Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753393AbWKHBgO (ORCPT ); Tue, 7 Nov 2006 20:36:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753827AbWKHBgO (ORCPT ); Tue, 7 Nov 2006 20:36:14 -0500 Received: from gateway-1237.mvista.com ([63.81.120.158]:30463 "EHLO gateway-1237.mvista.com") by vger.kernel.org with ESMTP id S1753393AbWKHBgN (ORCPT ); Tue, 7 Nov 2006 20:36:13 -0500 Message-ID: <4551348B.6070604@mvista.com> Date: Tue, 07 Nov 2006 17:36:11 -0800 From: Kevin Hilman User-Agent: Thunderbird 1.5.0.7 (X11/20060918) MIME-Version: 1.0 To: Ingo Molnar Cc: Thomas Gleixner , linux-kernel@vger.kernel.org Subject: 2.6.18-rt7: rollover with 32-bit cycles_t Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 750 Lines: 22 On ARM, I'm noticing the 'bug' message from check_critical_timing() where two calls to get_cycles() are compared and the 2nd is assumed to be >= the first. This isn't properly handling the case of rollover which occurs relatively often with fast hardware clocks and 32-bit cycle counters. Is this really a bug? If the get_cycles() can be assumed to run between 0 and (cycles_t)~0, using the right unsigned math could get a proper delta even in the rollover case. Is this a safe assumption? Kevin - 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/