linux-kernel - Re: [PATCH]sched/rt: Simplify pick_rt_task: remove next

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Date:	Thu, 31 Jan 2013 11:12:01 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Kirill Tkhai <tkhai@...dex.ru>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: Re: [PATCH]sched/rt: Simplify pick_rt_task: remove next_prio()
 inheritance

On Thu, 2013-01-31 at 18:56 +0400, Kirill Tkhai wrote:
> Function next_prio() has been removed and pull_rt_task() is the only
> user of pick_next_highest_task_rt() at the moment.
> 
> pull_rt_task is not interested in p->nr_cpus_allowed, its only interest
> is the fact that cpu is allowed to execute p. If nr_cpus_allowed == 1,
> cpu != task_cpu(p) and cpu is allowed then it means that task p is in
> the middle of the migration techniques; the task waits until it is moved
> by migration thread. So, lets pull it earlier.
> 
> Signed-off-by: Kirill V Tkhai <tkhai@...dex.ru>

Acked-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve

> CC: Ingo Molnar <mingo@...nel.org>
> CC: Peter Zijlstra <peterz@...radead.org>
> CC: linux-rt-users <linux-rt-users@...r.kernel.org>
> ---
>  kernel/sched/rt.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 4e8f0f4..9aa2921 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1427,8 +1427,7 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
>  static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
>  {
>  	if (!task_running(rq, p) &&
> -	    (cpu < 0 || cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) &&
> -	    (p->nr_cpus_allowed > 1))
> +	    cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
>  		return 1;
>  	return 0;
>  }


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