From owner-freebsd-arch@FreeBSD.ORG  Mon Nov 12 04:49:59 2007
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
Delivered-To: freebsd-arch@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 8E4EF16A468
	for <freebsd-arch@FreeBSD.org>; Mon, 12 Nov 2007 04:49:59 +0000 (UTC)
	(envelope-from julian@elischer.org)
Received: from outW.internet-mail-service.net (outW.internet-mail-service.net
	[216.240.47.246])
	by mx1.freebsd.org (Postfix) with ESMTP id 6E7D413C494
	for <freebsd-arch@FreeBSD.org>; Mon, 12 Nov 2007 04:49:59 +0000 (UTC)
	(envelope-from julian@elischer.org)
Received: from mx0.idiom.com (HELO idiom.com) (216.240.32.160)
	by out.internet-mail-service.net (qpsmtpd/0.40) with ESMTP;
	Sun, 11 Nov 2007 20:34:42 -0800
X-Client-Authorized: MaGic Cook1e
X-Client-Authorized: MaGic Cook1e
X-Client-Authorized: MaGic Cook1e
X-Client-Authorized: MaGic Cook1e
Received: from julian-mac.elischer.org (home.elischer.org [216.240.48.38])
	by idiom.com (Postfix) with ESMTP id 6078512697A;
	Sun, 11 Nov 2007 20:34:42 -0800 (PST)
Message-ID: <4737D7E3.3090500@elischer.org>
Date: Sun, 11 Nov 2007 20:34:43 -0800
From: Julian Elischer <julian@elischer.org>
User-Agent: Thunderbird 2.0.0.6 (Macintosh/20070728)
MIME-Version: 1.0
To: Marcel Moolenaar <xcllnt@mac.com>
References: <1191187393.00807485.1191175801@10.7.7.3>
	<1191189248.00807488.1191177603@10.7.7.3>
	<4736D8AF.7010209@FreeBSD.org>
	<20071111163815.GJ37471@deviant.kiev.zoral.com.ua>
	<47373C5E.2080800@elischer.org>
	<0414590D-0C2A-4EBD-9617-7AC193ABD1E8@mac.com>
	<4737696A.7050605@FreeBSD.org>
	<06618562-A789-4B5E-94BF-0ED8AB51A1FF@mac.com>
In-Reply-To: <06618562-A789-4B5E-94BF-0ED8AB51A1FF@mac.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: Kostik Belousov <kostikbel@gmail.com>, Alexander Motin <mav@FreeBSD.org>,
	freebsd-arch@FreeBSD.org
Subject: Re: Kernel thread stack usage
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch>
List-Post: <mailto:freebsd-arch@freebsd.org>
List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 12 Nov 2007 04:49:59 -0000

Marcel Moolenaar wrote:
> 
> On Nov 11, 2007, at 12:43 PM, Alexander Motin wrote:
> 
>> Marcel Moolenaar wrote:
>>> This is not theoretical at all: On ia64 there are 2 stacks. One
>>> growing down and one growing up. The downward stack is used for
>>> stack-based variables and the pward growing stack is used by
>>> the processor for stacked registers.
>>
>> Hmm, interesting. And which one is pointed by td_kstack there? Or they 
>> are using same segment but from opposite sides?
> 
> The latter. The td_kstack variable points to the bottom,
> which is where the register stack starts. The memory stack
> start from td_kstack + td_kstack_size.
> 
>>> The code suggested will not be meaningful on ia64.
>>
>> Why? If variable stack growing down and it's segment is pointed by 
>> td_kstack then where is the problem? Or you mean that system will die 
>> earlier when those two stacks in same segment will reach each other?
> 
> It's the register stack that grows faster in general and
> yes, they grow towards each other so they can eventually
> run into each other.
> 

so one could write something that detects tha tyou are getting close,
but it would have to be machine dependent..