From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753405Ab0EWGlJ (ORCPT ); Sun, 23 May 2010 02:41:09 -0400 Received: from www.tglx.de ([62.245.132.106]:37021 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753029Ab0EWGlF (ORCPT ); Sun, 23 May 2010 02:41:05 -0400 Date: Sun, 23 May 2010 08:40:55 +0200 (CEST) From: Thomas Gleixner To: "Rafael J. Wysocki" cc: John Stultz , Linus Torvalds , LKML , Andrew Morton Subject: Re: [Regression] Negative time on Acer Ferrari One with current -git In-Reply-To: <201005222320.01506.rjw@sisk.pl> Message-ID: References: <201005212343.25184.rjw@sisk.pl> <201005222255.27301.rjw@sisk.pl> <201005222320.01506.rjw@sisk.pl> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ? @John: Can you please check the other users of timespec_add_safe() in timekeeping as well ? 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 --- 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); }