Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752356AbaLCXWE (ORCPT ); Wed, 3 Dec 2014 18:22:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45776 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751173AbaLCXWB (ORCPT ); Wed, 3 Dec 2014 18:22:01 -0500 Date: Wed, 3 Dec 2014 18:21:15 -0500 From: Dave Jones To: Thomas Gleixner Cc: Linus Torvalds , Chris Mason , Mike Galbraith , Ingo Molnar , Peter Zijlstra , =?iso-8859-1?Q?D=E2niel?= Fraga , Sasha Levin , "Paul E. McKenney" , Linux Kernel Mailing List , John Stultz Subject: Re: frequent lockups in 3.18rc4 Message-ID: <20141203232115.GA13266@redhat.com> Mail-Followup-To: Dave Jones , Thomas Gleixner , Linus Torvalds , Chris Mason , Mike Galbraith , Ingo Molnar , Peter Zijlstra , =?iso-8859-1?Q?D=E2niel?= Fraga , Sasha Levin , "Paul E. McKenney" , Linux Kernel Mailing List , John Stultz References: <20141203184111.GA32005@redhat.com> <20141203190045.GB32005@redhat.com> <20141203200906.GA3118@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 03, 2014 at 11:19:11PM +0100, Thomas Gleixner wrote: > On Wed, 3 Dec 2014, Linus Torvalds wrote: > > On Wed, Dec 3, 2014 at 12:55 PM, Thomas Gleixner wrote: > > > > > > But it's always negative, which means HPET is always ahead of > > > TSC. That excludes pretty much the clocksource watchdog starvation > > > issue which results in TSC being ahead of HPET due to a HPET > > > wraparound (which takes ~300s). > > > > Still, I'd be more likely to trust the TSC than the HPET on modern > > machines.. And DaveJ's machine isn't some old one. > > Well, that does not explain the softlock watchdog which is solely > relying on the TSC. > > > Of course, there's always BIOS games. Can we read the TSC offset > > register and check it being constant (modulo sleep events)? > > The kernel does not touch it. Here is a untested hack to verify it on > every local apic timer interrupt. Not nice, but simple :) > + pr_err("TSC adjustment on cpu %d changed %llu -> %llu\n", > + cpu, > + (unsigned long long) __this_cpu_read(tsc_adjust), > + (unsigned long long) adj); I just got [ 1472.614433] Clocksource tsc unstable (delta = -26373048906 ns) without any sign of the pr_err above. Dave -- 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/