include/linux/sched/clock.h

   1 #ifndef _LINUX_SCHED_CLOCK_H
   2 #define _LINUX_SCHED_CLOCK_H
   3
   4 #include <linux/smp.h>
   5
   6 /*
   7  * Do not use outside of architecture code which knows its limitations.
   8  *
   9  * sched_clock() has no promise of monotonicity or bounded drift between
  10  * CPUs, use (which you should not) requires disabling IRQs.
  11  *
  12  * Please use one of the three interfaces below.
  13  */
  14 extern unsigned long long notrace sched_clock(void);
  15
  16 /*
  17  * See the comment in kernel/sched/clock.c
  18  */
  19 extern u64 running_clock(void);
  20 extern u64 sched_clock_cpu(int cpu);
  21
  22
  23 extern void sched_clock_init(void);
  24
  25 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
  26 static inline void sched_clock_init_late(void)
  27 {
  28 }
  29
  30 static inline void sched_clock_tick(void)
  31 {
  32 }
  33
  34 static inline void clear_sched_clock_stable(void)
  35 {
  36 }
  37
  38 static inline void sched_clock_idle_sleep_event(void)
  39 {
  40 }
  41
  42 static inline void sched_clock_idle_wakeup_event(u64 delta_ns)
  43 {
  44 }
  45
  46 static inline u64 cpu_clock(int cpu)
  47 {
  48         return sched_clock();
  49 }
  50
  51 static inline u64 local_clock(void)
  52 {
  53         return sched_clock();
  54 }
  55 #else
  56 extern void sched_clock_init_late(void);
  57 /*
  58  * Architectures can set this to 1 if they have specified
  59  * CONFIG_HAVE_UNSTABLE_SCHED_CLOCK in their arch Kconfig,
  60  * but then during bootup it turns out that sched_clock()
  61  * is reliable after all:
  62  */
  63 extern int sched_clock_stable(void);
  64 extern void clear_sched_clock_stable(void);
  65
  66 extern void sched_clock_tick(void);
  67 extern void sched_clock_idle_sleep_event(void);
  68 extern void sched_clock_idle_wakeup_event(u64 delta_ns);
  69
  70 /*
  71  * As outlined in clock.c, provides a fast, high resolution, nanosecond
  72  * time source that is monotonic per cpu argument and has bounded drift
  73  * between cpus.
  74  *
  75  * ######################### BIG FAT WARNING ##########################
  76  * # when comparing cpu_clock(i) to cpu_clock(j) for i != j, time can #
  77  * # go backwards !!                                                  #
  78  * ####################################################################
  79  */
  80 static inline u64 cpu_clock(int cpu)
  81 {
  82         return sched_clock_cpu(cpu);
  83 }
  84
  85 static inline u64 local_clock(void)
  86 {
  87         return sched_clock_cpu(raw_smp_processor_id());
  88 }
  89 #endif
  90
  91 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
  92 /*
  93  * An i/f to runtime opt-in for irq time accounting based off of sched_clock.
  94  * The reason for this explicit opt-in is not to have perf penalty with
  95  * slow sched_clocks.
  96  */
  97 extern void enable_sched_clock_irqtime(void);
  98 extern void disable_sched_clock_irqtime(void);
  99 #else
 100 static inline void enable_sched_clock_irqtime(void) {}
 101 static inline void disable_sched_clock_irqtime(void) {}
 102 #endif
 103
 104 #endif /* _LINUX_SCHED_CLOCK_H */