timekeeping: Update multiplier when NTP frequency is set directly

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When the NTP frequency is set directly from userspace using the
ADJ_FREQUENCY or ADJ_TICK timex mode, immediately update the
timekeeper's multiplier instead of waiting for the next tick.

This removes a hidden non-deterministic delay in setting of the
frequency and allows an extremely tight control of the system clock
with update rates close to or even exceeding the kernel HZ.

The update is limited to archs using modern timekeeping
(!ARCH_USES_GETTIMEOFFSET).

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 <sboyd@kernel.org>
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

...

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Miroslav Lichvar 2018-06-04 15:34:21 +02:00 • committed by John Stultz

parent 1416270f4a

commit b061c7a513

1 changed files with 30 additions and 6 deletions

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kernel/time/timekeeping.c

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