linux-kernel - Re: [RFC][PATCH 3/8] sched/deadline/rtmutex: Dont miss the dl_runtime/dl

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Date:	Tue, 14 Jun 2016 14:09:10 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	mingo@...nel.org, tglx@...utronix.de, rostedt@...dmis.org,
	xlpang@...hat.com, linux-kernel@...r.kernel.org,
	mathieu.desnoyers@...icios.com, jdesfossez@...icios.com,
	bristot@...hat.com, Ingo Molnar <mingo@...hat.com>
Subject: Re: [RFC][PATCH 3/8] sched/deadline/rtmutex: Dont miss the
 dl_runtime/dl_period update

On Tue, Jun 14, 2016 at 11:43:39AM +0100, Juri Lelli wrote:
> > [peterz: I should introduce more task state comparators like
> > rt_mutex_waiter_less, all PI prio comparisons already have this DL
> > exception, except this one]

> > +++ b/kernel/locking/rtmutex.c
> > @@ -488,7 +488,7 @@ static int rt_mutex_adjust_prio_chain(st
> >  	 * enabled we continue, but stop the requeueing in the chain
> >  	 * walk.
> >  	 */
> > -	if (waiter->prio == task->prio) {
> > +	if (waiter->prio == task->prio && !dl_task(task)) {
> 
> Right. Do we want a rt_mutex_waiter_equal() helper? As I think the
> comment in the changelog was also saying?

rt_mutex_waiter_equal() isn't going to help; it will not work on code
that doesn't have access to rt_mutex_waiter thingies, like
rt_mutex_setprio() for example. 

Then again, I already wondered about making rt_mutex_waiter available to
sched code, but tglx didn't much like that iirc.

Esp. given the last patch in this series, I wondered if perhaps the
second argument to rt_mutex_setprio() should be a struct
rt_mutex_waiter, instead of struct task_struct.