From owner-freebsd-hackers@FreeBSD.ORG  Wed Nov  2 19:16:30 2005
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
X-Original-To: freebsd-hackers@freebsd.org
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 4F7B216A41F
	for <freebsd-hackers@freebsd.org>; Wed,  2 Nov 2005 19:16:30 +0000 (GMT)
	(envelope-from julian@elischer.org)
Received: from a50.ironport.com (a50.ironport.com [63.251.108.112])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 17CD943D5F
	for <freebsd-hackers@freebsd.org>; Wed,  2 Nov 2005 19:16:23 +0000 (GMT)
	(envelope-from julian@elischer.org)
Received: from unknown (HELO [10.251.23.117]) ([10.251.23.117])
	by a50.ironport.com with ESMTP; 02 Nov 2005 11:09:38 -0800
X-IronPort-Anti-Spam-Filtered: true
Message-ID: <43690EED.10703@elischer.org>
Date: Wed, 02 Nov 2005 11:09:33 -0800
From: Julian Elischer <julian@elischer.org>
User-Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US;
	rv:1.7.11) Gecko/20050727
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: Dinesh Nair <dinesh@alphaque.com>
References: <4360B8EE.4070605@alphaque.com>	<4360DD7B.20900@samsco.org>	<4361044B.50807@alphaque.com>	<20051027.205250.55834228.imp@bsdimp.com>
	<43690424.1040904@alphaque.com>
In-Reply-To: <43690424.1040904@alphaque.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: freebsd-hackers@freebsd.org
Subject: Re: locking in a device driver
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 02 Nov 2005 19:16:30 -0000

Dinesh Nair wrote:

>
>
> On 10/28/05 10:52 M. Warner Losh said the following:
>
>> libc_r will block all other threads in the application while an ioctl
>> executes.  libpthread and libthr won't.  I've had several bugs at work
>
>
> so if the userland thread does an ioctl, and the the driver goes to 
> tsleep() when the ioctl is received, all other threads are also 
> blocked from executing, i.e wont be context switched to run ?

in 4.x and earlier. a tsleep saves your spl level but re-enables the 
interrupts (from memory)
when you re-awaken you are given your spl level again..  All other 
threads are allowed to run.

lower level code (the interupt executed part is not allowed to ever sleep)

>
> is this behaviour only 4.x specific or is it also there in 5.x ?