Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762528AbYAQWxk (ORCPT ); Thu, 17 Jan 2008 17:53:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760979AbYAQWmw (ORCPT ); Thu, 17 Jan 2008 17:42:52 -0500 Received: from homer.mvista.com ([63.81.120.158]:3199 "EHLO gateway-1237.mvista.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1760858AbYAQWmv (ORCPT ); Thu, 17 Jan 2008 17:42:51 -0500 Subject: Re: setting jiffies as the clocksource stops time From: Daniel Walker To: Jan Engelhardt Cc: Balaji Rao , linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner In-Reply-To: References: <200801170209.42138.balajirrao@gmail.com> <1200518450.18731.129.camel@imap.mvista.com> Content-Type: text/plain Date: Thu, 17 Jan 2008 14:39:40 -0800 Message-Id: <1200609581.18731.152.camel@imap.mvista.com> Mime-Version: 1.0 X-Mailer: Evolution 2.12.2 (2.12.2-2.fc8) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1368 Lines: 33 On Thu, 2008-01-17 at 23:34 +0100, Jan Engelhardt wrote: > On Jan 16 2008 13:20, Daniel Walker wrote: > >On Thu, 2008-01-17 at 02:09 +0530, Balaji Rao wrote: > >> Hi, > >> > >> When i set jiffies as the current_clocksource, date(1) tells me > >> that wallclock time has stopped, and soon after that, the system > >> becomes unresponsive. This is not seen with CONFIG_NO_HZ disabled. > >> > >> I wonder how can jiffies be used as a clocksource.. Its value > >> depends on the tick and when we turn off ticks, we would stop > >> incrementing jiffies and when we come come out of idle, we update > >> the jiffies by reading the current_clocksource which now is > >> 'jiffies', and hence jiffies wouldn't get updated. Could this be > >> the explanation ? > > > >Your right, It can't be used as a clocksource with nohz , and the system > >will refuse to automatically switch to it .. > > I think that manually changing to jiffies by echoing into sysfs > should also be prohibited. Yeah, I wasn't suggesting we shouldn't prevent it .. However, there are tons of way to kill your system by manual changing things .. Daniel -- 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/