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printk wants to store various timestamps (MONOTONIC, REALTIME, BOOTTIME) to
make correlation of dmesg from several systems easier.
Provide an interface to retrieve all three timestamps in one go.
There are some caveats:
1) Boot time and late sleep time injection
Boot time is a racy access on 32bit systems if the sleep time injection
happens late during resume and not in timekeeping_resume(). That could be
avoided by expanding struct tk_read_base with boot offset for 32bit and
adding more overhead to the update. As this is a hard to observe once per
resume event which can be filtered with reasonable effort using the
accurate mono/real timestamps, it's probably not worth the trouble.
Aside of that it might be possible on 32 and 64 bit to observe the
following when the sleep time injection happens late:
CPU 0 CPU 1
timekeeping_resume()
ktime_get_fast_timestamps()
mono, real = __ktime_get_real_fast()
inject_sleep_time()
update boot offset
boot = mono + bootoffset;
That means that boot time already has the sleep time adjustment, but
real time does not. On the next readout both are in sync again.
Preventing this for 64bit is not really feasible without destroying the
careful cache layout of the timekeeper because the sequence count and
struct tk_read_base would then need two cache lines instead of one.
2) Suspend/resume timestamps
Access to the time keeper clock source is disabled accross the innermost
steps of suspend/resume. The accessors still work, but the timestamps
are frozen until time keeping is resumed which happens very early.
For regular suspend/resume there is no observable difference vs. sched
clock, but it might affect some of the nasty low level debug printks.
OTOH, access to sched clock is not guaranteed accross suspend/resume on
all systems either so it depends on the hardware in use.
If that turns out to be a real problem then this could be mitigated by
using sched clock in a similar way as during early boot. But it's not as
trivial as on early boot because it needs some careful protection
against the clock monotonic timestamp jumping backwards on resume.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200814115512.159981360@linutronix.de
309 lines
7.5 KiB
C
309 lines
7.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_TIMEKEEPING_H
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#define _LINUX_TIMEKEEPING_H
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#include <linux/errno.h>
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/* Included from linux/ktime.h */
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void timekeeping_init(void);
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extern int timekeeping_suspended;
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/* Architecture timer tick functions: */
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extern void update_process_times(int user);
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extern void xtime_update(unsigned long ticks);
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/*
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* Get and set timeofday
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*/
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extern int do_settimeofday64(const struct timespec64 *ts);
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extern int do_sys_settimeofday64(const struct timespec64 *tv,
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const struct timezone *tz);
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/*
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* ktime_get() family: read the current time in a multitude of ways,
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*
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* The default time reference is CLOCK_MONOTONIC, starting at
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* boot time but not counting the time spent in suspend.
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* For other references, use the functions with "real", "clocktai",
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* "boottime" and "raw" suffixes.
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*
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* To get the time in a different format, use the ones wit
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* "ns", "ts64" and "seconds" suffix.
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*
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* See Documentation/core-api/timekeeping.rst for more details.
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*/
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/*
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* timespec64 based interfaces
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*/
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extern void ktime_get_raw_ts64(struct timespec64 *ts);
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extern void ktime_get_ts64(struct timespec64 *ts);
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extern void ktime_get_real_ts64(struct timespec64 *tv);
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extern void ktime_get_coarse_ts64(struct timespec64 *ts);
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extern void ktime_get_coarse_real_ts64(struct timespec64 *ts);
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void getboottime64(struct timespec64 *ts);
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/*
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* time64_t base interfaces
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*/
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extern time64_t ktime_get_seconds(void);
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extern time64_t __ktime_get_real_seconds(void);
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extern time64_t ktime_get_real_seconds(void);
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/*
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* ktime_t based interfaces
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*/
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enum tk_offsets {
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TK_OFFS_REAL,
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TK_OFFS_BOOT,
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TK_OFFS_TAI,
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TK_OFFS_MAX,
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};
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extern ktime_t ktime_get(void);
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extern ktime_t ktime_get_with_offset(enum tk_offsets offs);
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extern ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs);
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extern ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs);
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extern ktime_t ktime_get_raw(void);
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extern u32 ktime_get_resolution_ns(void);
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/**
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* ktime_get_real - get the real (wall-) time in ktime_t format
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*/
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static inline ktime_t ktime_get_real(void)
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{
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return ktime_get_with_offset(TK_OFFS_REAL);
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}
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static inline ktime_t ktime_get_coarse_real(void)
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{
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return ktime_get_coarse_with_offset(TK_OFFS_REAL);
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}
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/**
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* ktime_get_boottime - Returns monotonic time since boot in ktime_t format
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*
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* This is similar to CLOCK_MONTONIC/ktime_get, but also includes the
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* time spent in suspend.
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*/
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static inline ktime_t ktime_get_boottime(void)
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{
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return ktime_get_with_offset(TK_OFFS_BOOT);
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}
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static inline ktime_t ktime_get_coarse_boottime(void)
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{
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return ktime_get_coarse_with_offset(TK_OFFS_BOOT);
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}
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/**
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* ktime_get_clocktai - Returns the TAI time of day in ktime_t format
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*/
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static inline ktime_t ktime_get_clocktai(void)
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{
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return ktime_get_with_offset(TK_OFFS_TAI);
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}
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static inline ktime_t ktime_get_coarse_clocktai(void)
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{
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return ktime_get_coarse_with_offset(TK_OFFS_TAI);
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}
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static inline ktime_t ktime_get_coarse(void)
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{
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struct timespec64 ts;
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ktime_get_coarse_ts64(&ts);
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return timespec64_to_ktime(ts);
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}
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static inline u64 ktime_get_coarse_ns(void)
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{
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return ktime_to_ns(ktime_get_coarse());
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}
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static inline u64 ktime_get_coarse_real_ns(void)
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{
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return ktime_to_ns(ktime_get_coarse_real());
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}
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static inline u64 ktime_get_coarse_boottime_ns(void)
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{
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return ktime_to_ns(ktime_get_coarse_boottime());
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}
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static inline u64 ktime_get_coarse_clocktai_ns(void)
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{
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return ktime_to_ns(ktime_get_coarse_clocktai());
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}
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/**
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* ktime_mono_to_real - Convert monotonic time to clock realtime
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*/
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static inline ktime_t ktime_mono_to_real(ktime_t mono)
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{
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return ktime_mono_to_any(mono, TK_OFFS_REAL);
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}
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static inline u64 ktime_get_ns(void)
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{
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return ktime_to_ns(ktime_get());
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}
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static inline u64 ktime_get_real_ns(void)
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{
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return ktime_to_ns(ktime_get_real());
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}
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static inline u64 ktime_get_boottime_ns(void)
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{
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return ktime_to_ns(ktime_get_boottime());
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}
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static inline u64 ktime_get_clocktai_ns(void)
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{
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return ktime_to_ns(ktime_get_clocktai());
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}
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static inline u64 ktime_get_raw_ns(void)
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{
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return ktime_to_ns(ktime_get_raw());
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}
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extern u64 ktime_get_mono_fast_ns(void);
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extern u64 ktime_get_raw_fast_ns(void);
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extern u64 ktime_get_boot_fast_ns(void);
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extern u64 ktime_get_real_fast_ns(void);
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/*
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* timespec64/time64_t interfaces utilizing the ktime based ones
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* for API completeness, these could be implemented more efficiently
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* if needed.
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*/
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static inline void ktime_get_boottime_ts64(struct timespec64 *ts)
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{
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*ts = ktime_to_timespec64(ktime_get_boottime());
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}
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static inline void ktime_get_coarse_boottime_ts64(struct timespec64 *ts)
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{
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*ts = ktime_to_timespec64(ktime_get_coarse_boottime());
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}
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static inline time64_t ktime_get_boottime_seconds(void)
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{
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return ktime_divns(ktime_get_coarse_boottime(), NSEC_PER_SEC);
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}
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static inline void ktime_get_clocktai_ts64(struct timespec64 *ts)
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{
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*ts = ktime_to_timespec64(ktime_get_clocktai());
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}
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static inline void ktime_get_coarse_clocktai_ts64(struct timespec64 *ts)
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{
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*ts = ktime_to_timespec64(ktime_get_coarse_clocktai());
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}
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static inline time64_t ktime_get_clocktai_seconds(void)
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{
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return ktime_divns(ktime_get_coarse_clocktai(), NSEC_PER_SEC);
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}
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/*
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* RTC specific
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*/
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extern bool timekeeping_rtc_skipsuspend(void);
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extern bool timekeeping_rtc_skipresume(void);
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extern void timekeeping_inject_sleeptime64(const struct timespec64 *delta);
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/*
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* struct ktime_timestanps - Simultaneous mono/boot/real timestamps
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* @mono: Monotonic timestamp
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* @boot: Boottime timestamp
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* @real: Realtime timestamp
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*/
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struct ktime_timestamps {
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u64 mono;
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u64 boot;
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u64 real;
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};
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/**
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* struct system_time_snapshot - simultaneous raw/real time capture with
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* counter value
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* @cycles: Clocksource counter value to produce the system times
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* @real: Realtime system time
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* @raw: Monotonic raw system time
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* @clock_was_set_seq: The sequence number of clock was set events
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* @cs_was_changed_seq: The sequence number of clocksource change events
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*/
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struct system_time_snapshot {
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u64 cycles;
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ktime_t real;
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ktime_t raw;
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unsigned int clock_was_set_seq;
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u8 cs_was_changed_seq;
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};
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/**
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* struct system_device_crosststamp - system/device cross-timestamp
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* (synchronized capture)
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* @device: Device time
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* @sys_realtime: Realtime simultaneous with device time
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* @sys_monoraw: Monotonic raw simultaneous with device time
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*/
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struct system_device_crosststamp {
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ktime_t device;
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ktime_t sys_realtime;
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ktime_t sys_monoraw;
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};
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/**
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* struct system_counterval_t - system counter value with the pointer to the
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* corresponding clocksource
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* @cycles: System counter value
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* @cs: Clocksource corresponding to system counter value. Used by
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* timekeeping code to verify comparibility of two cycle values
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*/
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struct system_counterval_t {
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u64 cycles;
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struct clocksource *cs;
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};
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/*
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* Get cross timestamp between system clock and device clock
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*/
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extern int get_device_system_crosststamp(
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int (*get_time_fn)(ktime_t *device_time,
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struct system_counterval_t *system_counterval,
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void *ctx),
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void *ctx,
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struct system_time_snapshot *history,
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struct system_device_crosststamp *xtstamp);
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/*
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* Simultaneously snapshot realtime and monotonic raw clocks
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*/
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extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
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/* NMI safe mono/boot/realtime timestamps */
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extern void ktime_get_fast_timestamps(struct ktime_timestamps *snap);
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/*
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* Persistent clock related interfaces
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*/
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extern int persistent_clock_is_local;
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extern void read_persistent_clock64(struct timespec64 *ts);
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void read_persistent_wall_and_boot_offset(struct timespec64 *wall_clock,
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struct timespec64 *boot_offset);
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extern int update_persistent_clock64(struct timespec64 now);
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#endif
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