATCH] cgroup: disable controllers at parse time > https://lore.kernel.org/linux-mm/20210512201946.2949351-1-shakeelb@goo= gle.com/ Thanks for running the test. > > -- > Jun'ichi Nomura, NEC Corporation / NEC Solution Innovators, Ltd.