timekeeper_internal.h

  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 */