linux-kernel - Re: [PATCH] sched: try to rewrite tg_has_rt

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Message-ID: <20110423141113.GA7747@zhy>
Date:	Sat, 23 Apr 2011 22:11:13 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Hillf Danton <dhillf@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] sched: try to rewrite tg_has_rt_tasks()

On Sat, Apr 23, 2011 at 09:39:40PM +0800, Hillf Danton wrote:
> It is reshuffled not based upon scanning the list of existing threads
> but upon the relevant info carried by the input task group. Compared
> with the original, it is simpler, and nothing important is missed.

Oh, no.

There may be sleep task which is attach this group.

Thanks,
Yong

> 
> Signed-off-by: Hillf Danton <dhillf@...il.com>
> ---
> 
> --- a/kernel/sched.c	2011-03-30 03:09:48.000000000 +0800
> +++ b/kernel/sched.c	2011-04-23 21:48:14.000000000 +0800
> @@ -8756,13 +8756,11 @@ static unsigned long to_ratio(u64 period
>  /* Must be called with tasklist_lock held */
>  static inline int tg_has_rt_tasks(struct task_group *tg)
>  {
> -	struct task_struct *g, *p;
> -
> -	do_each_thread(g, p) {
> -		if (rt_task(p) && rt_rq_of_se(&p->rt)->tg == tg)
> +	int cpu;
> +	for_each_online_cpu(cpu) {
> +		if (tg->rt_rq[cpu]->rt_nr_running != 0)
>  			return 1;
> -	} while_each_thread(g, p);
> -
> +	}
>  	return 0;
>  }
> --
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