linux-kernel - Re: [PATCH] sched: shorten setting the allowed cpu mask of task

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Message-ID: <BANLkTimjkK-q63x5DrEj+9=pF8zbW7mJ2g@mail.gmail.com>
Date:	Mon, 9 May 2011 12:39:39 +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>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH] sched: shorten setting the allowed cpu mask of task

On Fri, May 6, 2011 at 8:52 PM, Hillf Danton <dhillf@...il.com> wrote:
> When setting the allowed cpu mask for a given task, if the task is
> already bound to certain cpu, after checking the validity of the new

Maybe we don't need to restrict it only on task bound to certain cpu.

> mask of allowed cpus, job is done, and no further efforts needed for
> the valid case as well.
>
> Signed-off-by: Hillf Danton <dhillf@...il.com>
> ---
>
> --- a/kernel/sched.c    2011-04-27 11:48:50.000000000 +0800
> +++ b/kernel/sched.c    2011-05-06 20:39:58.000000000 +0800
> @@ -5899,9 +5899,9 @@ again:
>                goto out;
>        }
>
> -       if (unlikely((p->flags & PF_THREAD_BOUND) && p != current &&
> -                    !cpumask_equal(&p->cpus_allowed, new_mask))) {
> -               ret = -EINVAL;
> +       if ((p->flags & PF_THREAD_BOUND) && p != current) {
> +               if (!cpumask_equal(&p->cpus_allowed, new_mask))

IOW, we could make '!cpumask_equal(&p->cpus_allowed, new_mask)'
be a separated condition. And I don't see any potential problem with it.

Thanks,
Yong


> +                       ret = -EINVAL;
>                goto out;
>        }
>



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