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![Peter Zijlstra](/assets/img/avatar_default.png)
Core2 marks its TSC unstable in ACPI Processor Idle, which is probed after sched_init_smp(). Luckily it appears both acpi_processor and intel_idle (which has a similar check) are mandatory built-in. This means we can delay switching to stable until after these drivers have ran (if they were modules, this would be impossible). Delay the stable switch to late_initcall() to allow these drivers to mark TSC unstable and avoid difficult stable->unstable transitions. Reported-by: Lofstedt, Marta <marta.lofstedt@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
100 lines
2.4 KiB
C
100 lines
2.4 KiB
C
#ifndef _LINUX_SCHED_CLOCK_H
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#define _LINUX_SCHED_CLOCK_H
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#include <linux/smp.h>
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/*
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* Do not use outside of architecture code which knows its limitations.
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*
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* sched_clock() has no promise of monotonicity or bounded drift between
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* CPUs, use (which you should not) requires disabling IRQs.
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*
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* Please use one of the three interfaces below.
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*/
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extern unsigned long long notrace sched_clock(void);
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/*
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* See the comment in kernel/sched/clock.c
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*/
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extern u64 running_clock(void);
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extern u64 sched_clock_cpu(int cpu);
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extern void sched_clock_init(void);
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#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
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static inline void sched_clock_tick(void)
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{
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}
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static inline void clear_sched_clock_stable(void)
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{
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}
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static inline void sched_clock_idle_sleep_event(void)
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{
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}
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static inline void sched_clock_idle_wakeup_event(void)
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{
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}
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static inline u64 cpu_clock(int cpu)
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{
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return sched_clock();
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}
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static inline u64 local_clock(void)
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{
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return sched_clock();
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}
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#else
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extern int sched_clock_stable(void);
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extern void clear_sched_clock_stable(void);
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/*
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* When sched_clock_stable(), __sched_clock_offset provides the offset
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* between local_clock() and sched_clock().
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*/
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extern u64 __sched_clock_offset;
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extern void sched_clock_tick(void);
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extern void sched_clock_tick_stable(void);
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extern void sched_clock_idle_sleep_event(void);
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extern void sched_clock_idle_wakeup_event(void);
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/*
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* As outlined in clock.c, provides a fast, high resolution, nanosecond
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* time source that is monotonic per cpu argument and has bounded drift
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* between cpus.
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*
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* ######################### BIG FAT WARNING ##########################
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* # when comparing cpu_clock(i) to cpu_clock(j) for i != j, time can #
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* # go backwards !! #
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* ####################################################################
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*/
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static inline u64 cpu_clock(int cpu)
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{
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return sched_clock_cpu(cpu);
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}
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static inline u64 local_clock(void)
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{
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return sched_clock_cpu(raw_smp_processor_id());
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}
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#endif
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#ifdef CONFIG_IRQ_TIME_ACCOUNTING
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/*
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* An i/f to runtime opt-in for irq time accounting based off of sched_clock.
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* The reason for this explicit opt-in is not to have perf penalty with
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* slow sched_clocks.
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*/
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extern void enable_sched_clock_irqtime(void);
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extern void disable_sched_clock_irqtime(void);
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#else
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static inline void enable_sched_clock_irqtime(void) {}
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static inline void disable_sched_clock_irqtime(void) {}
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#endif
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#endif /* _LINUX_SCHED_CLOCK_H */
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