2 * linux/kernel/time/timekeeping.c
4 * Kernel timekeeping code and accessor functions
6 * This code was moved from linux/kernel/timer.c.
7 * Please see that file for copyright and history logs.
11 #include <linux/timekeeper_internal.h>
12 #include <linux/module.h>
13 #include <linux/interrupt.h>
14 #include <linux/percpu.h>
15 #include <linux/init.h>
17 #include <linux/sched.h>
18 #include <linux/syscore_ops.h>
19 #include <linux/clocksource.h>
20 #include <linux/jiffies.h>
21 #include <linux/time.h>
22 #include <linux/tick.h>
23 #include <linux/stop_machine.h>
24 #include <linux/pvclock_gtod.h>
25 #include <linux/compiler.h>
27 #include "tick-internal.h"
28 #include "ntp_internal.h"
29 #include "timekeeping_internal.h"
31 #define TK_CLEAR_NTP (1 << 0)
32 #define TK_MIRROR (1 << 1)
33 #define TK_CLOCK_WAS_SET (1 << 2)
36 * The most important data for readout fits into a single 64 byte
41 struct timekeeper timekeeper;
42 } tk_core ____cacheline_aligned;
44 static DEFINE_RAW_SPINLOCK(timekeeper_lock);
45 static struct timekeeper shadow_timekeeper;
48 * struct tk_fast - NMI safe timekeeper
49 * @seq: Sequence counter for protecting updates. The lowest bit
50 * is the index for the tk_read_base array
51 * @base: tk_read_base array. Access is indexed by the lowest bit of
54 * See @update_fast_timekeeper() below.
58 struct tk_read_base base[2];
61 static struct tk_fast tk_fast_mono ____cacheline_aligned;
62 static struct tk_fast tk_fast_raw ____cacheline_aligned;
64 /* flag for if timekeeping is suspended */
65 int __read_mostly timekeeping_suspended;
67 static inline void tk_normalize_xtime(struct timekeeper *tk)
69 while (tk->tkr_mono.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr_mono.shift)) {
70 tk->tkr_mono.xtime_nsec -= (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
75 static inline struct timespec64 tk_xtime(struct timekeeper *tk)
79 ts.tv_sec = tk->xtime_sec;
80 ts.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
84 static void tk_set_xtime(struct timekeeper *tk, const struct timespec64 *ts)
86 tk->xtime_sec = ts->tv_sec;
87 tk->tkr_mono.xtime_nsec = (u64)ts->tv_nsec << tk->tkr_mono.shift;
90 static void tk_xtime_add(struct timekeeper *tk, const struct timespec64 *ts)
92 tk->xtime_sec += ts->tv_sec;
93 tk->tkr_mono.xtime_nsec += (u64)ts->tv_nsec << tk->tkr_mono.shift;
94 tk_normalize_xtime(tk);
97 static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec64 wtm)
99 struct timespec64 tmp;
102 * Verify consistency of: offset_real = -wall_to_monotonic
103 * before modifying anything
105 set_normalized_timespec64(&tmp, -tk->wall_to_monotonic.tv_sec,
106 -tk->wall_to_monotonic.tv_nsec);
107 WARN_ON_ONCE(tk->offs_real.tv64 != timespec64_to_ktime(tmp).tv64);
108 tk->wall_to_monotonic = wtm;
109 set_normalized_timespec64(&tmp, -wtm.tv_sec, -wtm.tv_nsec);
110 tk->offs_real = timespec64_to_ktime(tmp);
111 tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tk->tai_offset, 0));
114 static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta)
116 tk->offs_boot = ktime_add(tk->offs_boot, delta);
119 #ifdef CONFIG_DEBUG_TIMEKEEPING
120 #define WARNING_FREQ (HZ*300) /* 5 minute rate-limiting */
122 static void timekeeping_check_update(struct timekeeper *tk, cycle_t offset)
125 cycle_t max_cycles = tk->tkr_mono.clock->max_cycles;
126 const char *name = tk->tkr_mono.clock->name;
128 if (offset > max_cycles) {
129 printk_deferred("WARNING: timekeeping: Cycle offset (%lld) is larger than allowed by the '%s' clock's max_cycles value (%lld): time overflow danger\n",
130 offset, name, max_cycles);
131 printk_deferred(" timekeeping: Your kernel is sick, but tries to cope by capping time updates\n");
133 if (offset > (max_cycles >> 1)) {
134 printk_deferred("INFO: timekeeping: Cycle offset (%lld) is larger than the '%s' clock's 50%% safety margin (%lld)\n",
135 offset, name, max_cycles >> 1);
136 printk_deferred(" timekeeping: Your kernel is still fine, but is feeling a bit nervous\n");
140 if (tk->underflow_seen) {
141 if (jiffies - tk->last_warning > WARNING_FREQ) {
142 printk_deferred("WARNING: Underflow in clocksource '%s' observed, time update ignored.\n", name);
143 printk_deferred(" Please report this, consider using a different clocksource, if possible.\n");
144 printk_deferred(" Your kernel is probably still fine.\n");
145 tk->last_warning = jiffies;
147 tk->underflow_seen = 0;
150 if (tk->overflow_seen) {
151 if (jiffies - tk->last_warning > WARNING_FREQ) {
152 printk_deferred("WARNING: Overflow in clocksource '%s' observed, time update capped.\n", name);
153 printk_deferred(" Please report this, consider using a different clocksource, if possible.\n");
154 printk_deferred(" Your kernel is probably still fine.\n");
155 tk->last_warning = jiffies;
157 tk->overflow_seen = 0;
161 static inline cycle_t timekeeping_get_delta(struct tk_read_base *tkr)
163 struct timekeeper *tk = &tk_core.timekeeper;
164 cycle_t now, last, mask, max, delta;
168 * Since we're called holding a seqlock, the data may shift
169 * under us while we're doing the calculation. This can cause
170 * false positives, since we'd note a problem but throw the
171 * results away. So nest another seqlock here to atomically
172 * grab the points we are checking with.
175 seq = read_seqcount_begin(&tk_core.seq);
176 now = tkr->read(tkr->clock);
177 last = tkr->cycle_last;
179 max = tkr->clock->max_cycles;
180 } while (read_seqcount_retry(&tk_core.seq, seq));
182 delta = clocksource_delta(now, last, mask);
185 * Try to catch underflows by checking if we are seeing small
186 * mask-relative negative values.
188 if (unlikely((~delta & mask) < (mask >> 3))) {
189 tk->underflow_seen = 1;
193 /* Cap delta value to the max_cycles values to avoid mult overflows */
194 if (unlikely(delta > max)) {
195 tk->overflow_seen = 1;
196 delta = tkr->clock->max_cycles;
202 static inline void timekeeping_check_update(struct timekeeper *tk, cycle_t offset)
205 static inline cycle_t timekeeping_get_delta(struct tk_read_base *tkr)
207 cycle_t cycle_now, delta;
209 /* read clocksource */
210 cycle_now = tkr->read(tkr->clock);
212 /* calculate the delta since the last update_wall_time */
213 delta = clocksource_delta(cycle_now, tkr->cycle_last, tkr->mask);
220 * tk_setup_internals - Set up internals to use clocksource clock.
222 * @tk: The target timekeeper to setup.
223 * @clock: Pointer to clocksource.
225 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
226 * pair and interval request.
228 * Unless you're the timekeeping code, you should not be using this!
230 static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
233 u64 tmp, ntpinterval;
234 struct clocksource *old_clock;
236 ++tk->cs_was_changed_seq;
237 old_clock = tk->tkr_mono.clock;
238 tk->tkr_mono.clock = clock;
239 tk->tkr_mono.read = clock->read;
240 tk->tkr_mono.mask = clock->mask;
241 tk->tkr_mono.cycle_last = tk->tkr_mono.read(clock);
243 tk->tkr_raw.clock = clock;
244 tk->tkr_raw.read = clock->read;
245 tk->tkr_raw.mask = clock->mask;
246 tk->tkr_raw.cycle_last = tk->tkr_mono.cycle_last;
248 /* Do the ns -> cycle conversion first, using original mult */
249 tmp = NTP_INTERVAL_LENGTH;
250 tmp <<= clock->shift;
252 tmp += clock->mult/2;
253 do_div(tmp, clock->mult);
257 interval = (cycle_t) tmp;
258 tk->cycle_interval = interval;
260 /* Go back from cycles -> shifted ns */
261 tk->xtime_interval = (u64) interval * clock->mult;
262 tk->xtime_remainder = ntpinterval - tk->xtime_interval;
264 ((u64) interval * clock->mult) >> clock->shift;
266 /* if changing clocks, convert xtime_nsec shift units */
268 int shift_change = clock->shift - old_clock->shift;
269 if (shift_change < 0)
270 tk->tkr_mono.xtime_nsec >>= -shift_change;
272 tk->tkr_mono.xtime_nsec <<= shift_change;
274 tk->tkr_raw.xtime_nsec = 0;
276 tk->tkr_mono.shift = clock->shift;
277 tk->tkr_raw.shift = clock->shift;
280 tk->ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
281 tk->ntp_tick = ntpinterval << tk->ntp_error_shift;
284 * The timekeeper keeps its own mult values for the currently
285 * active clocksource. These value will be adjusted via NTP
286 * to counteract clock drifting.
288 tk->tkr_mono.mult = clock->mult;
289 tk->tkr_raw.mult = clock->mult;
290 tk->ntp_err_mult = 0;
293 /* Timekeeper helper functions. */
295 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
296 static u32 default_arch_gettimeoffset(void) { return 0; }
297 u32 (*arch_gettimeoffset)(void) = default_arch_gettimeoffset;
299 static inline u32 arch_gettimeoffset(void) { return 0; }
302 static inline s64 timekeeping_delta_to_ns(struct tk_read_base *tkr,
307 nsec = delta * tkr->mult + tkr->xtime_nsec;
310 /* If arch requires, add in get_arch_timeoffset() */
311 return nsec + arch_gettimeoffset();
314 static inline s64 timekeeping_get_ns(struct tk_read_base *tkr)
318 delta = timekeeping_get_delta(tkr);
319 return timekeeping_delta_to_ns(tkr, delta);
322 static inline s64 timekeeping_cycles_to_ns(struct tk_read_base *tkr,
327 /* calculate the delta since the last update_wall_time */
328 delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
329 return timekeeping_delta_to_ns(tkr, delta);
333 * update_fast_timekeeper - Update the fast and NMI safe monotonic timekeeper.
334 * @tkr: Timekeeping readout base from which we take the update
336 * We want to use this from any context including NMI and tracing /
337 * instrumenting the timekeeping code itself.
339 * Employ the latch technique; see @raw_write_seqcount_latch.
341 * So if a NMI hits the update of base[0] then it will use base[1]
342 * which is still consistent. In the worst case this can result is a
343 * slightly wrong timestamp (a few nanoseconds). See
344 * @ktime_get_mono_fast_ns.
346 static void update_fast_timekeeper(struct tk_read_base *tkr, struct tk_fast *tkf)
348 struct tk_read_base *base = tkf->base;
350 /* Force readers off to base[1] */
351 raw_write_seqcount_latch(&tkf->seq);
354 memcpy(base, tkr, sizeof(*base));
356 /* Force readers back to base[0] */
357 raw_write_seqcount_latch(&tkf->seq);
360 memcpy(base + 1, base, sizeof(*base));
364 * ktime_get_mono_fast_ns - Fast NMI safe access to clock monotonic
366 * This timestamp is not guaranteed to be monotonic across an update.
367 * The timestamp is calculated by:
369 * now = base_mono + clock_delta * slope
371 * So if the update lowers the slope, readers who are forced to the
372 * not yet updated second array are still using the old steeper slope.
381 * |12345678---> reader order
387 * So reader 6 will observe time going backwards versus reader 5.
389 * While other CPUs are likely to be able observe that, the only way
390 * for a CPU local observation is when an NMI hits in the middle of
391 * the update. Timestamps taken from that NMI context might be ahead
392 * of the following timestamps. Callers need to be aware of that and
395 static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
397 struct tk_read_base *tkr;
402 seq = raw_read_seqcount_latch(&tkf->seq);
403 tkr = tkf->base + (seq & 0x01);
404 now = ktime_to_ns(tkr->base);
406 now += timekeeping_delta_to_ns(tkr,
408 tkr->read(tkr->clock),
411 } while (read_seqcount_retry(&tkf->seq, seq));
416 u64 ktime_get_mono_fast_ns(void)
418 return __ktime_get_fast_ns(&tk_fast_mono);
420 EXPORT_SYMBOL_GPL(ktime_get_mono_fast_ns);
422 u64 ktime_get_raw_fast_ns(void)
424 return __ktime_get_fast_ns(&tk_fast_raw);
426 EXPORT_SYMBOL_GPL(ktime_get_raw_fast_ns);
428 /* Suspend-time cycles value for halted fast timekeeper. */
429 static cycle_t cycles_at_suspend;
431 static cycle_t dummy_clock_read(struct clocksource *cs)
433 return cycles_at_suspend;
437 * halt_fast_timekeeper - Prevent fast timekeeper from accessing clocksource.
438 * @tk: Timekeeper to snapshot.
440 * It generally is unsafe to access the clocksource after timekeeping has been
441 * suspended, so take a snapshot of the readout base of @tk and use it as the
442 * fast timekeeper's readout base while suspended. It will return the same
443 * number of cycles every time until timekeeping is resumed at which time the
444 * proper readout base for the fast timekeeper will be restored automatically.
446 static void halt_fast_timekeeper(struct timekeeper *tk)
448 static struct tk_read_base tkr_dummy;
449 struct tk_read_base *tkr = &tk->tkr_mono;
451 memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
452 cycles_at_suspend = tkr->read(tkr->clock);
453 tkr_dummy.read = dummy_clock_read;
454 update_fast_timekeeper(&tkr_dummy, &tk_fast_mono);
457 memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
458 tkr_dummy.read = dummy_clock_read;
459 update_fast_timekeeper(&tkr_dummy, &tk_fast_raw);
462 #ifdef CONFIG_GENERIC_TIME_VSYSCALL_OLD
464 static inline void update_vsyscall(struct timekeeper *tk)
466 struct timespec xt, wm;
468 xt = timespec64_to_timespec(tk_xtime(tk));
469 wm = timespec64_to_timespec(tk->wall_to_monotonic);
470 update_vsyscall_old(&xt, &wm, tk->tkr_mono.clock, tk->tkr_mono.mult,
471 tk->tkr_mono.cycle_last);
474 static inline void old_vsyscall_fixup(struct timekeeper *tk)
479 * Store only full nanoseconds into xtime_nsec after rounding
480 * it up and add the remainder to the error difference.
481 * XXX - This is necessary to avoid small 1ns inconsistnecies caused
482 * by truncating the remainder in vsyscalls. However, it causes
483 * additional work to be done in timekeeping_adjust(). Once
484 * the vsyscall implementations are converted to use xtime_nsec
485 * (shifted nanoseconds), and CONFIG_GENERIC_TIME_VSYSCALL_OLD
486 * users are removed, this can be killed.
488 remainder = tk->tkr_mono.xtime_nsec & ((1ULL << tk->tkr_mono.shift) - 1);
489 if (remainder != 0) {
490 tk->tkr_mono.xtime_nsec -= remainder;
491 tk->tkr_mono.xtime_nsec += 1ULL << tk->tkr_mono.shift;
492 tk->ntp_error += remainder << tk->ntp_error_shift;
493 tk->ntp_error -= (1ULL << tk->tkr_mono.shift) << tk->ntp_error_shift;
497 #define old_vsyscall_fixup(tk)
500 static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
502 static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)
504 raw_notifier_call_chain(&pvclock_gtod_chain, was_set, tk);
508 * pvclock_gtod_register_notifier - register a pvclock timedata update listener
510 int pvclock_gtod_register_notifier(struct notifier_block *nb)
512 struct timekeeper *tk = &tk_core.timekeeper;
516 raw_spin_lock_irqsave(&timekeeper_lock, flags);
517 ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);
518 update_pvclock_gtod(tk, true);
519 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
523 EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
526 * pvclock_gtod_unregister_notifier - unregister a pvclock
527 * timedata update listener
529 int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
534 raw_spin_lock_irqsave(&timekeeper_lock, flags);
535 ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
536 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
540 EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
543 * tk_update_leap_state - helper to update the next_leap_ktime
545 static inline void tk_update_leap_state(struct timekeeper *tk)
547 tk->next_leap_ktime = ntp_get_next_leap();
548 if (tk->next_leap_ktime.tv64 != KTIME_MAX)
549 /* Convert to monotonic time */
550 tk->next_leap_ktime = ktime_sub(tk->next_leap_ktime, tk->offs_real);
554 * Update the ktime_t based scalar nsec members of the timekeeper
556 static inline void tk_update_ktime_data(struct timekeeper *tk)
562 * The xtime based monotonic readout is:
563 * nsec = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec + now();
564 * The ktime based monotonic readout is:
565 * nsec = base_mono + now();
566 * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec
568 seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
569 nsec = (u32) tk->wall_to_monotonic.tv_nsec;
570 tk->tkr_mono.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
572 /* Update the monotonic raw base */
573 tk->tkr_raw.base = timespec64_to_ktime(tk->raw_time);
576 * The sum of the nanoseconds portions of xtime and
577 * wall_to_monotonic can be greater/equal one second. Take
578 * this into account before updating tk->ktime_sec.
580 nsec += (u32)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
581 if (nsec >= NSEC_PER_SEC)
583 tk->ktime_sec = seconds;
586 /* must hold timekeeper_lock */
587 static void timekeeping_update(struct timekeeper *tk, unsigned int action)
589 if (action & TK_CLEAR_NTP) {
594 tk_update_leap_state(tk);
595 tk_update_ktime_data(tk);
598 update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
600 update_fast_timekeeper(&tk->tkr_mono, &tk_fast_mono);
601 update_fast_timekeeper(&tk->tkr_raw, &tk_fast_raw);
603 if (action & TK_CLOCK_WAS_SET)
604 tk->clock_was_set_seq++;
606 * The mirroring of the data to the shadow-timekeeper needs
607 * to happen last here to ensure we don't over-write the
608 * timekeeper structure on the next update with stale data
610 if (action & TK_MIRROR)
611 memcpy(&shadow_timekeeper, &tk_core.timekeeper,
612 sizeof(tk_core.timekeeper));
616 * timekeeping_forward_now - update clock to the current time
618 * Forward the current clock to update its state since the last call to
619 * update_wall_time(). This is useful before significant clock changes,
620 * as it avoids having to deal with this time offset explicitly.
622 static void timekeeping_forward_now(struct timekeeper *tk)
624 struct clocksource *clock = tk->tkr_mono.clock;
625 cycle_t cycle_now, delta;
628 cycle_now = tk->tkr_mono.read(clock);
629 delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
630 tk->tkr_mono.cycle_last = cycle_now;
631 tk->tkr_raw.cycle_last = cycle_now;
633 tk->tkr_mono.xtime_nsec += delta * tk->tkr_mono.mult;
635 /* If arch requires, add in get_arch_timeoffset() */
636 tk->tkr_mono.xtime_nsec += (u64)arch_gettimeoffset() << tk->tkr_mono.shift;
638 tk_normalize_xtime(tk);
640 nsec = clocksource_cyc2ns(delta, tk->tkr_raw.mult, tk->tkr_raw.shift);
641 timespec64_add_ns(&tk->raw_time, nsec);
645 * __getnstimeofday64 - Returns the time of day in a timespec64.
646 * @ts: pointer to the timespec to be set
648 * Updates the time of day in the timespec.
649 * Returns 0 on success, or -ve when suspended (timespec will be undefined).
651 int __getnstimeofday64(struct timespec64 *ts)
653 struct timekeeper *tk = &tk_core.timekeeper;
658 seq = read_seqcount_begin(&tk_core.seq);
660 ts->tv_sec = tk->xtime_sec;
661 nsecs = timekeeping_get_ns(&tk->tkr_mono);
663 } while (read_seqcount_retry(&tk_core.seq, seq));
666 timespec64_add_ns(ts, nsecs);
669 * Do not bail out early, in case there were callers still using
670 * the value, even in the face of the WARN_ON.
672 if (unlikely(timekeeping_suspended))
676 EXPORT_SYMBOL(__getnstimeofday64);
679 * getnstimeofday64 - Returns the time of day in a timespec64.
680 * @ts: pointer to the timespec64 to be set
682 * Returns the time of day in a timespec64 (WARN if suspended).
684 void getnstimeofday64(struct timespec64 *ts)
686 WARN_ON(__getnstimeofday64(ts));
688 EXPORT_SYMBOL(getnstimeofday64);
690 ktime_t ktime_get(void)
692 struct timekeeper *tk = &tk_core.timekeeper;
697 WARN_ON(timekeeping_suspended);
700 seq = read_seqcount_begin(&tk_core.seq);
701 base = tk->tkr_mono.base;
702 nsecs = timekeeping_get_ns(&tk->tkr_mono);
704 } while (read_seqcount_retry(&tk_core.seq, seq));
706 return ktime_add_ns(base, nsecs);
708 EXPORT_SYMBOL_GPL(ktime_get);
710 u32 ktime_get_resolution_ns(void)
712 struct timekeeper *tk = &tk_core.timekeeper;
716 WARN_ON(timekeeping_suspended);
719 seq = read_seqcount_begin(&tk_core.seq);
720 nsecs = tk->tkr_mono.mult >> tk->tkr_mono.shift;
721 } while (read_seqcount_retry(&tk_core.seq, seq));
725 EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);
727 static ktime_t *offsets[TK_OFFS_MAX] = {
728 [TK_OFFS_REAL] = &tk_core.timekeeper.offs_real,
729 [TK_OFFS_BOOT] = &tk_core.timekeeper.offs_boot,
730 [TK_OFFS_TAI] = &tk_core.timekeeper.offs_tai,
733 ktime_t ktime_get_with_offset(enum tk_offsets offs)
735 struct timekeeper *tk = &tk_core.timekeeper;
737 ktime_t base, *offset = offsets[offs];
740 WARN_ON(timekeeping_suspended);
743 seq = read_seqcount_begin(&tk_core.seq);
744 base = ktime_add(tk->tkr_mono.base, *offset);
745 nsecs = timekeeping_get_ns(&tk->tkr_mono);
747 } while (read_seqcount_retry(&tk_core.seq, seq));
749 return ktime_add_ns(base, nsecs);
752 EXPORT_SYMBOL_GPL(ktime_get_with_offset);
755 * ktime_mono_to_any() - convert mononotic time to any other time
756 * @tmono: time to convert.
757 * @offs: which offset to use
759 ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
761 ktime_t *offset = offsets[offs];
766 seq = read_seqcount_begin(&tk_core.seq);
767 tconv = ktime_add(tmono, *offset);
768 } while (read_seqcount_retry(&tk_core.seq, seq));
772 EXPORT_SYMBOL_GPL(ktime_mono_to_any);
775 * ktime_get_raw - Returns the raw monotonic time in ktime_t format
777 ktime_t ktime_get_raw(void)
779 struct timekeeper *tk = &tk_core.timekeeper;
785 seq = read_seqcount_begin(&tk_core.seq);
786 base = tk->tkr_raw.base;
787 nsecs = timekeeping_get_ns(&tk->tkr_raw);
789 } while (read_seqcount_retry(&tk_core.seq, seq));
791 return ktime_add_ns(base, nsecs);
793 EXPORT_SYMBOL_GPL(ktime_get_raw);
796 * ktime_get_ts64 - get the monotonic clock in timespec64 format
797 * @ts: pointer to timespec variable
799 * The function calculates the monotonic clock from the realtime
800 * clock and the wall_to_monotonic offset and stores the result
801 * in normalized timespec64 format in the variable pointed to by @ts.
803 void ktime_get_ts64(struct timespec64 *ts)
805 struct timekeeper *tk = &tk_core.timekeeper;
806 struct timespec64 tomono;
810 WARN_ON(timekeeping_suspended);
813 seq = read_seqcount_begin(&tk_core.seq);
814 ts->tv_sec = tk->xtime_sec;
815 nsec = timekeeping_get_ns(&tk->tkr_mono);
816 tomono = tk->wall_to_monotonic;
818 } while (read_seqcount_retry(&tk_core.seq, seq));
820 ts->tv_sec += tomono.tv_sec;
822 timespec64_add_ns(ts, nsec + tomono.tv_nsec);
824 EXPORT_SYMBOL_GPL(ktime_get_ts64);
827 * ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
829 * Returns the seconds portion of CLOCK_MONOTONIC with a single non
830 * serialized read. tk->ktime_sec is of type 'unsigned long' so this
831 * works on both 32 and 64 bit systems. On 32 bit systems the readout
832 * covers ~136 years of uptime which should be enough to prevent
833 * premature wrap arounds.
835 time64_t ktime_get_seconds(void)
837 struct timekeeper *tk = &tk_core.timekeeper;
839 WARN_ON(timekeeping_suspended);
840 return tk->ktime_sec;
842 EXPORT_SYMBOL_GPL(ktime_get_seconds);
845 * ktime_get_real_seconds - Get the seconds portion of CLOCK_REALTIME
847 * Returns the wall clock seconds since 1970. This replaces the
848 * get_seconds() interface which is not y2038 safe on 32bit systems.
850 * For 64bit systems the fast access to tk->xtime_sec is preserved. On
851 * 32bit systems the access must be protected with the sequence
852 * counter to provide "atomic" access to the 64bit tk->xtime_sec
855 time64_t ktime_get_real_seconds(void)
857 struct timekeeper *tk = &tk_core.timekeeper;
861 if (IS_ENABLED(CONFIG_64BIT))
862 return tk->xtime_sec;
865 seq = read_seqcount_begin(&tk_core.seq);
866 seconds = tk->xtime_sec;
868 } while (read_seqcount_retry(&tk_core.seq, seq));
872 EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
875 * __ktime_get_real_seconds - The same as ktime_get_real_seconds
876 * but without the sequence counter protect. This internal function
877 * is called just when timekeeping lock is already held.
879 time64_t __ktime_get_real_seconds(void)
881 struct timekeeper *tk = &tk_core.timekeeper;
883 return tk->xtime_sec;
887 * ktime_get_snapshot - snapshots the realtime/monotonic raw clocks with counter
888 * @systime_snapshot: pointer to struct receiving the system time snapshot
890 void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
892 struct timekeeper *tk = &tk_core.timekeeper;
900 WARN_ON_ONCE(timekeeping_suspended);
903 seq = read_seqcount_begin(&tk_core.seq);
905 now = tk->tkr_mono.read(tk->tkr_mono.clock);
906 systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
907 systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
908 base_real = ktime_add(tk->tkr_mono.base,
909 tk_core.timekeeper.offs_real);
910 base_raw = tk->tkr_raw.base;
911 nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, now);
912 nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw, now);
913 } while (read_seqcount_retry(&tk_core.seq, seq));
915 systime_snapshot->cycles = now;
916 systime_snapshot->real = ktime_add_ns(base_real, nsec_real);
917 systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
919 EXPORT_SYMBOL_GPL(ktime_get_snapshot);
921 /* Scale base by mult/div checking for overflow */
922 static int scale64_check_overflow(u64 mult, u64 div, u64 *base)
926 tmp = div64_u64_rem(*base, div, &rem);
928 if (((int)sizeof(u64)*8 - fls64(mult) < fls64(tmp)) ||
929 ((int)sizeof(u64)*8 - fls64(mult) < fls64(rem)))
940 * adjust_historical_crosststamp - adjust crosstimestamp previous to current interval
941 * @history: Snapshot representing start of history
942 * @partial_history_cycles: Cycle offset into history (fractional part)
943 * @total_history_cycles: Total history length in cycles
944 * @discontinuity: True indicates clock was set on history period
945 * @ts: Cross timestamp that should be adjusted using
946 * partial/total ratio
948 * Helper function used by get_device_system_crosststamp() to correct the
949 * crosstimestamp corresponding to the start of the current interval to the
950 * system counter value (timestamp point) provided by the driver. The
951 * total_history_* quantities are the total history starting at the provided
952 * reference point and ending at the start of the current interval. The cycle
953 * count between the driver timestamp point and the start of the current
954 * interval is partial_history_cycles.
956 static int adjust_historical_crosststamp(struct system_time_snapshot *history,
957 cycle_t partial_history_cycles,
958 cycle_t total_history_cycles,
960 struct system_device_crosststamp *ts)
962 struct timekeeper *tk = &tk_core.timekeeper;
963 u64 corr_raw, corr_real;
967 if (total_history_cycles == 0 || partial_history_cycles == 0)
970 /* Interpolate shortest distance from beginning or end of history */
971 interp_forward = partial_history_cycles > total_history_cycles/2 ?
973 partial_history_cycles = interp_forward ?
974 total_history_cycles - partial_history_cycles :
975 partial_history_cycles;
978 * Scale the monotonic raw time delta by:
979 * partial_history_cycles / total_history_cycles
981 corr_raw = (u64)ktime_to_ns(
982 ktime_sub(ts->sys_monoraw, history->raw));
983 ret = scale64_check_overflow(partial_history_cycles,
984 total_history_cycles, &corr_raw);
989 * If there is a discontinuity in the history, scale monotonic raw
991 * mult(real)/mult(raw) yielding the realtime correction
992 * Otherwise, calculate the realtime correction similar to monotonic
996 corr_real = mul_u64_u32_div
997 (corr_raw, tk->tkr_mono.mult, tk->tkr_raw.mult);
999 corr_real = (u64)ktime_to_ns(
1000 ktime_sub(ts->sys_realtime, history->real));
1001 ret = scale64_check_overflow(partial_history_cycles,
1002 total_history_cycles, &corr_real);
1007 /* Fixup monotonic raw and real time time values */
1008 if (interp_forward) {
1009 ts->sys_monoraw = ktime_add_ns(history->raw, corr_raw);
1010 ts->sys_realtime = ktime_add_ns(history->real, corr_real);
1012 ts->sys_monoraw = ktime_sub_ns(ts->sys_monoraw, corr_raw);
1013 ts->sys_realtime = ktime_sub_ns(ts->sys_realtime, corr_real);
1020 * cycle_between - true if test occurs chronologically between before and after
1022 static bool cycle_between(cycle_t before, cycle_t test, cycle_t after)
1024 if (test > before && test < after)
1026 if (test < before && before > after)
1032 * get_device_system_crosststamp - Synchronously capture system/device timestamp
1033 * @get_time_fn: Callback to get simultaneous device time and
1034 * system counter from the device driver
1035 * @ctx: Context passed to get_time_fn()
1036 * @history_begin: Historical reference point used to interpolate system
1037 * time when counter provided by the driver is before the current interval
1038 * @xtstamp: Receives simultaneously captured system and device time
1040 * Reads a timestamp from a device and correlates it to system time
1042 int get_device_system_crosststamp(int (*get_time_fn)
1043 (ktime_t *device_time,
1044 struct system_counterval_t *sys_counterval,
1047 struct system_time_snapshot *history_begin,
1048 struct system_device_crosststamp *xtstamp)
1050 struct system_counterval_t system_counterval;
1051 struct timekeeper *tk = &tk_core.timekeeper;
1052 cycle_t cycles, now, interval_start;
1053 unsigned int clock_was_set_seq = 0;
1054 ktime_t base_real, base_raw;
1055 s64 nsec_real, nsec_raw;
1056 u8 cs_was_changed_seq;
1062 seq = read_seqcount_begin(&tk_core.seq);
1064 * Try to synchronously capture device time and a system
1065 * counter value calling back into the device driver
1067 ret = get_time_fn(&xtstamp->device, &system_counterval, ctx);
1072 * Verify that the clocksource associated with the captured
1073 * system counter value is the same as the currently installed
1074 * timekeeper clocksource
1076 if (tk->tkr_mono.clock != system_counterval.cs)
1078 cycles = system_counterval.cycles;
1081 * Check whether the system counter value provided by the
1082 * device driver is on the current timekeeping interval.
1084 now = tk->tkr_mono.read(tk->tkr_mono.clock);
1085 interval_start = tk->tkr_mono.cycle_last;
1086 if (!cycle_between(interval_start, cycles, now)) {
1087 clock_was_set_seq = tk->clock_was_set_seq;
1088 cs_was_changed_seq = tk->cs_was_changed_seq;
1089 cycles = interval_start;
1095 base_real = ktime_add(tk->tkr_mono.base,
1096 tk_core.timekeeper.offs_real);
1097 base_raw = tk->tkr_raw.base;
1099 nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono,
1100 system_counterval.cycles);
1101 nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw,
1102 system_counterval.cycles);
1103 } while (read_seqcount_retry(&tk_core.seq, seq));
1105 xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
1106 xtstamp->sys_monoraw = ktime_add_ns(base_raw, nsec_raw);
1109 * Interpolate if necessary, adjusting back from the start of the
1113 cycle_t partial_history_cycles, total_history_cycles;
1117 * Check that the counter value occurs after the provided
1118 * history reference and that the history doesn't cross a
1119 * clocksource change
1121 if (!history_begin ||
1122 !cycle_between(history_begin->cycles,
1123 system_counterval.cycles, cycles) ||
1124 history_begin->cs_was_changed_seq != cs_was_changed_seq)
1126 partial_history_cycles = cycles - system_counterval.cycles;
1127 total_history_cycles = cycles - history_begin->cycles;
1129 history_begin->clock_was_set_seq != clock_was_set_seq;
1131 ret = adjust_historical_crosststamp(history_begin,
1132 partial_history_cycles,
1133 total_history_cycles,
1134 discontinuity, xtstamp);
1141 EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
1144 * do_gettimeofday - Returns the time of day in a timeval
1145 * @tv: pointer to the timeval to be set
1147 * NOTE: Users should be converted to using getnstimeofday()
1149 void do_gettimeofday(struct timeval *tv)
1151 struct timespec64 now;
1153 getnstimeofday64(&now);
1154 tv->tv_sec = now.tv_sec;
1155 tv->tv_usec = now.tv_nsec/1000;
1157 EXPORT_SYMBOL(do_gettimeofday);
1160 * do_settimeofday64 - Sets the time of day.
1161 * @ts: pointer to the timespec64 variable containing the new time
1163 * Sets the time of day to the new time and update NTP and notify hrtimers
1165 int do_settimeofday64(const struct timespec64 *ts)
1167 struct timekeeper *tk = &tk_core.timekeeper;
1168 struct timespec64 ts_delta, xt;
1169 unsigned long flags;
1172 if (!timespec64_valid_strict(ts))
1175 raw_spin_lock_irqsave(&timekeeper_lock, flags);
1176 write_seqcount_begin(&tk_core.seq);
1178 timekeeping_forward_now(tk);
1181 ts_delta.tv_sec = ts->tv_sec - xt.tv_sec;
1182 ts_delta.tv_nsec = ts->tv_nsec - xt.tv_nsec;
1184 if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) {
1189 tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));
1191 tk_set_xtime(tk, ts);
1193 timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1195 write_seqcount_end(&tk_core.seq);
1196 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1198 /* signal hrtimers about time change */
1203 EXPORT_SYMBOL(do_settimeofday64);
1206 * timekeeping_inject_offset - Adds or subtracts from the current time.
1207 * @tv: pointer to the timespec variable containing the offset
1209 * Adds or subtracts an offset value from the current time.
1211 int timekeeping_inject_offset(struct timespec *ts)
1213 struct timekeeper *tk = &tk_core.timekeeper;
1214 unsigned long flags;
1215 struct timespec64 ts64, tmp;
1218 if (!timespec_inject_offset_valid(ts))
1221 ts64 = timespec_to_timespec64(*ts);
1223 raw_spin_lock_irqsave(&timekeeper_lock, flags);
1224 write_seqcount_begin(&tk_core.seq);
1226 timekeeping_forward_now(tk);
1228 /* Make sure the proposed value is valid */
1229 tmp = timespec64_add(tk_xtime(tk), ts64);
1230 if (timespec64_compare(&tk->wall_to_monotonic, &ts64) > 0 ||
1231 !timespec64_valid_strict(&tmp)) {
1236 tk_xtime_add(tk, &ts64);
1237 tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts64));
1239 error: /* even if we error out, we forwarded the time, so call update */
1240 timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1242 write_seqcount_end(&tk_core.seq);
1243 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1245 /* signal hrtimers about time change */
1250 EXPORT_SYMBOL(timekeeping_inject_offset);
1254 * timekeeping_get_tai_offset - Returns current TAI offset from UTC
1257 s32 timekeeping_get_tai_offset(void)
1259 struct timekeeper *tk = &tk_core.timekeeper;
1264 seq = read_seqcount_begin(&tk_core.seq);
1265 ret = tk->tai_offset;
1266 } while (read_seqcount_retry(&tk_core.seq, seq));
1272 * __timekeeping_set_tai_offset - Lock free worker function
1275 static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)
1277 tk->tai_offset = tai_offset;
1278 tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tai_offset, 0));
1282 * timekeeping_set_tai_offset - Sets the current TAI offset from UTC
1285 void timekeeping_set_tai_offset(s32 tai_offset)
1287 struct timekeeper *tk = &tk_core.timekeeper;
1288 unsigned long flags;
1290 raw_spin_lock_irqsave(&timekeeper_lock, flags);
1291 write_seqcount_begin(&tk_core.seq);
1292 __timekeeping_set_tai_offset(tk, tai_offset);
1293 timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1294 write_seqcount_end(&tk_core.seq);
1295 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1300 * change_clocksource - Swaps clocksources if a new one is available
1302 * Accumulates current time interval and initializes new clocksource
1304 static int change_clocksource(void *data)
1306 struct timekeeper *tk = &tk_core.timekeeper;
1307 struct clocksource *new, *old;
1308 unsigned long flags;
1310 new = (struct clocksource *) data;
1312 raw_spin_lock_irqsave(&timekeeper_lock, flags);
1313 write_seqcount_begin(&tk_core.seq);
1315 timekeeping_forward_now(tk);
1317 * If the cs is in module, get a module reference. Succeeds
1318 * for built-in code (owner == NULL) as well.
1320 if (try_module_get(new->owner)) {
1321 if (!new->enable || new->enable(new) == 0) {
1322 old = tk->tkr_mono.clock;
1323 tk_setup_internals(tk, new);
1326 module_put(old->owner);
1328 module_put(new->owner);
1331 timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1333 write_seqcount_end(&tk_core.seq);
1334 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1340 * timekeeping_notify - Install a new clock source
1341 * @clock: pointer to the clock source
1343 * This function is called from clocksource.c after a new, better clock
1344 * source has been registered. The caller holds the clocksource_mutex.
1346 int timekeeping_notify(struct clocksource *clock)
1348 struct timekeeper *tk = &tk_core.timekeeper;
1350 if (tk->tkr_mono.clock == clock)
1352 stop_machine(change_clocksource, clock, NULL);
1353 tick_clock_notify();
1354 return tk->tkr_mono.clock == clock ? 0 : -1;
1358 * getrawmonotonic64 - Returns the raw monotonic time in a timespec
1359 * @ts: pointer to the timespec64 to be set
1361 * Returns the raw monotonic time (completely un-modified by ntp)
1363 void getrawmonotonic64(struct timespec64 *ts)
1365 struct timekeeper *tk = &tk_core.timekeeper;
1366 struct timespec64 ts64;
1371 seq = read_seqcount_begin(&tk_core.seq);
1372 nsecs = timekeeping_get_ns(&tk->tkr_raw);
1373 ts64 = tk->raw_time;
1375 } while (read_seqcount_retry(&tk_core.seq, seq));
1377 timespec64_add_ns(&ts64, nsecs);
1380 EXPORT_SYMBOL(getrawmonotonic64);
1384 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
1386 int timekeeping_valid_for_hres(void)
1388 struct timekeeper *tk = &tk_core.timekeeper;
1393 seq = read_seqcount_begin(&tk_core.seq);
1395 ret = tk->tkr_mono.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
1397 } while (read_seqcount_retry(&tk_core.seq, seq));
1403 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
1405 u64 timekeeping_max_deferment(void)
1407 struct timekeeper *tk = &tk_core.timekeeper;
1412 seq = read_seqcount_begin(&tk_core.seq);
1414 ret = tk->tkr_mono.clock->max_idle_ns;
1416 } while (read_seqcount_retry(&tk_core.seq, seq));
1422 * read_persistent_clock - Return time from the persistent clock.
1424 * Weak dummy function for arches that do not yet support it.
1425 * Reads the time from the battery backed persistent clock.
1426 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
1428 * XXX - Do be sure to remove it once all arches implement it.
1430 void __weak read_persistent_clock(struct timespec *ts)
1436 void __weak read_persistent_clock64(struct timespec64 *ts64)
1440 read_persistent_clock(&ts);
1441 *ts64 = timespec_to_timespec64(ts);
1445 * read_boot_clock64 - Return time of the system start.
1447 * Weak dummy function for arches that do not yet support it.
1448 * Function to read the exact time the system has been started.
1449 * Returns a timespec64 with tv_sec=0 and tv_nsec=0 if unsupported.
1451 * XXX - Do be sure to remove it once all arches implement it.
1453 void __weak read_boot_clock64(struct timespec64 *ts)
1459 /* Flag for if timekeeping_resume() has injected sleeptime */
1460 static bool sleeptime_injected;
1462 /* Flag for if there is a persistent clock on this platform */
1463 static bool persistent_clock_exists;
1466 * timekeeping_init - Initializes the clocksource and common timekeeping values
1468 void __init timekeeping_init(void)
1470 struct timekeeper *tk = &tk_core.timekeeper;
1471 struct clocksource *clock;
1472 unsigned long flags;
1473 struct timespec64 now, boot, tmp;
1475 read_persistent_clock64(&now);
1476 if (!timespec64_valid_strict(&now)) {
1477 pr_warn("WARNING: Persistent clock returned invalid value!\n"
1478 " Check your CMOS/BIOS settings.\n");
1481 } else if (now.tv_sec || now.tv_nsec)
1482 persistent_clock_exists = true;
1484 read_boot_clock64(&boot);
1485 if (!timespec64_valid_strict(&boot)) {
1486 pr_warn("WARNING: Boot clock returned invalid value!\n"
1487 " Check your CMOS/BIOS settings.\n");
1492 raw_spin_lock_irqsave(&timekeeper_lock, flags);
1493 write_seqcount_begin(&tk_core.seq);
1496 clock = clocksource_default_clock();
1498 clock->enable(clock);
1499 tk_setup_internals(tk, clock);
1501 tk_set_xtime(tk, &now);
1502 tk->raw_time.tv_sec = 0;
1503 tk->raw_time.tv_nsec = 0;
1504 if (boot.tv_sec == 0 && boot.tv_nsec == 0)
1505 boot = tk_xtime(tk);
1507 set_normalized_timespec64(&tmp, -boot.tv_sec, -boot.tv_nsec);
1508 tk_set_wall_to_mono(tk, tmp);
1510 timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1512 write_seqcount_end(&tk_core.seq);
1513 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1516 /* time in seconds when suspend began for persistent clock */
1517 static struct timespec64 timekeeping_suspend_time;
1520 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
1521 * @delta: pointer to a timespec delta value
1523 * Takes a timespec offset measuring a suspend interval and properly
1524 * adds the sleep offset to the timekeeping variables.
1526 static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
1527 struct timespec64 *delta)
1529 if (!timespec64_valid_strict(delta)) {
1530 printk_deferred(KERN_WARNING
1531 "__timekeeping_inject_sleeptime: Invalid "
1532 "sleep delta value!\n");
1535 tk_xtime_add(tk, delta);
1536 tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));
1537 tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
1538 tk_debug_account_sleep_time(delta);
1541 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
1543 * We have three kinds of time sources to use for sleep time
1544 * injection, the preference order is:
1545 * 1) non-stop clocksource
1546 * 2) persistent clock (ie: RTC accessible when irqs are off)
1549 * 1) and 2) are used by timekeeping, 3) by RTC subsystem.
1550 * If system has neither 1) nor 2), 3) will be used finally.
1553 * If timekeeping has injected sleeptime via either 1) or 2),
1554 * 3) becomes needless, so in this case we don't need to call
1555 * rtc_resume(), and this is what timekeeping_rtc_skipresume()
1558 bool timekeeping_rtc_skipresume(void)
1560 return sleeptime_injected;
1564 * 1) can be determined whether to use or not only when doing
1565 * timekeeping_resume() which is invoked after rtc_suspend(),
1566 * so we can't skip rtc_suspend() surely if system has 1).
1568 * But if system has 2), 2) will definitely be used, so in this
1569 * case we don't need to call rtc_suspend(), and this is what
1570 * timekeeping_rtc_skipsuspend() means.
1572 bool timekeeping_rtc_skipsuspend(void)
1574 return persistent_clock_exists;
1578 * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values
1579 * @delta: pointer to a timespec64 delta value
1581 * This hook is for architectures that cannot support read_persistent_clock64
1582 * because their RTC/persistent clock is only accessible when irqs are enabled.
1583 * and also don't have an effective nonstop clocksource.
1585 * This function should only be called by rtc_resume(), and allows
1586 * a suspend offset to be injected into the timekeeping values.
1588 void timekeeping_inject_sleeptime64(struct timespec64 *delta)
1590 struct timekeeper *tk = &tk_core.timekeeper;
1591 unsigned long flags;
1593 raw_spin_lock_irqsave(&timekeeper_lock, flags);
1594 write_seqcount_begin(&tk_core.seq);
1596 timekeeping_forward_now(tk);
1598 __timekeeping_inject_sleeptime(tk, delta);
1600 timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1602 write_seqcount_end(&tk_core.seq);
1603 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1605 /* signal hrtimers about time change */
1611 * timekeeping_resume - Resumes the generic timekeeping subsystem.
1613 void timekeeping_resume(void)
1615 struct timekeeper *tk = &tk_core.timekeeper;
1616 struct clocksource *clock = tk->tkr_mono.clock;
1617 unsigned long flags;
1618 struct timespec64 ts_new, ts_delta;
1619 cycle_t cycle_now, cycle_delta;
1621 sleeptime_injected = false;
1622 read_persistent_clock64(&ts_new);
1624 clockevents_resume();
1625 clocksource_resume();
1627 raw_spin_lock_irqsave(&timekeeper_lock, flags);
1628 write_seqcount_begin(&tk_core.seq);
1631 * After system resumes, we need to calculate the suspended time and
1632 * compensate it for the OS time. There are 3 sources that could be
1633 * used: Nonstop clocksource during suspend, persistent clock and rtc
1636 * One specific platform may have 1 or 2 or all of them, and the
1637 * preference will be:
1638 * suspend-nonstop clocksource -> persistent clock -> rtc
1639 * The less preferred source will only be tried if there is no better
1640 * usable source. The rtc part is handled separately in rtc core code.
1642 cycle_now = tk->tkr_mono.read(clock);
1643 if ((clock->flags & CLOCK_SOURCE_SUSPEND_NONSTOP) &&
1644 cycle_now > tk->tkr_mono.cycle_last) {
1645 u64 num, max = ULLONG_MAX;
1646 u32 mult = clock->mult;
1647 u32 shift = clock->shift;
1650 cycle_delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last,
1654 * "cycle_delta * mutl" may cause 64 bits overflow, if the
1655 * suspended time is too long. In that case we need do the
1656 * 64 bits math carefully
1659 if (cycle_delta > max) {
1660 num = div64_u64(cycle_delta, max);
1661 nsec = (((u64) max * mult) >> shift) * num;
1662 cycle_delta -= num * max;
1664 nsec += ((u64) cycle_delta * mult) >> shift;
1666 ts_delta = ns_to_timespec64(nsec);
1667 sleeptime_injected = true;
1668 } else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
1669 ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
1670 sleeptime_injected = true;
1673 if (sleeptime_injected)
1674 __timekeeping_inject_sleeptime(tk, &ts_delta);
1676 /* Re-base the last cycle value */
1677 tk->tkr_mono.cycle_last = cycle_now;
1678 tk->tkr_raw.cycle_last = cycle_now;
1681 timekeeping_suspended = 0;
1682 timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1683 write_seqcount_end(&tk_core.seq);
1684 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1686 touch_softlockup_watchdog();
1692 int timekeeping_suspend(void)
1694 struct timekeeper *tk = &tk_core.timekeeper;
1695 unsigned long flags;
1696 struct timespec64 delta, delta_delta;
1697 static struct timespec64 old_delta;
1699 read_persistent_clock64(&timekeeping_suspend_time);
1702 * On some systems the persistent_clock can not be detected at
1703 * timekeeping_init by its return value, so if we see a valid
1704 * value returned, update the persistent_clock_exists flag.
1706 if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec)
1707 persistent_clock_exists = true;
1709 raw_spin_lock_irqsave(&timekeeper_lock, flags);
1710 write_seqcount_begin(&tk_core.seq);
1711 timekeeping_forward_now(tk);
1712 timekeeping_suspended = 1;
1714 if (persistent_clock_exists) {
1716 * To avoid drift caused by repeated suspend/resumes,
1717 * which each can add ~1 second drift error,
1718 * try to compensate so the difference in system time
1719 * and persistent_clock time stays close to constant.
1721 delta = timespec64_sub(tk_xtime(tk), timekeeping_suspend_time);
1722 delta_delta = timespec64_sub(delta, old_delta);
1723 if (abs(delta_delta.tv_sec) >= 2) {
1725 * if delta_delta is too large, assume time correction
1726 * has occurred and set old_delta to the current delta.
1730 /* Otherwise try to adjust old_system to compensate */
1731 timekeeping_suspend_time =
1732 timespec64_add(timekeeping_suspend_time, delta_delta);
1736 timekeeping_update(tk, TK_MIRROR);
1737 halt_fast_timekeeper(tk);
1738 write_seqcount_end(&tk_core.seq);
1739 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1742 clocksource_suspend();
1743 clockevents_suspend();
1748 /* sysfs resume/suspend bits for timekeeping */
1749 static struct syscore_ops timekeeping_syscore_ops = {
1750 .resume = timekeeping_resume,
1751 .suspend = timekeeping_suspend,
1754 static int __init timekeeping_init_ops(void)
1756 register_syscore_ops(&timekeeping_syscore_ops);
1759 device_initcall(timekeeping_init_ops);
1762 * Apply a multiplier adjustment to the timekeeper
1764 static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
1769 s64 interval = tk->cycle_interval;
1773 mult_adj = -mult_adj;
1774 interval = -interval;
1777 mult_adj <<= adj_scale;
1778 interval <<= adj_scale;
1779 offset <<= adj_scale;
1782 * So the following can be confusing.
1784 * To keep things simple, lets assume mult_adj == 1 for now.
1786 * When mult_adj != 1, remember that the interval and offset values
1787 * have been appropriately scaled so the math is the same.
1789 * The basic idea here is that we're increasing the multiplier
1790 * by one, this causes the xtime_interval to be incremented by
1791 * one cycle_interval. This is because:
1792 * xtime_interval = cycle_interval * mult
1793 * So if mult is being incremented by one:
1794 * xtime_interval = cycle_interval * (mult + 1)
1796 * xtime_interval = (cycle_interval * mult) + cycle_interval
1797 * Which can be shortened to:
1798 * xtime_interval += cycle_interval
1800 * So offset stores the non-accumulated cycles. Thus the current
1801 * time (in shifted nanoseconds) is:
1802 * now = (offset * adj) + xtime_nsec
1803 * Now, even though we're adjusting the clock frequency, we have
1804 * to keep time consistent. In other words, we can't jump back
1805 * in time, and we also want to avoid jumping forward in time.
1807 * So given the same offset value, we need the time to be the same
1808 * both before and after the freq adjustment.
1809 * now = (offset * adj_1) + xtime_nsec_1
1810 * now = (offset * adj_2) + xtime_nsec_2
1812 * (offset * adj_1) + xtime_nsec_1 =
1813 * (offset * adj_2) + xtime_nsec_2
1817 * (offset * adj_1) + xtime_nsec_1 =
1818 * (offset * (adj_1+1)) + xtime_nsec_2
1819 * (offset * adj_1) + xtime_nsec_1 =
1820 * (offset * adj_1) + offset + xtime_nsec_2
1821 * Canceling the sides:
1822 * xtime_nsec_1 = offset + xtime_nsec_2
1824 * xtime_nsec_2 = xtime_nsec_1 - offset
1825 * Which simplfies to:
1826 * xtime_nsec -= offset
1828 * XXX - TODO: Doc ntp_error calculation.
1830 if ((mult_adj > 0) && (tk->tkr_mono.mult + mult_adj < mult_adj)) {
1831 /* NTP adjustment caused clocksource mult overflow */
1836 tk->tkr_mono.mult += mult_adj;
1837 tk->xtime_interval += interval;
1838 tk->tkr_mono.xtime_nsec -= offset;
1839 tk->ntp_error -= (interval - offset) << tk->ntp_error_shift;
1843 * Calculate the multiplier adjustment needed to match the frequency
1846 static __always_inline void timekeeping_freqadjust(struct timekeeper *tk,
1849 s64 interval = tk->cycle_interval;
1850 s64 xinterval = tk->xtime_interval;
1851 u32 base = tk->tkr_mono.clock->mult;
1852 u32 max = tk->tkr_mono.clock->maxadj;
1853 u32 cur_adj = tk->tkr_mono.mult;
1858 /* Remove any current error adj from freq calculation */
1859 if (tk->ntp_err_mult)
1860 xinterval -= tk->cycle_interval;
1862 tk->ntp_tick = ntp_tick_length();
1864 /* Calculate current error per tick */
1865 tick_error = ntp_tick_length() >> tk->ntp_error_shift;
1866 tick_error -= (xinterval + tk->xtime_remainder);
1868 /* Don't worry about correcting it if its small */
1869 if (likely((tick_error >= 0) && (tick_error <= interval)))
1872 /* preserve the direction of correction */
1873 negative = (tick_error < 0);
1875 /* If any adjustment would pass the max, just return */
1876 if (negative && (cur_adj - 1) <= (base - max))
1878 if (!negative && (cur_adj + 1) >= (base + max))
1881 * Sort out the magnitude of the correction, but
1882 * avoid making so large a correction that we go
1883 * over the max adjustment.
1886 tick_error = abs(tick_error);
1887 while (tick_error > interval) {
1888 u32 adj = 1 << (adj_scale + 1);
1890 /* Check if adjustment gets us within 1 unit from the max */
1891 if (negative && (cur_adj - adj) <= (base - max))
1893 if (!negative && (cur_adj + adj) >= (base + max))
1900 /* scale the corrections */
1901 timekeeping_apply_adjustment(tk, offset, negative, adj_scale);
1905 * Adjust the timekeeper's multiplier to the correct frequency
1906 * and also to reduce the accumulated error value.
1908 static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
1910 /* Correct for the current frequency error */
1911 timekeeping_freqadjust(tk, offset);
1913 /* Next make a small adjustment to fix any cumulative error */
1914 if (!tk->ntp_err_mult && (tk->ntp_error > 0)) {
1915 tk->ntp_err_mult = 1;
1916 timekeeping_apply_adjustment(tk, offset, 0, 0);
1917 } else if (tk->ntp_err_mult && (tk->ntp_error <= 0)) {
1918 /* Undo any existing error adjustment */
1919 timekeeping_apply_adjustment(tk, offset, 1, 0);
1920 tk->ntp_err_mult = 0;
1923 if (unlikely(tk->tkr_mono.clock->maxadj &&
1924 (abs(tk->tkr_mono.mult - tk->tkr_mono.clock->mult)
1925 > tk->tkr_mono.clock->maxadj))) {
1926 printk_once(KERN_WARNING
1927 "Adjusting %s more than 11%% (%ld vs %ld)\n",
1928 tk->tkr_mono.clock->name, (long)tk->tkr_mono.mult,
1929 (long)tk->tkr_mono.clock->mult + tk->tkr_mono.clock->maxadj);
1933 * It may be possible that when we entered this function, xtime_nsec
1934 * was very small. Further, if we're slightly speeding the clocksource
1935 * in the code above, its possible the required corrective factor to
1936 * xtime_nsec could cause it to underflow.
1938 * Now, since we already accumulated the second, cannot simply roll
1939 * the accumulated second back, since the NTP subsystem has been
1940 * notified via second_overflow. So instead we push xtime_nsec forward
1941 * by the amount we underflowed, and add that amount into the error.
1943 * We'll correct this error next time through this function, when
1944 * xtime_nsec is not as small.
1946 if (unlikely((s64)tk->tkr_mono.xtime_nsec < 0)) {
1947 s64 neg = -(s64)tk->tkr_mono.xtime_nsec;
1948 tk->tkr_mono.xtime_nsec = 0;
1949 tk->ntp_error += neg << tk->ntp_error_shift;
1954 * accumulate_nsecs_to_secs - Accumulates nsecs into secs
1956 * Helper function that accumulates the nsecs greater than a second
1957 * from the xtime_nsec field to the xtime_secs field.
1958 * It also calls into the NTP code to handle leapsecond processing.
1961 static inline unsigned int accumulate_nsecs_to_secs(struct timekeeper *tk)
1963 u64 nsecps = (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
1964 unsigned int clock_set = 0;
1966 while (tk->tkr_mono.xtime_nsec >= nsecps) {
1969 tk->tkr_mono.xtime_nsec -= nsecps;
1972 /* Figure out if its a leap sec and apply if needed */
1973 leap = second_overflow(tk->xtime_sec);
1974 if (unlikely(leap)) {
1975 struct timespec64 ts;
1977 tk->xtime_sec += leap;
1981 tk_set_wall_to_mono(tk,
1982 timespec64_sub(tk->wall_to_monotonic, ts));
1984 __timekeeping_set_tai_offset(tk, tk->tai_offset - leap);
1986 clock_set = TK_CLOCK_WAS_SET;
1993 * logarithmic_accumulation - shifted accumulation of cycles
1995 * This functions accumulates a shifted interval of cycles into
1996 * into a shifted interval nanoseconds. Allows for O(log) accumulation
1999 * Returns the unconsumed cycles.
2001 static cycle_t logarithmic_accumulation(struct timekeeper *tk, cycle_t offset,
2003 unsigned int *clock_set)
2005 cycle_t interval = tk->cycle_interval << shift;
2008 /* If the offset is smaller than a shifted interval, do nothing */
2009 if (offset < interval)
2012 /* Accumulate one shifted interval */
2014 tk->tkr_mono.cycle_last += interval;
2015 tk->tkr_raw.cycle_last += interval;
2017 tk->tkr_mono.xtime_nsec += tk->xtime_interval << shift;
2018 *clock_set |= accumulate_nsecs_to_secs(tk);
2020 /* Accumulate raw time */
2021 raw_nsecs = (u64)tk->raw_interval << shift;
2022 raw_nsecs += tk->raw_time.tv_nsec;
2023 if (raw_nsecs >= NSEC_PER_SEC) {
2024 u64 raw_secs = raw_nsecs;
2025 raw_nsecs = do_div(raw_secs, NSEC_PER_SEC);
2026 tk->raw_time.tv_sec += raw_secs;
2028 tk->raw_time.tv_nsec = raw_nsecs;
2030 /* Accumulate error between NTP and clock interval */
2031 tk->ntp_error += tk->ntp_tick << shift;
2032 tk->ntp_error -= (tk->xtime_interval + tk->xtime_remainder) <<
2033 (tk->ntp_error_shift + shift);
2039 * update_wall_time - Uses the current clocksource to increment the wall time
2042 void update_wall_time(void)
2044 struct timekeeper *real_tk = &tk_core.timekeeper;
2045 struct timekeeper *tk = &shadow_timekeeper;
2047 int shift = 0, maxshift;
2048 unsigned int clock_set = 0;
2049 unsigned long flags;
2051 raw_spin_lock_irqsave(&timekeeper_lock, flags);
2053 /* Make sure we're fully resumed: */
2054 if (unlikely(timekeeping_suspended))
2057 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
2058 offset = real_tk->cycle_interval;
2060 offset = clocksource_delta(tk->tkr_mono.read(tk->tkr_mono.clock),
2061 tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
2064 /* Check if there's really nothing to do */
2065 if (offset < real_tk->cycle_interval)
2068 /* Do some additional sanity checking */
2069 timekeeping_check_update(real_tk, offset);
2072 * With NO_HZ we may have to accumulate many cycle_intervals
2073 * (think "ticks") worth of time at once. To do this efficiently,
2074 * we calculate the largest doubling multiple of cycle_intervals
2075 * that is smaller than the offset. We then accumulate that
2076 * chunk in one go, and then try to consume the next smaller
2079 shift = ilog2(offset) - ilog2(tk->cycle_interval);
2080 shift = max(0, shift);
2081 /* Bound shift to one less than what overflows tick_length */
2082 maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
2083 shift = min(shift, maxshift);
2084 while (offset >= tk->cycle_interval) {
2085 offset = logarithmic_accumulation(tk, offset, shift,
2087 if (offset < tk->cycle_interval<<shift)
2091 /* correct the clock when NTP error is too big */
2092 timekeeping_adjust(tk, offset);
2095 * XXX This can be killed once everyone converts
2096 * to the new update_vsyscall.
2098 old_vsyscall_fixup(tk);
2101 * Finally, make sure that after the rounding
2102 * xtime_nsec isn't larger than NSEC_PER_SEC
2104 clock_set |= accumulate_nsecs_to_secs(tk);
2106 write_seqcount_begin(&tk_core.seq);
2108 * Update the real timekeeper.
2110 * We could avoid this memcpy by switching pointers, but that
2111 * requires changes to all other timekeeper usage sites as
2112 * well, i.e. move the timekeeper pointer getter into the
2113 * spinlocked/seqcount protected sections. And we trade this
2114 * memcpy under the tk_core.seq against one before we start
2117 timekeeping_update(tk, clock_set);
2118 memcpy(real_tk, tk, sizeof(*tk));
2119 /* The memcpy must come last. Do not put anything here! */
2120 write_seqcount_end(&tk_core.seq);
2122 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2124 /* Have to call _delayed version, since in irq context*/
2125 clock_was_set_delayed();
2129 * getboottime64 - Return the real time of system boot.
2130 * @ts: pointer to the timespec64 to be set
2132 * Returns the wall-time of boot in a timespec64.
2134 * This is based on the wall_to_monotonic offset and the total suspend
2135 * time. Calls to settimeofday will affect the value returned (which
2136 * basically means that however wrong your real time clock is at boot time,
2137 * you get the right time here).
2139 void getboottime64(struct timespec64 *ts)
2141 struct timekeeper *tk = &tk_core.timekeeper;
2142 ktime_t t = ktime_sub(tk->offs_real, tk->offs_boot);
2144 *ts = ktime_to_timespec64(t);
2146 EXPORT_SYMBOL_GPL(getboottime64);
2148 unsigned long get_seconds(void)
2150 struct timekeeper *tk = &tk_core.timekeeper;
2152 return tk->xtime_sec;
2154 EXPORT_SYMBOL(get_seconds);
2156 struct timespec __current_kernel_time(void)
2158 struct timekeeper *tk = &tk_core.timekeeper;
2160 return timespec64_to_timespec(tk_xtime(tk));
2163 struct timespec64 current_kernel_time64(void)
2165 struct timekeeper *tk = &tk_core.timekeeper;
2166 struct timespec64 now;
2170 seq = read_seqcount_begin(&tk_core.seq);
2173 } while (read_seqcount_retry(&tk_core.seq, seq));
2177 EXPORT_SYMBOL(current_kernel_time64);
2179 struct timespec64 get_monotonic_coarse64(void)
2181 struct timekeeper *tk = &tk_core.timekeeper;
2182 struct timespec64 now, mono;
2186 seq = read_seqcount_begin(&tk_core.seq);
2189 mono = tk->wall_to_monotonic;
2190 } while (read_seqcount_retry(&tk_core.seq, seq));
2192 set_normalized_timespec64(&now, now.tv_sec + mono.tv_sec,
2193 now.tv_nsec + mono.tv_nsec);
2197 EXPORT_SYMBOL(get_monotonic_coarse64);
2200 * Must hold jiffies_lock
2202 void do_timer(unsigned long ticks)
2204 jiffies_64 += ticks;
2205 calc_global_load(ticks);
2209 * ktime_get_update_offsets_now - hrtimer helper
2210 * @cwsseq: pointer to check and store the clock was set sequence number
2211 * @offs_real: pointer to storage for monotonic -> realtime offset
2212 * @offs_boot: pointer to storage for monotonic -> boottime offset
2213 * @offs_tai: pointer to storage for monotonic -> clock tai offset
2215 * Returns current monotonic time and updates the offsets if the
2216 * sequence number in @cwsseq and timekeeper.clock_was_set_seq are
2219 * Called from hrtimer_interrupt() or retrigger_next_event()
2221 ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
2222 ktime_t *offs_boot, ktime_t *offs_tai)
2224 struct timekeeper *tk = &tk_core.timekeeper;
2230 seq = read_seqcount_begin(&tk_core.seq);
2232 base = tk->tkr_mono.base;
2233 nsecs = timekeeping_get_ns(&tk->tkr_mono);
2234 base = ktime_add_ns(base, nsecs);
2236 if (*cwsseq != tk->clock_was_set_seq) {
2237 *cwsseq = tk->clock_was_set_seq;
2238 *offs_real = tk->offs_real;
2239 *offs_boot = tk->offs_boot;
2240 *offs_tai = tk->offs_tai;
2243 /* Handle leapsecond insertion adjustments */
2244 if (unlikely(base.tv64 >= tk->next_leap_ktime.tv64))
2245 *offs_real = ktime_sub(tk->offs_real, ktime_set(1, 0));
2247 } while (read_seqcount_retry(&tk_core.seq, seq));
2253 * do_adjtimex() - Accessor function to NTP __do_adjtimex function
2255 int do_adjtimex(struct timex *txc)
2257 struct timekeeper *tk = &tk_core.timekeeper;
2258 unsigned long flags;
2259 struct timespec64 ts;
2263 /* Validate the data before disabling interrupts */
2264 ret = ntp_validate_timex(txc);
2268 if (txc->modes & ADJ_SETOFFSET) {
2269 struct timespec delta;
2270 delta.tv_sec = txc->time.tv_sec;
2271 delta.tv_nsec = txc->time.tv_usec;
2272 if (!(txc->modes & ADJ_NANO))
2273 delta.tv_nsec *= 1000;
2274 ret = timekeeping_inject_offset(&delta);
2279 getnstimeofday64(&ts);
2281 raw_spin_lock_irqsave(&timekeeper_lock, flags);
2282 write_seqcount_begin(&tk_core.seq);
2284 orig_tai = tai = tk->tai_offset;
2285 ret = __do_adjtimex(txc, &ts, &tai);
2287 if (tai != orig_tai) {
2288 __timekeeping_set_tai_offset(tk, tai);
2289 timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
2291 tk_update_leap_state(tk);
2293 write_seqcount_end(&tk_core.seq);
2294 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2296 if (tai != orig_tai)
2299 ntp_notify_cmos_timer();
2304 #ifdef CONFIG_NTP_PPS
2306 * hardpps() - Accessor function to NTP __hardpps function
2308 void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
2310 unsigned long flags;
2312 raw_spin_lock_irqsave(&timekeeper_lock, flags);
2313 write_seqcount_begin(&tk_core.seq);
2315 __hardpps(phase_ts, raw_ts);
2317 write_seqcount_end(&tk_core.seq);
2318 raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2320 EXPORT_SYMBOL(hardpps);
2324 * xtime_update() - advances the timekeeping infrastructure
2325 * @ticks: number of ticks, that have elapsed since the last call.
2327 * Must be called with interrupts disabled.
2329 void xtime_update(unsigned long ticks)
2331 write_seqlock(&jiffies_lock);
2333 write_sequnlock(&jiffies_lock);