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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 * timekeeper_ids - IDs for various time keepers in the kernel
16 * @TIMEKEEPER_CORE: The central core timekeeper managing system time
17 * @TIMEKEEPER_AUX_FIRST: The first AUX timekeeper
18 * @TIMEKEEPER_AUX_LAST: The last AUX timekeeper
19 * @TIMEKEEPERS_MAX: The maximum number of timekeepers managed
20 */
21enum timekeeper_ids {
22 TIMEKEEPER_CORE,
23#ifdef CONFIG_POSIX_AUX_CLOCKS
24 TIMEKEEPER_AUX_FIRST,
25 TIMEKEEPER_AUX_LAST = TIMEKEEPER_AUX_FIRST + MAX_AUX_CLOCKS - 1,
26#endif
27 TIMEKEEPERS_MAX,
28};
29
30/**
31 * struct tk_read_base - base structure for timekeeping readout
32 * @clock: Current clocksource used for timekeeping.
33 * @mask: Bitmask for two's complement subtraction of non 64bit clocks
34 * @cycle_last: @clock cycle value at last update
35 * @mult: (NTP adjusted) multiplier for scaled math conversion
36 * @shift: Shift value for scaled math conversion
37 * @xtime_nsec: Shifted (fractional) nano seconds offset for readout
38 * @base: ktime_t (nanoseconds) base time for readout
39 * @base_real: Nanoseconds base value for clock REALTIME readout
40 *
41 * This struct has size 56 byte on 64 bit. Together with a seqcount it
42 * occupies a single 64byte cache line.
43 *
44 * The struct is separate from struct timekeeper as it is also used
45 * for the fast NMI safe accessors.
46 *
47 * @base_real is for the fast NMI safe accessor to allow reading clock
48 * realtime from any context.
49 */
50struct tk_read_base {
51 struct clocksource *clock;
52 u64 mask;
53 u64 cycle_last;
54 u32 mult;
55 u32 shift;
56 u64 xtime_nsec;
57 ktime_t base;
58 u64 base_real;
59};
60
61/**
62 * struct timekeeper - Structure holding internal timekeeping values.
63 * @tkr_mono: The readout base structure for CLOCK_MONOTONIC
64 * @xtime_sec: Current CLOCK_REALTIME time in seconds
65 * @ktime_sec: Current CLOCK_MONOTONIC time in seconds
66 * @wall_to_monotonic: CLOCK_REALTIME to CLOCK_MONOTONIC offset
67 * @offs_real: Offset clock monotonic -> clock realtime
68 * @offs_boot: Offset clock monotonic -> clock boottime
69 * @offs_tai: Offset clock monotonic -> clock tai
70 * @offs_aux: Offset clock monotonic -> clock AUX
71 * @coarse_nsec: The nanoseconds part for coarse time getters
72 * @id: The timekeeper ID
73 * @tkr_raw: The readout base structure for CLOCK_MONOTONIC_RAW
74 * @raw_sec: CLOCK_MONOTONIC_RAW time in seconds
75 * @clock_was_set_seq: The sequence number of clock was set events
76 * @cs_was_changed_seq: The sequence number of clocksource change events
77 * @clock_valid: Indicator for valid clock
78 * @monotonic_to_boot: CLOCK_MONOTONIC to CLOCK_BOOTTIME offset
79 * @monotonic_to_aux: CLOCK_MONOTONIC to CLOCK_AUX offset
80 * @cycle_interval: Number of clock cycles in one NTP interval
81 * @xtime_interval: Number of clock shifted nano seconds in one NTP
82 * interval.
83 * @xtime_remainder: Shifted nano seconds left over when rounding
84 * @cycle_interval
85 * @raw_interval: Shifted raw nano seconds accumulated per NTP interval.
86 * @next_leap_ktime: CLOCK_MONOTONIC time value of a pending leap-second
87 * @ntp_tick: The ntp_tick_length() value currently being
88 * used. This cached copy ensures we consistently
89 * apply the tick length for an entire tick, as
90 * ntp_tick_length may change mid-tick, and we don't
91 * want to apply that new value to the tick in
92 * progress.
93 * @ntp_error: Difference between accumulated time and NTP time in ntp
94 * shifted nano seconds.
95 * @ntp_error_shift: Shift conversion between clock shifted nano seconds and
96 * ntp shifted nano seconds.
97 * @ntp_err_mult: Multiplication factor for scaled math conversion
98 * @skip_second_overflow: Flag used to avoid updating NTP twice with same second
99 * @tai_offset: The current UTC to TAI offset in seconds
100 *
101 * Note: For timespec(64) based interfaces wall_to_monotonic is what
102 * we need to add to xtime (or xtime corrected for sub jiffy times)
103 * to get to monotonic time. Monotonic is pegged at zero at system
104 * boot time, so wall_to_monotonic will be negative, however, we will
105 * ALWAYS keep the tv_nsec part positive so we can use the usual
106 * normalization.
107 *
108 * wall_to_monotonic is moved after resume from suspend for the
109 * monotonic time not to jump. We need to add total_sleep_time to
110 * wall_to_monotonic to get the real boot based time offset.
111 *
112 * wall_to_monotonic is no longer the boot time, getboottime must be
113 * used instead.
114 *
115 * @monotonic_to_boottime is a timespec64 representation of @offs_boot to
116 * accelerate the VDSO update for CLOCK_BOOTTIME.
117 *
118 * @offs_aux is used by the auxiliary timekeepers which do not utilize any
119 * of the regular timekeeper offset fields.
120 *
121 * @monotonic_to_aux is a timespec64 representation of @offs_aux to
122 * accelerate the VDSO update for CLOCK_AUX.
123 *
124 * The cacheline ordering of the structure is optimized for in kernel usage of
125 * the ktime_get() and ktime_get_ts64() family of time accessors. Struct
126 * timekeeper is prepended in the core timekeeping code with a sequence count,
127 * which results in the following cacheline layout:
128 *
129 * 0: seqcount, tkr_mono
130 * 1: xtime_sec ... id
131 * 2: tkr_raw, raw_sec
132 * 3,4: Internal variables
133 *
134 * Cacheline 0,1 contain the data which is used for accessing
135 * CLOCK_MONOTONIC/REALTIME/BOOTTIME/TAI, while cacheline 2 contains the
136 * data for accessing CLOCK_MONOTONIC_RAW. Cacheline 3,4 are internal
137 * variables which are only accessed during timekeeper updates once per
138 * tick.
139 */
140struct timekeeper {
141 /* Cacheline 0 (together with prepended seqcount of timekeeper core): */
142 struct tk_read_base tkr_mono;
143
144 /* Cacheline 1: */
145 u64 xtime_sec;
146 unsigned long ktime_sec;
147 struct timespec64 wall_to_monotonic;
148 ktime_t offs_real;
149 ktime_t offs_boot;
150 union {
151 ktime_t offs_tai;
152 ktime_t offs_aux;
153 };
154 u32 coarse_nsec;
155 enum timekeeper_ids id;
156
157 /* Cacheline 2: */
158 struct tk_read_base tkr_raw;
159 u64 raw_sec;
160
161 /* Cachline 3 and 4 (timekeeping internal variables): */
162 unsigned int clock_was_set_seq;
163 u8 cs_was_changed_seq;
164 u8 clock_valid;
165
166 union {
167 struct timespec64 monotonic_to_boot;
168 struct timespec64 monotonic_to_aux;
169 };
170
171 u64 cycle_interval;
172 u64 xtime_interval;
173 s64 xtime_remainder;
174 u64 raw_interval;
175
176 ktime_t next_leap_ktime;
177 u64 ntp_tick;
178 s64 ntp_error;
179 u32 ntp_error_shift;
180 u32 ntp_err_mult;
181 u32 skip_second_overflow;
182 s32 tai_offset;
183};
184
185#ifdef CONFIG_GENERIC_TIME_VSYSCALL
186
187extern void update_vsyscall(struct timekeeper *tk);
188extern void update_vsyscall_tz(void);
189
190#else
191
192static inline void update_vsyscall(struct timekeeper *tk)
193{
194}
195static inline void update_vsyscall_tz(void)
196{
197}
198#endif
199
200#if defined(CONFIG_GENERIC_GETTIMEOFDAY) && defined(CONFIG_POSIX_AUX_CLOCKS)
201extern void vdso_time_update_aux(struct timekeeper *tk);
202#else
203static inline void vdso_time_update_aux(struct timekeeper *tk) { }
204#endif
205
206#endif /* _LINUX_TIMEKEEPER_INTERNAL_H */
207

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