From owner-freebsd-x11@FreeBSD.ORG  Thu Feb 28 21:07:43 2008
Return-Path: <owner-freebsd-x11@FreeBSD.ORG>
Delivered-To: freebsd-x11@FreeBSD.org
Received: from [127.0.0.1] (freefall.freebsd.org [IPv6:2001:4f8:fff6::28])
	by hub.freebsd.org (Postfix) with ESMTP id E80A31065670;
	Thu, 28 Feb 2008 21:07:40 +0000 (UTC)
	(envelope-from jkim@FreeBSD.org)
From: Jung-uk Kim <jkim@FreeBSD.org>
To: freebsd-x11@FreeBSD.org
Date: Thu, 28 Feb 2008 16:07:25 -0500
User-Agent: KMail/1.6.2
References: <47C320DB.70004@delphij.net>
	<18371.11144.568407.26227@gromit.timing.com>
	<20080227103210.694787ec@tom.ulm.sysgo.com>
In-Reply-To: <20080227103210.694787ec@tom.ulm.sysgo.com>
MIME-Version: 1.0
Content-Disposition: inline
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <200802281607.30178.jkim@FreeBSD.org>
Cc: delphij@delphij.net, Thomas Mueller <tmueller@sysgo.com>
Subject: Re: Xorg vs gettimeofday() and clock_gettime()
X-BeenThere: freebsd-x11@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: X11 on FreeBSD -- maintaining and support <freebsd-x11.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-x11>,
	<mailto:freebsd-x11-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-x11>
List-Post: <mailto:freebsd-x11@freebsd.org>
List-Help: <mailto:freebsd-x11-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-x11>,
	<mailto:freebsd-x11-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 28 Feb 2008 21:07:43 -0000

On Wednesday 27 February 2008 04:32 am, Thomas Mueller wrote:
> On Mon, 25 Feb 2008 13:56:40 -0700, John Hein wrote:
> > Xin LI wrote at 12:11 -0800 on Feb 25, 2008:
> >  > Shall we make some source-level change to Xorg (either
> >  > upstream under ifdef FreeBSD or our own port, _FAST clocks are
> >  > not available on some other operating systems) so that we can
> >  > override the gettimeofday() direct calls and X_GETTIMEOFDAY's
> >  > to use clock_gettime with a faster clock?
> >
> > Sounds good to me.
> > I vote for putting in a patch in the x11-servers/xorg-server port
> > so it gets some quick exposure and then feeding it back upstream
> > where it can be added on their schedule.
>
> FWIW, xorg already has support for clock_gettime(CLOCK_MONOTONIC)
> in xorg-server-1.4/os/utils.c:
>
>  _X_EXPORT CARD32
>  GetTimeInMillis(void)
>  {
>     struct timeval tv;
>
>  #ifdef MONOTONIC_CLOCK
>     struct timespec tp;
>     if (clock_gettime(CLOCK_MONOTONIC, &tp) == 0)
>         return (tp.tv_sec * 1000) + (tp.tv_nsec / 1000000L);
>  #endif
>
>     X_GETTIMEOFDAY(&tv);
>     return(tv.tv_sec * 1000) + (tv.tv_usec / 1000);
>  }
>
> Apparently the autoconf check for presence of CLOCK_MONOTONIC fails
> on FreeBSD:
>
>  #define _POSIX_C_SOURCE 199309L
>  #include <time.h>
>
>  int main(int argc, char *argv[]) {
>     struct timespec tp;
>
>     if (clock_gettime(CLOCK_MONOTONIC, &tp) == 0)
>         return 0;
>     else
>         return 1;
>  }
>
> /usr/include/time.h:
>  #if !defined(CLOCK_REALTIME) && __POSIX_VISIBLE >= 200112
>  #define CLOCK_REALTIME  0
>  [...]
>  #define CLOCK_MONOTONIC 4
>
> Was CLOCK_MONOTONIC already defined for _POSIX_C_SOURCE 199309?

So this test was introduced in the following commit:

http://lists.freedesktop.org/archives/xorg-commit/2006-November/009390.html

Google found me this:

http://www.opengroup.org/austin/mailarchives/ag-review/msg00489.html

'The recently-approved 1003.1j-2000 adds CLOCK_MONOTONIC to the list.'

I think 1003.1b-1993 added clock_gettime(2) and configure.ac tests 
bogus spec.

Jung-uk Kim