linux.git/kernel/time, branch v3.12.11

timekeeping: Fix missing timekeeping_update in suspend path

2014-02-13T21:50:26+00:00

commit 330a1617b0a6268d427aa5922c94d082b1d3e96d upstream.

Since 48cdc135d4840 (Implement a shadow timekeeper), we have to
call timekeeping_update() after any adjustment to the timekeeping
structure in order to make sure that any adjustments to the structure
persist.

In the timekeeping suspend path, we udpate the timekeeper
structure, so we should be sure to update the shadow-timekeeper
before releasing the timekeeping locks. Currently this isn't done.

In most cases, the next time related code to run would be
timekeeping_resume, which does update the shadow-timekeeper, but
in an abundence of caution, this patch adds the call to
timekeeping_update() in the suspend path.

Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Ingo Molnar 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Fix CLOCK_TAI timer/nanosleep delays

2014-02-13T21:50:26+00:00

commit 04005f6011e3b504cd4d791d9769f7cb9a3b2eae upstream.

A think-o in the calculation of the monotonic -> tai time offset
results in CLOCK_TAI timers and nanosleeps to expire late (the
latency is ~2x the tai offset).

Fix this by adding the tai offset from the realtime offset instead
of subtracting.

Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Ingo Molnar 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

3.13.y: timekeeping: Fix clock_set/clock_was_set think-o

2014-02-13T21:50:25+00:00

In backporting 6fdda9a9c5db367130cf32df5d6618d08b89f46a
(timekeeping: Avoid possible deadlock from clock_was_set_delayed),
I ralized the patch had a think-o where instead of checking
clock_set I accidentally typed clock_was_set (which is a function
- so the conditional always is true).

Upstream this was resolved in the immediately following patch
47a1b796306356f358e515149d86baf0cc6bf007 (tick/timekeeping: Call
update_wall_time outside the jiffies lock). But since that patch
really isn't -stable material, so this patch only pulls
the name change.

Cc: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Ingo Molnar 
Cc: Sasha Levin 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Avoid possible deadlock from clock_was_set_delayed

2014-02-13T21:50:25+00:00

commit 6fdda9a9c5db367130cf32df5d6618d08b89f46a upstream.

As part of normal operaions, the hrtimer subsystem frequently calls
into the timekeeping code, creating a locking order of
  hrtimer locks -> timekeeping locks

clock_was_set_delayed() was suppoed to allow us to avoid deadlocks
between the timekeeping the hrtimer subsystem, so that we could
notify the hrtimer subsytem the time had changed while holding
the timekeeping locks. This was done by scheduling delayed work
that would run later once we were out of the timekeeing code.

But unfortunately the lock chains are complex enoguh that in
scheduling delayed work, we end up eventually trying to grab
an hrtimer lock.

Sasha Levin noticed this in testing when the new seqlock lockdep
enablement triggered the following (somewhat abrieviated) message:

[  251.100221] ======================================================
[  251.100221] [ INFO: possible circular locking dependency detected ]
[  251.100221] 3.13.0-rc2-next-20131206-sasha-00005-g8be2375-dirty #4053 Not tainted
[  251.101967] -------------------------------------------------------
[  251.101967] kworker/10:1/4506 is trying to acquire lock:
[  251.101967]  (timekeeper_seq){----..}, at: [] retrigger_next_event+0x56/0x70
[  251.101967]
[  251.101967] but task is already holding lock:
[  251.101967]  (hrtimer_bases.lock#11){-.-...}, at: [] retrigger_next_event+0x3c/0x70
[  251.101967]
[  251.101967] which lock already depends on the new lock.
[  251.101967]
[  251.101967]
[  251.101967] the existing dependency chain (in reverse order) is:
[  251.101967]
-> #5 (hrtimer_bases.lock#11){-.-...}:
[snipped]
-> #4 (&rt_b->rt_runtime_lock){-.-...}:
[snipped]
-> #3 (&rq->lock){-.-.-.}:
[snipped]
-> #2 (&p->pi_lock){-.-.-.}:
[snipped]
-> #1 (&(&pool->lock)->rlock){-.-...}:
[  251.101967]        [] validate_chain+0x6c3/0x7b0
[  251.101967]        [] __lock_acquire+0x4ad/0x580
[  251.101967]        [] lock_acquire+0x182/0x1d0
[  251.101967]        [] _raw_spin_lock+0x40/0x80
[  251.101967]        [] __queue_work+0x1a9/0x3f0
[  251.101967]        [] queue_work_on+0x98/0x120
[  251.101967]        [] clock_was_set_delayed+0x21/0x30
[  251.101967]        [] do_adjtimex+0x111/0x160
[  251.101967]        [] compat_sys_adjtimex+0x41/0x70
[  251.101967]        [] ia32_sysret+0x0/0x5
[  251.101967]
-> #0 (timekeeper_seq){----..}:
[snipped]
[  251.101967] other info that might help us debug this:
[  251.101967]
[  251.101967] Chain exists of:
  timekeeper_seq --> &rt_b->rt_runtime_lock --> hrtimer_bases.lock#11

[  251.101967]  Possible unsafe locking scenario:
[  251.101967]
[  251.101967]        CPU0                    CPU1
[  251.101967]        ----                    ----
[  251.101967]   lock(hrtimer_bases.lock#11);
[  251.101967]                                lock(&rt_b->rt_runtime_lock);
[  251.101967]                                lock(hrtimer_bases.lock#11);
[  251.101967]   lock(timekeeper_seq);
[  251.101967]
[  251.101967]  *** DEADLOCK ***
[  251.101967]
[  251.101967] 3 locks held by kworker/10:1/4506:
[  251.101967]  #0:  (events){.+.+.+}, at: [] process_one_work+0x200/0x530
[  251.101967]  #1:  (hrtimer_work){+.+...}, at: [] process_one_work+0x200/0x530
[  251.101967]  #2:  (hrtimer_bases.lock#11){-.-...}, at: [] retrigger_next_event+0x3c/0x70
[  251.101967]
[  251.101967] stack backtrace:
[  251.101967] CPU: 10 PID: 4506 Comm: kworker/10:1 Not tainted 3.13.0-rc2-next-20131206-sasha-00005-g8be2375-dirty #4053
[  251.101967] Workqueue: events clock_was_set_work

So the best solution is to avoid calling clock_was_set_delayed() while
holding the timekeeping lock, and instead using a flag variable to
decide if we should call clock_was_set() once we've released the locks.

This works for the case here, where the do_adjtimex() was the deadlock
trigger point. Unfortuantely, in update_wall_time() we still hold
the jiffies lock, which would deadlock with the ipi triggered by
clock_was_set(), preventing us from calling it even after we drop the
timekeeping lock. So instead call clock_was_set_delayed() at that point.

Cc: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Ingo Molnar 
Cc: Sasha Levin 
Reported-by: Sasha Levin 
Tested-by: Sasha Levin 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Fix potential lost pv notification of time change

2014-02-13T21:50:25+00:00

commit 5258d3f25c76f6ab86e9333abf97a55a877d3870 upstream.

In 780427f0e11 (Indicate that clock was set in the pvclock
gtod notifier), logic was added to pass a CLOCK_WAS_SET
notification to the pvclock notifier chain.

While that patch added a action flag returned from
accumulate_nsecs_to_secs(), it only uses the returned value
in one location, and not in the logarithmic accumulation.

This means if a leap second triggered during the logarithmic
accumulation (which is most likely where it would happen),
the notification that the clock was set would not make it to
the pv notifiers.

This patch extends the logarithmic_accumulation pass down
that action flag so proper notification will occur.

This patch also changes the varialbe action -> clock_set
per Ingo's suggestion.

Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: David Vrabel 
Cc: Konrad Rzeszutek Wilk 
Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Fix lost updates to tai adjustment

2014-02-13T21:50:25+00:00

commit f55c07607a38f84b5c7e6066ee1cfe433fa5643c upstream.

Since 48cdc135d4840 (Implement a shadow timekeeper), we have to
call timekeeping_update() after any adjustment to the timekeeping
structure in order to make sure that any adjustments to the structure
persist.

Unfortunately, the updates to the tai offset via adjtimex do not
trigger this update, causing adjustments to the tai offset to be
made and then over-written by the previous value at the next
update_wall_time() call.

This patch resovles the issue by calling timekeeping_update()
right after setting the tai offset.

Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Ingo Molnar 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

time: Fix 1ns/tick drift w/ GENERIC_TIME_VSYSCALL_OLD

2013-12-12T06:37:54+00:00

commit 4be77398ac9d948773116b6be4a3c91b3d6ea18c upstream.

Since commit 1e75fa8be9f (time: Condense timekeeper.xtime
into xtime_sec - merged in v3.6), there has been an problem
with the error accounting in the timekeeping code, such that
when truncating to nanoseconds, we round up to the next nsec,
but the balancing adjustment to the ntp_error value was dropped.

This causes 1ns per tick drift forward of the clock.

In 3.7, this logic was isolated to only GENERIC_TIME_VSYSCALL_OLD
architectures (s390, ia64, powerpc).

The fix is simply to balance the accounting and to subtract the
added nanosecond from ntp_error. This allows the internal long-term
clock steering to keep the clock accurate.

While this fix removes the regression added in 1e75fa8be9f, the
ideal solution is to move away from GENERIC_TIME_VSYSCALL_OLD
and use the new VSYSCALL method, which avoids entirely the
nanosecond granular rounding, and the resulting short-term clock
adjustment oscillation needed to keep long term accurate time.

[ jstultz: Many thanks to Martin for his efforts identifying this
  	   subtle bug, and providing the fix. ]

Originally-from: Martin Schwidefsky 
Cc: Tony Luck 
Cc: Paul Mackerras 
Cc: Benjamin Herrenschmidt 
Cc: Andy Lutomirski 
Cc: Paul Turner 
Cc: Steven Rostedt 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Cc: Fenghua Yu 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1385149491-20307-1-git-send-email-john.stultz@linaro.org
Signed-off-by: John Stultz 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

ntp: Make periodic RTC update more reliable

2013-12-08T15:29:16+00:00

commit a97ad0c4b447a132a322cedc3a5f7fa4cab4b304 upstream.

The current code requires that the scheduled update of the RTC happens
in the closest tick to the half of the second. This seems to be
difficult to achieve reliably. The scheduled work may be missing the
target time by a tick or two and be constantly rescheduled every second.

Relax the limit to 10 ticks. As a typical RTC drifts in the 11-minute
update interval by several milliseconds, this shouldn't affect the
overall accuracy of the RTC much.

Signed-off-by: Miroslav Lichvar 
Signed-off-by: John Stultz 
Cc: Josh Boyer 
Signed-off-by: Greg Kroah-Hartman

alarmtimer: return EINVAL instead of ENOTSUPP if rtcdev doesn't exist

2013-12-04T19:05:10+00:00

commit 98d6f4dd84a134d942827584a3c5f67ffd8ec35f upstream.

Fedora Ruby maintainer reported latest Ruby doesn't work on Fedora Rawhide
on ARM. (http://bugs.ruby-lang.org/issues/9008)

Because of, commit 1c6b39ad3f (alarmtimers: Return -ENOTSUPP if no
RTC device is present) intruduced to return ENOTSUPP when
clock_get{time,res} can't find a RTC device. However this is incorrect.

First, ENOTSUPP isn't exported to userland (ENOTSUP or EOPNOTSUP are the
closest userland equivlents).

Second, Posix and Linux man pages agree that clock_gettime and
clock_getres should return EINVAL if clk_id argument is invalid.
While the arugment that the clockid is valid, but just not supported
on this hardware could be made, this is just a technicality that
doesn't help userspace applicaitons, and only complicates error
handling.

Thus, this patch changes the code to use EINVAL.

Cc: Thomas Gleixner 
Cc: Frederic Weisbecker 
Reported-by: Vit Ondruch 
Signed-off-by: KOSAKI Motohiro 
[jstultz: Tweaks to commit message to include full rational]
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

clockevents: Sanitize ticks to nsec conversion

2013-10-23T10:51:21+00:00

Marc Kleine-Budde pointed out, that commit 77cc982 "clocksource: use
clockevents_config_and_register() where possible" caused a regression
for some of the converted subarchs.

The reason is, that the clockevents core code converts the minimal
hardware tick delta to a nanosecond value for core internal
usage. This conversion is affected by integer math rounding loss, so
the backwards conversion to hardware ticks will likely result in a
value which is less than the configured hardware limitation. The
affected subarchs used their own workaround (SIGH!) which got lost in
the conversion.

The solution for the issue at hand is simple: adding evt->mult - 1 to
the shifted value before the integer divison in the core conversion
function takes care of it. But this only works for the case where for
the scaled math mult/shift pair "mult <= 1 << shift" is true. For the
case where "mult > 1 << shift" we can apply the rounding add only for
the minimum delta value to make sure that the backward conversion is
not less than the given hardware limit. For the upper bound we need to
omit the rounding add, because the backwards conversion is always
larger than the original latch value. That would violate the upper
bound of the hardware device.

Though looking closer at the details of that function reveals another
bogosity: The upper bounds check is broken as well. Checking for a
resulting "clc" value greater than KTIME_MAX after the conversion is
pointless. The conversion does:

      u64 clc = (latch << evt->shift) / evt->mult;

So there is no sanity check for (latch << evt->shift) exceeding the
64bit boundary. The latch argument is "unsigned long", so on a 64bit
arch the handed in argument could easily lead to an unnoticed shift
overflow. With the above rounding fix applied the calculation before
the divison is:

       u64 clc = (latch << evt->shift) + evt->mult - 1;

So we need to make sure, that neither the shift nor the rounding add
is overflowing the u64 boundary.

[ukl: move assignment to rnd after eventually changing mult, fix build
 issue and correct comment with the right math]

Signed-off-by: Thomas Gleixner 
Cc: Russell King - ARM Linux 
Cc: Marc Kleine-Budde 
Cc: nicolas.ferre@atmel.com
Cc: Marc Pignat 
Cc: john.stultz@linaro.org
Cc: kernel@pengutronix.de
Cc: Ronald Wahl 
Cc: LAK 
Cc: Ludovic Desroches 
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1380052223-24139-1-git-send-email-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König