From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965715AbZLHR5K (ORCPT ); Tue, 8 Dec 2009 12:57:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965706AbZLHR5I (ORCPT ); Tue, 8 Dec 2009 12:57:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:16492 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965695AbZLHR5H (ORCPT ); Tue, 8 Dec 2009 12:57:07 -0500 Date: Tue, 8 Dec 2009 18:51:10 +0100 From: Oleg Nesterov To: Peter Zijlstra Cc: Alexey Dobriyan , Ananth Mavinakayanahalli , Christoph Hellwig , "Frank Ch. Eigler" , Ingo Molnar , Roland McGrath , linux-kernel@vger.kernel.org, utrace-devel@redhat.com Subject: Re: [RFC,PATCH 14/14] utrace core Message-ID: <20091208175110.GB14815@redhat.com> References: <20091124200220.GA5828@redhat.com> <1259697242.1697.1075.camel@laptop> <20091201220847.GA25400@redhat.com> <1260210877.3935.594.camel@laptop> <20091208150417.GA11883@redhat.com> <1260286534.3935.1511.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1260286534.3935.1511.camel@laptop> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/08, Peter Zijlstra wrote: > > On Tue, 2009-12-08 at 16:04 +0100, Oleg Nesterov wrote: > > The > > problem is, this code was developed out-of-tree. That is why we would > > like to merge it asap, then do other changes which could be easily > > reviewed. > > > > Now, do you really mean we should throw out the working code, rewrite > > it avoiding these barriers, and resubmit? Sure, everything is possible. > > But this means another round of out-of-tree development with unclear > > results. > > Out-of-tree development is bad, it having taken lot of effort is no > excuse for merging ugly. > > Now, I'm not against barriers at all, but code that is as barrier heavy > as this, with such bad comments and no clear indication it was actually > worth using so many barriers make me wonder. Well. First of all, I agree at least partly. If you ask me, I feel that in any case utrace needs more cleanups (in fact, like almost any code in kernel) even if we forget about the barriers. In no way utrace is finished or perfect. I think that Roland won't argue ;) But. It would be much easier to do the futher development step by step, patch by patch, which the changelogs, with the possibilty to have the review. And it is much easier to change the code which is already used by people. And, cleanups/simplifications are the most hard part of the development. However, of course I can't "prove" that the current code is "good enough" for merging. > Barriers aren't free either, and having multiple such things in quick > succession isn't nessecarily faster than a lock, but much less obvious. It is hardly possible to argue. Oleg.