linux-kernel - Re: [RFC PATCH] hrtimers: system-wide and per-task hrtimer slacks

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Message-ID: <4F7EB406.5020703@linaro.org>
Date:	Fri, 06 Apr 2012 13:14:46 +0400
From:	Dmitry Antipov <dmitry.antipov@...aro.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	linaro-dev@...ts.linaro.org, patches@...aro.org,
	linux-man@...r.kernel.org
Subject: Re: [RFC PATCH] hrtimers: system-wide and per-task hrtimer slacks

On 04/05/2012 04:10 AM, Andrew Morton wrote:

> Well..  there are some back-incompatibilities here.
> prctl(PR_SET_TIMERSLACK, -1) used to restore current's slack setting to
> whatever-we-inherited-at-fork, but that has been removed.  What are the
> implications of this, and did we need to do it?

It seems you're looking at the previous version of this patch
(http://lkml.org/lkml/2012/2/20/55). Latest proposal is
http://lwn.net/Articles/484162/, which defines PR_SET_TIMERSLACK
action as:
...
case PR_SET_TIMERSLACK:
         if (arg2 <= 0)
                 current->timer_slack_ns =
                         default_timer_slack_ns;
         else if (arg2 <= HRTIMER_MAX_SLACK)
                 current->timer_slack_ns = arg2;
         else
                 error = -EINVAL;
         break;
...

> If we do make changes in this area then the prctl manpage should be
> updated, please.  And if
> http://www.spinics.net/lists/linux-man/msg01149.html represents the
> current state of that manpage then it should be updated anyway - that
> entry doesn't say anything about the (arg2<= 0) case.

I sent a patch for man pages too, it should be one of the recent posts
at http://www.spinics.net/lists/linux-man/index.html.

Dmitry


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