linux-kernel - Re: [PATCH] sched/deadline: remove useless param from setup_new_dl

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Message-ID: <20160627155229.GE30909@twins.programming.kicks-ass.net>
Date:	Mon, 27 Jun 2016 17:52:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	mingo@...hat.com, luca.abeni@...tn.it
Subject: Re: [PATCH] sched/deadline: remove useless param from
 setup_new_dl_entity

On Fri, Jun 17, 2016 at 05:28:37PM +0100, Juri Lelli wrote:
> On 17/06/16 09:49, Steven Rostedt wrote:
> > On Fri, 17 Jun 2016 10:48:41 +0100
> > Juri Lelli <juri.lelli@....com> wrote:
> > 
> > > setup_new_dl_entity() takes two parameters, but it only actually uses
> > > one of them to setup a new dl_entity.
> > > 
> > 
> > Actually this patch is making it so that setup_new_dl_entity() only
> > uses one of the parameters. Can you note why that change happened.
> > Because this change log implies that the second parameter wasn't used
> > before this patch, and that is incorrect.
> > 
> 
> 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? Maybe we broke the situation where a
> task is currently boosted by a DEADLINE waiter and we swich the holder
> to DEADLINE?
> 
> > 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.

Will you be reposting with a new Changelog?