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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A5F49C47255 for ; Mon, 11 May 2020 17:03:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8560E206CC for ; Mon, 11 May 2020 17:03:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730901AbgEKRDe (ORCPT ); Mon, 11 May 2020 13:03:34 -0400 Received: from foss.arm.com ([217.140.110.172]:36284 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730743AbgEKRDa (ORCPT ); Mon, 11 May 2020 13:03:30 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C417E30E; Mon, 11 May 2020 10:03:29 -0700 (PDT) Received: from [192.168.0.7] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A84C53F305; Mon, 11 May 2020 10:03:28 -0700 (PDT) Subject: Re: [PATCH v2] sched/fair: Fix enqueue_task_fair warning some more To: Tao Zhou Cc: Vincent Guittot , Phil Auld , Peter Zijlstra , linux-kernel , Ingo Molnar , Juri Lelli References: <20200506141821.GA9773@lorien.usersys.redhat.com> <20200507203612.GF19331@lorien.usersys.redhat.com> <20200508151515.GA25974@geo.homenetwork> <20200508170213.GA27353@geo.homenetwork> <801229de-200d-c9d5-7fd3-8556c5abc064@arm.com> From: Dietmar Eggemann Message-ID: <8300e553-a90f-3708-8a65-4f906ad5c807@arm.com> Date: Mon, 11 May 2020 19:03:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tao, On 11/05/2020 17:44, Tao Zhou wrote: > Hi Dietmar, [...] > On Mon, May 11, 2020 at 12:39:52PM +0200, Dietmar Eggemann wrote: >> On 11/05/2020 11:36, Vincent Guittot wrote: >>> On Mon, 11 May 2020 at 10:40, Dietmar Eggemann wrote: >>>> >>>> On 08/05/2020 19:02, Tao Zhou wrote: >>>>> On Fri, May 08, 2020 at 05:27:44PM +0200, Vincent Guittot wrote: >>>>>> On Fri, 8 May 2020 at 17:12, Tao Zhou wrote: >>>>>>> >>>>>>> Hi Phil, >>>>>>> >>>>>>> On Thu, May 07, 2020 at 04:36:12PM -0400, Phil Auld wrote: >>>>>>>> sched/fair: Fix enqueue_task_fair warning some more [...] >> I don't grasp how can cfs_a->on_list=1, when cfs_a is throttled and >> cfs_b, cfs_c are in a throttled hierarchy? > > I remember that Vincent explained that in this thread: > > https://lore.kernel.org/lkml/CAKfTPtDxE32RrTusYTBUcwYoJFvadLLaMUp7gOsXdj_zQcaWdA@mail.gmail.com/ > > This was what I confused also. When enqueue one task, the throttled > cfs_rq may be added back to the leaf_cfs_rq list. As long as we only consider one hierarchy than I can't see how we can enqueue a task and hit cfs_a->on_list=1 on a throttled cfs_a. But there might be a cfs_b' (another child of cfs_a) sub hierarchy which had a task enqueue just before and this set cfs_a->on_list=1. Tried to read the email you pointed at carefully but can't see it there ... pretty tired right now, maybe tomorrow?