From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932687AbVKYN2W (ORCPT ); Fri, 25 Nov 2005 08:28:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932688AbVKYN2W (ORCPT ); Fri, 25 Nov 2005 08:28:22 -0500 Received: from ms-smtp-01.nyroc.rr.com ([24.24.2.55]:32163 "EHLO ms-smtp-01.nyroc.rr.com") by vger.kernel.org with ESMTP id S932687AbVKYN2W (ORCPT ); Fri, 25 Nov 2005 08:28:22 -0500 Subject: Re: duration of udelay differs with activated realtime-preempt patch? From: Steven Rostedt To: "Schultheiss, Christoph" Cc: john stultz , Ingo Molnar , linux-kernel@vger.kernel.org In-Reply-To: References: Content-Type: text/plain Date: Fri, 25 Nov 2005 08:28:05 -0500 Message-Id: <1132925285.6694.9.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2005-11-25 at 11:26 +0100, Schultheiss, Christoph wrote: > kernel: 2.6.14 with and without the realtime-preempt patch > > hi list, > > after measuring the duration of the function udelay (with oscilloscope > at parallel port), I figured out that udelay (5usec) with activated > realtime- preempt patch lasts a little bit longer. Without the patch the > time is exact. > All kernel debug switches are turned off at compile time. > Can anyone suggest why this happens? Well, the -rt patch, has changed the udelay function. BTW, you are using the constant udelay, right? Maybe an example of the code you used to test might be useful. Ingo or John? -- Steve