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=-3.8 required=3.0 tests=BAYES_00, 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 025B1C4363A for ; Thu, 29 Oct 2020 16:27:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A549220838 for ; Thu, 29 Oct 2020 16:27:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726691AbgJ2Q1O (ORCPT ); Thu, 29 Oct 2020 12:27:14 -0400 Received: from foss.arm.com ([217.140.110.172]:40338 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726177AbgJ2Q1O (ORCPT ); Thu, 29 Oct 2020 12:27:14 -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 64FA0139F; Thu, 29 Oct 2020 09:27:13 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 48CAE3F66E; Thu, 29 Oct 2020 09:27:11 -0700 (PDT) References: <20201023101158.088940906@infradead.org> <20201023102347.067278757@infradead.org> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Peter Zijlstra Cc: tglx@linutronix.de, mingo@kernel.org, linux-kernel@vger.kernel.org, bigeasy@linutronix.de, qais.yousef@arm.com, swood@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vincent.donnefort@arm.com, tj@kernel.org, ouwen210@hotmail.com Subject: Re: [PATCH v4 11/19] sched/core: Make migrate disable and CPU hotplug cooperative In-reply-to: <20201023102347.067278757@infradead.org> Date: Thu, 29 Oct 2020 16:27:09 +0000 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/10/20 11:12, Peter Zijlstra wrote: > @@ -7006,15 +7024,20 @@ static bool balance_push(struct rq *rq) > * Both the cpu-hotplug and stop task are in this case and are > * required to complete the hotplug process. > */ > - if (is_per_cpu_kthread(push_task)) { > + if (is_per_cpu_kthread(push_task) || is_migration_disabled(push_task)) { is_migration_disabled(p) implies rq_has_pinned_tasks(task_rq(p)), right? So having a "simple" if (is_migration_disabled(push_task)) return; would help simpletons like me trying to read through this. > /* > * If this is the idle task on the outgoing CPU try to wake > * up the hotplug control thread which might wait for the > * last task to vanish. The rcuwait_active() check is > * accurate here because the waiter is pinned on this CPU > * and can't obviously be running in parallel. > + * > + * On RT kernels this also has to check whether there are > + * pinned and scheduled out tasks on the runqueue. They > + * need to leave the migrate disabled section first. > */ > - if (!rq->nr_running && rcuwait_active(&rq->hotplug_wait)) { > + if (!rq->nr_running && !rq_has_pinned_tasks(rq) && > + rcuwait_active(&rq->hotplug_wait)) { > raw_spin_unlock(&rq->lock); > rcuwait_wake_up(&rq->hotplug_wait); > raw_spin_lock(&rq->lock);