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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 AE866C5519F for ; Wed, 25 Nov 2020 13:44:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C93C2206D8 for ; Wed, 25 Nov 2020 13:44:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="n+767GOp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729639AbgKYNnn (ORCPT ); Wed, 25 Nov 2020 08:43:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727858AbgKYNnm (ORCPT ); Wed, 25 Nov 2020 08:43:42 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 644C8C0613D4 for ; Wed, 25 Nov 2020 05:43:42 -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=CXjJBBQ509MLNGRCW6YegSHGZPRzXtIgnFrJbQeTLDg=; b=n+767GOpL38zFly8/odSqqLSuc WKrZ63sg+Iz63A3vJoVwiJ8sfA3EgoUSVs/35q5sPyoIdYYU16sX+R+n3VZxv/JsrQNDF3JtWz5Pa 5s3fVTy+t+TiVZKpRPx/px/3q+L+1jPJsDwcunHIzNHq0tzqUWpeXaJADyJ5ptO1RxO3OnH3SZ25S QZtmI95KW8Fc9QEkxx8MIy0jJMsbivDnrmZ/rZQ5s9Y/XIfb3e7H5YGFb2mkezyiNXlcAAXiEqBjk nqRWp7qarVDmOHPRxYHqDXjWVAxIFuLf2A68K5RWmfOKSfzk2qHZiZ4VPJ5UkgDBCcteHVXchmCnI t2FnXaaA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1khv4C-0007xr-2H; Wed, 25 Nov 2020 13:42:40 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 3178B3012DF; Wed, 25 Nov 2020 14:42:38 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E0EDC200DF1C9; Wed, 25 Nov 2020 14:42:37 +0100 (CET) Date: Wed, 25 Nov 2020 14:42:37 +0100 From: Peter Zijlstra To: "Joel Fernandes (Google)" Cc: Nishanth Aravamudan , Julien Desfossez , Tim Chen , Vineeth Pillai , Aaron Lu , Aubrey Li , tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org, torvalds@linux-foundation.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , vineeth@bitbyteword.org, Chen Yu , Christian Brauner , Agata Gruza , Antonio Gomez Iglesias , graf@amazon.com, konrad.wilk@oracle.com, dfaggioli@suse.com, pjt@google.com, rostedt@goodmis.org, derkling@google.com, benbjiang@tencent.com, Alexandre Chartre , James.Bottomley@hansenpartnership.com, OWeisse@umich.edu, Dhaval Giani , Junaid Shahid , jsbarnes@google.com, chris.hyser@oracle.com, Ben Segall , Josh Don , Hao Luo , Tom Lendacky , Aubrey Li , "Paul E. McKenney" , Tim Chen Subject: Re: [PATCH -tip 26/32] sched: Add a second-level tag for nested CGroup usecase Message-ID: <20201125134237.GZ2414@hirez.programming.kicks-ass.net> References: <20201117232003.3580179-1-joel@joelfernandes.org> <20201117232003.3580179-27-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201117232003.3580179-27-joel@joelfernandes.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 17, 2020 at 06:19:56PM -0500, Joel Fernandes (Google) wrote: > From: Josh Don > > Google has a usecase where the first level tag to tag a CGroup is not > sufficient. So, a patch is carried for years where a second tag is added which > is writeable by unprivileged users. > > Google uses DAC controls to make the 'tag' possible to set only by root while > the second-level 'color' can be changed by anyone. The actual names that > Google uses is different, but the concept is the same. > > The hierarchy looks like: > > Root group > / \ > A B (These are created by the root daemon - borglet). > / \ \ > C D E (These are created by AppEngine within the container). > > The reason why Google has two parts is that AppEngine wants to allow a subset of > subcgroups within a parent tagged cgroup sharing execution. Think of these > subcgroups belong to the same customer or project. Because these subcgroups are > created by AppEngine, they are not tracked by borglet (the root daemon), > therefore borglet won't have a chance to set a color for them. That's where > 'color' file comes from. Color could be set by AppEngine, and once set, the > normal tasks within the subcgroup would not be able to overwrite it. This is > enforced by promoting the permission of the color file in cgroupfs. Why can't the above work by setting 'tag' (that's a terrible name, why does that still live) in CDE? Have the most specific tag live. Same with that thread stuff. All this API stuff here is a complete and utter trainwreck. Please just delete the patches and start over. Hint: if you use stop_machine(), you're doing it wrong. At best you now have the requirements sorted.