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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45160C25B08 for ; Wed, 17 Aug 2022 17:40:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240677AbiHQRkj (ORCPT ); Wed, 17 Aug 2022 13:40:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39452 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238083AbiHQRkf (ORCPT ); Wed, 17 Aug 2022 13:40:35 -0400 Received: from mail-pg1-x532.google.com (mail-pg1-x532.google.com [IPv6:2607:f8b0:4864:20::532]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BE0BFA1D62; Wed, 17 Aug 2022 10:40:34 -0700 (PDT) Received: by mail-pg1-x532.google.com with SMTP id q16so12558513pgq.6; Wed, 17 Aug 2022 10:40:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc; bh=T2VfnDiJkdhY/17kNIzqsKCO/jg0LojKsxYaZr+7Rkg=; b=KusRphF5DTFe7mhRnFmNMOI7jOlvj2TNyhLSCDAfuKCkSZkVyILc9k4eWlCXBjo/D8 2J2lHM41jl4/+729s5SBzsqUMEvrC57GMo+IgkG1gNUzbCt9r3jDVrQTcIU+h/Ltg40v /WBy0rO5O4U24ET4N/ABS9JvMy0TJRmIIIOBHh0kT93W1Mw5dEnTfEkSHdViKcuks9vK iLbVHtjFTztE53D3sBOZqsmTce3BHEOgwhyvwKl3adB3ENzkvc4mRxl8MlYYm94htLUG +Ztsng8Hqv8SEzQRYgLzU9Iy35ACCmGVIWJS/G/haSnqrp2BafNL88aZARskAu+SuQJ8 4EMQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc; bh=T2VfnDiJkdhY/17kNIzqsKCO/jg0LojKsxYaZr+7Rkg=; b=WTM2Gwlxty95rhFveUzMKw+sukHm4RdFhDXGQ4BRriuLI7HgUyDloR70XHPdsCgb0N 0PSkKmGcgga5I33J9al4ggeu2UYLWYksPYnc3OtvAc/mJy09z6VQRhC61U8DAsTnxdgR /9BVCVZmW9qiwqtQSiIEQ0qbQGmU0chynCyFdFy96xOKuBEuy1/peZjny7Tj8BuW4McN ZmE2XFYu8PVTi8nmOl8BldyxLmQcLlP0UzHhQsr70GFcalrAJJlUMyt0Vw67KH9nZDjN nNNgDMfJgLQdDZhiCccC2YZfRbkSZKihFmYEi8SMW1jdx7JVlGsapujUwVqh4fkelTlk Ry1A== X-Gm-Message-State: ACgBeo3AWMfwJp8cJezvTcRneU8yPODpcHbXg8rmv2G+sPkgGgDqJ/Fo J7GDyU1AQot5rh25iAopxIQ= X-Google-Smtp-Source: AA6agR6+7z7osmZv0Xqd5YkMvSapXLzjYDM02hv/ytXpbZkfU+WfpooBrrnWGc43yI1lf8QcdP+Cag== X-Received: by 2002:a63:80c7:0:b0:41c:62dc:7d10 with SMTP id j190-20020a6380c7000000b0041c62dc7d10mr23382200pgd.313.1660758034134; Wed, 17 Aug 2022 10:40:34 -0700 (PDT) Received: from localhost (2603-800c-1a02-1bae-a7fa-157f-969a-4cde.res6.spectrum.com. [2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id r21-20020a170902e3d500b0016f1319d2a7sm160185ple.297.2022.08.17.10.40.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Aug 2022 10:40:33 -0700 (PDT) Sender: Tejun Heo Date: Wed, 17 Aug 2022 07:40:32 -1000 From: Tejun Heo To: Mukesh Ojha Cc: Michal =?iso-8859-1?Q?Koutn=FD?= , Xuewen Yan , Imran Khan , lizefan.x@bytedance.com, hannes@cmpxchg.org, tglx@linutronix.de, steven.price@arm.com, peterz@infradead.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Zhao Gongyi , Zhang Qiao Subject: Re: [PATCH cgroup/for-6.0-fixes] cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock Message-ID: References: <224b19f3-912d-b858-7af4-185b8e55bc66@quicinc.com> <20220815090556.GB27407@blackbody.suse.cz> <20220815093934.GA29323@blackbody.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 15, 2022 at 01:27:38PM -1000, Tejun Heo wrote: > Bringing up a CPU may involve creating new tasks which requires read-locking > threadgroup_rwsem, so threadgroup_rwsem nests inside cpus_read_lock(). > However, cpuset's ->attach(), which may be called with thredagroup_rwsem > write-locked, also wants to disable CPU hotplug and acquires > cpus_read_lock(), leading to a deadlock. > > Fix it by guaranteeing that ->attach() is always called with CPU hotplug > disabled and removing cpus_read_lock() call from cpuset_attach(). > > Signed-off-by: Tejun Heo Applied to cgroup/for-6.0-fixes w/ commit message and comment update suggested by Xuewen and Fixes / stable tags added. Thanks. -- tejun