linux-kernel - Re: [RFC][PATCH 3/7] sched: Allow balance callbacks for check_class

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Date:	Tue, 02 Jun 2015 16:27:10 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Kirill Tkhai <tkhai@...dex.ru>
Cc:	"umgwanakikbuti@...il.com" <umgwanakikbuti@...il.com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ktkhai@...allels.com" <ktkhai@...allels.com>,
	"rostedt@...dmis.org" <rostedt@...dmis.org>,
	"juri.lelli@...il.com" <juri.lelli@...il.com>,
	"pang.xunlei@...aro.org" <pang.xunlei@...aro.org>,
	"oleg@...hat.com" <oleg@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 3/7] sched: Allow balance callbacks for
 check_class_changed()

On Tue, 2015-06-02 at 16:58 +0300, Kirill Tkhai wrote:
> 01.06.2015, 17:13, "Peter Zijlstra" <peterz@...radead.org>:

> > @@ -1010,7 +1014,7 @@ static inline void check_class_changed(s
> >          if (prev_class != p->sched_class) {
> >                  if (prev_class->switched_from)
> >                          prev_class->switched_from(rq, p);
> > - /* Possble rq->lock 'hole'.  */
> > +
> 
> But switched_from_dl()->cancel_dl_timer() still unlocks rq->lock.
> 
> It seems we should drop it (cancel_dl_timer) and move hrtimer_cancel()
> from switched_from_dl() to finish_task_switch(). It will be executed
> for all classes and completely take the functionality we implement
> cancel_dl_timer() for.

*groan* yes.. I don't like moving it into generic code though.

more thinking required.

> >                  p->sched_class->switched_to(rq, p);
> >          } else if (oldprio != p->prio || dl_task(p))
> >                  p->sched_class->prio_changed(rq, p, oldprio);

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