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    Subject[PATCH 1/3] clocksource: Also tweak ->maxadj in clocksource_calc_mult_shift()
    Date
    There is still user of clocksource_calc_mult_shift(), and it's
    complement to commit d65670a7 [clocksource: Avoid selecting mult
    values that might overflow when adjusted]

    Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
    Cc: John Stultz <johnstul@us.ibm.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    ---
    include/linux/clocksource.h | 8 ++------
    kernel/time/clocksource.c | 18 ++++++++++++++++++
    2 files changed, 20 insertions(+), 6 deletions(-)

    diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
    index c86c940..a02a8d7 100644
    --- a/include/linux/clocksource.h
    +++ b/include/linux/clocksource.h
    @@ -314,12 +314,8 @@ static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
    __clocksource_updatefreq_scale(cs, 1000, khz);
    }

    -static inline void
    -clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec)
    -{
    - return clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
    - NSEC_PER_SEC, minsec);
    -}
    +extern void
    +clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec);

    #ifdef CONFIG_GENERIC_TIME_VSYSCALL
    extern void
    diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
    index cfc65e1..5119042 100644
    --- a/kernel/time/clocksource.c
    +++ b/kernel/time/clocksource.c
    @@ -724,6 +724,24 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
    }
    EXPORT_SYMBOL_GPL(__clocksource_register_scale);

    +void clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec)
    +{
    + clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
    + NSEC_PER_SEC, minsec);
    +
    + /*
    + * for clocksources that have large mults, to avoid overflow.
    + * Since mult may be adjusted by ntp, add an safety extra margin
    + *
    + */
    + cs->maxadj = clocksource_max_adjustment(cs);
    + while ((cs->mult + cs->maxadj < cs->mult)
    + || (cs->mult - cs->maxadj > cs->mult)) {
    + cs->mult >>= 1;
    + cs->shift--;
    + cs->maxadj = clocksource_max_adjustment(cs);
    + }
    +}

    /**
    * clocksource_register - Used to install new clocksources
    --
    1.7.5.4


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