From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753371AbcGDJDe (ORCPT ); Mon, 4 Jul 2016 05:03:34 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:36349 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750895AbcGDJDc (ORCPT ); Mon, 4 Jul 2016 05:03:32 -0400 Date: Mon, 4 Jul 2016 11:03:24 +0200 From: luca abeni To: Juri Lelli Cc: peterz@infradead.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org, mingo@redhat.com Subject: Re: [PATCH v2] sched/deadline: remove useless param from setup_new_dl_entity Message-ID: <20160704110324.129bebb4@utopia> In-Reply-To: <1467227263-31349-1-git-send-email-juri.lelli@arm.com> References: <1467227263-31349-1-git-send-email-juri.lelli@arm.com> Organization: university of trento X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-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 Hi Juri, On Wed, 29 Jun 2016 20:07:43 +0100 Juri Lelli wrote: > setup_new_dl_entity() takes two parameters, but it only actually uses > one of them, under a different name, to setup a new dl_entity, after: > > 2f9f3fdc928 "sched/deadline: Remove dl_new from struct > sched_dl_entity" > > as we currently do > > setup_new_dl_entity(&p->dl, &p->dl) > > However, 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: we were using pi_se's > parameters (the potential PI donor) for setting up a new entity. > > Restore this behaviour (as we want to correctly initialize parameters > of a boosted task that enters DEADLINE) by removing the useless second > parameter of setup_new_dl_entity() and retrieving the top waiter > directly from inside that function. I did not have time to test this patch yet, but it still looks good to me. Thanks, Luca > > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Steven Rostedt > Cc: Luca Abeni > Signed-off-by: Juri Lelli > > --- > Changes from v1: > - Steve pointed out that we were actually using the second > parameter to permorm initialization > - Luca confirmed that behavior is slightly changed w.r.t. before > his change > - changelog updated and original behavior restored > --- > kernel/sched/deadline.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index fcb7f0217ff4..2000ad2294d5 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -346,11 +346,12 @@ 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); > + struct task_struct *pi_task = > rt_mutex_get_top_task(dl_task_of(dl_se)); > + struct sched_dl_entity *pi_se = dl_se; > > WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline)); > > @@ -363,6 +364,13 @@ static inline void setup_new_dl_entity(struct > sched_dl_entity *dl_se, return; > > /* > + * Use the scheduling parameters of the top pi-waiter task, > + * if we have one from which we can inherit a deadline. > + */ > + if (pi_task && dl_se->dl_boosted && > dl_prio(pi_task->normal_prio)) > + pi_se = &pi_task->dl; > + > + /* > * We use the regular wall clock time to set deadlines in the > * future; in fact, we must consider execution overheads > (time > * spent on hardirq context, etc.). > @@ -1721,7 +1729,7 @@ 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