From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
Subject: Re: [PATCH, v6 2/3] Implement timer slack notifier chain
Date: Mon, 14 Feb 2011 14:32:23 +0100 (CET)
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To: "Kirill A. Shutsemov" <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
Cc: jacob.jun.pan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Paul Menage <menage-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Arjan van de Ven <arjan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
List-Id: linux-api@vger.kernel.org

On Mon, 14 Feb 2011, Kirill A. Shutsemov wrote:

> From: Kirill A. Shutemov <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
> 
> Process can change its timer slack using prctl(). Timer slack notifier
> call chain allows to react on such change or forbid it.

So we add a notifier call chain and more exports to allow what ?
 
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1691,15 +1691,10 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>  			error = perf_event_task_enable();
>  			break;
>  		case PR_GET_TIMERSLACK:
> -			error = current->timer_slack_ns;
> +			error = prctl_get_timer_slack();

  What's the point of replacing current->timer_slack_ns with a
  function which does exactly the same ?

> +long prctl_set_timer_slack(long timer_slack_ns)
> +{
> +	int err;
> +
> +	/* Reset timer slack to default value */
> +	if (timer_slack_ns <= 0) {
> +		current->timer_slack_ns = current->default_timer_slack_ns;
> +		return 0;

  That does not make any sense at all. Why is setting
  default_timer_slack_ns not subject to validation ? Why is it
  treaded seperately ?

> +	}
> +
> +	err = blocking_notifier_call_chain(&timer_slack_notify_list,
> +			timer_slack_ns, NULL);
> +	if (err == NOTIFY_DONE)
> +		current->timer_slack_ns = timer_slack_ns;
> +
> +	return notifier_to_errno(err);

Thanks,

	tglx