Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933826Ab3GEPYM (ORCPT ); Fri, 5 Jul 2013 11:24:12 -0400 Received: from www.linutronix.de ([62.245.132.108]:45716 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757373Ab3GEPYL (ORCPT ); Fri, 5 Jul 2013 11:24:11 -0400 Date: Fri, 5 Jul 2013 17:24:09 +0200 (CEST) From: Thomas Gleixner To: Peter Zijlstra cc: Frederic Weisbecker , Alex Shi , hpa@linux.intel.com, tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org, andi.kleen@intel.com, mingo@elte.hu Subject: Re: [URGENT rfc patch 0/3] tsc clocksource bug fix In-Reply-To: <20130705143833.GT23916@twins.programming.kicks-ass.net> Message-ID: References: <1372916056-24301-1-git-send-email-alex.shi@intel.com> <20130704075840.GH18898@dyad.programming.kicks-ass.net> <20130705143833.GT23916@twins.programming.kicks-ass.net> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1189 Lines: 37 On Fri, 5 Jul 2013, Peter Zijlstra wrote: > On Fri, Jul 05, 2013 at 04:23:33PM +0200, Frederic Weisbecker wrote: > > Nope, I haven't touched that. I prefer not to fiddle with unstable > > clocksource for now :) > > > > As for unstable TSCs, if sched_clock_tick() needs to be fed, we simply > > don't stop the tick. > > Not entirely the same thing; I thought the clocksource watchdog was ran > even when we have a 'stable' TSC, just to make sure it stays stable. > There's known cases where the BIOS f*cks us over and wrecks TSC sync. See arch/x86/kernel/tsc.c We disable the watchdog for the TSC when tsc_clocksource_reliable is set. tsc_clocksource_reliable is set when: - you add tsc=reliable to the kernel command line - boot_cpu_has(X86_FEATURE_TSC_RELIABLE) X86_FEATURE_TSC_RELIABLE is a software flag, set by vmware and moorsetown. So all other machines keep the watchdog enabled. - On Geode LX (OLPC) Thanks, tglx -- 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/