From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Date: Wed, 21 May 2008 12:59:37 +0200 Subject: [Ocfs2-devel] [RFC][PATCH 0/3] configfs: Make nested default groups lockdep-friendly In-Reply-To: <4833F89F.7080707@kerlabs.com> 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> Message-ID: <1211367577.6463.91.camel@lappy.programming.kicks-ass.net> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Louis Rilling Cc: Arjan van de Ven , Joel Becker , linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com 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. 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.. As to modifying lockdep - it currently doesn't know about trees and teaching it about them isn't easy. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764368AbYEULAA (ORCPT ); Wed, 21 May 2008 07:00:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755251AbYEUK7v (ORCPT ); Wed, 21 May 2008 06:59:51 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:44389 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755027AbYEUK7u (ORCPT ); Wed, 21 May 2008 06:59:50 -0400 Subject: Re: [RFC][PATCH 0/3] configfs: Make nested default groups lockdep-friendly From: Peter Zijlstra To: Louis Rilling Cc: Arjan van de Ven , Joel Becker , linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com In-Reply-To: <4833F89F.7080707@kerlabs.com> 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> Content-Type: text/plain Date: Wed, 21 May 2008 12:59:37 +0200 Message-Id: <1211367577.6463.91.camel@lappy.programming.kicks-ass.net> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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.. As to modifying lockdep - it currently doesn't know about trees and teaching it about them isn't easy.