From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758228AbZHQWYb (ORCPT ); Mon, 17 Aug 2009 18:24:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751632AbZHQWYa (ORCPT ); Mon, 17 Aug 2009 18:24:30 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:34503 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753344AbZHQWY3 (ORCPT ); Mon, 17 Aug 2009 18:24:29 -0400 Subject: Re: clocksource changes in 2.6.31 - possible regression From: john stultz To: Stephen Hemminger Cc: Andrew Morton , Thomas Gleixner , linux-kernel@vger.kernel.org In-Reply-To: <20090817144546.7f1d6572@nehalam> References: <20090817090319.20979986@nehalam> <1250531337.26171.12.camel@work-vm> <20090817110127.40ee5c29@nehalam> <1250532954.26171.35.camel@work-vm> <20090817112704.2b4b2987@nehalam> <1250543459.7212.41.camel@localhost.localdomain> <1250545077.7212.49.camel@localhost.localdomain> <20090817144546.7f1d6572@nehalam> Content-Type: text/plain Date: Mon, 17 Aug 2009 15:23:22 -0700 Message-Id: <1250547802.7212.82.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.24.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2009-08-17 at 14:45 -0700, Stephen Hemminger wrote: > On Mon, 17 Aug 2009 14:37:57 -0700 > john stultz wrote: > > However, I think its fair, that as your TSC is being disqualified for > > being an old AMD SMP box, and there is a *possibility* that if you don't > > run with cpufreq and the SUMA-ness of the box didn't get in the way of > > TSC synchronization, you might have an argument for overriding the > > unsynchronized_tsc() heuristics. > > > > Luckily the option is already there. :) > > > > So try booting with "tsc=reliable" to override those checks, and I think > > you'll be able to do what you want to do. > > > > Good idea, doesn't work. > > vyatta@amd1:~$ cat /proc/cmdline > BOOT_IMAGE=/boot/vmlinuz-2.6.31-rc6 root=/dev/sda1 ro tsc=reliable > vyatta@amd1:~$ cat /sys/devices/system/clocksource/clocksource0/available_clocksource > acpi_pm Bah! My apologies for half-assing this. How about with the following *tested* patch (includes a variant of Thomas' fix). thanks -john Signed-off-by: John Stultz diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 71f4368..648fb26 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -825,6 +825,9 @@ __cpuinit int unsynchronized_tsc(void) if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) return 0; + + if (tsc_clocksource_reliable) + return 0; /* * Intel systems are normally all synchronized. * Exceptions must mark TSC as unstable: @@ -832,10 +835,10 @@ __cpuinit int unsynchronized_tsc(void) if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) { /* assume multi socket systems are not synchronized: */ if (num_possible_cpus() > 1) - tsc_unstable = 1; + return 1; } - return tsc_unstable; + return 0; } static void __init init_tsc_clocksource(void)