linux-toradex.git/kernel/time/clocksource.c, branch v4.13-rc4

x86/tsc, sched/clock, clocksource: Use clocksource watchdog to provide stable sync points

2017-05-15T08:15:18+00:00

Currently we keep sched_clock_tick() active for stable TSC in order to
keep the per-CPU state semi up-to-date. The (obvious) problem is that
by the time we detect TSC is borked, our per-CPU state is also borked.

So hook into the clocksource watchdog and call a method after we've
found it to still be stable.

There's the obvious race where the TSC goes wonky between finding it
stable and us running the callback, but closing that is too much work
and not really worth it, since we're already detecting TSC wobbles
after the fact, so we cannot, per definition, fully avoid funny clock
values.

And since the watchdog runs less often than the tick, this is also an
optimization.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/clock, clocksource: Add optional cs::mark_unstable() method

2017-01-14T10:29:43+00:00

PeterZ reported that we'd fail to mark the TSC unstable when the
clocksource watchdog finds it unsuitable.

Allow a clocksource to run a custom action when its being marked
unstable and hook up the TSC unstable code.

Reported-by: Peter Zijlstra (Intel) 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

clocksource: Use a plain u64 instead of cycle_t

2016-12-25T10:04:12+00:00

There is no point in having an extra type for extra confusion. u64 is
unambiguous.

Conversion was done with the following coccinelle script:

@rem@
@@
-typedef u64 cycle_t;

@fix@
typedef cycle_t;
@@
-cycle_t
+u64

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

clocksource: export the clocks_calc_mult_shift to use by timestamp code

2016-12-07T16:13:48+00:00

The CPSW CPTS driver is capable of doing timestamping on tx/rx packets and
requires to know mult and shift factors for timestamp conversion from raw
value to nanoseconds (ptp clock). Now these mult and shift factors are
calculated manually and provided through DT, which makes very hard to
support of a lot number of platforms, especially if CPTS refclk is not the
same for some kind of boards and depends on efuse settings (Keystone 2
platforms). Hence, export clocks_calc_mult_shift() to allow drivers like
CPSW CPTS (and other ptp drivesr) to benefit from automaitc calculation of
mult and shift factors.

Cc: John Stultz 
Signed-off-by: Murali Karicheri 
Signed-off-by: Grygorii Strashko 
Acked-by: Thomas Gleixner 
Signed-off-by: David S. Miller

clocksource: Defer override invalidation unless clock is unstable

2016-08-31T21:43:33+00:00

Clocksources don't get the VALID_FOR_HRES flag until they have been
checked by a watchdog. However, when using an override, the
clocksource_select logic will clear the override value if the
clocksource is not marked VALID_FOR_HRES during that inititial check.
When using the boot arguments clocksource=, this selection can
run before the watchdog, and can cause the override to be incorrectly
cleared.

To address this condition, the override_name is only invalidated for
unstable clocksources. Otherwise, the override is left intact until after
the watchdog has validated the clocksource as stable/unstable.

Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Cc: Martin Schwidefsky 
Signed-off-by: Kyle Walker 
Signed-off-by: John Stultz

clocksource: Make clocksource insert entry more efficient

2016-06-20T19:46:34+00:00

In clocksource_enqueue(), it is unnecessary to continue looping
the list, if we find there is an entry that the value of rating
is smaller than the new one. It is safe to be out the loop,
because all of entry are inserted in descending order.

Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Signed-off-by: Minfei Huang 
Signed-off-by: John Stultz

clocksource: Allow unregistering the watchdog

2016-01-27T11:38:05+00:00

Hyper-V vmbus module registers TSC page clocksource when loaded. This is
the clocksource with the highest rating and thus it becomes the watchdog
making unloading of the vmbus module impossible.
Separate clocksource_select_watchdog() from clocksource_enqueue_watchdog()
and use it on clocksource register/rating change/unregister.

After all, lobotomized monkeys may need some love too.

Signed-off-by: Vitaly Kuznetsov 
Cc: John Stultz 
Cc: Dexuan Cui 
Cc: K. Y. Srinivasan 
Link: http://lkml.kernel.org/r/1453483913-25672-1-git-send-email-vkuznets@redhat.com
Signed-off-by: Thomas Gleixner

clocksource: Add CPU info to clocksource watchdog reporting

2015-12-07T20:15:28+00:00

The clocksource watchdog reporting was improved by 0b046b217ad4c6.
I want to add the info of CPU where the watchdog detects a
deviation because it is necessary to identify the trouble spot
if the clocksource is TSC.

Signed-off-by: Seiichi Ikarashi 
[jstultz: Tweaked commit message]
Signed-off-by: John Stultz

remove abs64()

2015-11-09T23:11:24+00:00

Switch everything to the new and more capable implementation of abs().
Mainly to give the new abs() a bit of a workout.

Cc: Michal Nazarewicz 
Cc: John Stultz 
Cc: Ingo Molnar 
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Cc: Masami Hiramatsu 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'v4.3-rc5' into timers/core, to pick up fixes before applying new changes

2015-10-12T07:51:18+00:00

Signed-off-by: Ingo Molnar