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 E6667C61DA4 for ; Fri, 3 Feb 2023 15:27:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233362AbjBCP1O (ORCPT ); Fri, 3 Feb 2023 10:27:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233137AbjBCP05 (ORCPT ); Fri, 3 Feb 2023 10:26:57 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8349D8F25C; Fri, 3 Feb 2023 07:26:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=lu9oAwbuGqgDnRk3vRAVJgv15QaK9kCnbeHbuhe5rA0=; b=EhPD/CV7Oko1TZWYSADXXYt/PG uzsAuah2fSS0d/3HtoipFVQbZThMDP1SWU4zX1HT+rMfviXg+CcgLJpkK2jf2ltOd/1roCgYA5TrN KO10wtlhuAkl61snmCxBejQ6AsB04IeqEFc98wGUvmfdfnyEyQ2XJz8q/sxBgsRJkj+zLD2/CARNZ spwWDcJ4A1H7P4g/XaxYH7SU3u8Sr3cjHa9KTtteLvXfXwp5QqEnV/Z7Jtm8Urs4j+0PrmZm+GQXt SZIuV4kyQKQNhUAzXAuBDMn+Hr0Ua0buCV/N4teDGZsmai6FZpSKA/EH9p/0djo/hJDDRaqayQk3x XcAMnqiQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pNxxI-00EPQd-LZ; Fri, 03 Feb 2023 15:26:25 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D85BC30012F; Fri, 3 Feb 2023 16:26:23 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AEAF42C14E63E; Fri, 3 Feb 2023 16:26:23 +0100 (CET) Date: Fri, 3 Feb 2023 16:26:23 +0100 From: Peter Zijlstra To: Waiman Long Cc: Will Deacon , linux-kernel@vger.kernel.org, kernel-team@android.com, Zefan Li , Tejun Heo , Johannes Weiner , cgroups@vger.kernel.org Subject: Re: [PATCH 1/2] cpuset: Fix cpuset_cpus_allowed() to not filter offline CPUs Message-ID: References: <20230131221719.3176-1-will@kernel.org> <20230131221719.3176-2-will@kernel.org> <6b068916-5e1b-a943-1aad-554964d8b746@redhat.com> <83e53632-27ed-8dde-84f4-68c6776d6da8@redhat.com> <773e2f22-211e-163f-64bb-15ae29ad161b@redhat.com> <20230203115045.GB5927@willie-the-truck> 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 Fri, Feb 03, 2023 at 10:13:10AM -0500, Waiman Long wrote: > I think I know where the problem is. It is due to the fact the cpuset > hotplug code doesn't update cpumasks of the tasks in the top cpuset (root) > at all when there is a cpu offline or online event. It is probably because > for some of the tasks in the top cpuset, especially the percpu kthread, > changing their cpumasks can be catastrophic. The hotplug code does update > the cpumasks of the tasks that are not in the top cpuset. This problem is > irrespective of whether v1 or v2 is in use. I've been saying this exact thing for how many mails now?