From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760396AbZBDV0N (ORCPT ); Wed, 4 Feb 2009 16:26:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754294AbZBDVZy (ORCPT ); Wed, 4 Feb 2009 16:25:54 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:36079 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753550AbZBDVZx (ORCPT ); Wed, 4 Feb 2009 16:25:53 -0500 Date: Wed, 4 Feb 2009 13:25:29 -0800 From: Andrew Morton To: Ingo Molnar Cc: jeremy@goop.org, jaswinderrajput@gmail.com, randy.dunlap@oracle.com, linux-kernel@vger.kernel.org, x86@kernel.org, righi.andrea@gmail.com Subject: Re: mmotm 2009-02-02-17-12 uploaded (x86/nopmd etc.) Message-Id: <20090204132529.4b77dd4a.akpm@linux-foundation.org> In-Reply-To: <20090204200846.GF22608@elte.hu> References: <200902030112.n131CNiq010549@imap1.linux-foundation.org> <498893C8.6080506@oracle.com> <20090203191804.GA24698@elte.hu> <20090203121706.423d5cab.akpm@linux-foundation.org> <20090203212538.GB20527@elte.hu> <20090203134128.37042ea8.akpm@linux-foundation.org> <20090204200846.GF22608@elte.hu> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 4 Feb 2009 21:08:46 +0100 Ingo Molnar wrote: > > * Andrew Morton wrote: > > > > > This is getting painful. > > > > > > the include file spaghetti is ... interesting there, and it's historic. > > > > > > I could blame it on highmem, PAE or paravirt - but i'll only blame it on > > > paravirt for now because those developers are still around! ;-) > > > > > > Jeremy, any ideas how to reduce the historic dependency mess in that area? > > > I think we should go on three routes at once: > > > > > > - agressive splitup and separation of type definitions from method > > > declaration (+ inline definitions). The spinlock_types.h / spinlock.h > > > splitup was really nice in solving such dependency problems. > > > > I like this one. The mixing up of declare-something with use-something > > is often the source of our woes. > > yes. I mapped this problem area once and this is how the include file > spaghetti gets generated in practice: > > - type A gets declared > - type A gets _used_ in the same file in an inline method, BUT, > > that usage also brings in instantiated use of type X1, X2 and X3. > > if all types are declared like that everywhere, it can be seen (and it's a > mathematical certainty) that the only conflict-free way of doing this is to: > > - initially add random #include lines to bring in type X1, X2 and X3. > Which brings in recursive dependencies from those X1 X2 and X3 files. > > - when the stuff hits the fan then folks are in a big mess already and > only a deep restructuring could gets them out of it - which they rarely > do in an iterative environment. So they work it around iteratively: > instead of new nice inline methods [which we really prefer] they delay > all the 'usage' instantiation to .c file via the use of CPP macros > [which we hate because they hide bugs and cause bugs]. None of which would happen if we didn't also have an inlining fetish.