include/linux/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  * 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  *
  80  * Note: For timespec(64) based interfaces wall_to_monotonic is what
  81  * we need to add to xtime (or xtime corrected for sub jiffy times)
  82  * to get to monotonic time.  Monotonic is pegged at zero at system
  83  * boot time, so wall_to_monotonic will be negative, however, we will
  84  * ALWAYS keep the tv_nsec part positive so we can use the usual
  85  * normalization.
  86  *
  87  * wall_to_monotonic is moved after resume from suspend for the
  88  * monotonic time not to jump. We need to add total_sleep_time to
  89  * wall_to_monotonic to get the real boot based time offset.
  90  *
  91  * wall_to_monotonic is no longer the boot time, getboottime must be
  92  * used instead.
  93  *
  94  * @monotonic_to_boottime is a timespec64 representation of @offs_boot to
  95  * accelerate the VDSO update for CLOCK_BOOTTIME.
  96  *
  97  * The cacheline ordering of the structure is optimized for in kernel usage of
  98  * the ktime_get() and ktime_get_ts64() family of time accessors. Struct
  99  * timekeeper is prepended in the core timekeeping code with a sequence count,
 100  * which results in the following cacheline layout:
 101  *
 102  * 0:   seqcount, tkr_mono
 103  * 1:   xtime_sec ... tai_offset
 104  * 2:   tkr_raw, raw_sec
 105  * 3,4: Internal variables
 106  *
 107  * Cacheline 0,1 contain the data which is used for accessing
 108  * CLOCK_MONOTONIC/REALTIME/BOOTTIME/TAI, while cacheline 2 contains the
 109  * data for accessing CLOCK_MONOTONIC_RAW.  Cacheline 3,4 are internal
 110  * variables which are only accessed during timekeeper updates once per
 111  * tick.
 112  */
 113 struct timekeeper {
 114         /* Cacheline 0 (together with prepended seqcount of timekeeper core): */
 115         struct tk_read_base     tkr_mono;
 116
 117         /* Cacheline 1: */
 118         u64                     xtime_sec;
 119         unsigned long           ktime_sec;
 120         struct timespec64       wall_to_monotonic;
 121         ktime_t                 offs_real;
 122         ktime_t                 offs_boot;
 123         ktime_t                 offs_tai;
 124         s32                     tai_offset;
 125
 126         /* Cacheline 2: */
 127         struct tk_read_base     tkr_raw;
 128         u64                     raw_sec;
 129
 130         /* Cachline 3 and 4 (timekeeping internal variables): */
 131         unsigned int            clock_was_set_seq;
 132         u8                      cs_was_changed_seq;
 133
 134         struct timespec64       monotonic_to_boot;
 135
 136         u64                     cycle_interval;
 137         u64                     xtime_interval;
 138         s64                     xtime_remainder;
 139         u64                     raw_interval;
 140
 141         ktime_t                 next_leap_ktime;
 142         u64                     ntp_tick;
 143         s64                     ntp_error;
 144         u32                     ntp_error_shift;
 145         u32                     ntp_err_mult;
 146         u32                     skip_second_overflow;
 147 };
 148
 149 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
 150
 151 extern void update_vsyscall(struct timekeeper *tk);
 152 extern void update_vsyscall_tz(void);
 153
 154 #else
 155
 156 static inline void update_vsyscall(struct timekeeper *tk)
 157 {
 158 }
 159 static inline void update_vsyscall_tz(void)
 160 {
 161 }
 162 #endif
 163
 164 #endif /* _LINUX_TIMEKEEPER_INTERNAL_H */