linux-kernel - Re: [PATCH 09/10] sched, fair: Fix the sd_parent

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Message-ID: <20130826120919.GL31370@twins.programming.kicks-ass.net>
Date:	Mon, 26 Aug 2013 14:09:19 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Paul Turner <pjt@...gle.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Mike Galbraith <efault@....de>, Alex Shi <alex.shi@...el.com>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Namhyung Kim <namhyung@...nel.org>,
	Lei Wen <leiwen@...vell.com>, Rik van Riel <riel@...riel.com>,
	Joonsoo Kim <js1304@...il.com>
Subject: Re: [PATCH 09/10] sched, fair: Fix the sd_parent_degenerate() code

On Sat, Aug 24, 2013 at 03:45:57AM -0700, Paul Turner wrote:
> > @@ -5157,6 +5158,13 @@ cpu_attach_domain(struct sched_domain *s
> >                         tmp->parent = parent->parent;
> >                         if (parent->parent)
> >                                 parent->parent->child = tmp;
> > +                       /*
> > +                        * Transfer SD_PREFER_SIBLING down in case of a
> > +                        * degenerate parent; the spans match for this
> > +                        * so the property transfers.
> > +                        */
> > +                       if (parent->flags & SD_PREFER_SIBLING)
> > +                               tmp->flags |= SD_PREFER_SIBLING;
> >                         destroy_sched_domain(parent, cpu);
> >                 } else
> >                         tmp = tmp->parent;
> >
> 
> Reviewed-by: Paul Turner <pjt@...gle.com>

BTW, did that comment make sense to you or would you suggest something
different? I had/am having a hard time with that comment. Somehow it
leaves me wanting. I know I understand the issue now, but I'll doubt the
comment will suffice in a years time :/
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