From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 30 Aug 2002 20:47:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 30 Aug 2002 20:47:57 -0400 Received: from nameservices.net ([208.234.25.16]:13602 "EHLO opersys.com") by vger.kernel.org with ESMTP id ; Fri, 30 Aug 2002 20:47:56 -0400 Message-ID: <3D7012EC.C1FEF112@opersys.com> Date: Fri, 30 Aug 2002 20:50:52 -0400 From: Karim Yaghmour Reply-To: karim@opersys.com X-Mailer: Mozilla 4.75 [en] (X11; U; Linux 2.4.19 i686) X-Accept-Language: en, French/Canada, French/France, fr-FR, fr-CA MIME-Version: 1.0 To: "Ph. Marek" CC: linux-kernel@vger.kernel.org, Richard Moore Subject: Re: AGAIN: Re: gettimeofday clock jump bug (on AMD 756) References: <200208291200.54694.marek@bmlv.gv.at> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "Ph. Marek" wrote: > The difference is both times about 4295 seconds - so I think that the problem > has something to do with 2^32 microseconds. This 2^32 jump is consistent with the jumps I saw. I was discussing this issue with Richard Moore (IBM) a couple of weeks ago and he mentionned that they had seen a similar problem with OS/2. In that case, the problems were due to the time it took to read some timer register. In other words, there may be a short time-window where the values available are valid and nothing is garanteed if we exceed this time-window. (This is second hand and I may have misunderstood a couple of details, so I attached Richard so he can confirm/deny what I'm saying here.) Linux reads the PIT (8253) every 10ms on a PC, so the question is: anyone know about 8253 reading deadlines ? Karim =================================================== Karim Yaghmour karim@opersys.com Embedded and Real-Time Linux Expert ===================================================