linux-kernel - Re: [PATCH] sched: remove resetting exec_start in put_prev_task

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Message-ID: <BANLkTikoO5F5H4sEUoDPKX3qiahuehp=Mg@mail.gmail.com>
Date:	Thu, 2 Jun 2011 16:04:53 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Hillf Danton <dhillf@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mike Galbraith <efault@....de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] sched: remove resetting exec_start in put_prev_task_rt()

On Wed, Jun 1, 2011 at 10:03 PM, Hillf Danton <dhillf@...il.com> wrote:
> Resetting exec_start, after updated in update_curr_rt(), could open window for
> messing up the subsequent computations of delta_exec of the given task.

I can't see how could this happen. what kind of 'subsequent computations'
do you mean?

But because exec_start will be reset by _pick_next_task_rt()/set_curr_task_rt(),
you patch is ok. IMHO it is not critical, it's just cleanup instead.

Thanks,
Yong

>
> Signed-off-by: Hillf Danton <dhillf@...il.com>
> ---
>  kernel/sched_rt.c |    1 -
>  1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
> index 88725c9..0f0cfce 100644
> --- a/kernel/sched_rt.c
> +++ b/kernel/sched_rt.c
> @@ -1166,7 +1166,6 @@ static struct task_struct
> *pick_next_task_rt(struct rq *rq)
>  static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
>  {
>        update_curr_rt(rq);
> -       p->se.exec_start = 0;
>
>        /*
>         * The previous task needs to be made eligible for pushing
>



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