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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 DD3E7C433FF for ; Thu, 8 Aug 2019 08:57:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B9DD12173E for ; Thu, 8 Aug 2019 08:57:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731470AbfHHI5R (ORCPT ); Thu, 8 Aug 2019 04:57:17 -0400 Received: from foss.arm.com ([217.140.110.172]:58214 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728289AbfHHI5R (ORCPT ); Thu, 8 Aug 2019 04:57:17 -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 68DD7337; Thu, 8 Aug 2019 01:57:16 -0700 (PDT) Received: from [0.0.0.0] (e107985-lin.cambridge.arm.com [10.1.194.38]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8D2323F706; Thu, 8 Aug 2019 01:57:14 -0700 (PDT) Subject: Re: [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers To: Juri Lelli Cc: Peter Zijlstra , mingo@kernel.org, linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it, bristot@redhat.com, balsini@android.com, dvyukov@google.com, tglx@linutronix.de, vpillai@digitalocean.com, rostedt@goodmis.org References: <20190726145409.947503076@infradead.org> <20190726161358.056107990@infradead.org> <34710762-f813-3913-0e55-fde7c91c6c2d@arm.com> <20190808075635.GB17205@worktop.programming.kicks-ass.net> <20cc05d3-0d0f-a558-2bbe-3b72527dd9bc@arm.com> <20190808084652.GG29310@localhost.localdomain> From: Dietmar Eggemann Message-ID: <99a8339d-8e06-bff8-284b-1829d0683a7a@arm.com> Date: Thu, 8 Aug 2019 10:57:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190808084652.GG29310@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/8/19 10:46 AM, Juri Lelli wrote: > On 08/08/19 10:11, Dietmar Eggemann wrote: >> On 8/8/19 9:56 AM, Peter Zijlstra wrote: >>> On Wed, Aug 07, 2019 at 06:31:59PM +0200, Dietmar Eggemann wrote: >>>> On 7/26/19 4:54 PM, Peter Zijlstra wrote: >>>>> >>>>> >>>>> Signed-off-by: Peter Zijlstra (Intel) >>>> >>>> [...] >>>> >>>>> @@ -889,6 +891,8 @@ static void update_curr(struct cfs_rq *c >>>>> trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); >>>>> cgroup_account_cputime(curtask, delta_exec); >>>>> account_group_exec_runtime(curtask, delta_exec); >>>>> + if (curtask->server) >>>>> + dl_server_update(curtask->server, delta_exec); >>>>> } >>>> >>>> I get a lockdep_assert_held(&rq->lock) related warning in start_dl_timer() >>>> when running the full stack. >>> >>> That would seem to imply a stale curtask->server value; the hunk below: >>> >>> --- a/kernel/sched/core.c >>> +++ b/kernel/sched/core.c >>> @@ -3756,8 +3756,11 @@ pick_next_task(struct rq *rq, struct tas >>> >>> for_each_class(class) { >>> p = class->pick_next_task(rq, NULL, NULL); >>> - if (p) >>> + if (p) { >>> + if (p->sched_class == class && p->server) >>> + p->server = NULL; >>> return p; >>> + } >>> } >>> >>> >>> Was supposed to clear p->server, but clearly something is going 'funny'. >> >> What about the fast path in pick_next_task()? >> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index bffe849b5a42..f1ea6ae16052 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -3742,6 +3742,9 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) >> if (unlikely(!p)) >> p = idle_sched_class.pick_next_task(rq, prev, rf); >> >> + if (p->sched_class == &fair_sched_class && p->server) >> + p->server = NULL; >> + > > Hummm, but then who sets it back to the correct server. AFAIU > update_curr() needs a ->server to do the correct DL accounting? Ah, OK, this would kill the whole functionality ;-)