From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753509AbYLZSd4 (ORCPT ); Fri, 26 Dec 2008 13:33:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751417AbYLZSdr (ORCPT ); Fri, 26 Dec 2008 13:33:47 -0500 Received: from pfepb.post.tele.dk ([195.41.46.236]:45130 "EHLO pfepb.post.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751333AbYLZSdq (ORCPT ); Fri, 26 Dec 2008 13:33:46 -0500 Date: Fri, 26 Dec 2008 19:35:12 +0100 From: Sam Ravnborg To: "Paul E. McKenney" Cc: Ingo Molnar , linux-kernel@vger.kernel.org, tglx@linutronix.de, akpm@linux-foundation.org, ralf@linux-mips.org, kernel@wantstofly.org, hskinnemoen@atmel.com, cooloney@kernel.org, tony.luck@intel.com, geert@linux-m68k.org, zippel@linux-m68k.org, jwboyer@linux.vnet.ibm.com, mporter@kernel.crashing.org, grant.likely@secretlab.ca, paulus@samba.org, benh@kernel.crashing.org, dhowells@redhat.com, yasutake.koichi@jp.panasonic.com, lethal@linux-sh.org, hpa@zytor.com Subject: Re: [PATCH -tip] Switch arm defconfig files from CONFIG_CLASSIC_RCU to CONFIG_TREE_RCU. Message-ID: <20081226183512.GA1520@uranus.ravnborg.org> References: <1229991147545-git-send-email-paulmck@linux.vnet.ibm.com> <12299911471985-git-send-email-paulmck@linux.vnet.ibm.com> <20081223142542.GC29151@elte.hu> <20081225083611.GA14968@elte.hu> <20081225093301.GB27896@uranus.ravnborg.org> <20081225192332.GI6912@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081225192332.GI6912@linux.vnet.ibm.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 25, 2008 at 11:23:32AM -0800, Paul E. McKenney wrote: > On Thu, Dec 25, 2008 at 10:33:01AM +0100, Sam Ravnborg wrote: > > On Thu, Dec 25, 2008 at 09:36:11AM +0100, Ingo Molnar wrote: > > > > > > below is the fix for another small buglet that hits architectures that do > > > not include kernel/Kconfig.preempt. > > > > What is needed to let all architectures include Kconfig.preempt? > > We should not advertise preemption if not supported, > > but we could do this by a simple Kconfig symbol: > > > > config HAVE_PREEMPT > > bool > > > > And let all architectures that supports preemption do: > > > > config "ARCH" > > select HAVE_PREEMPT > > > > But maybe there is a simpler solution > > The idea being to make things like PREEMPT then depend on HAVE_PREEMPT? Yes - exactly. So an arch can say that is includes support for preemption using the following Kconfig snippet: config X86 select HAVE_PREEMPT And then in the spot where we have a prompt we do: config PREEMPT bool "Do you want preemption?" depends on HAVE_PREEMPT Thne we will only present this option to the user for the architectures where it has indicated preemption support by selecting HAVE_PREEMPT. It is on purpose that HAVE_PREEMPT is a single boolean with no prompt or anything so we do not hit any of the pitfalls of using select. We use a similar pattern in many places today. Sam