Date: Wed, 31 Mar 2004 13:40:09 -0800
From: "Randy.Dunlap" <rddunlap@osdl.org>
To: Peter Williams <peterw@aurema.com>
Cc: albert@users.sourceforge.net, arjanv@redhat.com, ak@muc.de,
       Richard.Curnow@superh.com, aeb@cwi.nl, linux-kernel@vger.kernel.org
Subject: Re: finding out the value of HZ from userspace
Message-Id: <20040331134009.76ca3b6d.rddunlap@osdl.org>
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On Sun, 21 Mar 2004 10:58:20 +1100 Peter Williams wrote:

| Albert Cahalan wrote:
| > On Sat, 2004-03-20 at 04:56, Arjan van de Ven wrote:
| > 
| >>On Tue, Mar 16, 2004 at 11:14:59AM -0500, Albert Cahalan wrote:
| >>
| >>>>there is one. Nothing uses it
| >>>>(sysconf() provides this info)
| >>>
| >>>If you have a recent glibc on a recent kernel, it might.
| >>>You could also get a -1 or a supposed ABI value that
| >>>has nothing to do with the kernel currently running.
| >>>The most reliable way is to first look around on the
| >>>stack in search of ELF notes, and then fall back to
| >>>some horribly gross hacks as needed.
| >>
| >>eh sysconf() is the nice way to get to the ELF notes
| >>instead of having to grovel yourself.
| > 
| > 
| > Unless there is some hidden feature that lets
| > me specify the ELF note number directly, no way.
| > 
| > The sysconf(_SC_CLK_TCK) call does not return an
| > error code when used on a 2.2.xx i386 kernel.
| > You get an arbitrary value that fails for ARM,
| > Alpha, and any system with modified HZ.
| 
| As Linux is supposed to be POSIX compliant this is a bug and should be 
| fixed.


My understanding (from a few years back) is that Linux is POSIX
if/when/where it makes sense, but not necessarily POSIX-just-to-be-POSIX.

--
~Randy
"You can't do anything without having to do something else first."
-- Belefant's Law
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