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 E407AC433DF for ; Fri, 19 Jun 2020 10:36:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C0D60207FC for ; Fri, 19 Jun 2020 10:36:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732377AbgFSKg1 (ORCPT ); Fri, 19 Jun 2020 06:36:27 -0400 Received: from foss.arm.com ([217.140.110.172]:51180 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729195AbgFSKgZ (ORCPT ); Fri, 19 Jun 2020 06:36:25 -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 50909D6E; Fri, 19 Jun 2020 03:36:24 -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 A0EB03F71F; Fri, 19 Jun 2020 03:36:22 -0700 (PDT) References: <20200618195525.7889-1-qais.yousef@arm.com> <20200618195525.7889-2-qais.yousef@arm.com> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Qais Yousef Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Patrick Bellasi , Chris Redpath , Lukasz Luba , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] sched/uclamp: Fix initialization of strut uclamp_rq In-reply-to: <20200618195525.7889-2-qais.yousef@arm.com> Date: Fri, 19 Jun 2020 11:36:17 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/06/20 20:55, Qais Yousef wrote: > struct uclamp_rq was zeroed out entirely in assumption that in the first > call to uclamp_rq_inc() they'd be initialized correctly in accordance to > default settings. > > But when next patch introduces a static key to skip > uclamp_rq_{inc,dec}() until userspace opts in to use uclamp, schedutil > will fail to perform any frequency changes because the > rq->uclamp[UCLAMP_MAX].value is zeroed at init and stays as such. Which > means all rqs are capped to 0 by default. > > Fix it by making sure we do proper initialization at init without > relying on uclamp_rq_inc() doing it later. > > Fixes: 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting") > Signed-off-by: Qais Yousef > Cc: Juri Lelli > Cc: Vincent Guittot > Cc: Dietmar Eggemann > Cc: Steven Rostedt > Cc: Ben Segall > Cc: Mel Gorman > CC: Patrick Bellasi > Cc: Chris Redpath > Cc: Lukasz Luba > Cc: linux-kernel@vger.kernel.org Small nit below, otherwise: Reviewed-by: Valentin Schneider > --- > kernel/sched/core.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index a43c84c27c6f..e19d2b915406 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1248,6 +1248,20 @@ static void uclamp_fork(struct task_struct *p) > } > } > > +static void __init init_uclamp_rq(struct rq *rq) > +{ > + enum uclamp_id clamp_id; > + struct uclamp_rq *uc_rq = rq->uclamp; > + > + for_each_clamp_id(clamp_id) { > + memset(uc_rq[clamp_id].bucket, > + 0, > + sizeof(struct uclamp_bucket)*UCLAMP_BUCKETS); > + > + uc_rq[clamp_id].value = uclamp_none(clamp_id); > + } > +} > + > static void __init init_uclamp(void) > { > struct uclamp_se uc_max = {}; > @@ -1257,8 +1271,7 @@ static void __init init_uclamp(void) > mutex_init(&uclamp_mutex); > > for_each_possible_cpu(cpu) { > - memset(&cpu_rq(cpu)->uclamp, 0, > - sizeof(struct uclamp_rq)*UCLAMP_CNT); > + init_uclamp_rq(cpu_rq(cpu)); > cpu_rq(cpu)->uclamp_flags = 0; That flags assignment ought to be squashed in the init function as well - and actually you do that in patch 2, so I suppose that's a rebase accident. > }