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| author | Thomas Gleixner <tglx@linutronix.de> | 2014-07-16 21:05:12 +0000 |
|---|---|---|
| committer | John Stultz <john.stultz@linaro.org> | 2014-07-23 15:01:51 -0700 |
| commit | 09ec54429c6d10f87d1f084de53ae2c1c3a81108 (patch) | |
| tree | 842749293edd755e8bb12e1433c2f9df7dd842cf /kernel | |
| parent | 3a97837784acbf9fed699fc04d1799b0eb742fdf (diff) | |
| download | linux-stable-09ec54429c6d10f87d1f084de53ae2c1c3a81108.tar.gz linux-stable-09ec54429c6d10f87d1f084de53ae2c1c3a81108.tar.bz2 linux-stable-09ec54429c6d10f87d1f084de53ae2c1c3a81108.zip | |
clocksource: Move cycle_last validation to core code
The only user of the cycle_last validation is the x86 TSC. In order to
provide NMI safe accessor functions for clock monotonic and
monotonic_raw we need to do that in the core.
We can't do the TSC specific
if (now < cycle_last)
now = cycle_last;
for the other wrapping around clocksources, but TSC has
CLOCKSOURCE_MASK(64) which actually does not mask out anything so if
now is less than cycle_last the subtraction will give a negative
result. So we can check for that in clocksource_delta() and return 0
for that case.
Implement and enable it for x86
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/time/Kconfig | 5 | ||||
| -rw-r--r-- | kernel/time/timekeeping_internal.h | 9 |
2 files changed, 14 insertions, 0 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index feccfd888732..d626dc98e8df 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -12,6 +12,11 @@ config CLOCKSOURCE_WATCHDOG config ARCH_CLOCKSOURCE_DATA bool +# Clocksources require validation of the clocksource against the last +# cycle update - x86/TSC misfeature +config CLOCKSOURCE_VALIDATE_LAST_CYCLE + bool + # Timekeeping vsyscall support config GENERIC_TIME_VSYSCALL bool diff --git a/kernel/time/timekeeping_internal.h b/kernel/time/timekeeping_internal.h index 05dfa6b25dc4..4ea005a7f9da 100644 --- a/kernel/time/timekeeping_internal.h +++ b/kernel/time/timekeeping_internal.h @@ -12,9 +12,18 @@ extern void tk_debug_account_sleep_time(struct timespec64 *t); #define tk_debug_account_sleep_time(x) #endif +#ifdef CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE +static inline cycle_t clocksource_delta(cycle_t now, cycle_t last, cycle_t mask) +{ + cycle_t ret = (now - last) & mask; + + return (s64) ret > 0 ? ret : 0; +} +#else static inline cycle_t clocksource_delta(cycle_t now, cycle_t last, cycle_t mask) { return (now - last) & mask; } +#endif #endif /* _TIMEKEEPING_INTERNAL_H */ |