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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 5E6C2C43613 for ; Thu, 20 Jun 2019 16:23:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3CF2A2084E for ; Thu, 20 Jun 2019 16:23:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732145AbfFTQXw (ORCPT ); Thu, 20 Jun 2019 12:23:52 -0400 Received: from foss.arm.com ([217.140.110.172]:47402 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726827AbfFTQXw (ORCPT ); Thu, 20 Jun 2019 12:23:52 -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 86B9F2B; Thu, 20 Jun 2019 09:23:51 -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 D64693F246; Thu, 20 Jun 2019 09:23:49 -0700 (PDT) Subject: Re: [PATCH 5/8] sched,cfs: use explicit cfs_rq of parent se helper To: Rik van Riel , peterz@infradead.org Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, kernel-team@fb.com, morten.rasmussen@arm.com, tglx@linutronix.de, dietmar.eggeman@arm.com, mgorman@techsingularity.com, vincent.guittot@linaro.org References: <20190612193227.993-1-riel@surriel.com> <20190612193227.993-6-riel@surriel.com> From: Dietmar Eggemann Message-ID: <55c0dc01-24b2-bb7f-6ceb-b65c52f7b46b@arm.com> Date: Thu, 20 Jun 2019 18:23:48 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190612193227.993-6-riel@surriel.com> 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 6/12/19 9:32 PM, Rik van Riel wrote: > Use an explicit "cfs_rq of parent sched_entity" helper in a few > strategic places, where cfs_rq_of(se) may no longer point at the > right runqueue once we flatten the hierarchical cgroup runqueues. > > No functional change. > > Signed-off-by: Rik van Riel > --- > kernel/sched/fair.c | 17 +++++++++++++---- > 1 file changed, 13 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index dcc521d251e3..c6ede2ecc935 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -275,6 +275,15 @@ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) > return grp->my_q; > } > > +/* runqueue owned by the parent entity */ > +static inline struct cfs_rq *group_cfs_rq_of_parent(struct sched_entity *se) > +{ > + if (se->parent) > + return group_cfs_rq(se->parent); > + > + return &cfs_rq_of(se)->rq->cfs; > +} > + > static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) > { > struct rq *rq = rq_of(cfs_rq); > @@ -3298,7 +3307,7 @@ static inline int propagate_entity_load_avg(struct sched_entity *se) > > gcfs_rq->propagate = 0; > > - cfs_rq = cfs_rq_of(se); > + cfs_rq = group_cfs_rq_of_parent(se); > > add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum); > > @@ -7779,7 +7788,7 @@ static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) > > WRITE_ONCE(cfs_rq->h_load_next, NULL); > for_each_sched_entity(se) { > - cfs_rq = cfs_rq_of(se); > + cfs_rq = group_cfs_rq_of_parent(se); Why do you change this here? task_se_h_load() calls update_cfs_rq_h_load() with cfs_rq = group_cfs_rq_of_parent(se) because the task might not be on the cfs_rq yet. But inside update_cfs_rq_h_load() the first se is derived from cfs_rq->tg->se[cpu_of(rq)] so in the first for_each_sched_entity() loop we should still start with group_cfs_rq() (se->my_q) ? The system doesn't barf with these two WARN_ON's in. @@ -7663,12 +7673,17 @@ static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) unsigned long now = jiffies; unsigned long load; + WARN_ON(se && (se != group_cfs_rq(se)->tg->se[cpu_of(rq)])); + if (cfs_rq->last_h_load_update == now) return; WRITE_ONCE(cfs_rq->h_load_next, NULL); for_each_sched_entity(se) { cfs_rq = group_cfs_rq_of_parent(se); + + WARN_ON(se != group_cfs_rq(se)->tg->se[cpu_of(rq)]); + WRITE_ONCE(cfs_rq->h_load_next, se); if (cfs_rq->last_h_load_update == now) break; [...]