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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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