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 */ 34 struct 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 * @tai_offset: The current UTC to TAI offset in seconds 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 * @last_warning: Warning ratelimiter (DEBUG_TIMEKEEPING) 80 * @underflow_seen: Underflow warning flag (DEBUG_TIMEKEEPING) 81 * @overflow_seen: Overflow warning flag (DEBUG_TIMEKEEPING) 82 * 83 * Note: For timespec(64) based interfaces wall_to_monotonic is what 84 * we need to add to xtime (or xtime corrected for sub jiffy times) 85 * to get to monotonic time. Monotonic is pegged at zero at system 86 * boot time, so wall_to_monotonic will be negative, however, we will 87 * ALWAYS keep the tv_nsec part positive so we can use the usual 88 * normalization. 89 * 90 * wall_to_monotonic is moved after resume from suspend for the 91 * monotonic time not to jump. We need to add total_sleep_time to 92 * wall_to_monotonic to get the real boot based time offset. 93 * 94 * wall_to_monotonic is no longer the boot time, getboottime must be 95 * used instead. 96 * 97 * @monotonic_to_boottime is a timespec64 representation of @offs_boot to 98 * accelerate the VDSO update for CLOCK_BOOTTIME. 99 * 100 * The cacheline ordering of the structure is optimized for in kernel usage of 101 * the ktime_get() and ktime_get_ts64() family of time accessors. Struct 102 * timekeeper is prepended in the core timekeeping code with a sequence count, 103 * which results in the following cacheline layout: 104 * 105 * 0: seqcount, tkr_mono 106 * 1: xtime_sec ... tai_offset 107 * 2: tkr_raw, raw_sec 108 * 3,4: Internal variables 109 * 110 * Cacheline 0,1 contain the data which is used for accessing 111 * CLOCK_MONOTONIC/REALTIME/BOOTTIME/TAI, while cacheline 2 contains the 112 * data for accessing CLOCK_MONOTONIC_RAW. Cacheline 3,4 are internal 113 * variables which are only accessed during timekeeper updates once per 114 * tick. 115 */ 116 struct timekeeper { 117 /* Cacheline 0 (together with prepended seqcount of timekeeper core): */ 118 struct tk_read_base tkr_mono; 119 120 /* Cacheline 1: */ 121 u64 xtime_sec; 122 unsigned long ktime_sec; 123 struct timespec64 wall_to_monotonic; 124 ktime_t offs_real; 125 ktime_t offs_boot; 126 ktime_t offs_tai; 127 s32 tai_offset; 128 129 /* Cacheline 2: */ 130 struct tk_read_base tkr_raw; 131 u64 raw_sec; 132 133 /* Cachline 3 and 4 (timekeeping internal variables): */ 134 unsigned int clock_was_set_seq; 135 u8 cs_was_changed_seq; 136 137 struct timespec64 monotonic_to_boot; 138 139 u64 cycle_interval; 140 u64 xtime_interval; 141 s64 xtime_remainder; 142 u64 raw_interval; 143 144 ktime_t next_leap_ktime; 145 u64 ntp_tick; 146 s64 ntp_error; 147 u32 ntp_error_shift; 148 u32 ntp_err_mult; 149 u32 skip_second_overflow; 150 151 #ifdef CONFIG_DEBUG_TIMEKEEPING 152 long last_warning; 153 /* 154 * These simple flag variables are managed 155 * without locks, which is racy, but they are 156 * ok since we don't really care about being 157 * super precise about how many events were 158 * seen, just that a problem was observed. 159 */ 160 int underflow_seen; 161 int overflow_seen; 162 #endif 163 }; 164 165 #ifdef CONFIG_GENERIC_TIME_VSYSCALL 166 167 extern void update_vsyscall(struct timekeeper *tk); 168 extern void update_vsyscall_tz(void); 169 170 #else 171 172 static inline void update_vsyscall(struct timekeeper *tk) 173 { 174 } 175 static inline void update_vsyscall_tz(void) 176 { 177 } 178 #endif 179 180 #endif /* _LINUX_TIMEKEEPER_INTERNAL_H */ 181