From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751643AbeA3KWH (ORCPT ); Tue, 30 Jan 2018 05:22:07 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:42595 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751373AbeA3KWF (ORCPT ); Tue, 30 Jan 2018 05:22:05 -0500 Date: Tue, 30 Jan 2018 11:21:56 +0100 From: Peter Zijlstra To: Tejun Heo Cc: Ingo Molnar , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Li Zefan , Johannes Weiner Subject: Re: [PATCH v4.15-rc9] sched, cgroup: Don't reject lower cpu.max on ancestors Message-ID: <20180130102156.GS2249@hirez.programming.kicks-ass.net> References: <20180122192618.GA1771050@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180122192618.GA1771050@devbig577.frc2.facebook.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 22, 2018 at 11:26:18AM -0800, Tejun Heo wrote: > While adding cgroup2 interface for the cpu controller, 0d5936344f30 > ("sched: Implement interface for cgroup unified hierarchy") forgot to > update input validation and left it to reject cpu.max config if any > descendant has set a higher value. > > cgroup2 officially supports delegation and a descendant must not be > able to restrict what its ancestors can configure. For absolute > limits such as cpu.max and memory.max, this means that the config at > each level should only act as the upper limit at that level and > shouldn't interfere with what other cgroups can configure. *blink* what? afaiu the existing code does exactly the opposite, it forces the descendants to configure less than the parent allows. You're taking out an error condition and silently allowing descentant misconfiguration. How does that make sense?