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From: Steven Rostedt <rostedt@goodmis.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>,
	Ronny Meeus <ronny.meeus@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] sched: Handle priority boosted tasks proper in setscheduler()
Date: Tue, 5 May 2015 12:42:44 -0400
Message-ID: <20150505124244.1f154dc9@gandalf.local.home> (raw)
In-Reply-To: <alpine.DEB.2.11.1505051830440.4225@nanos>

On Tue, 5 May 2015 18:31:20 +0200 (CEST)
Thomas Gleixner <tglx@linutronix.de> wrote:

> On Tue, 5 May 2015, Steven Rostedt wrote:
> > I got pulled onto other things so I never finished it, but one thing
> > that worried me about this fix is this:
> > 
> > 	T1 - FIFO policy (prio = 10)
> > 	  lock(rtmutex);
> > 
> > 	T2 (prio = 20)
> > 	  lock(rtmutex)
> > 	    boost T1 (prio = 20)
> > 
> >         TI (prio = 20)
> > 	  sys_sched_setscheduler(prio = 30)
> > 	  TI (prio = 30)
> > 
> > 	T1 (prio = 30)
> > 	  sys_sched_setscheduler(SCHED_OTHER)
> > 	  new_effective_prio = 20, oldprio = 30
> > 
> > Before the code stopped at the rt_mutex_check_prio(), but now it
> > continues. Will having the policy change cause problems here?
> 
> No, because it stays effective in the FIFO domain.
> 

Ah, the policy passed in isn't used, so we are safe. But, but I also
found that we still call __setscheduler(), which does:

	p->prio = normal_prio();

Isn't that going to null out the boosting?

-- Steve

  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-05 16:08 Thomas Gleixner
2015-05-05 16:29 ` Steven Rostedt
2015-05-05 16:31   ` Thomas Gleixner
2015-05-05 16:42     ` Steven Rostedt [this message]
2015-05-05 16:50       ` Thomas Gleixner
2015-05-05 17:01         ` Steven Rostedt
2015-05-05 17:49           ` [PATCH V2] " Thomas Gleixner
2015-05-05 20:20             ` Steven Rostedt
2015-05-08 13:18 ` [tip:sched/core] " tip-bot for Thomas Gleixner

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