Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754524AbXI0HjR (ORCPT ); Thu, 27 Sep 2007 03:39:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752134AbXI0HjE (ORCPT ); Thu, 27 Sep 2007 03:39:04 -0400 Received: from public.id2-vpn.continvity.gns.novell.com ([195.33.99.129]:4422 "EHLO public.id2-vpn.continvity.gns.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752077AbXI0HjD convert rfc822-to-8bit (ORCPT ); Thu, 27 Sep 2007 03:39:03 -0400 Message-Id: <46FB7A7A.76E4.0078.0@novell.com> X-Mailer: Novell GroupWise Internet Agent 7.0.2 HP Date: Thu, 27 Sep 2007 08:40:10 +0100 From: "Jan Beulich" To: "Stephen Hemminger" Cc: , Subject: Re: [PATCH] Module use count must be updated as bridges are created/destroyed References: <46FA2C17.76E4.0078.0@novell.com> <20070926083705.6bc65ea5@fujitsu-loaner> <46FAA013.76E4.0078.0@novell.com> <20070926101252.3ccbb987@freepuppy.rosehill> In-Reply-To: <20070926101252.3ccbb987@freepuppy.rosehill> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1862 Lines: 44 >>> Stephen Hemminger 26.09.07 19:12 >>> >On Wed, 26 Sep 2007 17:08:19 +0100 >"Jan Beulich" wrote: > >> >>> Stephen Hemminger 26.09.07 17:37 >>> >> >On Wed, 26 Sep 2007 08:53:27 +0100 >> >"Jan Beulich" wrote: >> > >> >> Otherwise 'modprobe -r' on a module having a dependency on bridge will >> >> implicitly unload bridge, bringing down all connectivity that was >> >> using bridges. >> >> >> >> Signed-off-by: Jan Beulich >> >> >> > >> >No, network devices don't do reference counting. >> >What is the dependency? Where is the source of the module interacting >> >with the bridge? >> >> On a Xen system, I loaded and then unloaded ebtable_broute. The unload >> implicitly unloaded bridge, destroying the network. The only way I could see >> to avoid the implicit unload was to bump the reference count on bridge >> creation. Otherwise I would have to ask why bridge has a zero reference >> count despite a bridge being configured. >> >> Jan > >Sounds like a module utilities problem since unloading one module doesn't >normally unload others. I have to disagree here - 'modprobe -r' is specifically unloading all modules the specified one references as long as they have a use count of zero. The difference to other networking modules is that the latter normally don't export symbols, and hence don't have dependent modules (and thus cannot be subject of implicit unloading). Bridge does have dependents, and hence must avoid implicit unloading by managing its use count. Jan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/