From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759118AbYCDU4T (ORCPT ); Tue, 4 Mar 2008 15:56:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763208AbYCDUzr (ORCPT ); Tue, 4 Mar 2008 15:55:47 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:33477 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762839AbYCDUzp (ORCPT ); Tue, 4 Mar 2008 15:55:45 -0500 Date: Tue, 4 Mar 2008 15:55:42 -0500 (EST) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: "Paul E. McKenney" cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, ego@in.ibm.com, Ingo Molnar , Dipankar Sarma , Ted Tso , dvhltc@us.ibm.com, Oleg Nesterov , Andrew Morton , bunk@kernel.org, Josh Triplett , Thomas Gleixner , Peter Zijlstra , zippel@linux-m68k.org Subject: Re: [PATCH] move PREEMPT_RCU config option back under PREEMPT In-Reply-To: <20080304202207.GA10926@linux.vnet.ibm.com> Message-ID: References: <20071213170348.GA25981@in.ibm.com> <20071213171658.GE25981@in.ibm.com> <200802290534.57040.zippel@linux-m68k.org> <20080229045328.GA18687@linux.vnet.ibm.com> <20080301193903.GC15887@linux.vnet.ibm.com> <20080303185511.GE12453@linux.vnet.ibm.com> <20080304202207.GA10926@linux.vnet.ibm.com> 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 Tue, 4 Mar 2008, Paul E. McKenney wrote: > > The original preemptible-RCU patch put the choice between classic and > preemptible RCU into kernel/Kconfig.preempt, which resulted in build > failures on machines not supporting CONFIG_PREEMPT. This choice was > therefore moved to init/Kconfig, which worked, but placed the choice > between classic and preemptible RCU at the top level, a very obtuse choice > indeed. This patch changes from the Kconfig "choice" mechanism to a pair > of booleans, only one of which (CONFIG_PREEMPT_RCU) is user-visible, > and is located in kernel/Kconfig.preempt, where one would expect it > to be. The other (CONFIG_CLASSIC_RCU) is in init/Kconfig so that it > is available to all architectures, hopefully avoiding build breakage. > Thanks to Roman Zippel for suggesting this approach. > > I have tested this, but sadly do not have access to a machine that does > not support CONFIG_PREEMPT. However, I did edit my config in an attempt > to simulate this situation. One minor comment, but otherwise: Acked-by: Steven Rostedt > > Signed-off-by: Paul E. McKenney > config CLASSIC_RCU > - bool "Classic RCU" > + def_bool !PREEMPT_RCU > help > This option selects the classic RCU implementation that is > designed for best read-side performance on non-realtime > - systems. > - > - Say Y if you are unsure. > - You can get rid of the "help" part since it isn't visible to users. -- Steve