From: Thomas Gleixner tglx@linutronix.de
[ 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.
clocksource_delta() is only used in the clocksource watchdog and in timekeeping_advance(). The extra conditional there is not hurting anyone.
Remove the config option and unconditionally prevent negative motion of the readout.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: John Stultz jstultz@google.com Link: https://lore.kernel.org/all/20241031120328.599430157@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/Kconfig | 1 - kernel/time/Kconfig | 5 ----- kernel/time/timekeeping_internal.h | 7 ------- 3 files changed, 13 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index df0a3a1b08ae0..a3e7f75a8cfa8 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -99,7 +99,6 @@ config X86 select ARCH_WANTS_THP_SWAP if X86_64 select BUILDTIME_EXTABLE_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 fcc42353f1253..4b9a8653a6327 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 bcbb52db22565..d7f99e69bce4b 100644 --- a/kernel/time/timekeeping_internal.h +++ b/kernel/time/timekeeping_internal.h @@ -13,7 +13,6 @@ 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; @@ -24,11 +23,5 @@ 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
#endif /* _TIMEKEEPING_INTERNAL_H */