linux-toradex.git/kernel/time, branch v2.6.23.12

ntp: fix typo that makes sync_cmos_clock erratic

2007-11-26T17:42:32+00:00

patch fa6a1a554b50cbb7763f6907e6fef927ead480d9 in mainline.

ntp: fix typo that makes sync_cmos_clock erratic

Fix a typo in ntp.c that has caused updating of the persistent (RTC)
clock when synced to NTP to behave erratically.

When debugging a freeze that arises on my AMD64 machines when I
run the ntpd service, I added a number of printk's to monitor the
sync_cmos_clock procedure.  I discovered that it was not syncing to
cmos RTC every 11 minutes as documented, but instead would keep trying
every second for hours at a time.  The reason turned out to be a typo
in sync_cmos_clock, where it attempts to ensure that
update_persistent_clock is called very close to 500 msec. after a 1
second boundary (required by the PC RTC's spec). That typo referred to
"xtime" in one spot, rather than "now", which is derived from "xtime"
but not equal to it.  This makes the test erratic, creating a
"coin-flip" that decides when update_persistent_clock is called - when
it is called, which is rarely, it may be at any time during the one
second period, rather than close to 500 msec, so the value written is
needlessly incorrect, too.

Signed-off-by: David P. Reed 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

Fix timer_stats printout of events/sec

2007-10-07T23:28:43+00:00

When using /proc/timer_stats on ppc64 I noticed the events/sec field wasnt
accurate.  Sometimes the integer part was incorrect due to rounding (we
werent taking the fractional seconds into consideration).

The fraction part is also wrong, we need to pad the printf statement and
take the bottom three digits of 1000 times the value.

Signed-off-by: Anton Blanchard 
Acked-by: Ingo Molnar 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

clockevents: remove the suspend/resume workaround^Wthinko

2007-09-23T00:15:34+00:00

In a desparate attempt to fix the suspend/resume problem on Andrews
VAIO I added a workaround which enforced the broadcast of the oneshot
timer on resume. This was actually resolving the problem on the VAIO
but was just a stupid workaround, which was not tackling the root
cause: the assignement of lower idle C-States in the ACPI processor_idle
code. The cpuidle patches, which utilize the dynamic tick feature and
go faster into deeper C-states exposed the problem again. The correct
solution is the previous patch, which prevents lower C-states across
the suspend/resume.

Remove the enforcement code, including the conditional broadcast timer
arming, which helped to pamper over the real problem for quite a time.
The oneshot broadcast flag for the cpu, which runs the resume code can
never be set at the time when this code is executed. It only gets set,
when the CPU is entering a lower idle C-State.

Signed-off-by: Thomas Gleixner 
Tested-by: Andrew Morton 
Cc: Len Brown 
Cc: Venkatesh Pallipadi 
Cc: Rafael J. Wysocki 
Signed-off-by: Linus Torvalds

clockevents: prevent stale tick update on offline cpu

2007-09-16T13:36:43+00:00

Taking a cpu offline removes the cpu from the online mask before the
CPU_DEAD notification is done. The clock events layer does the cleanup
of the dead CPU from the CPU_DEAD notifier chain. tick_do_timer_cpu is
used to avoid xtime lock contention by assigning the task of jiffies
xtime updates to one CPU. If a CPU is taken offline, then this
assignment becomes stale. This went unnoticed because most of the time
the offline CPU went dead before the online CPU reached __cpu_die(),
where the CPU_DEAD state is checked. In the case that the offline CPU did
not reach the DEAD state before we reach __cpu_die(), the code in there
goes to sleep for 100ms. Due to the stale time update assignment, the
system is stuck forever.

Take the assignment away when a cpu is not longer in the cpu_online_mask.
We do this in the last call to tick_nohz_stop_sched_tick() when the offline
CPU is on the way to the final play_dead() idle entry.

Signed-off-by: Thomas Gleixner

clockevents: do not shutdown the oneshot broadcast device

2007-09-16T13:36:43+00:00

When a cpu goes offline it is removed from the broadcast masks. If the
mask becomes empty the code shuts down the broadcast device. This is
wrong, because the broadcast device needs to be ready for the online
cpu going idle (into a c-state, which stops the local apic timer).

Signed-off-by: Thomas Gleixner

clockevents: Enforce oneshot broadcast when broadcast mask is set on resume

2007-09-16T13:36:43+00:00

The jinxed VAIO refuses to resume without hitting keys on the keyboard
when this is not enforced. It is unclear why the cpu ends up in a lower
C State without notifying the clock events layer, but enforcing the
oneshot broadcast here is safe.

Signed-off-by: Thomas Gleixner

timekeeping: Prevent time going backwards on resume

2007-09-16T13:36:43+00:00

Timekeeping resume adjusts xtime by adding the slept time in seconds and
resets the reference value of the clock source (clock->cycle_last).
clock->cycle last is used to calculate the delta between the last xtime
update and the readout of the clock source in __get_nsec_offset(). xtime
plus the offset is the current time. The resume code ignores the delta
which had already elapsed between the last xtime update and the actual
time of suspend. If the suspend time is short, then we can see time
going backwards on resume.

Suspend:
offs_s = clock->read() - clock->cycle_last;
now = xtime + offs_s;
timekeeping_suspend_time = read_rtc();

Resume:
sleep_time = read_rtc() - timekeeping_suspend_time;
xtime.tv_sec += sleep_time;
clock->cycle_last = clock->read();
offs_r = clock->read() - clock->cycle_last;
now = xtime + offs_r;

if sleep_time_seconds == 0 and offs_r < offs_s, then time goes
backwards.

Fix this by storing the offset from the last xtime update and add it to
xtime during resume, when we reset clock->cycle_last:

sleep_time = read_rtc() - timekeeping_suspend_time;
xtime.tv_sec += sleep_time;
xtime += offs_s;	/* Fixup xtime offset at suspend time */
clock->cycle_last = clock->read();
offs_r = clock->read() - clock->cycle_last;
now = xtime + offs_r;

Thanks to Marcelo for tracking this down on the OLPC and providing the
necessary details to analyze the root cause.

Signed-off-by: Thomas Gleixner 
Cc: John Stultz 
Cc: Tosatti

timekeeping: access rtc outside of xtime lock

2007-09-16T13:36:43+00:00

Lockdep complains about the access of rtc in timekeeping_suspend
inside the interrupt disabled region of the write locked xtime lock.
Move the access outside.

Signed-off-by: Thomas Gleixner 
Cc: John Stultz

Fix "no_sync_cmos_clock" logic inversion in kernel/time/ntp.c

2007-09-12T00:21:27+00:00

Seems to me that this timer will only get started on platforms that say
they don't want it?

Signed-off-by: Tony Breeds 
Cc: Paul Mackerras 
Cc: Gabriel Paubert 
Cc: Zachary Amsden 
Acked-by: Thomas Gleixner 
Cc: John Stultz 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

timer: remove clockevents_unregister_notifier

2007-08-11T22:47:42+00:00

I find a function(clockevents_unregister_notifier) which is not called by
anything in tree.

Signed-off-by: Miao Xie 
Acked-by: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds