user/sven/linux.git/kernel/time/timekeeping.c, branch v4.0.2

PM / sleep: Make it possible to quiesce timers during suspend-to-idle

2015-02-15T18:40:09Z

The efficiency of suspend-to-idle depends on being able to keep CPUs in the deepest available idle states for as much time as possible. Ideally, they should only be brought out of idle by system wakeup interrupts. However, timer interrupts occurring periodically prevent that from happening and it is not practical to chase all of the "misbehaving" timers in a whack-a-mole fashion. A much more effective approach is to suspend the local ticks for all CPUs and the entire timekeeping along the lines of what is done during full suspend, which also helps to keep suspend-to-idle and full suspend reasonably similar. The idea is to suspend the local tick on each CPU executing cpuidle_enter_freeze() and to make the last of them suspend the entire timekeeping. That should prevent timer interrupts from triggering until an IO interrupt wakes up one of the CPUs. It needs to be done with interrupts disabled on all of the CPUs, though, because otherwise the suspended clocksource might be accessed by an interrupt handler which might lead to fatal consequences. Unfortunately, the existing ->enter callbacks provided by cpuidle drivers generally cannot be used for implementing that, because some of them re-enable interrupts temporarily and some idle entry methods cause interrupts to be re-enabled automatically on exit. Also some of these callbacks manipulate local clock event devices of the CPUs which really shouldn't be done after suspending their ticks. To overcome that difficulty, introduce a new cpuidle state callback, ->enter_freeze, that will be guaranteed (1) to keep interrupts disabled all the time (and return with interrupts disabled) and (2) not to touch the CPU timer devices. Modify cpuidle_enter_freeze() to look for the deepest available idle state with ->enter_freeze present and to make the CPU execute that callback with suspended tick (and the last of the online CPUs to execute it with suspended timekeeping). Suggested-by: Thomas Gleixner Signed-off-by: Rafael J. Wysocki Acked-by: Peter Zijlstra (Intel)

timekeeping: Make it safe to use the fast timekeeper while suspended

2015-02-15T18:39:40Z

Theoretically, ktime_get_mono_fast_ns() may be executed after timekeeping has been suspended (or before it is resumed) which in turn may lead to undefined behavior, for example, when the clocksource read from timekeeping_get_ns() called by it is not accessible at that time. Prevent that from happening by setting up a dummy readout base for the fast timekeeper during timekeeping_suspend() such that it will always return the same number of cycles. After the last timekeeping_update() in timekeeping_suspend() the clocksource is read and the result is stored as cycles_at_suspend. The readout base from the current timekeeper is copied onto the dummy and the ->read pointer of the dummy is set to a routine unconditionally returning cycles_at_suspend. Next, the dummy is passed to update_fast_timekeeper(). Then, ktime_get_mono_fast_ns() will work until the subsequent timekeeping_resume() and the proper readout base for the fast timekeeper will be restored by the timekeeping_update() called right after clearing timekeeping_suspended. Signed-off-by: Rafael J. Wysocki Acked-by: John Stultz Acked-by: Peter Zijlstra (Intel)

timekeeping: Pass readout base to update_fast_timekeeper()

2015-02-13T22:49:36Z

Modify update_fast_timekeeper() to take a struct tk_read_base pointer as its argument (instead of a struct timekeeper pointer) and update its kerneldoc comment to reflect that. That will allow a struct tk_read_base that is not part of a struct timekeeper to be passed to it in the next patch. Signed-off-by: Rafael J. Wysocki Acked-by: Peter Zijlstra (Intel) Acked-by: John Stultz

time: Expose getboottime64 for in-kernel uses

2015-01-24T01:21:54Z

Adds a timespec64 based getboottime64() implementation that can be used as we convert internal users of getboottime away from using timespecs. Cc: pang.xunlei Cc: Arnd Bergmann Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: John Stultz

Merge branch 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-12-10T18:13:28Z

Pull more 2038 timer work from Thomas Gleixner: "Two more patches for the ongoing 2038 work: - New accessors to clock MONOTONIC and REALTIME seconds This is a seperate branch as Arnd has follow up work depending on this" * 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: timekeeping: Provide y2038 safe accessor to the seconds portion of CLOCK_REALTIME timekeeping: Provide fast accessor to the seconds part of CLOCK_MONOTONIC

time: Fix sign bug in NTP mult overflow warning

2014-11-25T06:18:34Z

In commit 6067dc5a8c2b ("time: Avoid possible NTP adjustment mult overflow") a new check was added to watch for adjustments that could cause a mult overflow. Unfortunately the check compares a signed with unsigned value and ignored the case where the adjustment was negative, which causes spurious warn-ons on some systems (and seems like it would result in problematic time adjustments there as well, due to the early return). Thus this patch adds a check to make sure the adjustment is positive before we check for an overflow, and resovles the issue in my testing. Reported-by: Fengguang Wu Debugged-by: pang.xunlei Signed-off-by: John Stultz Link: http://lkml.kernel.org/r/1416890145-30048-1-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

time: Fixup comments to reflect usage of timespec64

2014-11-21T19:59:59Z

Fix up a few comments that weren't updated when the functions were converted to use timespec64 structures. Acked-by: Arnd Bergmann Signed-off-by: John Stultz

time: Expose get_monotonic_coarse64() for in-kernel uses

2014-11-21T19:59:59Z

Adds a timespec64 based get_monotonic_coarse64() implementation that can be used as we convert internal users of get_monotonic_coarse away from using timespecs. Signed-off-by: John Stultz

time: Expose getrawmonotonic64 for in-kernel uses

2014-11-21T19:59:58Z

Adds a timespec64 based getrawmonotonic64() implementation that can be used as we convert internal users of getrawmonotonic away from using timespecs. Signed-off-by: John Stultz

time: Provide y2038 safe timekeeping_inject_sleeptime() replacement

2014-11-21T19:59:57Z

As part of addressing "y2038 problem" for in-kernel uses, this patch adds timekeeping_inject_sleeptime64() using timespec64. After this patch, timekeeping_inject_sleeptime() is deprecated and all its call sites will be fixed using the new interface, after that it can be removed. NOTE: timekeeping_inject_sleeptime() is safe actually, but we want to eliminate timespec eventually, so comes this patch. Signed-off-by: pang.xunlei Signed-off-by: John Stultz