From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755250Ab0EWVVH (ORCPT ); Sun, 23 May 2010 17:21:07 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:58142 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753593Ab0EWVVD (ORCPT ); Sun, 23 May 2010 17:21:03 -0400 Subject: Re: [Regression] Negative time on Acer Ferrari One with current -git From: john stultz To: Thomas Gleixner Cc: "Rafael J. Wysocki" , Linus Torvalds , LKML , Andrew Morton In-Reply-To: References: <201005212343.25184.rjw@sisk.pl> <201005222255.27301.rjw@sisk.pl> <201005222320.01506.rjw@sisk.pl> Content-Type: text/plain; charset="UTF-8" Date: Sun, 23 May 2010 14:20:58 -0700 Message-ID: <1274649658.1932.13.camel@work-vm> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2010-05-23 at 08:40 +0200, Thomas Gleixner wrote: > On Sat, 22 May 2010, Rafael J. Wysocki wrote: > > After reverting commit 64ce4c2f above things work again. > > > > To be precise, I reverted both commit 64ce4c2f and commit 6a867a3 (time: > > Remove xtime_cache), but since the symptoms continued to apprear after > > reverting the latter alone, it's quite clear that commit 64ce4c2f breaks things > > on this box. > > I assume the cmos clock of this machine is not on UTC, right ? Does > the patch below fix the issue ? Oof. Thanks for catching that. > @John: Can you please check the other users of timespec_add_safe() in > timekeeping as well ? So monotonic_to_bootbased() looks ok, as total_sleep_time should always be positive. timekeeping_resume() also looks ok, since it we make sure the delta between the resume time and the suspend time is positive. That said, it may be worth open coding the: set_normalized_timespec(&ret, a.tv_sec + b.tv_sec, a.tv_nsec + b.tv_nsec); just so we don't have similar mix ups in the future, since timespec_add_safe is just such a reassuring and comforting name :) > Thanks, > > tglx > > ----------> > Subject: timekeeping: Fix timezone update > From: Thomas Gleixner > Date: Sun, 23 May 2010 08:14:45 +0200 > > commit 64ce4c2f (time: Clean up warp_clock()) breaks the timezone > update in a very subtle way. To avoid the direct access to timekeeping > internals it adds the timezone delta to the current time with > timespec_add_safe(). This works nicely when the timezone delta is > 0. > If timezone delta is < 0 then the wrap check in timespec_add_safe() > triggers and timespec_add_safe() returns TIME_MAX and screws up > timekeeping completely. > > This is not surprising as the comment above timespec_add_safe() says: > It's assumed that both values are valid (>= 0) > > The function was created to avoid overflow issues when adding the > select() timeout to current time, where the above applies. > > Add the timezone seconds adjustment directly. > > Reported-by: Rafael J. Wysocki > Signed-off-by: Thomas Gleixner \ Acked-by: John Stultz > --- > kernel/time.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > Index: linux-2.6/kernel/time.c > =================================================================== > --- linux-2.6.orig/kernel/time.c > +++ linux-2.6/kernel/time.c > @@ -132,10 +132,10 @@ SYSCALL_DEFINE2(gettimeofday, struct tim > */ > static inline void warp_clock(void) > { > - struct timespec delta, adjust; > - delta.tv_sec = sys_tz.tz_minuteswest * 60; > - delta.tv_nsec = 0; > - adjust = timespec_add_safe(current_kernel_time(), delta); > + struct timespec adjust; > + > + adjust = current_kernel_time(); > + adjust.tv_sec += sys_tz.tz_minuteswest * 60; > do_settimeofday(&adjust); > } >