Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [Regression] Negative time on Acer Ferrari One with current -git | Date | Sun, 23 May 2010 15:21:02 +0200 |
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On Sunday 23 May 2010, 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 ?
Yup.
> Does the patch below fix the issue ?
Yes, it does, thanks!
> @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 <tglx@linutronix.de> > 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 <rjw@sisk.pl> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > 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); > }
Rafael
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