From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756066Ab1KKHIH (ORCPT ); Fri, 11 Nov 2011 02:08:07 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:36906 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752395Ab1KKHIG (ORCPT ); Fri, 11 Nov 2011 02:08:06 -0500 Date: Fri, 11 Nov 2011 08:06:15 +0100 From: Ingo Molnar To: John Stultz Cc: Thomas Gleixner , lkml , Peter Zijlstra Subject: Re: [GIT PULL] TSC sched_clock overflow workaround Message-ID: <20111111070615.GA14347@elte.hu> References: <1320987192.15791.13.camel@js-netbook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1320987192.15791.13.camel@js-netbook> User-Agent: Mutt/1.5.21 (2010-09-15) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=AWL,BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] 0.0 AWL AWL: From: address is in the auto white-list Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * John Stultz wrote: > 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. I'd *much* rather see a real fix for this than an ugly workaround that disables a very real speedup. Thanks, Ingo