From owner-freebsd-geom@FreeBSD.ORG  Thu Oct 25 08:41:20 2012
Return-Path: <owner-freebsd-geom@FreeBSD.ORG>
Delivered-To: freebsd-geom@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
 by hub.freebsd.org (Postfix) with ESMTP id CDB48386;
 Thu, 25 Oct 2012 08:41:20 +0000 (UTC)
 (envelope-from phk@phk.freebsd.dk)
Received: from phk.freebsd.dk (phk.freebsd.dk [130.225.244.222])
 by mx1.freebsd.org (Postfix) with ESMTP id 857C78FC1A;
 Thu, 25 Oct 2012 08:41:20 +0000 (UTC)
Received: from critter.freebsd.dk (critter.freebsd.dk [192.168.61.3])
 by phk.freebsd.dk (Postfix) with ESMTP id E96C73B74C;
 Thu, 25 Oct 2012 08:41:18 +0000 (UTC)
Received: from critter.freebsd.dk (localhost [127.0.0.1])
 by critter.freebsd.dk (8.14.5/8.14.5) with ESMTP id q9P8fIsh070961;
 Thu, 25 Oct 2012 08:41:18 GMT (envelope-from phk@phk.freebsd.dk)
To: Andriy Gapon <avg@FreeBSD.org>
Subject: Re: geom access method and g_topology_lock
In-reply-to: <5088FA15.30205@FreeBSD.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
References: <5088E0E0.2080307@FreeBSD.org>
 <28185.1351150111@critter.freebsd.dk> <5088FA15.30205@FreeBSD.org>
Date: Thu, 25 Oct 2012 08:41:18 +0000
Message-ID: <70960.1351154478@critter.freebsd.dk>
Cc: freebsd-geom@FreeBSD.org
X-BeenThere: freebsd-geom@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: GEOM-specific discussions and implementations
 <freebsd-geom.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-geom>,
 <mailto:freebsd-geom-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-geom>
List-Post: <mailto:freebsd-geom@freebsd.org>
List-Help: <mailto:freebsd-geom-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-geom>,
 <mailto:freebsd-geom-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 25 Oct 2012 08:41:20 -0000

--------
In message <5088FA15.30205@FreeBSD.org>, Andriy Gapon writes:

>Both pieces look sane and non-racy (because of g_topology_assert) until we allow
>g_access (some geom access method, rather) to drop the topology lock.

You lost me there.

g_access() cannot do its job without holding the topology lock.


-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.