[PATCH 0/2] validate the delta of cycle_now and cycle_last on arm64

From: Yang Yingliang
Date: Tue Oct 27 2015 - 09:22:52 EST

In multi-core system, if the clock is not sync perfectly, it
will make cycle_last that recorded by CPU-A is a little more
than cycle_now that read by CPU-B. With the negative result,
hrtimer_update_base() return a huge and wrong time. It leads
to the cpu can not finish the while loop in hrtimer_interrupt()
until the real nowtime which is returned from ktime_get() catch
up with the wrong time on clock monotonic base.


Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Yang Yingliang (2):
clocksource: replace cycle_last validation with an equal way
arm64: validate the cycle_last to prevent time going backwards

arch/arm64/Kconfig | 1 +
kernel/time/timekeeping_internal.h | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)


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