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Diffstat (limited to 'include/linux/timekeeper_internal.h')
| -rw-r--r-- | include/linux/timekeeper_internal.h | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h new file mode 100644 index 000000000..4486dfd5d --- /dev/null +++ b/include/linux/timekeeper_internal.h @@ -0,0 +1,214 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * You SHOULD NOT be including this unless you're vsyscall + * handling code or timekeeping internal code! + */ + +#ifndef _LINUX_TIMEKEEPER_INTERNAL_H +#define _LINUX_TIMEKEEPER_INTERNAL_H + +#include <linux/clocksource.h> +#include <linux/jiffies.h> +#include <linux/time.h> + +/** + * timekeeper_ids - IDs for various time keepers in the kernel + * @TIMEKEEPER_CORE: The central core timekeeper managing system time + * @TIMEKEEPER_AUX_FIRST: The first AUX timekeeper + * @TIMEKEEPER_AUX_LAST: The last AUX timekeeper + * @TIMEKEEPERS_MAX: The maximum number of timekeepers managed + */ +enum timekeeper_ids { + TIMEKEEPER_CORE, +#ifdef CONFIG_POSIX_AUX_CLOCKS + TIMEKEEPER_AUX_FIRST, + TIMEKEEPER_AUX_LAST = TIMEKEEPER_AUX_FIRST + MAX_AUX_CLOCKS - 1, +#endif + TIMEKEEPERS_MAX, +}; + +/** + * struct tk_read_base - base structure for timekeeping readout + * @clock: Current clocksource used for timekeeping. + * @mask: Bitmask for two's complement subtraction of non 64bit clocks + * @cycle_last: @clock cycle value at last update + * @mult: (NTP adjusted) multiplier for scaled math conversion + * @shift: Shift value for scaled math conversion + * @xtime_nsec: Shifted (fractional) nano seconds offset for readout + * @base: ktime_t (nanoseconds) base time for readout + * @base_real: Nanoseconds base value for clock REALTIME readout + * + * This struct has size 56 byte on 64 bit. Together with a seqcount it + * occupies a single 64byte cache line. + * + * The struct is separate from struct timekeeper as it is also used + * for the fast NMI safe accessors. + * + * @base_real is for the fast NMI safe accessor to allow reading clock + * realtime from any context. + */ +struct tk_read_base { + struct clocksource *clock; + u64 mask; + u64 cycle_last; + u32 mult; + u32 shift; + u64 xtime_nsec; + ktime_t base; + u64 base_real; +}; + +/** + * struct timekeeper - Structure holding internal timekeeping values. + * @tkr_mono: The readout base structure for CLOCK_MONOTONIC + * @xtime_sec: Current CLOCK_REALTIME time in seconds + * @ktime_sec: Current CLOCK_MONOTONIC time in seconds + * @wall_to_monotonic: CLOCK_REALTIME to CLOCK_MONOTONIC offset + * @offs_real: Offset clock monotonic -> clock realtime + * @offs_boot: Offset clock monotonic -> clock boottime + * @offs_tai: Offset clock monotonic -> clock tai + * @offs_aux: Offset clock monotonic -> clock AUX + * @coarse_nsec: The nanoseconds part for coarse time getters + * @id: The timekeeper ID + * @tkr_raw: The readout base structure for CLOCK_MONOTONIC_RAW + * @raw_sec: CLOCK_MONOTONIC_RAW time in seconds + * @cs_id: The ID of the current clocksource + * @cs_ns_to_cyc_mult: Multiplicator for nanoseconds to cycles conversion + * @cs_ns_to_cyc_shift: Shift value for nanoseconds to cycles conversion + * @cs_ns_to_cyc_maxns: Maximum nanoseconds to cyles conversion range + * @clock_was_set_seq: The sequence number of clock was set events + * @cs_was_changed_seq: The sequence number of clocksource change events + * @clock_valid: Indicator for valid clock + * @monotonic_to_boot: CLOCK_MONOTONIC to CLOCK_BOOTTIME offset + * @monotonic_to_aux: CLOCK_MONOTONIC to CLOCK_AUX offset + * @cycle_interval: Number of clock cycles in one NTP interval + * @xtime_interval: Number of clock shifted nano seconds in one NTP + * interval. + * @xtime_remainder: Shifted nano seconds left over when rounding + * @cycle_interval + * @raw_interval: Shifted raw nano seconds accumulated per NTP interval. + * @next_leap_ktime: CLOCK_MONOTONIC time value of a pending leap-second + * @ntp_tick: The ntp_tick_length() value currently being + * used. This cached copy ensures we consistently + * apply the tick length for an entire tick, as + * ntp_tick_length may change mid-tick, and we don't + * want to apply that new value to the tick in + * progress. + * @ntp_error: Difference between accumulated time and NTP time in ntp + * shifted nano seconds. + * @ntp_error_shift: Shift conversion between clock shifted nano seconds and + * ntp shifted nano seconds. + * @ntp_err_mult: Multiplication factor for scaled math conversion + * @skip_second_overflow: Flag used to avoid updating NTP twice with same second + * @tai_offset: The current UTC to TAI offset in seconds + * + * Note: For timespec(64) based interfaces wall_to_monotonic is what + * we need to add to xtime (or xtime corrected for sub jiffy times) + * to get to monotonic time. Monotonic is pegged at zero at system + * boot time, so wall_to_monotonic will be negative, however, we will + * ALWAYS keep the tv_nsec part positive so we can use the usual + * normalization. + * + * wall_to_monotonic is moved after resume from suspend for the + * monotonic time not to jump. We need to add total_sleep_time to + * wall_to_monotonic to get the real boot based time offset. + * + * wall_to_monotonic is no longer the boot time, getboottime must be + * used instead. + * + * @monotonic_to_boottime is a timespec64 representation of @offs_boot to + * accelerate the VDSO update for CLOCK_BOOTTIME. + * + * @offs_aux is used by the auxiliary timekeepers which do not utilize any + * of the regular timekeeper offset fields. + * + * @monotonic_to_aux is a timespec64 representation of @offs_aux to + * accelerate the VDSO update for CLOCK_AUX. + * + * The cacheline ordering of the structure is optimized for in kernel usage of + * the ktime_get() and ktime_get_ts64() family of time accessors. Struct + * timekeeper is prepended in the core timekeeping code with a sequence count, + * which results in the following cacheline layout: + * + * 0: seqcount, tkr_mono + * 1: xtime_sec ... id + * 2: tkr_raw, raw_sec + * 3,4: Internal variables + * + * Cacheline 0,1 contain the data which is used for accessing + * CLOCK_MONOTONIC/REALTIME/BOOTTIME/TAI, while cacheline 2 contains the + * data for accessing CLOCK_MONOTONIC_RAW. Cacheline 3,4 are internal + * variables which are only accessed during timekeeper updates once per + * tick. + */ +struct timekeeper { + /* Cacheline 0 (together with prepended seqcount of timekeeper core): */ + struct tk_read_base tkr_mono; + + /* Cacheline 1: */ + u64 xtime_sec; + unsigned long ktime_sec; + struct timespec64 wall_to_monotonic; + ktime_t offs_real; + ktime_t offs_boot; + union { + ktime_t offs_tai; + ktime_t offs_aux; + }; + u32 coarse_nsec; + enum timekeeper_ids id; + + /* Cacheline 2: */ + struct tk_read_base tkr_raw; + u64 raw_sec; + + /* Cachline 3 and 4 (timekeeping internal variables): */ + enum clocksource_ids cs_id; + u32 cs_ns_to_cyc_mult; + u32 cs_ns_to_cyc_shift; + u64 cs_ns_to_cyc_maxns; + unsigned int clock_was_set_seq; + u8 cs_was_changed_seq; + u8 clock_valid; + + union { + struct timespec64 monotonic_to_boot; + struct timespec64 monotonic_to_aux; + }; + + u64 cycle_interval; + u64 xtime_interval; + s64 xtime_remainder; + u64 raw_interval; + + ktime_t next_leap_ktime; + u64 ntp_tick; + s64 ntp_error; + u32 ntp_error_shift; + u32 ntp_err_mult; + u32 skip_second_overflow; + s32 tai_offset; +}; + +#ifdef CONFIG_GENERIC_GETTIMEOFDAY + +extern void update_vsyscall(struct timekeeper *tk); +extern void update_vsyscall_tz(void); + +#else + +static inline void update_vsyscall(struct timekeeper *tk) +{ +} +static inline void update_vsyscall_tz(void) +{ +} +#endif + +#if defined(CONFIG_GENERIC_GETTIMEOFDAY) && defined(CONFIG_POSIX_AUX_CLOCKS) +extern void vdso_time_update_aux(struct timekeeper *tk); +#else +static inline void vdso_time_update_aux(struct timekeeper *tk) { } +#endif + +#endif /* _LINUX_TIMEKEEPER_INTERNAL_H */ |