Messages in this thread | | | Subject | Re: [Regression] Negative time on Acer Ferrari One with current -git | From | john stultz <> | Date | Sun, 23 May 2010 14:20:58 -0700 |
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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 <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>\
Acked-by: John Stultz <johnstul@us.ibm.com>
> --- > 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); > } >
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