From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753996Ab2HAGuT (ORCPT ); Wed, 1 Aug 2012 02:50:19 -0400 Received: from www.linutronix.de ([62.245.132.108]:48277 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750824Ab2HAGuS (ORCPT ); Wed, 1 Aug 2012 02:50:18 -0400 Date: Wed, 1 Aug 2012 08:50:12 +0200 (CEST) From: Thomas Gleixner To: John Stultz cc: CAI Qian , linux-kernel , Ingo Molnar , Peter Zijlstra , Prarit Bhargava , Zhouping Liu Subject: Re: boot panic regression introduced in 3.5-rc7 In-Reply-To: <501771CA.1090304@us.ibm.com> Message-ID: References: <1971950954.1278169.1343620316300.JavaMail.root@redhat.com> <501771CA.1090304@us.ibm.com> User-Agent: Alpine 2.02 (LFD 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 On Mon, 30 Jul 2012, John Stultz wrote: > On 07/29/2012 08:51 PM, CAI Qian wrote: > Now, one of the reasons Thomas and I changed the logic was that using the > precalculated realtime_offset was slightly more efficient then re-adding xtime > and wall_to_monotonic's components separately. But how valuable this > unmeasured slight efficiency is vs extra robustness for crazy time values is > questionable. Well, I guess it unearthed a weakness which has been there forever: Trusting random values which are supplied by cmos or whatever. So the right fix is: > 2) Validate that time values we accept are smaller the ktime_t before using > them. I really don't like the magic workaround by nulling out the effect of crap data with a more expensive calculation. Thanks, tglx