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

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Message-ID: <20140310173731.06d41157@gandalf.local.home>
Date:	Mon, 10 Mar 2014 17:37:31 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Thomas Gleixner <tglx@...utronix.de>
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 22:18:56 +0100 (CET)
Thomas Gleixner <tglx@...utronix.de> wrote:


> 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

Yep, I talked with Sebastian on IRC and that seems to be the case.

> 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.

Yeah, when I looked at the -rt version, it appeared to have my fix
already. But in reality, the forward port broke it. Here's the problem
part of the commit:

+       set_load_weight(p);
+}
 
-       p->normal_prio = normal_prio(p);
-       p->prio = rt_mutex_getprio(p);

Your patch never deleted the above two. And it kept them in the
locations that I placed them in, in my patch.

-- Steve


+/* Actually do priority change: must hold pi & rq lock. */
+static void __setscheduler(struct rq *rq, struct task_struct *p,
+                          const struct sched_attr *attr)
+{


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