linux-toradex.git/kernel/time, branch v3.4.10

ntp: Fix STA_INS/DEL clearing bug

2012-07-29T15:04:18+00:00

commit 6b1859dba01c7d512b72d77e3fd7da8354235189 upstream.

In commit 6b43ae8a619d17c4935c3320d2ef9e92bdeed05d, I
introduced a bug that kept the STA_INS or STA_DEL bit
from being cleared from time_status via adjtimex()
without forcing STA_PLL first.

Usually once the STA_INS is set, it isn't cleared
until the leap second is applied, so its unlikely this
affected anyone. However during testing I noticed it
took some effort to cancel a leap second once STA_INS
was set.

Signed-off-by: John Stultz 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Link: http://lkml.kernel.org/r/1342156917-25092-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Add missing update call in timekeeping_resume()

2012-07-19T15:59:00+00:00

This is a backport of 3e997130bd2e8c6f5aaa49d6e3161d4d29b43ab0

The leap second rework unearthed another issue of inconsistent data.

On timekeeping_resume() the timekeeper data is updated, but nothing
calls timekeeping_update(), so now the update code in the timer
interrupt sees stale values.

This has been the case before those changes, but then the timer
interrupt was using stale data as well so this went unnoticed for quite
some time.

Add the missing update call, so all the data is consistent everywhere.

Reported-by: Andreas Schwab 
Reported-and-tested-by: "Rafael J. Wysocki" 
Reported-and-tested-by: Martin Steigerwald 
Cc: John Stultz 
Cc: Ingo Molnar 
Cc: Peter Zijlstra ,
Cc: Prarit Bhargava 
Signed-off-by: Thomas Gleixner 
Signed-off-by: John Stultz 
Signed-off-by: Linus Torvalds 
Cc: Prarit Bhargava 
Cc: Thomas Gleixner 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Provide hrtimer update function

2012-07-19T15:59:00+00:00

This is a backport of f6c06abfb3972ad4914cef57d8348fcb2932bc3b

To finally fix the infamous leap second issue and other race windows
caused by functions which change the offsets between the various time
bases (CLOCK_MONOTONIC, CLOCK_REALTIME and CLOCK_BOOTTIME) we need a
function which atomically gets the current monotonic time and updates
the offsets of CLOCK_REALTIME and CLOCK_BOOTTIME with minimalistic
overhead. The previous patch which provides ktime_t offsets allows us
to make this function almost as cheap as ktime_get() which is going to
be replaced in hrtimer_interrupt().

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Acked-by: Prarit Bhargava 
Signed-off-by: John Stultz 
Link: http://lkml.kernel.org/r/1341960205-56738-7-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Thomas Gleixner 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Maintain ktime_t based offsets for hrtimers

2012-07-19T15:58:59+00:00

This is a backport of 5b9fe759a678e05be4937ddf03d50e950207c1c0

We need to update the hrtimer clock offsets from the hrtimer interrupt
context. To avoid conversions from timespec to ktime_t maintain a
ktime_t based representation of those offsets in the timekeeper. This
puts the conversion overhead into the code which updates the
underlying offsets and provides fast accessible values in the hrtimer
interrupt.

Signed-off-by: Thomas Gleixner 
Signed-off-by: John Stultz 
Reviewed-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Acked-by: Prarit Bhargava 
Link: http://lkml.kernel.org/r/1341960205-56738-4-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Thomas Gleixner 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Fix leapsecond triggered load spike issue

2012-07-19T15:58:59+00:00

This is a backport of 4873fa070ae84a4115f0b3c9dfabc224f1bc7c51

The timekeeping code misses an update of the hrtimer subsystem after a
leap second happened. Due to that timers based on CLOCK_REALTIME are
either expiring a second early or late depending on whether a leap
second has been inserted or deleted until an operation is initiated
which causes that update. Unless the update happens by some other
means this discrepancy between the timekeeping and the hrtimer data
stays forever and timers are expired either early or late.

The reported immediate workaround - $ data -s "`date`" - is causing a
call to clock_was_set() which updates the hrtimer data structures.
See: http://www.sheeri.com/content/mysql-and-leap-second-high-cpu-and-fix

Add the missing clock_was_set() call to update_wall_time() in case of
a leap second event. The actual update is deferred to softirq context
as the necessary smp function call cannot be invoked from hard
interrupt context.

Signed-off-by: John Stultz 
Reported-by: Jan Engelhardt 
Reviewed-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Acked-by: Prarit Bhargava 
Link: http://lkml.kernel.org/r/1341960205-56738-3-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Thomas Gleixner 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

sched/nohz: Rewrite and fix load-avg computation -- again

2012-07-19T15:58:56+00:00

commit 5167e8d5417bf5c322a703d2927daec727ea40dd upstream.

Thanks to Charles Wang for spotting the defects in the current code:

 - If we go idle during the sample window -- after sampling, we get a
   negative bias because we can negate our own sample.

 - If we wake up during the sample window we get a positive bias
   because we push the sample to a known active period.

So rewrite the entire nohz load-avg muck once again, now adding
copious documentation to the code.

Reported-and-tested-by: Doug Smythies 
Reported-and-tested-by: Charles Wang 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/1340373782.18025.74.camel@twins
[ minor edits ]
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

ntp: Correct TAI offset during leap second

2012-06-22T18:37:16+00:00

commit dd48d708ff3e917f6d6b6c2b696c3f18c019feed upstream.

When repeating a UTC time value during a leap second (when the UTC
time should be 23:59:60), the TAI timescale should not stop. The kernel
NTP code increments the TAI offset one second too late. This patch fixes
the issue by incrementing the offset during the leap second itself.

Signed-off-by: Richard Cochran 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Fix CLOCK_MONOTONIC inconsistency during leapsecond

2012-06-17T18:21:23+00:00

commit fad0c66c4bb836d57a5f125ecd38bed653ca863a upstream.

Commit 6b43ae8a61 (ntp: Fix leap-second hrtimer livelock) broke the
leapsecond update of CLOCK_MONOTONIC. The missing leapsecond update to
wall_to_monotonic causes discontinuities in CLOCK_MONOTONIC.

Adjust wall_to_monotonic when NTP inserted a leapsecond.

Reported-by: Richard Cochran 
Signed-off-by: John Stultz 
Tested-by: Richard Cochran 
Link: http://lkml.kernel.org/r/1338400497-12420-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

tick: Fix the spurious broadcast timer ticks after resume

2012-04-19T19:27:50+00:00

During resume, tick_resume_broadcast() programs the broadcast timer in
oneshot mode unconditionally. On the platforms where broadcast timer
is not really required, this will generate spurious broadcast timer
ticks upon resume. For example, on the always running apic timer
platforms with HPET, I see spurious hpet tick once every ~5minutes
(which is the 32-bit hpet counter wraparound time).

Similar to boot time, during resume make the oneshot mode setting of
the broadcast clock event device conditional on the state of active
broadcast users.

Signed-off-by: Suresh Siddha 
Tested-by: Santosh Shilimkar 
Tested-by: svenjoac@gmx.de
Cc: torvalds@linux-foundation.org
Cc: rjw@sisk.pl
Link: http://lkml.kernel.org/r/1334802459.28674.209.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Thomas Gleixner

tick: Ensure that the broadcast device is initialized

2012-04-19T19:27:35+00:00

Santosh found another trap when we avoid to initialize the broadcast
device in the switch_to_oneshot code. The broadcast device might be
still in SHUTDOWN state when we actually need to use it. That
obviously breaks, as set_next_event() is called on a shutdown
device. This did not break on x86, but Suresh analyzed it:

From the review, most likely on Sven's system we are force enabling
the hpet using the pci quirk's method very late. And in this case,
hpet_clockevent (which will be global_clock_event) handler can be
null, specifically as this platform might not be using deeper c-states
and using the reliable APIC timer.

Prior to commit 'fa4da365bc7772c', that handler will be set to
'tick_handle_oneshot_broadcast' when we switch the broadcast timer to
oneshot mode, even though we don't use it. Post commit
'fa4da365bc7772c', we stopped switching the broadcast mode to oneshot
as this is not really needed and his platform's global_clock_event's
handler will remain null. While on my SNB laptop, same is set to
'clockevents_handle_noop' because hpet gets enabled very early. (noop
handler on my platform set when the early enabled hpet timer gets
replaced by the lapic timer).

But the commit 'fa4da365bc7772c' tracked the broadcast timer mode in
the SW as oneshot, even though it didn't touch the HW timer. During
resume however, tick_resume_broadcast() saw the SW broadcast mode as
oneshot and actually programmed the broadcast device also into oneshot
mode. So this triggered the null pointer de-reference after the hpet
wraps around and depending on what the hpet counter is set to. On the
normal platforms where hpet gets enabled early we should be seeing a
spurious interrupt (in my SNB laptop I see one spurious interrupt
after around 5 minutes ;) which is 32-bit hpet counter wraparound
time), but that's a separate issue.

Enforce the mode setting when trying to set an event.

Reported-and-tested-by: Santosh Shilimkar 
Signed-off-by: Thomas Gleixner 
Acked-by: Suresh Siddha 
Cc: torvalds@linux-foundation.org
Cc: svenjoac@gmx.de
Cc: rjw@sisk.pl
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1204181723350.2542@ionos