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| author | Thomas Gleixner <tglx@linutronix.de> | 2024-10-31 13:04:08 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-12-14 20:03:38 +0100 |
| commit | e26cbab9821a6e511ec839884517838ec596751e (patch) | |
| tree | 6bfe7a0d4dbe69b440c22ead2e790b63cf6d29f4 /kernel/time | |
| parent | c7559dc2047e655eaa7e9be78bc7efab956463b9 (diff) | |
| download | linux-e26cbab9821a6e511ec839884517838ec596751e.tar.gz linux-e26cbab9821a6e511ec839884517838ec596751e.tar.bz2 linux-e26cbab9821a6e511ec839884517838ec596751e.zip | |
timekeeping: Always check for negative motion
[ 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>
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/Kconfig | 5 | ||||
| -rw-r--r-- | kernel/time/timekeeping_internal.h | 7 |
2 files changed, 0 insertions, 12 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 8ebb6d5a106b..b0b97a60aaa6 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 4ca2787d1642..1d4854d5c386 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; |