linux-kernel - Re: [patch 1/8] Add rt_nr

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Message-ID: <b647ffbd0710200945p2bb87d7fk1110bdcf56f6218d@mail.gmail.com>
Date:	Sat, 20 Oct 2007 18:45:12 +0200
From:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Gregory Haskins" <ghaskins@...ell.com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Subject: Re: [patch 1/8] Add rt_nr_running accounting

On 19/10/2007, Steven Rostedt <rostedt@...dmis.org> wrote:
> [ ... ]
> Index: linux-test.git/kernel/sched.c
> ===================================================================
> --- linux-test.git.orig/kernel/sched.c  2007-10-19 12:32:39.000000000 -0400
> +++ linux-test.git/kernel/sched.c       2007-10-19 12:33:09.000000000 -0400
> @@ -300,6 +300,8 @@ struct rq {
>          */
>         unsigned long nr_uninterruptible;
>
> +       unsigned long rt_nr_running;

could it be a part of the 'struct rt_rq' instead?

>
> +static inline void inc_rt_tasks(struct task_struct *p, struct rq *rq)
> +{
> +       if (rt_task(p))
> +               rq->rt_nr_running++;
> +}
> +
> +static inline void dec_rt_tasks(struct task_struct *p, struct rq *rq)
> +{
> +       if (rt_task(p)) {
> +               WARN_ON(!rq->rt_nr_running);
> +               rq->rt_nr_running--;
> +       }
> +}
> +
>  static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
>  {
>         struct rt_prio_array *array = &rq->rt.active;
>
>         list_add_tail(&p->run_list, array->queue + p->prio);
>         __set_bit(p->prio, array->bitmap);
> +
> +       inc_rt_tasks(p, rq);

why do you need the rt_task(p) check in {inc,dec}_rt_tasks() ?

{enqueue,dequeue}_task_rt() seem to be the only callers and they will
crash (or corrupt memory) anyway in the case of ! rt_task(p) (sure,
this case would mean something is broken somewhere wrt sched_class
handling).


-- 
Best regards,
Dmitry Adamushko
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