Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751071AbVJSPID (ORCPT ); Wed, 19 Oct 2005 11:08:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751075AbVJSPID (ORCPT ); Wed, 19 Oct 2005 11:08:03 -0400 Received: from 213-239-205-147.clients.your-server.de ([213.239.205.147]:23209 "EHLO mail.tglx.de") by vger.kernel.org with ESMTP id S1751071AbVJSPIA (ORCPT ); Wed, 19 Oct 2005 11:08:00 -0400 Subject: Re: Ktimer / -rt9 (+custom) monotonic_clock going backwards. From: Thomas Gleixner Reply-To: tglx@linutronix.de To: Steven Rostedt Cc: john stultz , Ingo Molnar , linux-kernel@vger.kernel.org In-Reply-To: References: Content-Type: text/plain Organization: linutronix Date: Wed, 19 Oct 2005 17:10:26 +0200 Message-Id: <1129734626.19559.275.camel@tglx.tec.linutronix.de> 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 Content-Length: 1146 Lines: 31 On Wed, 2005-10-19 at 10:59 -0400, Steven Rostedt wrote: > Hi Thomas, > > I switched my custom kernel timer to use the ktimers with the prio of -1 > as you mentioned to me offline. I set up the timer to be monotonic and > have a requirement that the returned time is always greater or equal to > the last time returned from do_get_ktime_mono. > > Now here's the results that I got between two calls of do_get_ktime_mono > > 358.069795728 secs then later 355.981483177. Should this ever happen? Definitely not. monotonic time must go forwards. > I haven't look to see if this happens in vanilla -rt10 but I haven't > touched your ktimer code except for my logging and the patch with the > unlock_ktimer_base (since I was based off of -rt9) The ktimer code itself calls the timeofday code, which provides the monotonic clock. I have no idea what might go wrong. Is this reproducible ? tglx - 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/