The following commit has been merged into the timers/core branch of tip:
Commit-ID: c163e40af9b2331b2c629fd4ec8b703ed4d4ae39
Gitweb: https://git.kernel.org/tip/c163e40af9b2331b2c629fd4ec8b703ed4d4ae39
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Thu, 31 Oct 2024 13:04:08 +01:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Sat, 02 Nov 2024 10:14:31 +01:00
timekeeping: Always check for negative motion
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@xxxxxxxxxxxxx>
Acked-by: John Stultz <jstultz@xxxxxxxxxx>
Link: https://lore.kernel.org/all/20241031120328.599430157@xxxxxxxxxxxxx
---
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 2852fcd..53a5eda 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -145,7 +145,6 @@ config X86
select ARCH_HAS_PARANOID_L1D_FLUSH
select BUILDTIME_TABLE_SORT
select CLKEVT_I8253
- select CLOCKSOURCE_VALIDATE_LAST_CYCLE
select CLOCKSOURCE_WATCHDOG
# Word-size accesses may read uninitialized data past the trailing \0
# in strings and cause false KMSAN reports.
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 8ebb6d5..b0b97a6 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 b3dca83..63e600e 100644
--- a/kernel/time/timekeeping_internal.h
+++ b/kernel/time/timekeeping_internal.h
@@ -30,7 +30,6 @@ static inline void timekeeping_inc_mg_floor_swaps(void)
#endif
-#ifdef CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE
static inline u64 clocksource_delta(u64 now, u64 last, u64 mask)
{
u64 ret = (now - last) & mask;
@@ -41,12 +40,6 @@ 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. */
unsigned long timekeeper_lock_irqsave(void);
|