Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751905Ab3IFSuq (ORCPT ); Fri, 6 Sep 2013 14:50:46 -0400 Received: from mail-pb0-f42.google.com ([209.85.160.42]:51834 "EHLO mail-pb0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750891Ab3IFSun (ORCPT ); Fri, 6 Sep 2013 14:50:43 -0400 MIME-Version: 1.0 In-Reply-To: <20130906173047.GT3966@linux.vnet.ibm.com> References: <20130820024700.GA31075@linux.vnet.ibm.com> <1376966841-31774-1-git-send-email-paulmck@linux.vnet.ibm.com> <1376966841-31774-8-git-send-email-paulmck@linux.vnet.ibm.com> <20130906173047.GT3966@linux.vnet.ibm.com> Date: Fri, 6 Sep 2013 20:50:41 +0200 X-Google-Sender-Auth: 0CY-eeHdw9xs2TdtWh5y8gicPCs Message-ID: Subject: Re: [PATCH tip/core/rcu 8/9] nohz_full: Add full-system-idle state machine From: Geert Uytterhoeven To: Paul McKenney Cc: "linux-kernel@vger.kernel.org" , Ingo Molnar , laijs@cn.fujitsu.com, dipankar@in.ibm.com, Andrew Morton , Mathieu Desnoyers , josh@joshtriplett.org, niv@us.ibm.com, Thomas Gleixner , Peter Zijlstra , Steven Rostedt , David Howells , edumazet@google.com, darren@dvhart.com, =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= , sbw@mit.edu, Linux-Arch , linux-kbuild Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1837 Lines: 52 On Fri, Sep 6, 2013 at 7:30 PM, Paul E. McKenney wrote: >> Furthermore, it seems only hexagon, metag, mips, and x86 set NR_CPUS to 1 >> if !SMP. On other architectures, NR_CPUS is not defined and presumed to be 0. > > Would it make sense to require that NR_CPUS=1 for !SMP? Yes, this looks reasonable to me. > I tried creating a NR_CPUS_REALLY as follows: > > config NR_CPUS_REALLY > int "Fixed version of NR_CPUS" > default NR_CPUS if NR_CPUS > default 1 if !NR_CPUS > > But this still gave a warning on the first "default" even though it > was not in effect. I also tried using Kconfig "if": IIRC, it tries to use the first default first, so the below may work (the "if SMP" is probably not needed): config NR_CPUS_REALLY int "Fixed version of NR_CPUS" default 1 if !SMP default NR_CPUS if SMP > Defining NR_CPUS=1 if !SMP is looking pretty good to me just now. > This would probably have other benefits -- I cannot be the only > person who ever wanted this. ;-) Sure. I just didn't want to create patches for all architectures without having a discussion first. And it would be nice if it cuould be done in a central place, without touching all architectures. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- 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/