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