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 8C93AC2BA2B for ; Thu, 16 Apr 2020 23:32:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 70807217D8 for ; Thu, 16 Apr 2020 23:32:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726438AbgDPXcb (ORCPT ); Thu, 16 Apr 2020 19:32:31 -0400 Received: from mga09.intel.com ([134.134.136.24]:7585 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725770AbgDPXcb (ORCPT ); Thu, 16 Apr 2020 19:32:31 -0400 IronPort-SDR: s3b+Xo8wUZoXGfmDMWg5SLrPRUk0HortSzvbDo2dN6S5TWHV31zPcejR56PC+H4iKKd2fEpCL7 pfd0l67G7Ytg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Apr 2020 16:32:30 -0700 IronPort-SDR: ym/zxMEgyXps61iGw/Ee6+UbniY5VWtuxaq2HPRAa8AHaB6gEZbO7MxoKsnjFsGQEm+IB0OaFg DC3YfjR3ed3Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,392,1580803200"; d="scan'208";a="246138657" Received: from schen9-mobl.amr.corp.intel.com ([10.212.43.163]) by fmsmga008.fm.intel.com with ESMTP; 16 Apr 2020 16:32:29 -0700 Subject: Re: [RFC PATCH 07/13] sched: Add core wide task selection and scheduling. To: Peter Zijlstra , vpillai Cc: Nishanth Aravamudan , Julien Desfossez , mingo@kernel.org, tglx@linutronix.de, pjt@google.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Aaron Lu , Aubrey Li , aubrey.li@linux.intel.com, Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , Joel Fernandes , joel@joelfernandes.org, Aaron Lu References: <20200414133559.GT20730@hirez.programming.kicks-ass.net> From: Tim Chen Message-ID: <1e587d48-2e61-e425-81cf-d304e13c91d4@linux.intel.com> Date: Thu, 16 Apr 2020 16:32:28 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200414133559.GT20730@hirez.programming.kicks-ass.net> 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 On 4/14/20 6:35 AM, Peter Zijlstra wrote: > On Wed, Mar 04, 2020 at 04:59:57PM +0000, vpillai wrote: >> +static struct task_struct * >> +pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) >> +{ >> + struct task_struct *next, *max = NULL; >> + const struct sched_class *class; >> + const struct cpumask *smt_mask; >> + int i, j, cpu; >> + bool need_sync = false; > > AFAICT that assignment is superfluous. Also, you violated the inverse > x-mas tree. > >> + >> + cpu = cpu_of(rq); >> + if (cpu_is_offline(cpu)) >> + return idle_sched_class.pick_next_task(rq); > > Are we actually hitting this one? > I did hit this race when I was testing taking cpu offline and online, which prompted the check of cpu being offline. Tim