Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965266AbVKBVmD (ORCPT ); Wed, 2 Nov 2005 16:42:03 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965269AbVKBVmD (ORCPT ); Wed, 2 Nov 2005 16:42:03 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:46562 "EHLO e31.co.us.ibm.com") by vger.kernel.org with ESMTP id S965266AbVKBVmB (ORCPT ); Wed, 2 Nov 2005 16:42:01 -0500 Subject: 2.6.14-rt4: __get_nsec_offset() false positives From: john stultz To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Steven Rostedt , Fernando Lopez-Lezcano , Mark Knecht , Florian Schmidt , "K.R. Foley" , Rui Nuno Capela In-Reply-To: <20051030133316.GA11225@elte.hu> References: <20051017160536.GA2107@elte.hu> <20051020195432.GA21903@elte.hu> <20051030133316.GA11225@elte.hu> Content-Type: text/plain Date: Wed, 02 Nov 2005 13:41:42 -0800 Message-Id: <1130967703.27168.503.camel@cog.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1179 Lines: 34 Hey Ingo, I just booted 2.6.14-rt4 and I'm getting lots of the __get_nsec_offset() warnings where there isn't really a problem. The main issue is that the clocksource may not be a TSC (acpi_pm in my case), so the check to see if the cycle value ever goes backwards will falsely trigger when the 24bit wide ACPI PM counter wraps. To properly check for algorithmic inconsistencies, the checks should probably be similar to what you had earlier inside __get_monotonic_clock(), since at __get_nsec_offset() you really don't have enough information to sort out if an inconsistency has occurred. If we want to watch for hardware inconsistencies (like unsynced TSCs), those checks really need to go inside the clocksource drivers themselves. I'll write up a paranoid debug patch that provides similar checks for both cases and include it in my patch set so you don't have to keep forward porting your own versions. thanks -john - 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/