From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751235AbeFAGSo (ORCPT ); Fri, 1 Jun 2018 02:18:44 -0400 Received: from mail-pl0-f65.google.com ([209.85.160.65]:36864 "EHLO mail-pl0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750812AbeFAGSn (ORCPT ); Fri, 1 Jun 2018 02:18:43 -0400 X-Google-Smtp-Source: ADUXVKK14wydnerswTqTaVKvgqqcY1z2Gtifnc4aMKBpNtdEUVhNokba29yUdKkC4r8MXt7EvO7IRQ== Date: Thu, 31 May 2018 23:18:41 -0700 From: Joel Fernandes To: byungchul park Cc: peterz@infradead.org, mingo@kernel.org, rostedt@goodmis.org, tglx@linutronix.de, raistlin@linux.it, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, bristot@redhat.com, kernel-team@lge.com Subject: Re: [RESEND, v3, 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value Message-ID: <20180601061841.GA191514@joelaf.mtv.corp.google.com> References: <1515392081-32320-2-git-send-email-byungchul.park@lge.com> <20180601061255.GA189147@joelaf.mtv.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180601061255.GA189147@joelaf.mtv.corp.google.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 31, 2018 at 11:12:55PM -0700, Joel Fernandes wrote: > On Mon, Jan 08, 2018 at 03:14:41PM +0900, byungchul park wrote: > > Currently, migrating tasks to cpu0 unconditionally happens when the > > heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0). > > We have to distinguish between the empty case and cpu0 to avoid the > > unnecessary migrations. Therefore, it has to return an invalid value > > e.i. -1 in that case. > > > > Signed-off-by: Byungchul Park > > Acked-by: Steven Rostedt (VMware) > > Acked-by: Daniel Bristot de Oliveira > > --- > > kernel/sched/cpudeadline.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c > > index 9f02035..bcf903f 100644 > > --- a/kernel/sched/cpudeadline.c > > +++ b/kernel/sched/cpudeadline.c > > @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, > > int best_cpu = cpudl_maximum_cpu(cp); > > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); > > > > + /* > > + * The heap tree is empty for now, just return. > > + */ > > + if (best_cpu == -1) > > + return 0; > > + > > if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) && > > dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) { > > if (later_mask) > > @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp) > > return -ENOMEM; > > } > > > > - for_each_possible_cpu(i) > > + for_each_possible_cpu(i) { > > + cp->elements[i].cpu = -1; > > cp->elements[i].idx = IDX_INVALID; > > Shouldn't you also set cp->elements[cpu].cpu to -1 in cpudl_clear (when you > set cp->elements[cpu].cpu to IDX_INVALID there)? I messed up my words, I meant : "when setting cp->elements[cpu].idx to IDX_INVALID there". Which means I need to call it a day :-) - Joel