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

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Date:	Mon, 27 Jun 2016 18:24:46 +0100
From:	Juri Lelli <juri.lelli@....com>
To:	Peter Zijlstra <peterz@...radead.org>
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 27/06/16 17:52, Peter Zijlstra wrote:
> 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?
> 

Yes. Sorry, I didn't have much time to follow up on this. I actually
think that a different change is required. Let's discuss that on v2.

Best,

- Juri