1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * You SHOULD NOT be including this unless you're vsyscall
4 * handling code or timekeeping internal code!
5 */
6
7#ifndef _LINUX_TIMEKEEPER_INTERNAL_H
8#define _LINUX_TIMEKEEPER_INTERNAL_H
9
10#include <linux/clocksource.h>
11#include <linux/jiffies.h>
12#include <linux/time.h>
13
14/**
15 * struct tk_read_base - base structure for timekeeping readout
16 * @clock: Current clocksource used for timekeeping.
17 * @mask: Bitmask for two's complement subtraction of non 64bit clocks
18 * @cycle_last: @clock cycle value at last update
19 * @mult: (NTP adjusted) multiplier for scaled math conversion
20 * @shift: Shift value for scaled math conversion
21 * @xtime_nsec: Shifted (fractional) nano seconds offset for readout
22 * @base: ktime_t (nanoseconds) base time for readout
23 * @base_real: Nanoseconds base value for clock REALTIME readout
24 *
25 * This struct has size 56 byte on 64 bit. Together with a seqcount it
26 * occupies a single 64byte cache line.
27 *
28 * The struct is separate from struct timekeeper as it is also used
29 * for the fast NMI safe accessors.
30 *
31 * @base_real is for the fast NMI safe accessor to allow reading clock
32 * realtime from any context.
33 */
34struct tk_read_base {
35 struct clocksource *clock;
36 u64 mask;
37 u64 cycle_last;
38 u32 mult;
39 u32 shift;
40 u64 xtime_nsec;
41 ktime_t base;
42 u64 base_real;
43};
44
45/**
46 * struct timekeeper - Structure holding internal timekeeping values.
47 * @tkr_mono: The readout base structure for CLOCK_MONOTONIC
48 * @xtime_sec: Current CLOCK_REALTIME time in seconds
49 * @ktime_sec: Current CLOCK_MONOTONIC time in seconds
50 * @wall_to_monotonic: CLOCK_REALTIME to CLOCK_MONOTONIC offset
51 * @offs_real: Offset clock monotonic -> clock realtime
52 * @offs_boot: Offset clock monotonic -> clock boottime
53 * @offs_tai: Offset clock monotonic -> clock tai
54 * @coarse_nsec: The nanoseconds part for coarse time getters
55 * @tkr_raw: The readout base structure for CLOCK_MONOTONIC_RAW
56 * @raw_sec: CLOCK_MONOTONIC_RAW time in seconds
57 * @clock_was_set_seq: The sequence number of clock was set events
58 * @cs_was_changed_seq: The sequence number of clocksource change events
59 * @monotonic_to_boot: CLOCK_MONOTONIC to CLOCK_BOOTTIME offset
60 * @cycle_interval: Number of clock cycles in one NTP interval
61 * @xtime_interval: Number of clock shifted nano seconds in one NTP
62 * interval.
63 * @xtime_remainder: Shifted nano seconds left over when rounding
64 * @cycle_interval
65 * @raw_interval: Shifted raw nano seconds accumulated per NTP interval.
66 * @next_leap_ktime: CLOCK_MONOTONIC time value of a pending leap-second
67 * @ntp_tick: The ntp_tick_length() value currently being
68 * used. This cached copy ensures we consistently
69 * apply the tick length for an entire tick, as
70 * ntp_tick_length may change mid-tick, and we don't
71 * want to apply that new value to the tick in
72 * progress.
73 * @ntp_error: Difference between accumulated time and NTP time in ntp
74 * shifted nano seconds.
75 * @ntp_error_shift: Shift conversion between clock shifted nano seconds and
76 * ntp shifted nano seconds.
77 * @ntp_err_mult: Multiplication factor for scaled math conversion
78 * @skip_second_overflow: Flag used to avoid updating NTP twice with same second
79 * @tai_offset: The current UTC to TAI offset in seconds
80 *
81 * Note: For timespec(64) based interfaces wall_to_monotonic is what
82 * we need to add to xtime (or xtime corrected for sub jiffy times)
83 * to get to monotonic time. Monotonic is pegged at zero at system
84 * boot time, so wall_to_monotonic will be negative, however, we will
85 * ALWAYS keep the tv_nsec part positive so we can use the usual
86 * normalization.
87 *
88 * wall_to_monotonic is moved after resume from suspend for the
89 * monotonic time not to jump. We need to add total_sleep_time to
90 * wall_to_monotonic to get the real boot based time offset.
91 *
92 * wall_to_monotonic is no longer the boot time, getboottime must be
93 * used instead.
94 *
95 * @monotonic_to_boottime is a timespec64 representation of @offs_boot to
96 * accelerate the VDSO update for CLOCK_BOOTTIME.
97 *
98 * The cacheline ordering of the structure is optimized for in kernel usage of
99 * the ktime_get() and ktime_get_ts64() family of time accessors. Struct
100 * timekeeper is prepended in the core timekeeping code with a sequence count,
101 * which results in the following cacheline layout:
102 *
103 * 0: seqcount, tkr_mono
104 * 1: xtime_sec ... coarse_nsec
105 * 2: tkr_raw, raw_sec
106 * 3,4: Internal variables
107 *
108 * Cacheline 0,1 contain the data which is used for accessing
109 * CLOCK_MONOTONIC/REALTIME/BOOTTIME/TAI, while cacheline 2 contains the
110 * data for accessing CLOCK_MONOTONIC_RAW. Cacheline 3,4 are internal
111 * variables which are only accessed during timekeeper updates once per
112 * tick.
113 */
114struct timekeeper {
115 /* Cacheline 0 (together with prepended seqcount of timekeeper core): */
116 struct tk_read_base tkr_mono;
117
118 /* Cacheline 1: */
119 u64 xtime_sec;
120 unsigned long ktime_sec;
121 struct timespec64 wall_to_monotonic;
122 ktime_t offs_real;
123 ktime_t offs_boot;
124 ktime_t offs_tai;
125 u32 coarse_nsec;
126
127 /* Cacheline 2: */
128 struct tk_read_base tkr_raw;
129 u64 raw_sec;
130
131 /* Cachline 3 and 4 (timekeeping internal variables): */
132 unsigned int clock_was_set_seq;
133 u8 cs_was_changed_seq;
134
135 struct timespec64 monotonic_to_boot;
136
137 u64 cycle_interval;
138 u64 xtime_interval;
139 s64 xtime_remainder;
140 u64 raw_interval;
141
142 ktime_t next_leap_ktime;
143 u64 ntp_tick;
144 s64 ntp_error;
145 u32 ntp_error_shift;
146 u32 ntp_err_mult;
147 u32 skip_second_overflow;
148 s32 tai_offset;
149};
150
151#ifdef CONFIG_GENERIC_TIME_VSYSCALL
152
153extern void update_vsyscall(struct timekeeper *tk);
154extern void update_vsyscall_tz(void);
155
156#else
157
158static inline void update_vsyscall(struct timekeeper *tk)
159{
160}
161static inline void update_vsyscall_tz(void)
162{
163}
164#endif
165
166#endif /* _LINUX_TIMEKEEPER_INTERNAL_H */
167

source code of linux/include/linux/timekeeper_internal.h

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