From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757353Ab0DAQBG (ORCPT ); Thu, 1 Apr 2010 12:01:06 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:39570 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757277Ab0DAQAx (ORCPT ); Thu, 1 Apr 2010 12:00:53 -0400 Date: Thu, 1 Apr 2010 08:55:59 -0700 (PDT) From: Linus Torvalds To: Nick Piggin cc: Rusty Russell , Nick Piggin , linux-kernel@vger.kernel.org, Jon Masters Subject: Re: Is module refcounting racy? In-Reply-To: <20100401080940.GA8356@laptop> Message-ID: References: <20100318105533.GE25636@laptop> <201003291942.56706.rusty@rustcorp.com.au> <201003311414.49364.rusty@rustcorp.com.au> <20100401080940.GA8356@laptop> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 1 Apr 2010, Nick Piggin wrote: > > I think it can be done racelessly with my patch, which is not really too > much overhead. I think if this is considered too much, then we should > either fix code and preferably de-export and remove module_refcount from > drivers, or remove module removal completely. I doubt your patch matters too much, but I like it conceptually and it seems to be a nice basis for perhaps doing something clever in the long run. [ ie avoiding the stop_machine and instead perhaps doing some optimistic thing like "see if we seem to be unused right now, then unregister us, and see - after unregistering - that the usage counts haven't increased, and re-register if they have. ] So I'd like to apply it as a "good improvement, even if module unloading which is the only thing that _should_ care deeply should already be under stop-machine". But I'd like an ack or two first. Linus