From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757244Ab1KKExX (ORCPT ); Thu, 10 Nov 2011 23:53:23 -0500 Received: from e1.ny.us.ibm.com ([32.97.182.141]:55964 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753448Ab1KKExV (ORCPT ); Thu, 10 Nov 2011 23:53:21 -0500 Message-ID: <1320987192.15791.13.camel@js-netbook> Subject: [GIT PULL] TSC sched_clock overflow workaround From: John Stultz To: Thomas Gleixner , Ingo Molnar Cc: lkml , Peter Zijlstra Date: Thu, 10 Nov 2011 20:53:12 -0800 Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.1- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 x-cbid: 11111104-6078-0000-0000-00000441A2A9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hey Thomas, Ingo, I thought Peter had sent this on, but apparently its not landed yet, so I wanted to make sure you got it. After ~208 days, the sched_clock multiplication overflows and causes some false positives in the softlockup watchdog. I don't think there are any actual panics going on, as an earlier related div by zero issue was already fixed. However, the false positives do continue to worry folks. We still need a proper fix, which will probably be in part making sched_clock do periodic accumulation, as well as possibly changing users of sched_clock (like the softlockup watchdog) use timekeeping timestamps rather then sched_clock. thanks -john Peter's workaround is available in the git repository at: git://git.linaro.org/people/jstultz/linux.git fortglx/3.2/tip/sched/clock Peter Zijlstra (1): x86, intel: Don't mark sched_clock() as stable arch/x86/kernel/cpu/intel.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-)