Hi!
[ Upstream commit c163e40af9b2331b2c629fd4ec8b703ed4d4ae39 ]
clocksource_delta() has two variants. One with a check for negative motion, which is only selected by x86. This is a historic leftover as this function was previously used in the time getter hot paths.
Since 135225a363ae timekeeping_cycles_to_ns() has unconditional protection against this as a by-product of the protection against 64bit math overflow. timekeeping_advance(). The extra conditional there is not hurting anyone.
We don't have 135225a363ae in 5.10. So we probably should not have this?
Best regards, Pavel
+++ b/arch/x86/Kconfig @@ -107,7 +107,6 @@ config X86 select ARCH_WANTS_THP_SWAP if X86_64 select BUILDTIME_TABLE_SORT select CLKEVT_I8253
- select CLOCKSOURCE_VALIDATE_LAST_CYCLE select CLOCKSOURCE_WATCHDOG select DCACHE_WORD_ACCESS select EDAC_ATOMIC_SCRUB
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index a09b1d61df6a5..5cbedc0a06efc 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -17,11 +17,6 @@ config ARCH_CLOCKSOURCE_DATA config ARCH_CLOCKSOURCE_INIT 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 4ca2787d1642e..1d4854d5c386e 100644 --- a/kernel/time/timekeeping_internal.h +++ b/kernel/time/timekeeping_internal.h @@ -15,7 +15,6 @@ extern void tk_debug_account_sleep_time(const struct timespec64 *t); #define tk_debug_account_sleep_time(x) #endif -#ifdef CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE static inline u64 clocksource_delta(u64 now, u64 last, u64 mask) { u64 ret = (now - last) & mask; @@ -26,12 +25,6 @@ static inline u64 clocksource_delta(u64 now, u64 last, u64 mask) */ return ret & ~(mask >> 1) ? 0 : ret; } -#else -static inline u64 clocksource_delta(u64 now, u64 last, u64 mask) -{
- return (now - last) & mask;
-} -#endif /* Semi public for serialization of non timekeeper VDSO updates. */ extern raw_spinlock_t timekeeper_lock;