From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755404AbcFQUPj (ORCPT ); Fri, 17 Jun 2016 16:15:39 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:35755 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753861AbcFQUPh (ORCPT ); Fri, 17 Jun 2016 16:15:37 -0400 Date: Fri, 17 Jun 2016 22:15:18 +0200 From: luca abeni To: Juri Lelli Cc: Steven Rostedt , linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@redhat.com Subject: Re: [PATCH] sched/deadline: remove useless param from setup_new_dl_entity Message-ID: <20160617221518.75427592@utopia> In-Reply-To: <20160617162837.GQ5981@e106622-lin> References: <1466156921-12417-1-git-send-email-juri.lelli@arm.com> <20160617094935.1d4df586@gandalf.local.home> <20160617162837.GQ5981@e106622-lin> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; i686-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 17 Jun 2016 17:28:37 +0100 Juri Lelli wrote: [...] > True, but we were practically already using the same parameter, under a > different name though, after > > 2f9f3fdc928 "sched/deadline: Remove dl_new from struct sched_dl_entity" > > as we currently do: > > setup_new_dl_entity(&p->dl, &p->dl) > > > This patch reverts part of the change done in > > commit 2d3d891d334 "sched/deadline: Add SCHED_DEADLINE inheritance > > logic" > > > > Before Luca's change we were doing > > setup_new_dl_entity(dl_se, pi_se) > > in update_dl_entity() for a dl_se->new entity. So, I guess the question > is actually why we wanted to use pi_se's parameters (the potential PI > donor) for setting up a new entity? That's a good question :) > Maybe we broke the situation where a > task is currently boosted by a DEADLINE waiter and we swich the holder > to DEADLINE? I remember I tested this setup (using linaro's version of rt-app), and it seemed to work correctly... Re-reading the code now, I actually wonder why my patch did not break inheritance in this situation... Luca > > > It would be nice to have the reason in the change log. > > > > Thanks a lot for pointing out what might be more than inaccuracy in the > changelog. > > Best, > > - Juri > > > > > > Remove the second, useless, parameter. > > > > > > Cc: Ingo Molnar > > > Cc: Peter Zijlstra > > > Cc: Steven Rostedt > > > Cc: Luca Abeni > > > Signed-off-by: Juri Lelli > > > --- > > > kernel/sched/deadline.c | 9 ++++----- > > > 1 file changed, 4 insertions(+), 5 deletions(-) > > > > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > > index fcb7f0217ff4..5229788a4765 100644 > > > --- a/kernel/sched/deadline.c > > > +++ b/kernel/sched/deadline.c > > > @@ -346,8 +346,7 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, > > > * one, and to (try to!) reconcile itself with its own scheduling > > > * parameters. > > > */ > > > -static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se, > > > - struct sched_dl_entity *pi_se) > > > +static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se) > > > { > > > struct dl_rq *dl_rq = dl_rq_of_se(dl_se); > > > struct rq *rq = rq_of_dl_rq(dl_rq); > > > @@ -367,8 +366,8 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se, > > > * future; in fact, we must consider execution overheads (time > > > * spent on hardirq context, etc.). > > > */ > > > - dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline; > > > - dl_se->runtime = pi_se->dl_runtime; > > > + dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline; > > > + dl_se->runtime = dl_se->dl_runtime; > > > } > > > > > > /* > > > @@ -1721,7 +1720,7 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p) > > > static void switched_to_dl(struct rq *rq, struct task_struct *p) > > > { > > > if (dl_time_before(p->dl.deadline, rq_clock(rq))) > > > - setup_new_dl_entity(&p->dl, &p->dl); > > > + setup_new_dl_entity(&p->dl); > > > > > > if (task_on_rq_queued(p) && rq->curr != p) { > > > #ifdef CONFIG_SMP > >