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Re: [RFC][PATCH 3/4] arm64: vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW

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On Fri, May 26, 2017 at 08:33:54PM -0700, John Stultz wrote:
> From: Will Deacon <will.deacon@arm.com>
> 
> Commit 45a7905fc48f ("arm64: vdso: defer shifting of nanosecond
> component of timespec") fixed sub-ns inaccuracies in our vDSO
> clock_gettime implementation by deferring the right-shift of the
> nanoseconds components until after the timespec addition, which
> operates on left-shifted values. That worked nicely until
> support for CLOCK_MONOTONIC_RAW was added in 49eea433b326
> ("arm64: Add support for CLOCK_MONOTONIC_RAW in clock_gettime()
> vDSO"). Noticing that the core timekeeping code never set
> tkr_raw.xtime_nsec, the vDSO implementation didn't bother
> exposing it via the data page and instead took the unshifted
> tk->raw_time.tv_nsec value which was then immediately shifted
> left in the vDSO code.
> 
> Now that the core code is actually setting tkr_raw.xtime_nsec,
> we need to take that into account in the vDSO by adding it to
> the shifted raw_time value. Rather than do that at each use (and
> expand the data page in the process), instead perform the
> shift/addition operation when populating the data page and
> remove the shift from the vDSO code entirely.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Miroslav Lichvar <mlichvar@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Stephen Boyd <stephen.boyd@linaro.org>
> Cc: Kevin Brodsky <kevin.brodsky@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Daniel Mentz <danielmentz@google.com>
> Reported-by: John Stultz <john.stultz@linaro.org>
> Acked-by: Acked-by: Kevin Brodsky <kevin.brodsky@arm.com>

I don't think Kevin liked it *that* much ^^

Will

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[RFC][PATCH 0/4] Fixes for two recently found timekeeping bugs John Stultz <john.stultz@linaro.org> - 2017-05-27 05:40 +0200
  [RFC][PATCH 4/4] time: Clean up CLOCK_MONOTONIC_RAW time handling John Stultz <john.stultz@linaro.org> - 2017-05-27 05:40 +0200
  [RFC][PATCH 2/4] time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting John Stultz <john.stultz@linaro.org> - 2017-05-27 05:40 +0200
    Re: [RFC][PATCH 2/4] time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond  accounting Ingo Molnar <mingo@kernel.org> - 2017-05-27 09:40 +0200
      Re: [RFC][PATCH 2/4] time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting Daniel Mentz <danielmentz@google.com> - 2017-05-30 20:50 +0200
  [RFC][PATCH 1/4] time: Fix clock->read(clock) race around clocksource changes John Stultz <john.stultz@linaro.org> - 2017-05-27 05:40 +0200
    Re: [RFC][PATCH 1/4] time: Fix clock->read(clock) race around  clocksource changes Ingo Molnar <mingo@kernel.org> - 2017-05-27 09:40 +0200
  [RFC][PATCH 3/4] arm64: vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW John Stultz <john.stultz@linaro.org> - 2017-05-27 06:20 +0200
    Re: [RFC][PATCH 3/4] arm64: vdso: Fix nsec handling for  CLOCK_MONOTONIC_RAW Will Deacon <will.deacon@arm.com> - 2017-05-30 11:40 +0200
  Re: [RFC][PATCH 0/4] Fixes for two recently found timekeeping bugs Ingo Molnar <mingo@kernel.org> - 2017-05-27 09:40 +0200
    Re: [RFC][PATCH 0/4] Fixes for two recently found timekeeping bugs John Stultz <john.stultz@linaro.org> - 2017-05-27 18:20 +0200
      Re: [RFC][PATCH 0/4] Fixes for two recently found timekeeping bugs Ingo Molnar <mingo@kernel.org> - 2017-05-28 11:00 +0200
  Re: [RFC][PATCH 0/4] Fixes for two recently found timekeeping bugs Daniel Mentz <danielmentz@google.com> - 2017-05-31 02:20 +0200

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