From owner-freebsd-arch@FreeBSD.ORG  Fri Dec 17 04:50:26 2004
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
Delivered-To: freebsd-arch@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 2BB2D16A4F5; Fri, 17 Dec 2004 04:50:26 +0000 (GMT)
Received: from server1.astraldream.net (astraldream.net [69.20.5.160])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 84C0443D3F; Fri, 17 Dec 2004 04:50:25 +0000 (GMT)
	(envelope-from ssouhlal@FreeBSD.org)
Received: from [192.168.0.98] (pool-138-88-246-116.res.east.verizon.net
	[138.88.246.116])	(authenticated (0 bits))
	by server1.astraldream.net (8.11.6/8.11.6) with ESMTP id iBH4oEW12433
	(using TLSv1/SSLv3 with cipher RC4-SHA (128 bits) verified NO);
	Thu, 16 Dec 2004 23:50:23 -0500
In-Reply-To: <200412131232.55051.max@love2party.net>
References: <94AE3F5A-4CD6-11D9-8BD6-000A95C4D7BC@FreeBSD.org>
	<200412130913.20215.max@love2party.net>
	<200412131232.55051.max@love2party.net>
Mime-Version: 1.0 (Apple Message framework v619)
Content-Type: text/plain; charset=US-ASCII; format=flowed
Message-Id: <21F934EB-4FE7-11D9-B1F7-000A95C4D7BC@FreeBSD.org>
Content-Transfer-Encoding: 7bit
From: Suleiman Souhlal <ssouhlal@FreeBSD.org>
Date: Thu, 16 Dec 2004 23:50:11 -0500
To: Max Laier <max@love2party.net>
X-Mailer: Apple Mail (2.619)
cc: freebsd-current@FreeBSD.org
cc: freebsd-arch@FreeBSD.org
Subject: Re: sysctl locking
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.1
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: Fri, 17 Dec 2004 04:50:26 -0000

Hello,

On Dec 13, 2004, at 6:32 AM, Max Laier wrote:

> 1) Extend sysctl_add_oid() to accept an additional mutex argument.
> 2) Extend the simple sysctl handler to use this mutex to protect the 
> actual
>    write(?read?). We must not hold the mutex during the useland copy 
> in/out so
>    we must move to temporary storage.
> 3) To maintain the current API and behavior we use &Giant as the 
> default
>    fallback argument. This might need some extension for complex 
> handler (i.e.
>    no mutex given -> acquire Giant before calling the complex handler).
>
> What do people think of this? Does it make any sense? Should we be 
> concerned
> at all? Does the extension make sense? Comments?

I have implemented this. The diff is at 
http://people.freebsd.org/~ssouhlal/sysctl-sx-locking-20041214.diff
It also needs the patch at 
http://people.freebsd.org/~ssouhlal/sx_xlocked.diff which introduces a 
sx_xlocked() function.

Unfortunately, we still need to look at every single SYSCTL_PROC, and 
make either grab Giant, lock correctly, or make sure it doesn't need 
any locking. :(

--
Suleiman Souhlal     | ssouhlal@vt.edu
The FreeBSD Project  | ssouhlal@FreeBSD.org