LXR linux/include/linux/sched

   1/* SPDX-License-Identifier: GPL-2.0-only */
   2/*
   3 * sched_clock.h: support for extending counters to full 64-bit ns counter
   4 */
   5#ifndef LINUX_SCHED_CLOCK
   6#define LINUX_SCHED_CLOCK
   7
   8#include <linux/types.h>
   9
  10#ifdef CONFIG_GENERIC_SCHED_CLOCK
  11/**
  12 * struct clock_read_data - data required to read from sched_clock()
  13 *
  14 * @epoch_ns:           sched_clock() value at last update
  15 * @epoch_cyc:          Clock cycle value at last update.
  16 * @sched_clock_mask:   Bitmask for two's complement subtraction of non 64bit
  17 *                      clocks.
  18 * @read_sched_clock:   Current clock source (or dummy source when suspended).
  19 * @mult:               Multiplier for scaled math conversion.
  20 * @shift:              Shift value for scaled math conversion.
  21 *
  22 * Care must be taken when updating this structure; it is read by
  23 * some very hot code paths. It occupies <=40 bytes and, when combined
  24 * with the seqcount used to synchronize access, comfortably fits into
  25 * a 64 byte cache line.
  26 */
  27struct clock_read_data {
  28        u64 epoch_ns;
  29        u64 epoch_cyc;
  30        u64 sched_clock_mask;
  31        u64 (*read_sched_clock)(void);
  32        u32 mult;
  33        u32 shift;
  34};
  35
  36extern struct clock_read_data *sched_clock_read_begin(unsigned int *seq);
  37extern int sched_clock_read_retry(unsigned int seq);
  38
  39extern void generic_sched_clock_init(void);
  40
  41extern void sched_clock_register(u64 (*read)(void), int bits,
  42                                 unsigned long rate);
  43#else
  44static inline void generic_sched_clock_init(void) { }
  45
  46static inline void sched_clock_register(u64 (*read)(void), int bits,
  47                                        unsigned long rate)
  48{
  49}
  50#endif
  51
  52#endif
  53