개념 설명 전체 · v6.6 / kernel/time/hrtimer.c

    1 // SPDX-License-Identifier: GPL-2.0
    2 /*
    3  *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
    4  *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
    5  *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner
    6  *
    7  *  High-resolution kernel timers
    8  *
    9  *  In contrast to the low-resolution timeout API, aka timer wheel,
   10  *  hrtimers provide finer resolution and accuracy depending on system
   11  *  configuration and capabilities.
   12  *
   13  *  Started by: Thomas Gleixner and Ingo Molnar
   14  *
   15  *  Credits:
   16  *	Based on the original timer wheel code
   17  *
   18  *	Help, testing, suggestions, bugfixes, improvements were
   19  *	provided by:
   20  *
   21  *	George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
   22  *	et. al.
   23  */
   24 
   25 #include <linux/cpu.h>
   26 #include <linux/export.h>
   27 #include <linux/percpu.h>
   28 #include <linux/hrtimer.h>
   29 #include <linux/notifier.h>
   30 #include <linux/syscalls.h>
   31 #include <linux/interrupt.h>
   32 #include <linux/tick.h>
   33 #include <linux/err.h>
   34 #include <linux/debugobjects.h>
   35 #include <linux/sched/signal.h>
   36 #include <linux/sched/sysctl.h>
   37 #include <linux/sched/rt.h>
   38 #include <linux/sched/deadline.h>
   39 #include <linux/sched/nohz.h>
   40 #include <linux/sched/debug.h>
   41 #include <linux/timer.h>
   42 #include <linux/freezer.h>
   43 #include <linux/compat.h>
   44 
   45 #include <linux/uaccess.h>
   46 
   47 #include <trace/events/timer.h>
   48 
   49 #include "tick-internal.h"
   50 
   51 /*
   52  * Masks for selecting the soft and hard context timers from
   53  * cpu_base->active
   54  */
   55 #define MASK_SHIFT		(HRTIMER_BASE_MONOTONIC_SOFT)
   56 #define HRTIMER_ACTIVE_HARD	((1U << MASK_SHIFT) - 1)
   57 #define HRTIMER_ACTIVE_SOFT	(HRTIMER_ACTIVE_HARD << MASK_SHIFT)
   58 #define HRTIMER_ACTIVE_ALL	(HRTIMER_ACTIVE_SOFT | HRTIMER_ACTIVE_HARD)
   59 
   60 /*
   61  * The timer bases:
   62  *
   63  * There are more clockids than hrtimer bases. Thus, we index
   64  * into the timer bases by the hrtimer_base_type enum. When trying
   65  * to reach a base using a clockid, hrtimer_clockid_to_base()
   66  * is used to convert from clockid to the proper hrtimer_base_type.
   67  */
   68 DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
   69 {
   70 	.lock = __RAW_SPIN_LOCK_UNLOCKED(hrtimer_bases.lock),
   71 	.clock_base =
   72 	{
   73 		{
   74 			.index = HRTIMER_BASE_MONOTONIC,
   75 			.clockid = CLOCK_MONOTONIC,
   76 			.get_time = &ktime_get,
   77 		},
   78 		{
   79 			.index = HRTIMER_BASE_REALTIME,
   80 			.clockid = CLOCK_REALTIME,
   81 			.get_time = &ktime_get_real,
   82 		},
   83 		{
   84 			.index = HRTIMER_BASE_BOOTTIME,
   85 			.clockid = CLOCK_BOOTTIME,
   86 			.get_time = &ktime_get_boottime,
   87 		},
   88 		{
   89 			.index = HRTIMER_BASE_TAI,
   90 			.clockid = CLOCK_TAI,
   91 			.get_time = &ktime_get_clocktai,
   92 		},
   93 		{
   94 			.index = HRTIMER_BASE_MONOTONIC_SOFT,
   95 			.clockid = CLOCK_MONOTONIC,
   96 			.get_time = &ktime_get,
   97 		},
   98 		{
   99 			.index = HRTIMER_BASE_REALTIME_SOFT,
  100 			.clockid = CLOCK_REALTIME,
  101 			.get_time = &ktime_get_real,
  102 		},
  103 		{
  104 			.index = HRTIMER_BASE_BOOTTIME_SOFT,
  105 			.clockid = CLOCK_BOOTTIME,
  106 			.get_time = &ktime_get_boottime,
  107 		},
  108 		{
  109 			.index = HRTIMER_BASE_TAI_SOFT,
  110 			.clockid = CLOCK_TAI,
  111 			.get_time = &ktime_get_clocktai,
  112 		},
  113 	}
  114 };
  115 
  116 static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
  117 	/* Make sure we catch unsupported clockids */
  118 	[0 ... MAX_CLOCKS - 1]	= HRTIMER_MAX_CLOCK_BASES,
  119 
  120 	[CLOCK_REALTIME]	= HRTIMER_BASE_REALTIME,
  121 	[CLOCK_MONOTONIC]	= HRTIMER_BASE_MONOTONIC,
  122 	[CLOCK_BOOTTIME]	= HRTIMER_BASE_BOOTTIME,
  123 	[CLOCK_TAI]		= HRTIMER_BASE_TAI,
  124 };
  125 
  126 /*
  127  * Functions and macros which are different for UP/SMP systems are kept in a
  128  * single place
  129  */
  130 #ifdef CONFIG_SMP
  131 
  132 /*
  133  * We require the migration_base for lock_hrtimer_base()/switch_hrtimer_base()
  134  * such that hrtimer_callback_running() can unconditionally dereference
  135  * timer->base->cpu_base
  136  */
  137 static struct hrtimer_cpu_base migration_cpu_base = {
  138 	.clock_base = { {
  139 		.cpu_base = &migration_cpu_base,
  140 		.seq      = SEQCNT_RAW_SPINLOCK_ZERO(migration_cpu_base.seq,
  141 						     &migration_cpu_base.lock),
  142 	}, },
  143 };
  144 
  145 #define migration_base	migration_cpu_base.clock_base[0]
  146 
  147 static inline bool is_migration_base(struct hrtimer_clock_base *base)
  148 {
  149 	return base == &migration_base;
  150 }
  151 
  152 /*
  153  * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
  154  * means that all timers which are tied to this base via timer->base are
  155  * locked, and the base itself is locked too.
  156  *
  157  * So __run_timers/migrate_timers can safely modify all timers which could
  158  * be found on the lists/queues.
  159  *
  160  * When the timer's base is locked, and the timer removed from list, it is
  161  * possible to set timer->base = &migration_base and drop the lock: the timer
  162  * remains locked.
  163  */
  164 static
  165 struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
  166 					     unsigned long *flags)
  167 	__acquires(&timer->base->lock)
  168 {
  169 	struct hrtimer_clock_base *base;
  170 
  171 	for (;;) {
  172 		base = READ_ONCE(timer->base);
  173 		if (likely(base != &migration_base)) {
  174 			raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
  175 			if (likely(base == timer->base))
  176 				return base;
  177 			/* The timer has migrated to another CPU: */
  178 			raw_spin_unlock_irqrestore(&base->cpu_base->lock, *flags);
  179 		}
  180 		cpu_relax();
  181 	}
  182 }
  183 
  184 /*
  185  * We do not migrate the timer when it is expiring before the next
  186  * event on the target cpu. When high resolution is enabled, we cannot
  187  * reprogram the target cpu hardware and we would cause it to fire
  188  * late. To keep it simple, we handle the high resolution enabled and
  189  * disabled case similar.
  190  *
  191  * Called with cpu_base->lock of target cpu held.
  192  */
  193 static int
  194 hrtimer_check_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base)
  195 {
  196 	ktime_t expires;
  197 
  198 	expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset);
  199 	return expires < new_base->cpu_base->expires_next;
  200 }
  201 
  202 static inline
  203 struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
  204 					 int pinned)
  205 {
  206 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
  207 	if (static_branch_likely(&timers_migration_enabled) && !pinned)
  208 		return &per_cpu(hrtimer_bases, get_nohz_timer_target());
  209 #endif
  210 	return base;
  211 }
  212 
  213 /*
  214  * We switch the timer base to a power-optimized selected CPU target,
  215  * if:
  216  *	- NO_HZ_COMMON is enabled
  217  *	- timer migration is enabled
  218  *	- the timer callback is not running
  219  *	- the timer is not the first expiring timer on the new target
  220  *
  221  * If one of the above requirements is not fulfilled we move the timer
  222  * to the current CPU or leave it on the previously assigned CPU if
  223  * the timer callback is currently running.
  224  */
  225 static inline struct hrtimer_clock_base *
  226 switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
  227 		    int pinned)
  228 {
  229 	struct hrtimer_cpu_base *new_cpu_base, *this_cpu_base;
  230 	struct hrtimer_clock_base *new_base;
  231 	int basenum = base->index;
  232 
  233 	this_cpu_base = this_cpu_ptr(&hrtimer_bases);
  234 	new_cpu_base = get_target_base(this_cpu_base, pinned);
  235 again:
  236 	new_base = &new_cpu_base->clock_base[basenum];
  237 
  238 	if (base != new_base) {
  239 		/*
  240 		 * We are trying to move timer to new_base.
  241 		 * However we can't change timer's base while it is running,
  242 		 * so we keep it on the same CPU. No hassle vs. reprogramming
  243 		 * the event source in the high resolution case. The softirq
  244 		 * code will take care of this when the timer function has
  245 		 * completed. There is no conflict as we hold the lock until
  246 		 * the timer is enqueued.
  247 		 */
  248 		if (unlikely(hrtimer_callback_running(timer)))
  249 			return base;
  250 
  251 		/* See the comment in lock_hrtimer_base() */
  252 		WRITE_ONCE(timer->base, &migration_base);
  253 		raw_spin_unlock(&base->cpu_base->lock);
  254 		raw_spin_lock(&new_base->cpu_base->lock);
  255 
  256 		if (new_cpu_base != this_cpu_base &&
  257 		    hrtimer_check_target(timer, new_base)) {
  258 			raw_spin_unlock(&new_base->cpu_base->lock);
  259 			raw_spin_lock(&base->cpu_base->lock);
  260 			new_cpu_base = this_cpu_base;
  261 			WRITE_ONCE(timer->base, base);
  262 			goto again;
  263 		}
  264 		WRITE_ONCE(timer->base, new_base);
  265 	} else {
  266 		if (new_cpu_base != this_cpu_base &&
  267 		    hrtimer_check_target(timer, new_base)) {
  268 			new_cpu_base = this_cpu_base;
  269 			goto again;
  270 		}
  271 	}
  272 	return new_base;
  273 }
  274 
  275 #else /* CONFIG_SMP */
  276 
  277 static inline bool is_migration_base(struct hrtimer_clock_base *base)
  278 {
  279 	return false;
  280 }
  281 
  282 static inline struct hrtimer_clock_base *
  283 lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
  284 	__acquires(&timer->base->cpu_base->lock)
  285 {
  286 	struct hrtimer_clock_base *base = timer->base;
  287 
  288 	raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
  289 
  290 	return base;
  291 }
  292 
  293 # define switch_hrtimer_base(t, b, p)	(b)
  294 
  295 #endif	/* !CONFIG_SMP */
  296 
  297 /*
  298  * Functions for the union type storage format of ktime_t which are
  299  * too large for inlining:
  300  */
  301 #if BITS_PER_LONG < 64
  302 /*
  303  * Divide a ktime value by a nanosecond value
  304  */
  305 s64 __ktime_divns(const ktime_t kt, s64 div)
  306 {
  307 	int sft = 0;
  308 	s64 dclc;
  309 	u64 tmp;
  310 
  311 	dclc = ktime_to_ns(kt);
  312 	tmp = dclc < 0 ? -dclc : dclc;
  313 
  314 	/* Make sure the divisor is less than 2^32: */
  315 	while (div >> 32) {
  316 		sft++;
  317 		div >>= 1;
  318 	}
  319 	tmp >>= sft;
  320 	do_div(tmp, (u32) div);
  321 	return dclc < 0 ? -tmp : tmp;
  322 }
  323 EXPORT_SYMBOL_GPL(__ktime_divns);
  324 #endif /* BITS_PER_LONG >= 64 */
  325 
  326 /*
  327  * Add two ktime values and do a safety check for overflow:
  328  */
  329 ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
  330 {
  331 	ktime_t res = ktime_add_unsafe(lhs, rhs);
  332 
  333 	/*
  334 	 * We use KTIME_SEC_MAX here, the maximum timeout which we can
  335 	 * return to user space in a timespec:
  336 	 */
  337 	if (res < 0 || res < lhs || res < rhs)
  338 		res = ktime_set(KTIME_SEC_MAX, 0);
  339 
  340 	return res;
  341 }
  342 
  343 EXPORT_SYMBOL_GPL(ktime_add_safe);
  344 
  345 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
  346 
  347 static const struct debug_obj_descr hrtimer_debug_descr;
  348 
  349 static void *hrtimer_debug_hint(void *addr)
  350 {
  351 	return ((struct hrtimer *) addr)->function;
  352 }
  353 
  354 /*
  355  * fixup_init is called when:
  356  * - an active object is initialized
  357  */
  358 static bool hrtimer_fixup_init(void *addr, enum debug_obj_state state)
  359 {
  360 	struct hrtimer *timer = addr;
  361 
  362 	switch (state) {
  363 	case ODEBUG_STATE_ACTIVE:
  364 		hrtimer_cancel(timer);
  365 		debug_object_init(timer, &hrtimer_debug_descr);
  366 		return true;
  367 	default:
  368 		return false;
  369 	}
  370 }
  371 
  372 /*
  373  * fixup_activate is called when:
  374  * - an active object is activated
  375  * - an unknown non-static object is activated
  376  */
  377 static bool hrtimer_fixup_activate(void *addr, enum debug_obj_state state)
  378 {
  379 	switch (state) {
  380 	case ODEBUG_STATE_ACTIVE:
  381 		WARN_ON(1);
  382 		fallthrough;
  383 	default:
  384 		return false;
  385 	}
  386 }
  387 
  388 /*
  389  * fixup_free is called when:
  390  * - an active object is freed
  391  */
  392 static bool hrtimer_fixup_free(void *addr, enum debug_obj_state state)
  393 {
  394 	struct hrtimer *timer = addr;
  395 
  396 	switch (state) {
  397 	case ODEBUG_STATE_ACTIVE:
  398 		hrtimer_cancel(timer);
  399 		debug_object_free(timer, &hrtimer_debug_descr);
  400 		return true;
  401 	default:
  402 		return false;
  403 	}
  404 }
  405 
  406 static const struct debug_obj_descr hrtimer_debug_descr = {
  407 	.name		= "hrtimer",
  408 	.debug_hint	= hrtimer_debug_hint,
  409 	.fixup_init	= hrtimer_fixup_init,
  410 	.fixup_activate	= hrtimer_fixup_activate,
  411 	.fixup_free	= hrtimer_fixup_free,
  412 };
  413 
  414 static inline void debug_hrtimer_init(struct hrtimer *timer)
  415 {
  416 	debug_object_init(timer, &hrtimer_debug_descr);
  417 }
  418 
  419 static inline void debug_hrtimer_activate(struct hrtimer *timer,
  420 					  enum hrtimer_mode mode)
  421 {
  422 	debug_object_activate(timer, &hrtimer_debug_descr);
  423 }
  424 
  425 static inline void debug_hrtimer_deactivate(struct hrtimer *timer)
  426 {
  427 	debug_object_deactivate(timer, &hrtimer_debug_descr);
  428 }
  429 
  430 static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
  431 			   enum hrtimer_mode mode);
  432 
  433 void hrtimer_init_on_stack(struct hrtimer *timer, clockid_t clock_id,
  434 			   enum hrtimer_mode mode)
  435 {
  436 	debug_object_init_on_stack(timer, &hrtimer_debug_descr);
  437 	__hrtimer_init(timer, clock_id, mode);
  438 }
  439 EXPORT_SYMBOL_GPL(hrtimer_init_on_stack);
  440 
  441 static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
  442 				   clockid_t clock_id, enum hrtimer_mode mode);
  443 
  444 void hrtimer_init_sleeper_on_stack(struct hrtimer_sleeper *sl,
  445 				   clockid_t clock_id, enum hrtimer_mode mode)
  446 {
  447 	debug_object_init_on_stack(&sl->timer, &hrtimer_debug_descr);
  448 	__hrtimer_init_sleeper(sl, clock_id, mode);
  449 }
  450 EXPORT_SYMBOL_GPL(hrtimer_init_sleeper_on_stack);
  451 
  452 void destroy_hrtimer_on_stack(struct hrtimer *timer)
  453 {
  454 	debug_object_free(timer, &hrtimer_debug_descr);
  455 }
  456 EXPORT_SYMBOL_GPL(destroy_hrtimer_on_stack);
  457 
  458 #else
  459 
  460 static inline void debug_hrtimer_init(struct hrtimer *timer) { }
  461 static inline void debug_hrtimer_activate(struct hrtimer *timer,
  462 					  enum hrtimer_mode mode) { }
  463 static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
  464 #endif
  465 
  466 static inline void
  467 debug_init(struct hrtimer *timer, clockid_t clockid,
  468 	   enum hrtimer_mode mode)
  469 {
  470 	debug_hrtimer_init(timer);
  471 	trace_hrtimer_init(timer, clockid, mode);
  472 }
  473 
  474 static inline void debug_activate(struct hrtimer *timer,
  475 				  enum hrtimer_mode mode)
  476 {
  477 	debug_hrtimer_activate(timer, mode);
  478 	trace_hrtimer_start(timer, mode);
  479 }
  480 
  481 static inline void debug_deactivate(struct hrtimer *timer)
  482 {
  483 	debug_hrtimer_deactivate(timer);
  484 	trace_hrtimer_cancel(timer);
  485 }
  486 
  487 static struct hrtimer_clock_base *
  488 __next_base(struct hrtimer_cpu_base *cpu_base, unsigned int *active)
  489 {
  490 	unsigned int idx;
  491 
  492 	if (!*active)
  493 		return NULL;
  494 
  495 	idx = __ffs(*active);
  496 	*active &= ~(1U << idx);
  497 
  498 	return &cpu_base->clock_base[idx];
  499 }
  500 
  501 #define for_each_active_base(base, cpu_base, active)	\
  502 	while ((base = __next_base((cpu_base), &(active))))
  503 
  504 static ktime_t __hrtimer_next_event_base(struct hrtimer_cpu_base *cpu_base,
  505 					 const struct hrtimer *exclude,
  506 					 unsigned int active,
  507 					 ktime_t expires_next)
  508 {
  509 	struct hrtimer_clock_base *base;
  510 	ktime_t expires;
  511 
  512 	for_each_active_base(base, cpu_base, active) {
  513 		struct timerqueue_node *next;
  514 		struct hrtimer *timer;
  515 
  516 		next = timerqueue_getnext(&base->active);
  517 		timer = container_of(next, struct hrtimer, node);
  518 		if (timer == exclude) {
  519 			/* Get to the next timer in the queue. */
  520 			next = timerqueue_iterate_next(next);
  521 			if (!next)
  522 				continue;
  523 
  524 			timer = container_of(next, struct hrtimer, node);
  525 		}
  526 		expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
  527 		if (expires < expires_next) {
  528 			expires_next = expires;
  529 
  530 			/* Skip cpu_base update if a timer is being excluded. */
  531 			if (exclude)
  532 				continue;
  533 
  534 			if (timer->is_soft)
  535 				cpu_base->softirq_next_timer = timer;
  536 			else
  537 				cpu_base->next_timer = timer;
  538 		}
  539 	}
  540 	/*
  541 	 * clock_was_set() might have changed base->offset of any of
  542 	 * the clock bases so the result might be negative. Fix it up
  543 	 * to prevent a false positive in clockevents_program_event().
  544 	 */
  545 	if (expires_next < 0)
  546 		expires_next = 0;
  547 	return expires_next;
  548 }
  549 
  550 /*
  551  * Recomputes cpu_base::*next_timer and returns the earliest expires_next
  552  * but does not set cpu_base::*expires_next, that is done by
  553  * hrtimer[_force]_reprogram and hrtimer_interrupt only. When updating
  554  * cpu_base::*expires_next right away, reprogramming logic would no longer
  555  * work.
  556  *
  557  * When a softirq is pending, we can ignore the HRTIMER_ACTIVE_SOFT bases,
  558  * those timers will get run whenever the softirq gets handled, at the end of
  559  * hrtimer_run_softirq(), hrtimer_update_softirq_timer() will re-add these bases.
  560  *
  561  * Therefore softirq values are those from the HRTIMER_ACTIVE_SOFT clock bases.
  562  * The !softirq values are the minima across HRTIMER_ACTIVE_ALL, unless an actual
  563  * softirq is pending, in which case they're the minima of HRTIMER_ACTIVE_HARD.
  564  *
  565  * @active_mask must be one of:
  566  *  - HRTIMER_ACTIVE_ALL,
  567  *  - HRTIMER_ACTIVE_SOFT, or
  568  *  - HRTIMER_ACTIVE_HARD.
  569  */
  570 static ktime_t
  571 __hrtimer_get_next_event(struct hrtimer_cpu_base *cpu_base, unsigned int active_mask)
  572 {
  573 	unsigned int active;
  574 	struct hrtimer *next_timer = NULL;
  575 	ktime_t expires_next = KTIME_MAX;
  576 
  577 	if (!cpu_base->softirq_activated && (active_mask & HRTIMER_ACTIVE_SOFT)) {
  578 		active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
  579 		cpu_base->softirq_next_timer = NULL;
  580 		expires_next = __hrtimer_next_event_base(cpu_base, NULL,
  581 							 active, KTIME_MAX);
  582 
  583 		next_timer = cpu_base->softirq_next_timer;
  584 	}
  585 
  586 	if (active_mask & HRTIMER_ACTIVE_HARD) {
  587 		active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
  588 		cpu_base->next_timer = next_timer;
  589 		expires_next = __hrtimer_next_event_base(cpu_base, NULL, active,
  590 							 expires_next);
  591 	}
  592 
  593 	return expires_next;
  594 }
  595 
  596 static ktime_t hrtimer_update_next_event(struct hrtimer_cpu_base *cpu_base)
  597 {
  598 	ktime_t expires_next, soft = KTIME_MAX;
  599 
  600 	/*
  601 	 * If the soft interrupt has already been activated, ignore the
  602 	 * soft bases. They will be handled in the already raised soft
  603 	 * interrupt.
  604 	 */
  605 	if (!cpu_base->softirq_activated) {
  606 		soft = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
  607 		/*
  608 		 * Update the soft expiry time. clock_settime() might have
  609 		 * affected it.
  610 		 */
  611 		cpu_base->softirq_expires_next = soft;
  612 	}
  613 
  614 	expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_HARD);
  615 	/*
  616 	 * If a softirq timer is expiring first, update cpu_base->next_timer
  617 	 * and program the hardware with the soft expiry time.
  618 	 */
  619 	if (expires_next > soft) {
  620 		cpu_base->next_timer = cpu_base->softirq_next_timer;
  621 		expires_next = soft;
  622 	}
  623 
  624 	return expires_next;
  625 }
  626 
  627 static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
  628 {
  629 	ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
  630 	ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
  631 	ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
  632 
  633 	ktime_t now = ktime_get_update_offsets_now(&base->clock_was_set_seq,
  634 					    offs_real, offs_boot, offs_tai);
  635 
  636 	base->clock_base[HRTIMER_BASE_REALTIME_SOFT].offset = *offs_real;
  637 	base->clock_base[HRTIMER_BASE_BOOTTIME_SOFT].offset = *offs_boot;
  638 	base->clock_base[HRTIMER_BASE_TAI_SOFT].offset = *offs_tai;
  639 
  640 	return now;
  641 }
  642 
  643 /*
  644  * Is the high resolution mode active ?
  645  */
  646 static inline int __hrtimer_hres_active(struct hrtimer_cpu_base *cpu_base)
  647 {
  648 	return IS_ENABLED(CONFIG_HIGH_RES_TIMERS) ?
  649 		cpu_base->hres_active : 0;
  650 }
  651 
  652 static inline int hrtimer_hres_active(void)
  653 {
  654 	return __hrtimer_hres_active(this_cpu_ptr(&hrtimer_bases));
  655 }
  656 
  657 static void __hrtimer_reprogram(struct hrtimer_cpu_base *cpu_base,
  658 				struct hrtimer *next_timer,
  659 				ktime_t expires_next)
  660 {
  661 	cpu_base->expires_next = expires_next;
  662 
  663 	/*
  664 	 * If hres is not active, hardware does not have to be
  665 	 * reprogrammed yet.
  666 	 *
  667 	 * If a hang was detected in the last timer interrupt then we
  668 	 * leave the hang delay active in the hardware. We want the
  669 	 * system to make progress. That also prevents the following
  670 	 * scenario:
  671 	 * T1 expires 50ms from now
  672 	 * T2 expires 5s from now
  673 	 *
  674 	 * T1 is removed, so this code is called and would reprogram
  675 	 * the hardware to 5s from now. Any hrtimer_start after that
  676 	 * will not reprogram the hardware due to hang_detected being
  677 	 * set. So we'd effectively block all timers until the T2 event
  678 	 * fires.
  679 	 */
  680 	if (!__hrtimer_hres_active(cpu_base) || cpu_base->hang_detected)
  681 		return;
  682 
  683 	tick_program_event(expires_next, 1);
  684 }
  685 
  686 /*
  687  * Reprogram the event source with checking both queues for the
  688  * next event
  689  * Called with interrupts disabled and base->lock held
  690  */
  691 static void
  692 hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
  693 {
  694 	ktime_t expires_next;
  695 
  696 	expires_next = hrtimer_update_next_event(cpu_base);
  697 
  698 	if (skip_equal && expires_next == cpu_base->expires_next)
  699 		return;
  700 
  701 	__hrtimer_reprogram(cpu_base, cpu_base->next_timer, expires_next);
  702 }
  703 
  704 /* High resolution timer related functions */
  705 #ifdef CONFIG_HIGH_RES_TIMERS
  706 
  707 /*
  708  * High resolution timer enabled ?
  709  */
  710 static bool hrtimer_hres_enabled __read_mostly  = true;
  711 unsigned int hrtimer_resolution __read_mostly = LOW_RES_NSEC;
  712 EXPORT_SYMBOL_GPL(hrtimer_resolution);
  713 
  714 /*
  715  * Enable / Disable high resolution mode
  716  */
  717 static int __init setup_hrtimer_hres(char *str)
  718 {
  719 	return (kstrtobool(str, &hrtimer_hres_enabled) == 0);
  720 }
  721 
  722 __setup("highres=", setup_hrtimer_hres);
  723 
  724 /*
  725  * hrtimer_high_res_enabled - query, if the highres mode is enabled
  726  */
  727 static inline int hrtimer_is_hres_enabled(void)
  728 {
  729 	return hrtimer_hres_enabled;
  730 }
  731 
  732 static void retrigger_next_event(void *arg);
  733 
  734 /*
  735  * Switch to high resolution mode
  736  */
  737 static void hrtimer_switch_to_hres(void)
  738 {
  739 	struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
  740 
  741 	if (tick_init_highres()) {
  742 		pr_warn("Could not switch to high resolution mode on CPU %u\n",
  743 			base->cpu);
  744 		return;
  745 	}
  746 	base->hres_active = 1;
  747 	hrtimer_resolution = HIGH_RES_NSEC;
  748 
  749 	tick_setup_sched_timer();
  750 	/* "Retrigger" the interrupt to get things going */
  751 	retrigger_next_event(NULL);
  752 }
  753 
  754 #else
  755 
  756 static inline int hrtimer_is_hres_enabled(void) { return 0; }
  757 static inline void hrtimer_switch_to_hres(void) { }
  758 
  759 #endif /* CONFIG_HIGH_RES_TIMERS */
  760 /*
  761  * Retrigger next event is called after clock was set with interrupts
  762  * disabled through an SMP function call or directly from low level
  763  * resume code.
  764  *
  765  * This is only invoked when:
  766  *	- CONFIG_HIGH_RES_TIMERS is enabled.
  767  *	- CONFIG_NOHZ_COMMON is enabled
  768  *
  769  * For the other cases this function is empty and because the call sites
  770  * are optimized out it vanishes as well, i.e. no need for lots of
  771  * #ifdeffery.
  772  */
  773 static void retrigger_next_event(void *arg)
  774 {
  775 	struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
  776 
  777 	/*
  778 	 * When high resolution mode or nohz is active, then the offsets of
  779 	 * CLOCK_REALTIME/TAI/BOOTTIME have to be updated. Otherwise the
  780 	 * next tick will take care of that.
  781 	 *
  782 	 * If high resolution mode is active then the next expiring timer
  783 	 * must be reevaluated and the clock event device reprogrammed if
  784 	 * necessary.
  785 	 *
  786 	 * In the NOHZ case the update of the offset and the reevaluation
  787 	 * of the next expiring timer is enough. The return from the SMP
  788 	 * function call will take care of the reprogramming in case the
  789 	 * CPU was in a NOHZ idle sleep.
  790 	 */
  791 	if (!__hrtimer_hres_active(base) && !tick_nohz_active)
  792 		return;
  793 
  794 	raw_spin_lock(&base->lock);
  795 	hrtimer_update_base(base);
  796 	if (__hrtimer_hres_active(base))
  797 		hrtimer_force_reprogram(base, 0);
  798 	else
  799 		hrtimer_update_next_event(base);
  800 	raw_spin_unlock(&base->lock);
  801 }
  802 
  803 /*
  804  * When a timer is enqueued and expires earlier than the already enqueued
  805  * timers, we have to check, whether it expires earlier than the timer for
  806  * which the clock event device was armed.
  807  *
  808  * Called with interrupts disabled and base->cpu_base.lock held
  809  */
  810 static void hrtimer_reprogram(struct hrtimer *timer, bool reprogram)
  811 {
  812 	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
  813 	struct hrtimer_clock_base *base = timer->base;
  814 	ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
  815 
  816 	WARN_ON_ONCE(hrtimer_get_expires_tv64(timer) < 0);
  817 
  818 	/*
  819 	 * CLOCK_REALTIME timer might be requested with an absolute
  820 	 * expiry time which is less than base->offset. Set it to 0.
  821 	 */
  822 	if (expires < 0)
  823 		expires = 0;
  824 
  825 	if (timer->is_soft) {
  826 		/*
  827 		 * soft hrtimer could be started on a remote CPU. In this
  828 		 * case softirq_expires_next needs to be updated on the
  829 		 * remote CPU. The soft hrtimer will not expire before the
  830 		 * first hard hrtimer on the remote CPU -
  831 		 * hrtimer_check_target() prevents this case.
  832 		 */
  833 		struct hrtimer_cpu_base *timer_cpu_base = base->cpu_base;
  834 
  835 		if (timer_cpu_base->softirq_activated)
  836 			return;
  837 
  838 		if (!ktime_before(expires, timer_cpu_base->softirq_expires_next))
  839 			return;
  840 
  841 		timer_cpu_base->softirq_next_timer = timer;
  842 		timer_cpu_base->softirq_expires_next = expires;
  843 
  844 		if (!ktime_before(expires, timer_cpu_base->expires_next) ||
  845 		    !reprogram)
  846 			return;
  847 	}
  848 
  849 	/*
  850 	 * If the timer is not on the current cpu, we cannot reprogram
  851 	 * the other cpus clock event device.
  852 	 */
  853 	if (base->cpu_base != cpu_base)
  854 		return;
  855 
  856 	if (expires >= cpu_base->expires_next)
  857 		return;
  858 
  859 	/*
  860 	 * If the hrtimer interrupt is running, then it will reevaluate the
  861 	 * clock bases and reprogram the clock event device.
  862 	 */
  863 	if (cpu_base->in_hrtirq)
  864 		return;
  865 
  866 	cpu_base->next_timer = timer;
  867 
  868 	__hrtimer_reprogram(cpu_base, timer, expires);
  869 }
  870 
  871 static bool update_needs_ipi(struct hrtimer_cpu_base *cpu_base,
  872 			     unsigned int active)
  873 {
  874 	struct hrtimer_clock_base *base;
  875 	unsigned int seq;
  876 	ktime_t expires;
  877 
  878 	/*
  879 	 * Update the base offsets unconditionally so the following
  880 	 * checks whether the SMP function call is required works.
  881 	 *
  882 	 * The update is safe even when the remote CPU is in the hrtimer
  883 	 * interrupt or the hrtimer soft interrupt and expiring affected
  884 	 * bases. Either it will see the update before handling a base or
  885 	 * it will see it when it finishes the processing and reevaluates
  886 	 * the next expiring timer.
  887 	 */
  888 	seq = cpu_base->clock_was_set_seq;
  889 	hrtimer_update_base(cpu_base);
  890 
  891 	/*
  892 	 * If the sequence did not change over the update then the
  893 	 * remote CPU already handled it.
  894 	 */
  895 	if (seq == cpu_base->clock_was_set_seq)
  896 		return false;
  897 
  898 	/*
  899 	 * If the remote CPU is currently handling an hrtimer interrupt, it
  900 	 * will reevaluate the first expiring timer of all clock bases
  901 	 * before reprogramming. Nothing to do here.
  902 	 */
  903 	if (cpu_base->in_hrtirq)
  904 		return false;
  905 
  906 	/*
  907 	 * Walk the affected clock bases and check whether the first expiring
  908 	 * timer in a clock base is moving ahead of the first expiring timer of
  909 	 * @cpu_base. If so, the IPI must be invoked because per CPU clock
  910 	 * event devices cannot be remotely reprogrammed.
  911 	 */
  912 	active &= cpu_base->active_bases;
  913 
  914 	for_each_active_base(base, cpu_base, active) {
  915 		struct timerqueue_node *next;
  916 
  917 		next = timerqueue_getnext(&base->active);
  918 		expires = ktime_sub(next->expires, base->offset);
  919 		if (expires < cpu_base->expires_next)
  920 			return true;
  921 
  922 		/* Extra check for softirq clock bases */
  923 		if (base->clockid < HRTIMER_BASE_MONOTONIC_SOFT)
  924 			continue;
  925 		if (cpu_base->softirq_activated)
  926 			continue;
  927 		if (expires < cpu_base->softirq_expires_next)
  928 			return true;
  929 	}
  930 	return false;
  931 }
  932 
  933 /*
  934  * Clock was set. This might affect CLOCK_REALTIME, CLOCK_TAI and
  935  * CLOCK_BOOTTIME (for late sleep time injection).
  936  *
  937  * This requires to update the offsets for these clocks
  938  * vs. CLOCK_MONOTONIC. When high resolution timers are enabled, then this
  939  * also requires to eventually reprogram the per CPU clock event devices
  940  * when the change moves an affected timer ahead of the first expiring
  941  * timer on that CPU. Obviously remote per CPU clock event devices cannot
  942  * be reprogrammed. The other reason why an IPI has to be sent is when the
  943  * system is in !HIGH_RES and NOHZ mode. The NOHZ mode updates the offsets
  944  * in the tick, which obviously might be stopped, so this has to bring out
  945  * the remote CPU which might sleep in idle to get this sorted.
  946  */
  947 void clock_was_set(unsigned int bases)
  948 {
  949 	struct hrtimer_cpu_base *cpu_base = raw_cpu_ptr(&hrtimer_bases);
  950 	cpumask_var_t mask;
  951 	int cpu;
  952 
  953 	if (!__hrtimer_hres_active(cpu_base) && !tick_nohz_active)
  954 		goto out_timerfd;
  955 
  956 	if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) {
  957 		on_each_cpu(retrigger_next_event, NULL, 1);
  958 		goto out_timerfd;
  959 	}
  960 
  961 	/* Avoid interrupting CPUs if possible */
  962 	cpus_read_lock();
  963 	for_each_online_cpu(cpu) {
  964 		unsigned long flags;
  965 
  966 		cpu_base = &per_cpu(hrtimer_bases, cpu);
  967 		raw_spin_lock_irqsave(&cpu_base->lock, flags);
  968 
  969 		if (update_needs_ipi(cpu_base, bases))
  970 			cpumask_set_cpu(cpu, mask);
  971 
  972 		raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
  973 	}
  974 
  975 	preempt_disable();
  976 	smp_call_function_many(mask, retrigger_next_event, NULL, 1);
  977 	preempt_enable();
  978 	cpus_read_unlock();
  979 	free_cpumask_var(mask);
  980 
  981 out_timerfd:
  982 	timerfd_clock_was_set();
  983 }
  984 
  985 static void clock_was_set_work(struct work_struct *work)
  986 {
  987 	clock_was_set(CLOCK_SET_WALL);
  988 }
  989 
  990 static DECLARE_WORK(hrtimer_work, clock_was_set_work);
  991 
  992 /*
  993  * Called from timekeeping code to reprogram the hrtimer interrupt device
  994  * on all cpus and to notify timerfd.
  995  */
  996 void clock_was_set_delayed(void)
  997 {
  998 	schedule_work(&hrtimer_work);
  999 }
 1000 
 1001 /*
 1002  * Called during resume either directly from via timekeeping_resume()
 1003  * or in the case of s2idle from tick_unfreeze() to ensure that the
 1004  * hrtimers are up to date.
 1005  */
 1006 void hrtimers_resume_local(void)
 1007 {
 1008 	lockdep_assert_irqs_disabled();
 1009 	/* Retrigger on the local CPU */
 1010 	retrigger_next_event(NULL);
 1011 }
 1012 
 1013 /*
 1014  * Counterpart to lock_hrtimer_base above:
 1015  */
 1016 static inline
 1017 void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
 1018 	__releases(&timer->base->cpu_base->lock)
 1019 {
 1020 	raw_spin_unlock_irqrestore(&timer->base->cpu_base->lock, *flags);
 1021 }
 1022 
 1023 /**
 1024  * hrtimer_forward - forward the timer expiry
 1025  * @timer:	hrtimer to forward
 1026  * @now:	forward past this time
 1027  * @interval:	the interval to forward
 1028  *
 1029  * Forward the timer expiry so it will expire in the future.
 1030  * Returns the number of overruns.
 1031  *
 1032  * Can be safely called from the callback function of @timer. If
 1033  * called from other contexts @timer must neither be enqueued nor
 1034  * running the callback and the caller needs to take care of
 1035  * serialization.
 1036  *
 1037  * Note: This only updates the timer expiry value and does not requeue
 1038  * the timer.
 1039  */
 1040 u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
 1041 {
 1042 	u64 orun = 1;
 1043 	ktime_t delta;
 1044 
 1045 	delta = ktime_sub(now, hrtimer_get_expires(timer));
 1046 
 1047 	if (delta < 0)
 1048 		return 0;
 1049 
 1050 	if (WARN_ON(timer->state & HRTIMER_STATE_ENQUEUED))
 1051 		return 0;
 1052 
 1053 	if (interval < hrtimer_resolution)
 1054 		interval = hrtimer_resolution;
 1055 
 1056 	if (unlikely(delta >= interval)) {
 1057 		s64 incr = ktime_to_ns(interval);
 1058 
 1059 		orun = ktime_divns(delta, incr);
 1060 		hrtimer_add_expires_ns(timer, incr * orun);
 1061 		if (hrtimer_get_expires_tv64(timer) > now)
 1062 			return orun;
 1063 		/*
 1064 		 * This (and the ktime_add() below) is the
 1065 		 * correction for exact:
 1066 		 */
 1067 		orun++;
 1068 	}
 1069 	hrtimer_add_expires(timer, interval);
 1070 
 1071 	return orun;
 1072 }
 1073 EXPORT_SYMBOL_GPL(hrtimer_forward);
 1074 
 1075 /*
 1076  * enqueue_hrtimer - internal function to (re)start a timer
 1077  *
 1078  * The timer is inserted in expiry order. Insertion into the
 1079  * red black tree is O(log(n)). Must hold the base lock.
 1080  *
 1081  * Returns 1 when the new timer is the leftmost timer in the tree.
 1082  */
 1083 static int enqueue_hrtimer(struct hrtimer *timer,
 1084 			   struct hrtimer_clock_base *base,
 1085 			   enum hrtimer_mode mode)
 1086 {
 1087 	debug_activate(timer, mode);
 1088 
 1089 	base->cpu_base->active_bases |= 1 << base->index;
 1090 
 1091 	/* Pairs with the lockless read in hrtimer_is_queued() */
 1092 	WRITE_ONCE(timer->state, HRTIMER_STATE_ENQUEUED);
 1093 
 1094 	return timerqueue_add(&base->active, &timer->node);
 1095 }
 1096 
 1097 /*
 1098  * __remove_hrtimer - internal function to remove a timer
 1099  *
 1100  * Caller must hold the base lock.
 1101  *
 1102  * High resolution timer mode reprograms the clock event device when the
 1103  * timer is the one which expires next. The caller can disable this by setting
 1104  * reprogram to zero. This is useful, when the context does a reprogramming
 1105  * anyway (e.g. timer interrupt)
 1106  */
 1107 static void __remove_hrtimer(struct hrtimer *timer,
 1108 			     struct hrtimer_clock_base *base,
 1109 			     u8 newstate, int reprogram)
 1110 {
 1111 	struct hrtimer_cpu_base *cpu_base = base->cpu_base;
 1112 	u8 state = timer->state;
 1113 
 1114 	/* Pairs with the lockless read in hrtimer_is_queued() */
 1115 	WRITE_ONCE(timer->state, newstate);
 1116 	if (!(state & HRTIMER_STATE_ENQUEUED))
 1117 		return;
 1118 
 1119 	if (!timerqueue_del(&base->active, &timer->node))
 1120 		cpu_base->active_bases &= ~(1 << base->index);
 1121 
 1122 	/*
 1123 	 * Note: If reprogram is false we do not update
 1124 	 * cpu_base->next_timer. This happens when we remove the first
 1125 	 * timer on a remote cpu. No harm as we never dereference
 1126 	 * cpu_base->next_timer. So the worst thing what can happen is
 1127 	 * an superfluous call to hrtimer_force_reprogram() on the
 1128 	 * remote cpu later on if the same timer gets enqueued again.
 1129 	 */
 1130 	if (reprogram && timer == cpu_base->next_timer)
 1131 		hrtimer_force_reprogram(cpu_base, 1);
 1132 }
 1133 
 1134 /*
 1135  * remove hrtimer, called with base lock held
 1136  */
 1137 static inline int
 1138 remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base,
 1139 	       bool restart, bool keep_local)
 1140 {
 1141 	u8 state = timer->state;
 1142 
 1143 	if (state & HRTIMER_STATE_ENQUEUED) {
 1144 		bool reprogram;
 1145 
 1146 		/*
 1147 		 * Remove the timer and force reprogramming when high
 1148 		 * resolution mode is active and the timer is on the current
 1149 		 * CPU. If we remove a timer on another CPU, reprogramming is
 1150 		 * skipped. The interrupt event on this CPU is fired and
 1151 		 * reprogramming happens in the interrupt handler. This is a
 1152 		 * rare case and less expensive than a smp call.
 1153 		 */
 1154 		debug_deactivate(timer);
 1155 		reprogram = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
 1156 
 1157 		/*
 1158 		 * If the timer is not restarted then reprogramming is
 1159 		 * required if the timer is local. If it is local and about
 1160 		 * to be restarted, avoid programming it twice (on removal
 1161 		 * and a moment later when it's requeued).
 1162 		 */
 1163 		if (!restart)
 1164 			state = HRTIMER_STATE_INACTIVE;
 1165 		else
 1166 			reprogram &= !keep_local;
 1167 
 1168 		__remove_hrtimer(timer, base, state, reprogram);
 1169 		return 1;
 1170 	}
 1171 	return 0;
 1172 }
 1173 
 1174 static inline ktime_t hrtimer_update_lowres(struct hrtimer *timer, ktime_t tim,
 1175 					    const enum hrtimer_mode mode)
 1176 {
 1177 #ifdef CONFIG_TIME_LOW_RES
 1178 	/*
 1179 	 * CONFIG_TIME_LOW_RES indicates that the system has no way to return
 1180 	 * granular time values. For relative timers we add hrtimer_resolution
 1181 	 * (i.e. one jiffie) to prevent short timeouts.
 1182 	 */
 1183 	timer->is_rel = mode & HRTIMER_MODE_REL;
 1184 	if (timer->is_rel)
 1185 		tim = ktime_add_safe(tim, hrtimer_resolution);
 1186 #endif
 1187 	return tim;
 1188 }
 1189 
 1190 static void
 1191 hrtimer_update_softirq_timer(struct hrtimer_cpu_base *cpu_base, bool reprogram)
 1192 {
 1193 	ktime_t expires;
 1194 
 1195 	/*
 1196 	 * Find the next SOFT expiration.
 1197 	 */
 1198 	expires = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
 1199 
 1200 	/*
 1201 	 * reprogramming needs to be triggered, even if the next soft
 1202 	 * hrtimer expires at the same time than the next hard
 1203 	 * hrtimer. cpu_base->softirq_expires_next needs to be updated!
 1204 	 */
 1205 	if (expires == KTIME_MAX)
 1206 		return;
 1207 
 1208 	/*
 1209 	 * cpu_base->*next_timer is recomputed by __hrtimer_get_next_event()
 1210 	 * cpu_base->*expires_next is only set by hrtimer_reprogram()
 1211 	 */
 1212 	hrtimer_reprogram(cpu_base->softirq_next_timer, reprogram);
 1213 }
 1214 
 1215 static int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 1216 				    u64 delta_ns, const enum hrtimer_mode mode,
 1217 				    struct hrtimer_clock_base *base)
 1218 {
 1219 	struct hrtimer_clock_base *new_base;
 1220 	bool force_local, first;
 1221 
 1222 	/*
 1223 	 * If the timer is on the local cpu base and is the first expiring
 1224 	 * timer then this might end up reprogramming the hardware twice
 1225 	 * (on removal and on enqueue). To avoid that by prevent the
 1226 	 * reprogram on removal, keep the timer local to the current CPU
 1227 	 * and enforce reprogramming after it is queued no matter whether
 1228 	 * it is the new first expiring timer again or not.
 1229 	 */
 1230 	force_local = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
 1231 	force_local &= base->cpu_base->next_timer == timer;
 1232 
 1233 	/*
 1234 	 * Remove an active timer from the queue. In case it is not queued
 1235 	 * on the current CPU, make sure that remove_hrtimer() updates the
 1236 	 * remote data correctly.
 1237 	 *
 1238 	 * If it's on the current CPU and the first expiring timer, then
 1239 	 * skip reprogramming, keep the timer local and enforce
 1240 	 * reprogramming later if it was the first expiring timer.  This
 1241 	 * avoids programming the underlying clock event twice (once at
 1242 	 * removal and once after enqueue).
 1243 	 */
 1244 	remove_hrtimer(timer, base, true, force_local);
 1245 
 1246 	if (mode & HRTIMER_MODE_REL)
 1247 		tim = ktime_add_safe(tim, base->get_time());
 1248 
 1249 	tim = hrtimer_update_lowres(timer, tim, mode);
 1250 
 1251 	hrtimer_set_expires_range_ns(timer, tim, delta_ns);
 1252 
 1253 	/* Switch the timer base, if necessary: */
 1254 	if (!force_local) {
 1255 		new_base = switch_hrtimer_base(timer, base,
 1256 					       mode & HRTIMER_MODE_PINNED);
 1257 	} else {
 1258 		new_base = base;
 1259 	}
 1260 
 1261 	first = enqueue_hrtimer(timer, new_base, mode);
 1262 	if (!force_local)
 1263 		return first;
 1264 
 1265 	/*
 1266 	 * Timer was forced to stay on the current CPU to avoid
 1267 	 * reprogramming on removal and enqueue. Force reprogram the
 1268 	 * hardware by evaluating the new first expiring timer.
 1269 	 */
 1270 	hrtimer_force_reprogram(new_base->cpu_base, 1);
 1271 	return 0;
 1272 }
 1273 
 1274 /**
 1275  * hrtimer_start_range_ns - (re)start an hrtimer
 1276  * @timer:	the timer to be added
 1277  * @tim:	expiry time
 1278  * @delta_ns:	"slack" range for the timer
 1279  * @mode:	timer mode: absolute (HRTIMER_MODE_ABS) or
 1280  *		relative (HRTIMER_MODE_REL), and pinned (HRTIMER_MODE_PINNED);
 1281  *		softirq based mode is considered for debug purpose only!
 1282  */
 1283 void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 1284 			    u64 delta_ns, const enum hrtimer_mode mode)
 1285 {
 1286 	struct hrtimer_clock_base *base;
 1287 	unsigned long flags;
 1288 
 1289 	/*
 1290 	 * Check whether the HRTIMER_MODE_SOFT bit and hrtimer.is_soft
 1291 	 * match on CONFIG_PREEMPT_RT = n. With PREEMPT_RT check the hard
 1292 	 * expiry mode because unmarked timers are moved to softirq expiry.
 1293 	 */
 1294 	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
 1295 		WARN_ON_ONCE(!(mode & HRTIMER_MODE_SOFT) ^ !timer->is_soft);
 1296 	else
 1297 		WARN_ON_ONCE(!(mode & HRTIMER_MODE_HARD) ^ !timer->is_hard);
 1298 
 1299 	base = lock_hrtimer_base(timer, &flags);
 1300 
 1301 	if (__hrtimer_start_range_ns(timer, tim, delta_ns, mode, base))
 1302 		hrtimer_reprogram(timer, true);
 1303 
 1304 	unlock_hrtimer_base(timer, &flags);
 1305 }
 1306 EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);
 1307 
 1308 /**
 1309  * hrtimer_try_to_cancel - try to deactivate a timer
 1310  * @timer:	hrtimer to stop
 1311  *
 1312  * Returns:
 1313  *
 1314  *  *  0 when the timer was not active
 1315  *  *  1 when the timer was active
 1316  *  * -1 when the timer is currently executing the callback function and
 1317  *    cannot be stopped
 1318  */
 1319 int hrtimer_try_to_cancel(struct hrtimer *timer)
 1320 {
 1321 	struct hrtimer_clock_base *base;
 1322 	unsigned long flags;
 1323 	int ret = -1;
 1324 
 1325 	/*
 1326 	 * Check lockless first. If the timer is not active (neither
 1327 	 * enqueued nor running the callback, nothing to do here.  The
 1328 	 * base lock does not serialize against a concurrent enqueue,
 1329 	 * so we can avoid taking it.
 1330 	 */
 1331 	if (!hrtimer_active(timer))
 1332 		return 0;
 1333 
 1334 	base = lock_hrtimer_base(timer, &flags);
 1335 
 1336 	if (!hrtimer_callback_running(timer))
 1337 		ret = remove_hrtimer(timer, base, false, false);
 1338 
 1339 	unlock_hrtimer_base(timer, &flags);
 1340 
 1341 	return ret;
 1342 
 1343 }
 1344 EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);
 1345 
 1346 #ifdef CONFIG_PREEMPT_RT
 1347 static void hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base)
 1348 {
 1349 	spin_lock_init(&base->softirq_expiry_lock);
 1350 }
 1351 
 1352 static void hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base)
 1353 {
 1354 	spin_lock(&base->softirq_expiry_lock);
 1355 }
 1356 
 1357 static void hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base)
 1358 {
 1359 	spin_unlock(&base->softirq_expiry_lock);
 1360 }
 1361 
 1362 /*
 1363  * The counterpart to hrtimer_cancel_wait_running().
 1364  *
 1365  * If there is a waiter for cpu_base->expiry_lock, then it was waiting for
 1366  * the timer callback to finish. Drop expiry_lock and reacquire it. That
 1367  * allows the waiter to acquire the lock and make progress.
 1368  */
 1369 static void hrtimer_sync_wait_running(struct hrtimer_cpu_base *cpu_base,
 1370 				      unsigned long flags)
 1371 {
 1372 	if (atomic_read(&cpu_base->timer_waiters)) {
 1373 		raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 1374 		spin_unlock(&cpu_base->softirq_expiry_lock);
 1375 		spin_lock(&cpu_base->softirq_expiry_lock);
 1376 		raw_spin_lock_irq(&cpu_base->lock);
 1377 	}
 1378 }
 1379 
 1380 /*
 1381  * This function is called on PREEMPT_RT kernels when the fast path
 1382  * deletion of a timer failed because the timer callback function was
 1383  * running.
 1384  *
 1385  * This prevents priority inversion: if the soft irq thread is preempted
 1386  * in the middle of a timer callback, then calling del_timer_sync() can
 1387  * lead to two issues:
 1388  *
 1389  *  - If the caller is on a remote CPU then it has to spin wait for the timer
 1390  *    handler to complete. This can result in unbound priority inversion.
 1391  *
 1392  *  - If the caller originates from the task which preempted the timer
 1393  *    handler on the same CPU, then spin waiting for the timer handler to
 1394  *    complete is never going to end.
 1395  */
 1396 void hrtimer_cancel_wait_running(const struct hrtimer *timer)
 1397 {
 1398 	/* Lockless read. Prevent the compiler from reloading it below */
 1399 	struct hrtimer_clock_base *base = READ_ONCE(timer->base);
 1400 
 1401 	/*
 1402 	 * Just relax if the timer expires in hard interrupt context or if
 1403 	 * it is currently on the migration base.
 1404 	 */
 1405 	if (!timer->is_soft || is_migration_base(base)) {
 1406 		cpu_relax();
 1407 		return;
 1408 	}
 1409 
 1410 	/*
 1411 	 * Mark the base as contended and grab the expiry lock, which is
 1412 	 * held by the softirq across the timer callback. Drop the lock
 1413 	 * immediately so the softirq can expire the next timer. In theory
 1414 	 * the timer could already be running again, but that's more than
 1415 	 * unlikely and just causes another wait loop.
 1416 	 */
 1417 	atomic_inc(&base->cpu_base->timer_waiters);
 1418 	spin_lock_bh(&base->cpu_base->softirq_expiry_lock);
 1419 	atomic_dec(&base->cpu_base->timer_waiters);
 1420 	spin_unlock_bh(&base->cpu_base->softirq_expiry_lock);
 1421 }
 1422 #else
 1423 static inline void
 1424 hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base) { }
 1425 static inline void
 1426 hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base) { }
 1427 static inline void
 1428 hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base) { }
 1429 static inline void hrtimer_sync_wait_running(struct hrtimer_cpu_base *base,
 1430 					     unsigned long flags) { }
 1431 #endif
 1432 
 1433 /**
 1434  * hrtimer_cancel - cancel a timer and wait for the handler to finish.
 1435  * @timer:	the timer to be cancelled
 1436  *
 1437  * Returns:
 1438  *  0 when the timer was not active
 1439  *  1 when the timer was active
 1440  */
 1441 int hrtimer_cancel(struct hrtimer *timer)
 1442 {
 1443 	int ret;
 1444 
 1445 	do {
 1446 		ret = hrtimer_try_to_cancel(timer);
 1447 
 1448 		if (ret < 0)
 1449 			hrtimer_cancel_wait_running(timer);
 1450 	} while (ret < 0);
 1451 	return ret;
 1452 }
 1453 EXPORT_SYMBOL_GPL(hrtimer_cancel);
 1454 
 1455 /**
 1456  * __hrtimer_get_remaining - get remaining time for the timer
 1457  * @timer:	the timer to read
 1458  * @adjust:	adjust relative timers when CONFIG_TIME_LOW_RES=y
 1459  */
 1460 ktime_t __hrtimer_get_remaining(const struct hrtimer *timer, bool adjust)
 1461 {
 1462 	unsigned long flags;
 1463 	ktime_t rem;
 1464 
 1465 	lock_hrtimer_base(timer, &flags);
 1466 	if (IS_ENABLED(CONFIG_TIME_LOW_RES) && adjust)
 1467 		rem = hrtimer_expires_remaining_adjusted(timer);
 1468 	else
 1469 		rem = hrtimer_expires_remaining(timer);
 1470 	unlock_hrtimer_base(timer, &flags);
 1471 
 1472 	return rem;
 1473 }
 1474 EXPORT_SYMBOL_GPL(__hrtimer_get_remaining);
 1475 
 1476 #ifdef CONFIG_NO_HZ_COMMON
 1477 /**
 1478  * hrtimer_get_next_event - get the time until next expiry event
 1479  *
 1480  * Returns the next expiry time or KTIME_MAX if no timer is pending.
 1481  */
 1482 u64 hrtimer_get_next_event(void)
 1483 {
 1484 	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
 1485 	u64 expires = KTIME_MAX;
 1486 	unsigned long flags;
 1487 
 1488 	raw_spin_lock_irqsave(&cpu_base->lock, flags);
 1489 
 1490 	if (!__hrtimer_hres_active(cpu_base))
 1491 		expires = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL);
 1492 
 1493 	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 1494 
 1495 	return expires;
 1496 }
 1497 
 1498 /**
 1499  * hrtimer_next_event_without - time until next expiry event w/o one timer
 1500  * @exclude:	timer to exclude
 1501  *
 1502  * Returns the next expiry time over all timers except for the @exclude one or
 1503  * KTIME_MAX if none of them is pending.
 1504  */
 1505 u64 hrtimer_next_event_without(const struct hrtimer *exclude)
 1506 {
 1507 	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
 1508 	u64 expires = KTIME_MAX;
 1509 	unsigned long flags;
 1510 
 1511 	raw_spin_lock_irqsave(&cpu_base->lock, flags);
 1512 
 1513 	if (__hrtimer_hres_active(cpu_base)) {
 1514 		unsigned int active;
 1515 
 1516 		if (!cpu_base->softirq_activated) {
 1517 			active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
 1518 			expires = __hrtimer_next_event_base(cpu_base, exclude,
 1519 							    active, KTIME_MAX);
 1520 		}
 1521 		active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
 1522 		expires = __hrtimer_next_event_base(cpu_base, exclude, active,
 1523 						    expires);
 1524 	}
 1525 
 1526 	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 1527 
 1528 	return expires;
 1529 }
 1530 #endif
 1531 
 1532 static inline int hrtimer_clockid_to_base(clockid_t clock_id)
 1533 {
 1534 	if (likely(clock_id < MAX_CLOCKS)) {
 1535 		int base = hrtimer_clock_to_base_table[clock_id];
 1536 
 1537 		if (likely(base != HRTIMER_MAX_CLOCK_BASES))
 1538 			return base;
 1539 	}
 1540 	WARN(1, "Invalid clockid %d. Using MONOTONIC\n", clock_id);
 1541 	return HRTIMER_BASE_MONOTONIC;
 1542 }
 1543 
 1544 static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 1545 			   enum hrtimer_mode mode)
 1546 {
 1547 	bool softtimer = !!(mode & HRTIMER_MODE_SOFT);
 1548 	struct hrtimer_cpu_base *cpu_base;
 1549 	int base;
 1550 
 1551 	/*
 1552 	 * On PREEMPT_RT enabled kernels hrtimers which are not explicitly
 1553 	 * marked for hard interrupt expiry mode are moved into soft
 1554 	 * interrupt context for latency reasons and because the callbacks
 1555 	 * can invoke functions which might sleep on RT, e.g. spin_lock().
 1556 	 */
 1557 	if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(mode & HRTIMER_MODE_HARD))
 1558 		softtimer = true;
 1559 
 1560 	memset(timer, 0, sizeof(struct hrtimer));
 1561 
 1562 	cpu_base = raw_cpu_ptr(&hrtimer_bases);
 1563 
 1564 	/*
 1565 	 * POSIX magic: Relative CLOCK_REALTIME timers are not affected by
 1566 	 * clock modifications, so they needs to become CLOCK_MONOTONIC to
 1567 	 * ensure POSIX compliance.
 1568 	 */
 1569 	if (clock_id == CLOCK_REALTIME && mode & HRTIMER_MODE_REL)
 1570 		clock_id = CLOCK_MONOTONIC;
 1571 
 1572 	base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
 1573 	base += hrtimer_clockid_to_base(clock_id);
 1574 	timer->is_soft = softtimer;
 1575 	timer->is_hard = !!(mode & HRTIMER_MODE_HARD);
 1576 	timer->base = &cpu_base->clock_base[base];
 1577 	timerqueue_init(&timer->node);
 1578 }
 1579 
 1580 /**
 1581  * hrtimer_init - initialize a timer to the given clock
 1582  * @timer:	the timer to be initialized
 1583  * @clock_id:	the clock to be used
 1584  * @mode:       The modes which are relevant for initialization:
 1585  *              HRTIMER_MODE_ABS, HRTIMER_MODE_REL, HRTIMER_MODE_ABS_SOFT,
 1586  *              HRTIMER_MODE_REL_SOFT
 1587  *
 1588  *              The PINNED variants of the above can be handed in,
 1589  *              but the PINNED bit is ignored as pinning happens
 1590  *              when the hrtimer is started
 1591  */
 1592 void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 1593 		  enum hrtimer_mode mode)
 1594 {
 1595 	debug_init(timer, clock_id, mode);
 1596 	__hrtimer_init(timer, clock_id, mode);
 1597 }
 1598 EXPORT_SYMBOL_GPL(hrtimer_init);
 1599 
 1600 /*
 1601  * A timer is active, when it is enqueued into the rbtree or the
 1602  * callback function is running or it's in the state of being migrated
 1603  * to another cpu.
 1604  *
 1605  * It is important for this function to not return a false negative.
 1606  */
 1607 bool hrtimer_active(const struct hrtimer *timer)
 1608 {
 1609 	struct hrtimer_clock_base *base;
 1610 	unsigned int seq;
 1611 
 1612 	do {
 1613 		base = READ_ONCE(timer->base);
 1614 		seq = raw_read_seqcount_begin(&base->seq);
 1615 
 1616 		if (timer->state != HRTIMER_STATE_INACTIVE ||
 1617 		    base->running == timer)
 1618 			return true;
 1619 
 1620 	} while (read_seqcount_retry(&base->seq, seq) ||
 1621 		 base != READ_ONCE(timer->base));
 1622 
 1623 	return false;
 1624 }
 1625 EXPORT_SYMBOL_GPL(hrtimer_active);
 1626 
 1627 /*
 1628  * The write_seqcount_barrier()s in __run_hrtimer() split the thing into 3
 1629  * distinct sections:
 1630  *
 1631  *  - queued:	the timer is queued
 1632  *  - callback:	the timer is being ran
 1633  *  - post:	the timer is inactive or (re)queued
 1634  *
 1635  * On the read side we ensure we observe timer->state and cpu_base->running
 1636  * from the same section, if anything changed while we looked at it, we retry.
 1637  * This includes timer->base changing because sequence numbers alone are
 1638  * insufficient for that.
 1639  *
 1640  * The sequence numbers are required because otherwise we could still observe
 1641  * a false negative if the read side got smeared over multiple consecutive
 1642  * __run_hrtimer() invocations.
 1643  */
 1644 
 1645 static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
 1646 			  struct hrtimer_clock_base *base,
 1647 			  struct hrtimer *timer, ktime_t *now,
 1648 			  unsigned long flags) __must_hold(&cpu_base->lock)
 1649 {
 1650 	enum hrtimer_restart (*fn)(struct hrtimer *);
 1651 	bool expires_in_hardirq;
 1652 	int restart;
 1653 
 1654 	lockdep_assert_held(&cpu_base->lock);
 1655 
 1656 	debug_deactivate(timer);
 1657 	base->running = timer;
 1658 
 1659 	/*
 1660 	 * Separate the ->running assignment from the ->state assignment.
 1661 	 *
 1662 	 * As with a regular write barrier, this ensures the read side in
 1663 	 * hrtimer_active() cannot observe base->running == NULL &&
 1664 	 * timer->state == INACTIVE.
 1665 	 */
 1666 	raw_write_seqcount_barrier(&base->seq);
 1667 
 1668 	__remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
 1669 	fn = timer->function;
 1670 
 1671 	/*
 1672 	 * Clear the 'is relative' flag for the TIME_LOW_RES case. If the
 1673 	 * timer is restarted with a period then it becomes an absolute
 1674 	 * timer. If its not restarted it does not matter.
 1675 	 */
 1676 	if (IS_ENABLED(CONFIG_TIME_LOW_RES))
 1677 		timer->is_rel = false;
 1678 
 1679 	/*
 1680 	 * The timer is marked as running in the CPU base, so it is
 1681 	 * protected against migration to a different CPU even if the lock
 1682 	 * is dropped.
 1683 	 */
 1684 	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 1685 	trace_hrtimer_expire_entry(timer, now);
 1686 	expires_in_hardirq = lockdep_hrtimer_enter(timer);
 1687 
 1688 	restart = fn(timer);
 1689 
 1690 	lockdep_hrtimer_exit(expires_in_hardirq);
 1691 	trace_hrtimer_expire_exit(timer);
 1692 	raw_spin_lock_irq(&cpu_base->lock);
 1693 
 1694 	/*
 1695 	 * Note: We clear the running state after enqueue_hrtimer and
 1696 	 * we do not reprogram the event hardware. Happens either in
 1697 	 * hrtimer_start_range_ns() or in hrtimer_interrupt()
 1698 	 *
 1699 	 * Note: Because we dropped the cpu_base->lock above,
 1700 	 * hrtimer_start_range_ns() can have popped in and enqueued the timer
 1701 	 * for us already.
 1702 	 */
 1703 	if (restart != HRTIMER_NORESTART &&
 1704 	    !(timer->state & HRTIMER_STATE_ENQUEUED))
 1705 		enqueue_hrtimer(timer, base, HRTIMER_MODE_ABS);
 1706 
 1707 	/*
 1708 	 * Separate the ->running assignment from the ->state assignment.
 1709 	 *
 1710 	 * As with a regular write barrier, this ensures the read side in
 1711 	 * hrtimer_active() cannot observe base->running.timer == NULL &&
 1712 	 * timer->state == INACTIVE.
 1713 	 */
 1714 	raw_write_seqcount_barrier(&base->seq);
 1715 
 1716 	WARN_ON_ONCE(base->running != timer);
 1717 	base->running = NULL;
 1718 }
 1719 
 1720 static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
 1721 				 unsigned long flags, unsigned int active_mask)
 1722 {
 1723 	struct hrtimer_clock_base *base;
 1724 	unsigned int active = cpu_base->active_bases & active_mask;
 1725 
 1726 	for_each_active_base(base, cpu_base, active) {
 1727 		struct timerqueue_node *node;
 1728 		ktime_t basenow;
 1729 
 1730 		basenow = ktime_add(now, base->offset);
 1731 
 1732 		while ((node = timerqueue_getnext(&base->active))) {
 1733 			struct hrtimer *timer;
 1734 
 1735 			timer = container_of(node, struct hrtimer, node);
 1736 
 1737 			/*
 1738 			 * The immediate goal for using the softexpires is
 1739 			 * minimizing wakeups, not running timers at the
 1740 			 * earliest interrupt after their soft expiration.
 1741 			 * This allows us to avoid using a Priority Search
 1742 			 * Tree, which can answer a stabbing query for
 1743 			 * overlapping intervals and instead use the simple
 1744 			 * BST we already have.
 1745 			 * We don't add extra wakeups by delaying timers that
 1746 			 * are right-of a not yet expired timer, because that
 1747 			 * timer will have to trigger a wakeup anyway.
 1748 			 */
 1749 			if (basenow < hrtimer_get_softexpires_tv64(timer))
 1750 				break;
 1751 
 1752 			__run_hrtimer(cpu_base, base, timer, &basenow, flags);
 1753 			if (active_mask == HRTIMER_ACTIVE_SOFT)
 1754 				hrtimer_sync_wait_running(cpu_base, flags);
 1755 		}
 1756 	}
 1757 }
 1758 
 1759 static __latent_entropy void hrtimer_run_softirq(struct softirq_action *h)
 1760 {
 1761 	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
 1762 	unsigned long flags;
 1763 	ktime_t now;
 1764 
 1765 	hrtimer_cpu_base_lock_expiry(cpu_base);
 1766 	raw_spin_lock_irqsave(&cpu_base->lock, flags);
 1767 
 1768 	now = hrtimer_update_base(cpu_base);
 1769 	__hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_SOFT);
 1770 
 1771 	cpu_base->softirq_activated = 0;
 1772 	hrtimer_update_softirq_timer(cpu_base, true);
 1773 
 1774 	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 1775 	hrtimer_cpu_base_unlock_expiry(cpu_base);
 1776 }
 1777 
 1778 #ifdef CONFIG_HIGH_RES_TIMERS
 1779 
 1780 /*
 1781  * High resolution timer interrupt
 1782  * Called with interrupts disabled
 1783  */
 1784 void hrtimer_interrupt(struct clock_event_device *dev)
 1785 {
 1786 	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
 1787 	ktime_t expires_next, now, entry_time, delta;
 1788 	unsigned long flags;
 1789 	int retries = 0;
 1790 
 1791 	BUG_ON(!cpu_base->hres_active);
 1792 	cpu_base->nr_events++;
 1793 	dev->next_event = KTIME_MAX;
 1794 
 1795 	raw_spin_lock_irqsave(&cpu_base->lock, flags);
 1796 	entry_time = now = hrtimer_update_base(cpu_base);
 1797 retry:
 1798 	cpu_base->in_hrtirq = 1;
 1799 	/*
 1800 	 * We set expires_next to KTIME_MAX here with cpu_base->lock
 1801 	 * held to prevent that a timer is enqueued in our queue via
 1802 	 * the migration code. This does not affect enqueueing of
 1803 	 * timers which run their callback and need to be requeued on
 1804 	 * this CPU.
 1805 	 */
 1806 	cpu_base->expires_next = KTIME_MAX;
 1807 
 1808 	if (!ktime_before(now, cpu_base->softirq_expires_next)) {
 1809 		cpu_base->softirq_expires_next = KTIME_MAX;
 1810 		cpu_base->softirq_activated = 1;
 1811 		raise_softirq_irqoff(HRTIMER_SOFTIRQ);
 1812 	}
 1813 
 1814 	__hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
 1815 
 1816 	/* Reevaluate the clock bases for the [soft] next expiry */
 1817 	expires_next = hrtimer_update_next_event(cpu_base);
 1818 	/*
 1819 	 * Store the new expiry value so the migration code can verify
 1820 	 * against it.
 1821 	 */
 1822 	cpu_base->expires_next = expires_next;
 1823 	cpu_base->in_hrtirq = 0;
 1824 	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 1825 
 1826 	/* Reprogramming necessary ? */
 1827 	if (!tick_program_event(expires_next, 0)) {
 1828 		cpu_base->hang_detected = 0;
 1829 		return;
 1830 	}
 1831 
 1832 	/*
 1833 	 * The next timer was already expired due to:
 1834 	 * - tracing
 1835 	 * - long lasting callbacks
 1836 	 * - being scheduled away when running in a VM
 1837 	 *
 1838 	 * We need to prevent that we loop forever in the hrtimer
 1839 	 * interrupt routine. We give it 3 attempts to avoid
 1840 	 * overreacting on some spurious event.
 1841 	 *
 1842 	 * Acquire base lock for updating the offsets and retrieving
 1843 	 * the current time.
 1844 	 */
 1845 	raw_spin_lock_irqsave(&cpu_base->lock, flags);
 1846 	now = hrtimer_update_base(cpu_base);
 1847 	cpu_base->nr_retries++;
 1848 	if (++retries < 3)
 1849 		goto retry;
 1850 	/*
 1851 	 * Give the system a chance to do something else than looping
 1852 	 * here. We stored the entry time, so we know exactly how long
 1853 	 * we spent here. We schedule the next event this amount of
 1854 	 * time away.
 1855 	 */
 1856 	cpu_base->nr_hangs++;
 1857 	cpu_base->hang_detected = 1;
 1858 	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 1859 
 1860 	delta = ktime_sub(now, entry_time);
 1861 	if ((unsigned int)delta > cpu_base->max_hang_time)
 1862 		cpu_base->max_hang_time = (unsigned int) delta;
 1863 	/*
 1864 	 * Limit it to a sensible value as we enforce a longer
 1865 	 * delay. Give the CPU at least 100ms to catch up.
 1866 	 */
 1867 	if (delta > 100 * NSEC_PER_MSEC)
 1868 		expires_next = ktime_add_ns(now, 100 * NSEC_PER_MSEC);
 1869 	else
 1870 		expires_next = ktime_add(now, delta);
 1871 	tick_program_event(expires_next, 1);
 1872 	pr_warn_once("hrtimer: interrupt took %llu ns\n", ktime_to_ns(delta));
 1873 }
 1874 
 1875 /* called with interrupts disabled */
 1876 static inline void __hrtimer_peek_ahead_timers(void)
 1877 {
 1878 	struct tick_device *td;
 1879 
 1880 	if (!hrtimer_hres_active())
 1881 		return;
 1882 
 1883 	td = this_cpu_ptr(&tick_cpu_device);
 1884 	if (td && td->evtdev)
 1885 		hrtimer_interrupt(td->evtdev);
 1886 }
 1887 
 1888 #else /* CONFIG_HIGH_RES_TIMERS */
 1889 
 1890 static inline void __hrtimer_peek_ahead_timers(void) { }
 1891 
 1892 #endif	/* !CONFIG_HIGH_RES_TIMERS */
 1893 
 1894 /*
 1895  * Called from run_local_timers in hardirq context every jiffy
 1896  */
 1897 void hrtimer_run_queues(void)
 1898 {
 1899 	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
 1900 	unsigned long flags;
 1901 	ktime_t now;
 1902 
 1903 	if (__hrtimer_hres_active(cpu_base))
 1904 		return;
 1905 
 1906 	/*
 1907 	 * This _is_ ugly: We have to check periodically, whether we
 1908 	 * can switch to highres and / or nohz mode. The clocksource
 1909 	 * switch happens with xtime_lock held. Notification from
 1910 	 * there only sets the check bit in the tick_oneshot code,
 1911 	 * otherwise we might deadlock vs. xtime_lock.
 1912 	 */
 1913 	if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())) {
 1914 		hrtimer_switch_to_hres();
 1915 		return;
 1916 	}
 1917 
 1918 	raw_spin_lock_irqsave(&cpu_base->lock, flags);
 1919 	now = hrtimer_update_base(cpu_base);
 1920 
 1921 	if (!ktime_before(now, cpu_base->softirq_expires_next)) {
 1922 		cpu_base->softirq_expires_next = KTIME_MAX;
 1923 		cpu_base->softirq_activated = 1;
 1924 		raise_softirq_irqoff(HRTIMER_SOFTIRQ);
 1925 	}
 1926 
 1927 	__hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
 1928 	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 1929 }
 1930 
 1931 /*
 1932  * Sleep related functions:
 1933  */
 1934 static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
 1935 {
 1936 	struct hrtimer_sleeper *t =
 1937 		container_of(timer, struct hrtimer_sleeper, timer);
 1938 	struct task_struct *task = t->task;
 1939 
 1940 	t->task = NULL;
 1941 	if (task)
 1942 		wake_up_process(task);
 1943 
 1944 	return HRTIMER_NORESTART;
 1945 }
 1946 
 1947 /**
 1948  * hrtimer_sleeper_start_expires - Start a hrtimer sleeper timer
 1949  * @sl:		sleeper to be started
 1950  * @mode:	timer mode abs/rel
 1951  *
 1952  * Wrapper around hrtimer_start_expires() for hrtimer_sleeper based timers
 1953  * to allow PREEMPT_RT to tweak the delivery mode (soft/hardirq context)
 1954  */
 1955 void hrtimer_sleeper_start_expires(struct hrtimer_sleeper *sl,
 1956 				   enum hrtimer_mode mode)
 1957 {
 1958 	/*
 1959 	 * Make the enqueue delivery mode check work on RT. If the sleeper
 1960 	 * was initialized for hard interrupt delivery, force the mode bit.
 1961 	 * This is a special case for hrtimer_sleepers because
 1962 	 * hrtimer_init_sleeper() determines the delivery mode on RT so the
 1963 	 * fiddling with this decision is avoided at the call sites.
 1964 	 */
 1965 	if (IS_ENABLED(CONFIG_PREEMPT_RT) && sl->timer.is_hard)
 1966 		mode |= HRTIMER_MODE_HARD;
 1967 
 1968 	hrtimer_start_expires(&sl->timer, mode);
 1969 }
 1970 EXPORT_SYMBOL_GPL(hrtimer_sleeper_start_expires);
 1971 
 1972 static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
 1973 				   clockid_t clock_id, enum hrtimer_mode mode)
 1974 {
 1975 	/*
 1976 	 * On PREEMPT_RT enabled kernels hrtimers which are not explicitly
 1977 	 * marked for hard interrupt expiry mode are moved into soft
 1978 	 * interrupt context either for latency reasons or because the
 1979 	 * hrtimer callback takes regular spinlocks or invokes other
 1980 	 * functions which are not suitable for hard interrupt context on
 1981 	 * PREEMPT_RT.
 1982 	 *
 1983 	 * The hrtimer_sleeper callback is RT compatible in hard interrupt
 1984 	 * context, but there is a latency concern: Untrusted userspace can
 1985 	 * spawn many threads which arm timers for the same expiry time on
 1986 	 * the same CPU. That causes a latency spike due to the wakeup of
 1987 	 * a gazillion threads.
 1988 	 *
 1989 	 * OTOH, privileged real-time user space applications rely on the
 1990 	 * low latency of hard interrupt wakeups. If the current task is in
 1991 	 * a real-time scheduling class, mark the mode for hard interrupt
 1992 	 * expiry.
 1993 	 */
 1994 	if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
 1995 		if (task_is_realtime(current) && !(mode & HRTIMER_MODE_SOFT))
 1996 			mode |= HRTIMER_MODE_HARD;
 1997 	}
 1998 
 1999 	__hrtimer_init(&sl->timer, clock_id, mode);
 2000 	sl->timer.function = hrtimer_wakeup;
 2001 	sl->task = current;
 2002 }
 2003 
 2004 /**
 2005  * hrtimer_init_sleeper - initialize sleeper to the given clock
 2006  * @sl:		sleeper to be initialized
 2007  * @clock_id:	the clock to be used
 2008  * @mode:	timer mode abs/rel
 2009  */
 2010 void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, clockid_t clock_id,
 2011 			  enum hrtimer_mode mode)
 2012 {
 2013 	debug_init(&sl->timer, clock_id, mode);
 2014 	__hrtimer_init_sleeper(sl, clock_id, mode);
 2015 
 2016 }
 2017 EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);
 2018 
 2019 int nanosleep_copyout(struct restart_block *restart, struct timespec64 *ts)
 2020 {
 2021 	switch(restart->nanosleep.type) {
 2022 #ifdef CONFIG_COMPAT_32BIT_TIME
 2023 	case TT_COMPAT:
 2024 		if (put_old_timespec32(ts, restart->nanosleep.compat_rmtp))
 2025 			return -EFAULT;
 2026 		break;
 2027 #endif
 2028 	case TT_NATIVE:
 2029 		if (put_timespec64(ts, restart->nanosleep.rmtp))
 2030 			return -EFAULT;
 2031 		break;
 2032 	default:
 2033 		BUG();
 2034 	}
 2035 	return -ERESTART_RESTARTBLOCK;
 2036 }
 2037 
 2038 static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
 2039 {
 2040 	struct restart_block *restart;
 2041 
 2042 	do {
 2043 		set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
 2044 		hrtimer_sleeper_start_expires(t, mode);
 2045 
 2046 		if (likely(t->task))
 2047 			schedule();
 2048 
 2049 		hrtimer_cancel(&t->timer);
 2050 		mode = HRTIMER_MODE_ABS;
 2051 
 2052 	} while (t->task && !signal_pending(current));
 2053 
 2054 	__set_current_state(TASK_RUNNING);
 2055 
 2056 	if (!t->task)
 2057 		return 0;
 2058 
 2059 	restart = &current->restart_block;
 2060 	if (restart->nanosleep.type != TT_NONE) {
 2061 		ktime_t rem = hrtimer_expires_remaining(&t->timer);
 2062 		struct timespec64 rmt;
 2063 
 2064 		if (rem <= 0)
 2065 			return 0;
 2066 		rmt = ktime_to_timespec64(rem);
 2067 
 2068 		return nanosleep_copyout(restart, &rmt);
 2069 	}
 2070 	return -ERESTART_RESTARTBLOCK;
 2071 }
 2072 
 2073 static long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
 2074 {
 2075 	struct hrtimer_sleeper t;
 2076 	int ret;
 2077 
 2078 	hrtimer_init_sleeper_on_stack(&t, restart->nanosleep.clockid,
 2079 				      HRTIMER_MODE_ABS);
 2080 	hrtimer_set_expires_tv64(&t.timer, restart->nanosleep.expires);
 2081 	ret = do_nanosleep(&t, HRTIMER_MODE_ABS);
 2082 	destroy_hrtimer_on_stack(&t.timer);
 2083 	return ret;
 2084 }
 2085 
 2086 long hrtimer_nanosleep(ktime_t rqtp, const enum hrtimer_mode mode,
 2087 		       const clockid_t clockid)
 2088 {
 2089 	struct restart_block *restart;
 2090 	struct hrtimer_sleeper t;
 2091 	int ret = 0;
 2092 	u64 slack;
 2093 
 2094 	slack = current->timer_slack_ns;
 2095 	if (rt_task(current))
 2096 		slack = 0;
 2097 
 2098 	hrtimer_init_sleeper_on_stack(&t, clockid, mode);
 2099 	hrtimer_set_expires_range_ns(&t.timer, rqtp, slack);
 2100 	ret = do_nanosleep(&t, mode);
 2101 	if (ret != -ERESTART_RESTARTBLOCK)
 2102 		goto out;
 2103 
 2104 	/* Absolute timers do not update the rmtp value and restart: */
 2105 	if (mode == HRTIMER_MODE_ABS) {
 2106 		ret = -ERESTARTNOHAND;
 2107 		goto out;
 2108 	}
 2109 
 2110 	restart = &current->restart_block;
 2111 	restart->nanosleep.clockid = t.timer.base->clockid;
 2112 	restart->nanosleep.expires = hrtimer_get_expires_tv64(&t.timer);
 2113 	set_restart_fn(restart, hrtimer_nanosleep_restart);
 2114 out:
 2115 	destroy_hrtimer_on_stack(&t.timer);
 2116 	return ret;
 2117 }
 2118 
 2119 #ifdef CONFIG_64BIT
 2120 
 2121 SYSCALL_DEFINE2(nanosleep, struct __kernel_timespec __user *, rqtp,
 2122 		struct __kernel_timespec __user *, rmtp)
 2123 {
 2124 	struct timespec64 tu;
 2125 
 2126 	if (get_timespec64(&tu, rqtp))
 2127 		return -EFAULT;
 2128 
 2129 	if (!timespec64_valid(&tu))
 2130 		return -EINVAL;
 2131 
 2132 	current->restart_block.fn = do_no_restart_syscall;
 2133 	current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;
 2134 	current->restart_block.nanosleep.rmtp = rmtp;
 2135 	return hrtimer_nanosleep(timespec64_to_ktime(tu), HRTIMER_MODE_REL,
 2136 				 CLOCK_MONOTONIC);
 2137 }
 2138 
 2139 #endif
 2140 
 2141 #ifdef CONFIG_COMPAT_32BIT_TIME
 2142 
 2143 SYSCALL_DEFINE2(nanosleep_time32, struct old_timespec32 __user *, rqtp,
 2144 		       struct old_timespec32 __user *, rmtp)
 2145 {
 2146 	struct timespec64 tu;
 2147 
 2148 	if (get_old_timespec32(&tu, rqtp))
 2149 		return -EFAULT;
 2150 
 2151 	if (!timespec64_valid(&tu))
 2152 		return -EINVAL;
 2153 
 2154 	current->restart_block.fn = do_no_restart_syscall;
 2155 	current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
 2156 	current->restart_block.nanosleep.compat_rmtp = rmtp;
 2157 	return hrtimer_nanosleep(timespec64_to_ktime(tu), HRTIMER_MODE_REL,
 2158 				 CLOCK_MONOTONIC);
 2159 }
 2160 #endif
 2161 
 2162 /*
 2163  * Functions related to boot-time initialization:
 2164  */
 2165 int hrtimers_prepare_cpu(unsigned int cpu)
 2166 {
 2167 	struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
 2168 	int i;
 2169 
 2170 	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
 2171 		struct hrtimer_clock_base *clock_b = &cpu_base->clock_base[i];
 2172 
 2173 		clock_b->cpu_base = cpu_base;
 2174 		seqcount_raw_spinlock_init(&clock_b->seq, &cpu_base->lock);
 2175 		timerqueue_init_head(&clock_b->active);
 2176 	}
 2177 
 2178 	cpu_base->cpu = cpu;
 2179 	cpu_base->active_bases = 0;
 2180 	cpu_base->hres_active = 0;
 2181 	cpu_base->hang_detected = 0;
 2182 	cpu_base->next_timer = NULL;
 2183 	cpu_base->softirq_next_timer = NULL;
 2184 	cpu_base->expires_next = KTIME_MAX;
 2185 	cpu_base->softirq_expires_next = KTIME_MAX;
 2186 	hrtimer_cpu_base_init_expiry_lock(cpu_base);
 2187 	return 0;
 2188 }
 2189 
 2190 #ifdef CONFIG_HOTPLUG_CPU
 2191 
 2192 static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
 2193 				struct hrtimer_clock_base *new_base)
 2194 {
 2195 	struct hrtimer *timer;
 2196 	struct timerqueue_node *node;
 2197 
 2198 	while ((node = timerqueue_getnext(&old_base->active))) {
 2199 		timer = container_of(node, struct hrtimer, node);
 2200 		BUG_ON(hrtimer_callback_running(timer));
 2201 		debug_deactivate(timer);
 2202 
 2203 		/*
 2204 		 * Mark it as ENQUEUED not INACTIVE otherwise the
 2205 		 * timer could be seen as !active and just vanish away
 2206 		 * under us on another CPU
 2207 		 */
 2208 		__remove_hrtimer(timer, old_base, HRTIMER_STATE_ENQUEUED, 0);
 2209 		timer->base = new_base;
 2210 		/*
 2211 		 * Enqueue the timers on the new cpu. This does not
 2212 		 * reprogram the event device in case the timer
 2213 		 * expires before the earliest on this CPU, but we run
 2214 		 * hrtimer_interrupt after we migrated everything to
 2215 		 * sort out already expired timers and reprogram the
 2216 		 * event device.
 2217 		 */
 2218 		enqueue_hrtimer(timer, new_base, HRTIMER_MODE_ABS);
 2219 	}
 2220 }
 2221 
 2222 int hrtimers_dead_cpu(unsigned int scpu)
 2223 {
 2224 	struct hrtimer_cpu_base *old_base, *new_base;
 2225 	int i;
 2226 
 2227 	BUG_ON(cpu_online(scpu));
 2228 	tick_cancel_sched_timer(scpu);
 2229 
 2230 	/*
 2231 	 * this BH disable ensures that raise_softirq_irqoff() does
 2232 	 * not wakeup ksoftirqd (and acquire the pi-lock) while
 2233 	 * holding the cpu_base lock
 2234 	 */
 2235 	local_bh_disable();
 2236 	local_irq_disable();
 2237 	old_base = &per_cpu(hrtimer_bases, scpu);
 2238 	new_base = this_cpu_ptr(&hrtimer_bases);
 2239 	/*
 2240 	 * The caller is globally serialized and nobody else
 2241 	 * takes two locks at once, deadlock is not possible.
 2242 	 */
 2243 	raw_spin_lock(&new_base->lock);
 2244 	raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
 2245 
 2246 	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
 2247 		migrate_hrtimer_list(&old_base->clock_base[i],
 2248 				     &new_base->clock_base[i]);
 2249 	}
 2250 
 2251 	/*
 2252 	 * The migration might have changed the first expiring softirq
 2253 	 * timer on this CPU. Update it.
 2254 	 */
 2255 	hrtimer_update_softirq_timer(new_base, false);
 2256 
 2257 	raw_spin_unlock(&old_base->lock);
 2258 	raw_spin_unlock(&new_base->lock);
 2259 
 2260 	/* Check, if we got expired work to do */
 2261 	__hrtimer_peek_ahead_timers();
 2262 	local_irq_enable();
 2263 	local_bh_enable();
 2264 	return 0;
 2265 }
 2266 
 2267 #endif /* CONFIG_HOTPLUG_CPU */
 2268 
 2269 void __init hrtimers_init(void)
 2270 {
 2271 	hrtimers_prepare_cpu(smp_processor_id());
 2272 	open_softirq(HRTIMER_SOFTIRQ, hrtimer_run_softirq);
 2273 }
 2274 
 2275 /**
 2276  * schedule_hrtimeout_range_clock - sleep until timeout
 2277  * @expires:	timeout value (ktime_t)
 2278  * @delta:	slack in expires timeout (ktime_t) for SCHED_OTHER tasks
 2279  * @mode:	timer mode
 2280  * @clock_id:	timer clock to be used
 2281  */
 2282 int __sched
 2283 schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta,
 2284 			       const enum hrtimer_mode mode, clockid_t clock_id)
 2285 {
 2286 	struct hrtimer_sleeper t;
 2287 
 2288 	/*
 2289 	 * Optimize when a zero timeout value is given. It does not
 2290 	 * matter whether this is an absolute or a relative time.
 2291 	 */
 2292 	if (expires && *expires == 0) {
 2293 		__set_current_state(TASK_RUNNING);
 2294 		return 0;
 2295 	}
 2296 
 2297 	/*
 2298 	 * A NULL parameter means "infinite"
 2299 	 */
 2300 	if (!expires) {
 2301 		schedule();
 2302 		return -EINTR;
 2303 	}
 2304 
 2305 	/*
 2306 	 * Override any slack passed by the user if under
 2307 	 * rt contraints.
 2308 	 */
 2309 	if (rt_task(current))
 2310 		delta = 0;
 2311 
 2312 	hrtimer_init_sleeper_on_stack(&t, clock_id, mode);
 2313 	hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
 2314 	hrtimer_sleeper_start_expires(&t, mode);
 2315 
 2316 	if (likely(t.task))
 2317 		schedule();
 2318 
 2319 	hrtimer_cancel(&t.timer);
 2320 	destroy_hrtimer_on_stack(&t.timer);
 2321 
 2322 	__set_current_state(TASK_RUNNING);
 2323 
 2324 	return !t.task ? 0 : -EINTR;
 2325 }
 2326 EXPORT_SYMBOL_GPL(schedule_hrtimeout_range_clock);
 2327 
 2328 /**
 2329  * schedule_hrtimeout_range - sleep until timeout
 2330  * @expires:	timeout value (ktime_t)
 2331  * @delta:	slack in expires timeout (ktime_t) for SCHED_OTHER tasks
 2332  * @mode:	timer mode
 2333  *
 2334  * Make the current task sleep until the given expiry time has
 2335  * elapsed. The routine will return immediately unless
 2336  * the current task state has been set (see set_current_state()).
 2337  *
 2338  * The @delta argument gives the kernel the freedom to schedule the
 2339  * actual wakeup to a time that is both power and performance friendly
 2340  * for regular (non RT/DL) tasks.
 2341  * The kernel give the normal best effort behavior for "@expires+@delta",
 2342  * but may decide to fire the timer earlier, but no earlier than @expires.
 2343  *
 2344  * You can set the task state as follows -
 2345  *
 2346  * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
 2347  * pass before the routine returns unless the current task is explicitly
 2348  * woken up, (e.g. by wake_up_process()).
 2349  *
 2350  * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
 2351  * delivered to the current task or the current task is explicitly woken
 2352  * up.
 2353  *
 2354  * The current task state is guaranteed to be TASK_RUNNING when this
 2355  * routine returns.
 2356  *
 2357  * Returns 0 when the timer has expired. If the task was woken before the
 2358  * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
 2359  * by an explicit wakeup, it returns -EINTR.
 2360  */
 2361 int __sched schedule_hrtimeout_range(ktime_t *expires, u64 delta,
 2362 				     const enum hrtimer_mode mode)
 2363 {
 2364 	return schedule_hrtimeout_range_clock(expires, delta, mode,
 2365 					      CLOCK_MONOTONIC);
 2366 }
 2367 EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);
 2368 
 2369 /**
 2370  * schedule_hrtimeout - sleep until timeout
 2371  * @expires:	timeout value (ktime_t)
 2372  * @mode:	timer mode
 2373  *
 2374  * Make the current task sleep until the given expiry time has
 2375  * elapsed. The routine will return immediately unless
 2376  * the current task state has been set (see set_current_state()).
 2377  *
 2378  * You can set the task state as follows -
 2379  *
 2380  * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
 2381  * pass before the routine returns unless the current task is explicitly
 2382  * woken up, (e.g. by wake_up_process()).
 2383  *
 2384  * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
 2385  * delivered to the current task or the current task is explicitly woken
 2386  * up.
 2387  *
 2388  * The current task state is guaranteed to be TASK_RUNNING when this
 2389  * routine returns.
 2390  *
 2391  * Returns 0 when the timer has expired. If the task was woken before the
 2392  * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
 2393  * by an explicit wakeup, it returns -EINTR.
 2394  */
 2395 int __sched schedule_hrtimeout(ktime_t *expires,
 2396 			       const enum hrtimer_mode mode)
 2397 {
 2398 	return schedule_hrtimeout_range(expires, 0, mode);
 2399 }
 2400 EXPORT_SYMBOL_GPL(schedule_hrtimeout);