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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 129FBC4363A for ; Thu, 29 Oct 2020 17:55:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AAE3A2076E for ; Thu, 29 Oct 2020 17:55:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726445AbgJ2Rzo (ORCPT ); Thu, 29 Oct 2020 13:55:44 -0400 Received: from foss.arm.com ([217.140.110.172]:41836 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725777AbgJ2Rzo (ORCPT ); Thu, 29 Oct 2020 13:55:44 -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 77E96139F; Thu, 29 Oct 2020 10:55:43 -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 591DD3F66E; Thu, 29 Oct 2020 10:55:41 -0700 (PDT) References: <20201023101158.088940906@infradead.org> <20201023102347.067278757@infradead.org> <20201029173409.GT2628@hirez.programming.kicks-ass.net> 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: <20201029173409.GT2628@hirez.programming.kicks-ass.net> Date: Thu, 29 Oct 2020 17:55:34 +0000 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29/10/20 17:34, Peter Zijlstra wrote: > On Thu, Oct 29, 2020 at 04:27:09PM +0000, Valentin Schneider wrote: [...] > Can do I suppose, although I'm no sure what, if anything that helps, > because then we needs yet another comment explaining things. > > I ended up with the below. Is that an improvement? I'm leaning towards "yes", but YMMV. > > --- > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 3d7d5b7b9c99..c9c69511ece4 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7226,11 +7226,19 @@ static void balance_push(struct rq *rq) > lockdep_assert_held(&rq->lock); > SCHED_WARN_ON(rq->cpu != smp_processor_id()); > > + /* > + * When migrate_disable(), we'll also have nr_pinned incremented due to > + * this being the tail end of schedule(). Therefore we do not need to wake > + * the hotplug_wait and go straight to jail^Wexit. > + */ > + if (is_migration_disabled(push_task)) > + return; > + > /* > * 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) || is_migration_disabled(push_task)) { > + if (is_per_cpu_kthread(push_task)) { > /* > * If this is the idle task on the outgoing CPU try to wake > * up the hotplug control thread which might wait for the