linux-kernel - Re: [PATCH v2] sched: Fix broken setscheduler()

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Date:	Mon, 10 Mar 2014 22:18:56 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Steven Rostedt <rostedt@...dmis.org>
cc:	Juri Lelli <juri.lelli@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v2] sched: Fix broken setscheduler()

On Mon, 10 Mar 2014, Steven Rostedt wrote:

> On Thu, 6 Mar 2014 21:43:50 +0100 (CET)
> Thomas Gleixner <tglx@...utronix.de> wrote:
>  
> > > Reading what the commit is suppose to do, I realize that the p->prio
> > > can't be set if the task is boosted with a higher prio, but the
> > > p->normal_prio still needs to be set regardless, otherwise, when the
> > > task is deboosted, it wont get the new priority.
> > 
> > Indeed.
> 
> Is this an Acked-by?
> 
> Peter, can you pull this patch please, it is still broken in tip/master.

Lemme look at it tomorrow again with an awake brain. This seems to be
some forward porting hickup which needs a closer look. Just look at
the 3.10-rt version of this:

@@ -3825,20 +3826,25 @@ static struct task_struct *find_process_by_pid(pid_t pid)
 	return pid ? find_task_by_vpid(pid) : current;
 }
 
-/* Actually do priority change: must hold rq lock. */
-static void
-__setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
+static void __setscheduler_params(struct task_struct *p, int policy, int prio)
 {
 	p->policy = policy;
 	p->rt_priority = prio;
 	p->normal_prio = normal_prio(p);
+	set_load_weight(p);
+}

That code has changed significantly probably due to the EDF merge. We
need to figure out whether there is more damage due to that.

Thanks,

	tglx
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