From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932732AbYEUMyr (ORCPT ); Wed, 21 May 2008 08:54:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750821AbYEUMyj (ORCPT ); Wed, 21 May 2008 08:54:39 -0400 Received: from bohort.kerlabs.com ([62.160.40.57]:60096 "EHLO bohort.kerlabs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754195AbYEUMyi (ORCPT ); Wed, 21 May 2008 08:54:38 -0400 Message-ID: <48341B8A.1050000@kerlabs.com> Date: Wed, 21 May 2008 14:54:34 +0200 From: Louis Rilling Organization: Kerlabs User-Agent: IceDove 1.5.0.14pre (X11/20071018) MIME-Version: 1.0 To: Peter Zijlstra CC: Arjan van de Ven , Joel Becker , linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com Subject: Re: [RFC][PATCH 0/3] configfs: Make nested default groups lockdep-friendly References: <20080520163320.025971210@kerlabs.com> <20080520095810.1d50d247@infradead.org> <20080520215639.GG26609@mail.oracle.com> <20080520151341.058f2df4@infradead.org> <1211361784.6463.68.camel@lappy.programming.kicks-ass.net> <4833F89F.7080707@kerlabs.com> <1211367577.6463.91.camel@lappy.programming.kicks-ass.net> In-Reply-To: <1211367577.6463.91.camel@lappy.programming.kicks-ass.net> X-Enigmail-Version: 0.94.2.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra a écrit : > On Wed, 2008-05-21 at 12:25 +0200, Louis Rilling wrote: > >>> http://programming.kicks-ass.net/kernel-patches/concurrent-pagecache/23-rc1-rt/radix-concurrent-lockdep.patch >> Thanks for pointing this out. >> >> Yes this could solve part of the issue, at the price of duplicating the >> inode mutex class. However, this still does not solve the issue when >> deleting config_groups, since in that case all nodes of the tree are >> locked. Thinking about adding lockdep support for concurrent locking of >> the direct children of a node in a tree... > > Why doesn't sysfs have this problem? - the code says configfs was > derived from sysfs. Perhaps because sysfs is driven from the kernel, where behaviors can be controlled, while in configfs only userspace creates/removes directories. > > Also, do you really need to hold all locks when removing something? > sound like a bit overdone. Also realise there is a maximum number of > held locks - various people have already requested it to be increased or > made dynamic. We're reluctant in doing so because we feel lock chains > should not be of unlimited length. The deeper the chains the bigger the > PI overhead etc.. I did not write configfs, so I can only observe that a whole inode tree is locked when removing a directory hierarchy. I suspect that this is intended to provide userspace and client sub-systems with some atomic semantics... > > As to modifying lockdep - it currently doesn't know about trees and > teaching it about them isn't easy. That was my guess. -- Dr Louis Rilling Kerlabs Skype: louis.rilling Batiment Germanium Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes http://www.kerlabs.com/ 35700 Rennes