From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933424Ab1JYNGN (ORCPT ); Tue, 25 Oct 2011 09:06:13 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:60158 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933213Ab1JYNGM (ORCPT ); Tue, 25 Oct 2011 09:06:12 -0400 From: "Rafael J. Wysocki" To: vbyravarasu@nvidia.com Subject: Re: [PATCH] PM: fix calculation mistake in roll-over cases Date: Tue, 25 Oct 2011 15:08:40 +0200 User-Agent: KMail/1.13.6 (Linux/3.1.0-rc10+; KDE/4.6.0; x86_64; ; ) Cc: pavel@ucw.cz, len.brown@intel.com, gregkh@suse.de, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Alan Stern References: <1319538052-2480-1-git-send-email-vbyravarasu@nvidia.com> In-Reply-To: <1319538052-2480-1-git-send-email-vbyravarasu@nvidia.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-2" Content-Transfer-Encoding: 7bit Message-Id: <201110251508.40854.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, October 25, 2011, vbyravarasu@nvidia.com wrote: > From: venu byravarasu > > In case of jiffies roll over, delta is made zero. > Hence fixing it, after taking roll over into consideration. > > Signed-off-by: venu byravarasu > --- > When jiffies roll over, calculation of time spent in the > current state (stored in variable 'delta') is incorrect. > Hence fixing it, after taking roll over into consideration. > > drivers/base/power/runtime.c | 7 ++++--- > 1 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c > index 1079e03..bd93fb0 100644 > --- a/drivers/base/power/runtime.c > +++ b/drivers/base/power/runtime.c > @@ -30,12 +30,13 @@ static int rpm_suspend(struct device *dev, int rpmflags); > void update_pm_runtime_accounting(struct device *dev) > { > unsigned long now = jiffies; > - int delta; > + unsigned long delta; > + unsigned long max_num = ~0; > > delta = now - dev->power.accounting_timestamp; > > - if (delta < 0) > - delta = 0; > + if (now < dev->power.accounting_timestamp) > + delta = max_num - dev->power.accounting_timestamp + now; > > dev->power.accounting_timestamp = now; I'm not sure how this is supposed to improve things. Care to give more details? Rafael