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c163e40af9
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 135225a363 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
49 lines
1.0 KiB
C
49 lines
1.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _TIMEKEEPING_INTERNAL_H
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#define _TIMEKEEPING_INTERNAL_H
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#include <linux/clocksource.h>
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#include <linux/spinlock.h>
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#include <linux/time.h>
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/*
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* timekeeping debug functions
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*/
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#ifdef CONFIG_DEBUG_FS
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DECLARE_PER_CPU(unsigned long, timekeeping_mg_floor_swaps);
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static inline void timekeeping_inc_mg_floor_swaps(void)
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{
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this_cpu_inc(timekeeping_mg_floor_swaps);
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}
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extern void tk_debug_account_sleep_time(const struct timespec64 *t);
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#else
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#define tk_debug_account_sleep_time(x)
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static inline void timekeeping_inc_mg_floor_swaps(void)
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{
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}
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#endif
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static inline u64 clocksource_delta(u64 now, u64 last, u64 mask)
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{
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u64 ret = (now - last) & mask;
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/*
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* Prevent time going backwards by checking the MSB of mask in
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* the result. If set, return 0.
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*/
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return ret & ~(mask >> 1) ? 0 : ret;
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}
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/* Semi public for serialization of non timekeeper VDSO updates. */
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unsigned long timekeeper_lock_irqsave(void);
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void timekeeper_unlock_irqrestore(unsigned long flags);
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#endif /* _TIMEKEEPING_INTERNAL_H */
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