Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755021Ab2JHXAB (ORCPT ); Mon, 8 Oct 2012 19:00:01 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:37949 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089Ab2JHW76 (ORCPT ); Mon, 8 Oct 2012 18:59:58 -0400 Date: Mon, 8 Oct 2012 15:59:39 -0700 From: "Paul E. McKenney" To: Kees Cook Cc: Dave Jones , Dave Airlie , Frederic Weisbecker , Matthew Garrett , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, "Eric W. Biederman" , Serge Hallyn , "David S. Miller" , Andrew Morton Subject: Re: [PATCH] make CONFIG_EXPERIMENTAL invisible and default Message-ID: <20121008225939.GM2453@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20121007014447.GB2485@linux.vnet.ibm.com> <20121007163029.GG2485@linux.vnet.ibm.com> <20121007201854.GA6628@redhat.com> <20121008010410.GL2485@linux.vnet.ibm.com> <20121008222939.GK2453@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) x-cbid: 12100822-1976-0000-0000-000012290EFB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3792 Lines: 74 On Mon, Oct 08, 2012 at 03:40:57PM -0700, Kees Cook wrote: > On Mon, Oct 8, 2012 at 3:37 PM, Kees Cook wrote: > > On Mon, Oct 8, 2012 at 3:29 PM, Paul E. McKenney > > wrote: > >> On Mon, Oct 08, 2012 at 03:07:24PM -0700, Kees Cook wrote: > >>> On Sun, Oct 7, 2012 at 6:04 PM, Paul E. McKenney > >>> wrote: > >>> > On Sun, Oct 07, 2012 at 04:18:54PM -0400, Dave Jones wrote: > >>> >> On Sun, Oct 07, 2012 at 09:30:29AM -0700, Paul E. McKenney wrote: > >>> >> > >>> >> > > I think Kconfig is mostly what distro would like to use the thing is > >>> >> > > the Kconfig text needs to be there upfront when its merged, not two > >>> >> > > months later, since then it too late for a distro to notice. > >>> >> > > > >>> >> > > I'd bet most distros would read the warnings, but in a lot of cases > >>> >> > > the warning don't exist until its too late. > >>> >> > > >>> >> > In the case of CONFIG_RCU_USER_QS you are quite right, the warning > >>> >> > should have been there from the beginning and was not. I suppose you > >>> >> > could argue that the warning was not sufficiently harsh in the case of > >>> >> > CONFIG_RCU_FAST_NO_HZ, but either way it did get ignored: > >>> >> > >>> >> Maybe if we had a universally agreed upon tag for kconfig, like > >>> >> "distro recommendation: N" that would make things obvious, and also allow > >>> >> those of us unfortunate enough to maintain distro kernels to have something > >>> >> to easily grep for. This would also catch the case when you eventually (hopefully) > >>> >> flip from an N to a Y. > >>> >> > >>> >> There will likely still be some distros that will decide they know better > >>> >> (and I'm pretty sure eventually I'll find reason to do so myself), but it at least > >>> >> gives the feature maintainer the "I told you so" clause. > >>> >> > >>> >> Something we do quite often for our in-development kernels is enable something > >>> >> that's shiny, new and unproven, and then when we branch for a release, we turn > >>> >> it back off. It would be great if a lot of this kind of thing could be more automated. > >>> > > >>> > One approach would be to have CONFIG_DISTRO, so that experimental > >>> > features could use "depends on !DISTRO", but also to have multiple > >>> > "BLEEDING" symbols. For example, given a CONFIG_DISTRO_BLEEDING_HPC > >>> > and CONFIG_DISTRO_BLEEDING_RT, CONFIG_RCU_USER_QS might eventually > >>> > use the following clause: > >>> > > >>> > depends on !DISTRO || DISTRO_BLEEDING_HPC || DISTRO_BLEEDING_RT > >>> > > >>> > A normal distro would define DISTRO, a distro looking to provide bleeding-edge > >>> > HPC or real-time features would also define DISTRO_BLEEDING_HPC or > >>> > DISTRO_BLEEDING_RT, respectively. > >>> > > >>> > Does that make sense, or am I being overly naive? > >>> > >>> I think we should avoid any global configs that disable things. We'll > >>> just end up in the same place with distros again. > >> > >> So you believe that we should taint the kernel or splat on boot to > >> warn distros off of features that might not be ready for 100 million > >> users? Or do you have some other approach in mind? > > > > Personally, I think taint+printk seems like the right way to go. > > Actually, I think printk is sufficient. I don't want kernel taint to > become the new CONFIG_EXPERIMENTAL. :) OK, I'll bite... Why would kernel taint be more likely to become the new CONFIG_EXPERIMENTAL than printk() would? Thanx, Paul -- 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/