1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * sched_clock.h: support for extending counters to full 64-bit ns counter
5 #ifndef LINUX_SCHED_CLOCK
6 #define LINUX_SCHED_CLOCK
8 #ifdef CONFIG_GENERIC_SCHED_CLOCK
10 * struct clock_read_data - data required to read from sched_clock()
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
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.
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.
25 struct clock_read_data {
29 u64 (*read_sched_clock)(void);
34 extern struct clock_read_data *sched_clock_read_begin(unsigned int *seq);
35 extern int sched_clock_read_retry(unsigned int seq);
37 extern void generic_sched_clock_init(void);
39 extern void sched_clock_register(u64 (*read)(void), int bits,
42 static inline void generic_sched_clock_init(void) { }
44 static inline void sched_clock_register(u64 (*read)(void), int bits,