From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754881AbZFGHBr (ORCPT ); Sun, 7 Jun 2009 03:01:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754115AbZFGHBj (ORCPT ); Sun, 7 Jun 2009 03:01:39 -0400 Received: from fg-out-1718.google.com ([72.14.220.152]:5803 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754112AbZFGHBi (ORCPT ); Sun, 7 Jun 2009 03:01:38 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=lyjMXYfwNfrLEGmqWJW3GjcIIy2Iw3HVI7vWKRp+uqgrUAbJIDTbaGONdf9Aw5q+DX D96wcFRMGqcVttoBTFKzzIroeI2XJWvaRNEzDi9xxK5j1fJ3D9xCso56fnjlr9PiHWqm jq4Kfg/s+WEt0cImHVrxTz5tvDrWNnKvauAEA= Date: Sun, 7 Jun 2009 11:01:36 +0400 From: Cyrill Gorcunov To: Yinghai Lu Cc: Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] x86: fix dummy apic read/write warning Message-ID: <20090607070136.GA4547@lenovo> References: <20090606073737.GA3163@elte.hu> <4A2AEAC6.8060404@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A2AEAC6.8060404@kernel.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Yinghai Lu - Sat, Jun 06, 2009 at 03:16:38PM -0700] | ingo got | [ 0.000000] Using APIC driver default | [ 0.000000] SMP: Allowing 1 CPUs, 0 hotplug CPUs | [ 0.000000] Local APIC disabled by BIOS -- you can enable it with "lapic" | [ 0.000000] APIC: disable apic facility | [ 0.000000] ------------[ cut here ]------------ | [ 0.000000] WARNING: at arch/x86/kernel/apic/apic.c:254 native_apic_read_dummy+0x2d/0x3b() | [ 0.000000] Hardware name: HP OmniBook PC | | we have wrong check in dummy read and write. | [we only test on system that have APIC with "disableapic"...] | | Signed-off-by: yinghai Lu | | --- | arch/x86/kernel/apic/apic.c | 4 ++-- | 1 file changed, 2 insertions(+), 2 deletions(-) | | Index: linux-2.6/arch/x86/kernel/apic/apic.c | =================================================================== | --- linux-2.6.orig/arch/x86/kernel/apic/apic.c | +++ linux-2.6/arch/x86/kernel/apic/apic.c | @@ -246,12 +246,12 @@ static int modern_apic(void) | */ | static void native_apic_write_dummy(u32 reg, u32 v) | { | - WARN_ON_ONCE((cpu_has_apic || !disable_apic)); | + WARN_ON_ONCE((cpu_has_apic && !disable_apic)); | } | | static u32 native_apic_read_dummy(u32 reg) | { | - WARN_ON_ONCE((cpu_has_apic || !disable_apic)); | + WARN_ON_ONCE((cpu_has_apic && !disable_apic)); | return 0; | } | | No Yinghai, this is wrong. native_apic_write_dummy is not admissible to be called after apic->write has been NOP'ified. If a site calls for apic->write after apic_disable() it's a plain *bug* in caller. So we should continute warning if cpu_has_apic _or_ !disable_apic. Though since for SMP compiled kernel we still rely on apic->read the snippet is to be changed to (cpu_has_apic && !disable_apic) indeed. -- Cyrill