TOMOYO Linux Cross Reference
Linux/kernel/time/hrtimer.c

   // SPDX-License-Identifier: GPL-2.0
   /*
    *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
    *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
    *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner
    *
    *  High-resolution kernel timers
    *
    *  In contrast to the low-resolution timeout API, aka timer wheel,
   *  hrtimers provide finer resolution and accuracy depending on system
   *  configuration and capabilities.
   *
   *  Started by: Thomas Gleixner and Ingo Molnar
   *
   *  Credits:
   *      Based on the original timer wheel code
   *
   *      Help, testing, suggestions, bugfixes, improvements were
   *      provided by:
   *
   *      George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
   *      et. al.
   */
  
  #include <linux/cpu.h>
  #include <linux/export.h>
  #include <linux/percpu.h>
  #include <linux/hrtimer.h>
  #include <linux/notifier.h>
  #include <linux/syscalls.h>
  #include <linux/interrupt.h>
  #include <linux/tick.h>
  #include <linux/err.h>
  #include <linux/debugobjects.h>
  #include <linux/sched/signal.h>
  #include <linux/sched/sysctl.h>
  #include <linux/sched/rt.h>
  #include <linux/sched/deadline.h>
  #include <linux/sched/nohz.h>
  #include <linux/sched/debug.h>
  #include <linux/sched/isolation.h>
  #include <linux/timer.h>
  #include <linux/freezer.h>
  #include <linux/compat.h>
  
  #include <linux/uaccess.h>
  
  #include <trace/events/timer.h>
  
  #include "tick-internal.h"
  
  /*
   * Masks for selecting the soft and hard context timers from
   * cpu_base->active
   */
  #define MASK_SHIFT              (HRTIMER_BASE_MONOTONIC_SOFT)
  #define HRTIMER_ACTIVE_HARD     ((1U << MASK_SHIFT) - 1)
  #define HRTIMER_ACTIVE_SOFT     (HRTIMER_ACTIVE_HARD << MASK_SHIFT)
  #define HRTIMER_ACTIVE_ALL      (HRTIMER_ACTIVE_SOFT | HRTIMER_ACTIVE_HARD)
  
  /*
   * The timer bases:
   *
   * There are more clockids than hrtimer bases. Thus, we index
   * into the timer bases by the hrtimer_base_type enum. When trying
   * to reach a base using a clockid, hrtimer_clockid_to_base()
   * is used to convert from clockid to the proper hrtimer_base_type.
   */
  DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
  {
          .lock = __RAW_SPIN_LOCK_UNLOCKED(hrtimer_bases.lock),
          .clock_base =
          {
                  {
                          .index = HRTIMER_BASE_MONOTONIC,
                          .clockid = CLOCK_MONOTONIC,
                          .get_time = &ktime_get,
                  },
                  {
                          .index = HRTIMER_BASE_REALTIME,
                          .clockid = CLOCK_REALTIME,
                          .get_time = &ktime_get_real,
                  },
                  {
                          .index = HRTIMER_BASE_BOOTTIME,
                          .clockid = CLOCK_BOOTTIME,
                          .get_time = &ktime_get_boottime,
                  },
                  {
                          .index = HRTIMER_BASE_TAI,
                          .clockid = CLOCK_TAI,
                          .get_time = &ktime_get_clocktai,
                  },
                  {
                          .index = HRTIMER_BASE_MONOTONIC_SOFT,
                          .clockid = CLOCK_MONOTONIC,
                          .get_time = &ktime_get,
                  },
                  {
                         .index = HRTIMER_BASE_REALTIME_SOFT,
                         .clockid = CLOCK_REALTIME,
                         .get_time = &ktime_get_real,
                 },
                 {
                         .index = HRTIMER_BASE_BOOTTIME_SOFT,
                         .clockid = CLOCK_BOOTTIME,
                         .get_time = &ktime_get_boottime,
                 },
                 {
                         .index = HRTIMER_BASE_TAI_SOFT,
                         .clockid = CLOCK_TAI,
                         .get_time = &ktime_get_clocktai,
                 },
         }
 };
 
 static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
         /* Make sure we catch unsupported clockids */
         [0 ... MAX_CLOCKS - 1]  = HRTIMER_MAX_CLOCK_BASES,
 
         [CLOCK_REALTIME]        = HRTIMER_BASE_REALTIME,
         [CLOCK_MONOTONIC]       = HRTIMER_BASE_MONOTONIC,
         [CLOCK_BOOTTIME]        = HRTIMER_BASE_BOOTTIME,
         [CLOCK_TAI]             = HRTIMER_BASE_TAI,
 };
 
 /*
  * Functions and macros which are different for UP/SMP systems are kept in a
  * single place
  */
 #ifdef CONFIG_SMP
 
 /*
  * We require the migration_base for lock_hrtimer_base()/switch_hrtimer_base()
  * such that hrtimer_callback_running() can unconditionally dereference
  * timer->base->cpu_base
  */
 static struct hrtimer_cpu_base migration_cpu_base = {
         .clock_base = { {
                 .cpu_base = &migration_cpu_base,
                 .seq      = SEQCNT_RAW_SPINLOCK_ZERO(migration_cpu_base.seq,
                                                      &migration_cpu_base.lock),
         }, },
 };
 
 #define migration_base  migration_cpu_base.clock_base[0]
 
 static inline bool is_migration_base(struct hrtimer_clock_base *base)
 {
         return base == &migration_base;
 }
 
 /*
  * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
  * means that all timers which are tied to this base via timer->base are
  * locked, and the base itself is locked too.
  *
  * So __run_timers/migrate_timers can safely modify all timers which could
  * be found on the lists/queues.
  *
  * When the timer's base is locked, and the timer removed from list, it is
  * possible to set timer->base = &migration_base and drop the lock: the timer
  * remains locked.
  */
 static
 struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
                                              unsigned long *flags)
         __acquires(&timer->base->lock)
 {
         struct hrtimer_clock_base *base;
 
         for (;;) {
                 base = READ_ONCE(timer->base);
                 if (likely(base != &migration_base)) {
                         raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
                         if (likely(base == timer->base))
                                 return base;
                         /* The timer has migrated to another CPU: */
                         raw_spin_unlock_irqrestore(&base->cpu_base->lock, *flags);
                 }
                 cpu_relax();
         }
 }
 
 /*
  * We do not migrate the timer when it is expiring before the next
  * event on the target cpu. When high resolution is enabled, we cannot
  * reprogram the target cpu hardware and we would cause it to fire
  * late. To keep it simple, we handle the high resolution enabled and
  * disabled case similar.
  *
  * Called with cpu_base->lock of target cpu held.
  */
 static int
 hrtimer_check_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base)
 {
         ktime_t expires;
 
         expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset);
         return expires < new_base->cpu_base->expires_next;
 }
 
 static inline
 struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
                                          int pinned)
 {
 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
         if (static_branch_likely(&timers_migration_enabled) && !pinned)
                 return &per_cpu(hrtimer_bases, get_nohz_timer_target());
 #endif
         return base;
 }
 
 /*
  * We switch the timer base to a power-optimized selected CPU target,
  * if:
  *      - NO_HZ_COMMON is enabled
  *      - timer migration is enabled
  *      - the timer callback is not running
  *      - the timer is not the first expiring timer on the new target
  *
  * If one of the above requirements is not fulfilled we move the timer
  * to the current CPU or leave it on the previously assigned CPU if
  * the timer callback is currently running.
  */
 static inline struct hrtimer_clock_base *
 switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
                     int pinned)
 {
         struct hrtimer_cpu_base *new_cpu_base, *this_cpu_base;
         struct hrtimer_clock_base *new_base;
         int basenum = base->index;
 
         this_cpu_base = this_cpu_ptr(&hrtimer_bases);
         new_cpu_base = get_target_base(this_cpu_base, pinned);
 again:
         new_base = &new_cpu_base->clock_base[basenum];
 
         if (base != new_base) {
                 /*
                  * We are trying to move timer to new_base.
                  * However we can't change timer's base while it is running,
                  * so we keep it on the same CPU. No hassle vs. reprogramming
                  * the event source in the high resolution case. The softirq
                  * code will take care of this when the timer function has
                  * completed. There is no conflict as we hold the lock until
                  * the timer is enqueued.
                  */
                 if (unlikely(hrtimer_callback_running(timer)))
                         return base;
 
                 /* See the comment in lock_hrtimer_base() */
                 WRITE_ONCE(timer->base, &migration_base);
                 raw_spin_unlock(&base->cpu_base->lock);
                 raw_spin_lock(&new_base->cpu_base->lock);
 
                 if (new_cpu_base != this_cpu_base &&
                     hrtimer_check_target(timer, new_base)) {
                         raw_spin_unlock(&new_base->cpu_base->lock);
                         raw_spin_lock(&base->cpu_base->lock);
                         new_cpu_base = this_cpu_base;
                         WRITE_ONCE(timer->base, base);
                         goto again;
                 }
                 WRITE_ONCE(timer->base, new_base);
         } else {
                 if (new_cpu_base != this_cpu_base &&
                     hrtimer_check_target(timer, new_base)) {
                         new_cpu_base = this_cpu_base;
                         goto again;
                 }
         }
         return new_base;
 }
 
 #else /* CONFIG_SMP */
 
 static inline bool is_migration_base(struct hrtimer_clock_base *base)
 {
         return false;
 }
 
 static inline struct hrtimer_clock_base *
 lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
         __acquires(&timer->base->cpu_base->lock)
 {
         struct hrtimer_clock_base *base = timer->base;
 
         raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
 
         return base;
 }
 
 # define switch_hrtimer_base(t, b, p)   (b)
 
 #endif  /* !CONFIG_SMP */
 
 /*
  * Functions for the union type storage format of ktime_t which are
  * too large for inlining:
  */
 #if BITS_PER_LONG < 64
 /*
  * Divide a ktime value by a nanosecond value
  */
 s64 __ktime_divns(const ktime_t kt, s64 div)
 {
         int sft = 0;
         s64 dclc;
         u64 tmp;
 
         dclc = ktime_to_ns(kt);
         tmp = dclc < 0 ? -dclc : dclc;
 
         /* Make sure the divisor is less than 2^32: */
         while (div >> 32) {
                 sft++;
                 div >>= 1;
         }
         tmp >>= sft;
         do_div(tmp, (u32) div);
         return dclc < 0 ? -tmp : tmp;
 }
 EXPORT_SYMBOL_GPL(__ktime_divns);
 #endif /* BITS_PER_LONG >= 64 */
 
 /*
  * Add two ktime values and do a safety check for overflow:
  */
 ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
 {
         ktime_t res = ktime_add_unsafe(lhs, rhs);
 
         /*
          * We use KTIME_SEC_MAX here, the maximum timeout which we can
          * return to user space in a timespec:
          */
         if (res < 0 || res < lhs || res < rhs)
                 res = ktime_set(KTIME_SEC_MAX, 0);
 
         return res;
 }
 
 EXPORT_SYMBOL_GPL(ktime_add_safe);
 
 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
 
 static const struct debug_obj_descr hrtimer_debug_descr;
 
 static void *hrtimer_debug_hint(void *addr)
 {
         return ((struct hrtimer *) addr)->function;
 }
 
 /*
  * fixup_init is called when:
  * - an active object is initialized
  */
 static bool hrtimer_fixup_init(void *addr, enum debug_obj_state state)
 {
         struct hrtimer *timer = addr;
 
         switch (state) {
         case ODEBUG_STATE_ACTIVE:
                 hrtimer_cancel(timer);
                 debug_object_init(timer, &hrtimer_debug_descr);
                 return true;
         default:
                 return false;
         }
 }
 
 /*
  * fixup_activate is called when:
  * - an active object is activated
  * - an unknown non-static object is activated
  */
 static bool hrtimer_fixup_activate(void *addr, enum debug_obj_state state)
 {
         switch (state) {
         case ODEBUG_STATE_ACTIVE:
                 WARN_ON(1);
                 fallthrough;
         default:
                 return false;
         }
 }
 
 /*
  * fixup_free is called when:
  * - an active object is freed
  */
 static bool hrtimer_fixup_free(void *addr, enum debug_obj_state state)
 {
         struct hrtimer *timer = addr;
 
         switch (state) {
         case ODEBUG_STATE_ACTIVE:
                 hrtimer_cancel(timer);
                 debug_object_free(timer, &hrtimer_debug_descr);
                 return true;
         default:
                 return false;
         }
 }
 
 static const struct debug_obj_descr hrtimer_debug_descr = {
         .name           = "hrtimer",
         .debug_hint     = hrtimer_debug_hint,
         .fixup_init     = hrtimer_fixup_init,
         .fixup_activate = hrtimer_fixup_activate,
         .fixup_free     = hrtimer_fixup_free,
 };
 
 static inline void debug_hrtimer_init(struct hrtimer *timer)
 {
         debug_object_init(timer, &hrtimer_debug_descr);
 }
 
 static inline void debug_hrtimer_activate(struct hrtimer *timer,
                                           enum hrtimer_mode mode)
 {
         debug_object_activate(timer, &hrtimer_debug_descr);
 }
 
 static inline void debug_hrtimer_deactivate(struct hrtimer *timer)
 {
         debug_object_deactivate(timer, &hrtimer_debug_descr);
 }
 
 static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
                            enum hrtimer_mode mode);
 
 void hrtimer_init_on_stack(struct hrtimer *timer, clockid_t clock_id,
                            enum hrtimer_mode mode)
 {
         debug_object_init_on_stack(timer, &hrtimer_debug_descr);
         __hrtimer_init(timer, clock_id, mode);
 }
 EXPORT_SYMBOL_GPL(hrtimer_init_on_stack);
 
 static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
                                    clockid_t clock_id, enum hrtimer_mode mode);
 
 void hrtimer_init_sleeper_on_stack(struct hrtimer_sleeper *sl,
                                    clockid_t clock_id, enum hrtimer_mode mode)
 {
         debug_object_init_on_stack(&sl->timer, &hrtimer_debug_descr);
         __hrtimer_init_sleeper(sl, clock_id, mode);
 }
 EXPORT_SYMBOL_GPL(hrtimer_init_sleeper_on_stack);
 
 void destroy_hrtimer_on_stack(struct hrtimer *timer)
 {
         debug_object_free(timer, &hrtimer_debug_descr);
 }
 EXPORT_SYMBOL_GPL(destroy_hrtimer_on_stack);
 
 #else
 
 static inline void debug_hrtimer_init(struct hrtimer *timer) { }
 static inline void debug_hrtimer_activate(struct hrtimer *timer,
                                           enum hrtimer_mode mode) { }
 static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
 #endif
 
 static inline void
 debug_init(struct hrtimer *timer, clockid_t clockid,
            enum hrtimer_mode mode)
 {
         debug_hrtimer_init(timer);
         trace_hrtimer_init(timer, clockid, mode);
 }
 
 static inline void debug_activate(struct hrtimer *timer,
                                   enum hrtimer_mode mode)
 {
         debug_hrtimer_activate(timer, mode);
         trace_hrtimer_start(timer, mode);
 }
 
 static inline void debug_deactivate(struct hrtimer *timer)
 {
         debug_hrtimer_deactivate(timer);
         trace_hrtimer_cancel(timer);
 }
 
 static struct hrtimer_clock_base *
 __next_base(struct hrtimer_cpu_base *cpu_base, unsigned int *active)
 {
         unsigned int idx;
 
         if (!*active)
                 return NULL;
 
         idx = __ffs(*active);
         *active &= ~(1U << idx);
 
         return &cpu_base->clock_base[idx];
 }
 
 #define for_each_active_base(base, cpu_base, active)    \
         while ((base = __next_base((cpu_base), &(active))))
 
 static ktime_t __hrtimer_next_event_base(struct hrtimer_cpu_base *cpu_base,
                                          const struct hrtimer *exclude,
                                          unsigned int active,
                                          ktime_t expires_next)
 {
         struct hrtimer_clock_base *base;
         ktime_t expires;
 
         for_each_active_base(base, cpu_base, active) {
                 struct timerqueue_node *next;
                 struct hrtimer *timer;
 
                 next = timerqueue_getnext(&base->active);
                 timer = container_of(next, struct hrtimer, node);
                 if (timer == exclude) {
                         /* Get to the next timer in the queue. */
                         next = timerqueue_iterate_next(next);
                         if (!next)
                                 continue;
 
                         timer = container_of(next, struct hrtimer, node);
                 }
                 expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
                 if (expires < expires_next) {
                         expires_next = expires;
 
                         /* Skip cpu_base update if a timer is being excluded. */
                         if (exclude)
                                 continue;
 
                         if (timer->is_soft)
                                 cpu_base->softirq_next_timer = timer;
                         else
                                 cpu_base->next_timer = timer;
                 }
         }
         /*
          * clock_was_set() might have changed base->offset of any of
          * the clock bases so the result might be negative. Fix it up
          * to prevent a false positive in clockevents_program_event().
          */
         if (expires_next < 0)
                 expires_next = 0;
         return expires_next;
 }
 
 /*
  * Recomputes cpu_base::*next_timer and returns the earliest expires_next
  * but does not set cpu_base::*expires_next, that is done by
  * hrtimer[_force]_reprogram and hrtimer_interrupt only. When updating
  * cpu_base::*expires_next right away, reprogramming logic would no longer
  * work.
  *
  * When a softirq is pending, we can ignore the HRTIMER_ACTIVE_SOFT bases,
  * those timers will get run whenever the softirq gets handled, at the end of
  * hrtimer_run_softirq(), hrtimer_update_softirq_timer() will re-add these bases.
  *
  * Therefore softirq values are those from the HRTIMER_ACTIVE_SOFT clock bases.
  * The !softirq values are the minima across HRTIMER_ACTIVE_ALL, unless an actual
  * softirq is pending, in which case they're the minima of HRTIMER_ACTIVE_HARD.
  *
  * @active_mask must be one of:
  *  - HRTIMER_ACTIVE_ALL,
  *  - HRTIMER_ACTIVE_SOFT, or
  *  - HRTIMER_ACTIVE_HARD.
  */
 static ktime_t
 __hrtimer_get_next_event(struct hrtimer_cpu_base *cpu_base, unsigned int active_mask)
 {
         unsigned int active;
         struct hrtimer *next_timer = NULL;
         ktime_t expires_next = KTIME_MAX;
 
         if (!cpu_base->softirq_activated && (active_mask & HRTIMER_ACTIVE_SOFT)) {
                 active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
                 cpu_base->softirq_next_timer = NULL;
                 expires_next = __hrtimer_next_event_base(cpu_base, NULL,
                                                          active, KTIME_MAX);
 
                 next_timer = cpu_base->softirq_next_timer;
         }
 
         if (active_mask & HRTIMER_ACTIVE_HARD) {
                 active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
                 cpu_base->next_timer = next_timer;
                 expires_next = __hrtimer_next_event_base(cpu_base, NULL, active,
                                                          expires_next);
         }
 
         return expires_next;
 }
 
 static ktime_t hrtimer_update_next_event(struct hrtimer_cpu_base *cpu_base)
 {
         ktime_t expires_next, soft = KTIME_MAX;
 
         /*
          * If the soft interrupt has already been activated, ignore the
          * soft bases. They will be handled in the already raised soft
          * interrupt.
          */
         if (!cpu_base->softirq_activated) {
                 soft = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
                 /*
                  * Update the soft expiry time. clock_settime() might have
                  * affected it.
                  */
                 cpu_base->softirq_expires_next = soft;
         }
 
         expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_HARD);
         /*
          * If a softirq timer is expiring first, update cpu_base->next_timer
          * and program the hardware with the soft expiry time.
          */
         if (expires_next > soft) {
                 cpu_base->next_timer = cpu_base->softirq_next_timer;
                 expires_next = soft;
         }
 
         return expires_next;
 }
 
 static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
 {
         ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
         ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
         ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
 
         ktime_t now = ktime_get_update_offsets_now(&base->clock_was_set_seq,
                                             offs_real, offs_boot, offs_tai);
 
         base->clock_base[HRTIMER_BASE_REALTIME_SOFT].offset = *offs_real;
         base->clock_base[HRTIMER_BASE_BOOTTIME_SOFT].offset = *offs_boot;
         base->clock_base[HRTIMER_BASE_TAI_SOFT].offset = *offs_tai;
 
         return now;
 }
 
 /*
  * Is the high resolution mode active ?
  */
 static inline int hrtimer_hres_active(struct hrtimer_cpu_base *cpu_base)
 {
         return IS_ENABLED(CONFIG_HIGH_RES_TIMERS) ?
                 cpu_base->hres_active : 0;
 }
 
 static void __hrtimer_reprogram(struct hrtimer_cpu_base *cpu_base,
                                 struct hrtimer *next_timer,
                                 ktime_t expires_next)
 {
         cpu_base->expires_next = expires_next;
 
         /*
          * If hres is not active, hardware does not have to be
          * reprogrammed yet.
          *
          * If a hang was detected in the last timer interrupt then we
          * leave the hang delay active in the hardware. We want the
          * system to make progress. That also prevents the following
          * scenario:
          * T1 expires 50ms from now
          * T2 expires 5s from now
          *
          * T1 is removed, so this code is called and would reprogram
          * the hardware to 5s from now. Any hrtimer_start after that
          * will not reprogram the hardware due to hang_detected being
          * set. So we'd effectively block all timers until the T2 event
          * fires.
          */
         if (!hrtimer_hres_active(cpu_base) || cpu_base->hang_detected)
                 return;
 
         tick_program_event(expires_next, 1);
 }
 
 /*
  * Reprogram the event source with checking both queues for the
  * next event
  * Called with interrupts disabled and base->lock held
  */
 static void
 hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
 {
         ktime_t expires_next;
 
         expires_next = hrtimer_update_next_event(cpu_base);
 
         if (skip_equal && expires_next == cpu_base->expires_next)
                 return;
 
         __hrtimer_reprogram(cpu_base, cpu_base->next_timer, expires_next);
 }
 
 /* High resolution timer related functions */
 #ifdef CONFIG_HIGH_RES_TIMERS
 
 /*
  * High resolution timer enabled ?
  */
 static bool hrtimer_hres_enabled __read_mostly  = true;
 unsigned int hrtimer_resolution __read_mostly = LOW_RES_NSEC;
 EXPORT_SYMBOL_GPL(hrtimer_resolution);
 
 /*
  * Enable / Disable high resolution mode
  */
 static int __init setup_hrtimer_hres(char *str)
 {
         return (kstrtobool(str, &hrtimer_hres_enabled) == 0);
 }
 
 __setup("highres=", setup_hrtimer_hres);
 
 /*
  * hrtimer_high_res_enabled - query, if the highres mode is enabled
  */
 static inline int hrtimer_is_hres_enabled(void)
 {
         return hrtimer_hres_enabled;
 }
 
 static void retrigger_next_event(void *arg);
 
 /*
  * Switch to high resolution mode
  */
 static void hrtimer_switch_to_hres(void)
 {
         struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
 
         if (tick_init_highres()) {
                 pr_warn("Could not switch to high resolution mode on CPU %u\n",
                         base->cpu);
                 return;
         }
         base->hres_active = 1;
         hrtimer_resolution = HIGH_RES_NSEC;
 
         tick_setup_sched_timer(true);
         /* "Retrigger" the interrupt to get things going */
         retrigger_next_event(NULL);
 }
 
 #else
 
 static inline int hrtimer_is_hres_enabled(void) { return 0; }
 static inline void hrtimer_switch_to_hres(void) { }
 
 #endif /* CONFIG_HIGH_RES_TIMERS */
 /*
  * Retrigger next event is called after clock was set with interrupts
  * disabled through an SMP function call or directly from low level
  * resume code.
  *
  * This is only invoked when:
  *      - CONFIG_HIGH_RES_TIMERS is enabled.
  *      - CONFIG_NOHZ_COMMON is enabled
  *
  * For the other cases this function is empty and because the call sites
  * are optimized out it vanishes as well, i.e. no need for lots of
  * #ifdeffery.
  */
 static void retrigger_next_event(void *arg)
 {
         struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
 
         /*
          * When high resolution mode or nohz is active, then the offsets of
          * CLOCK_REALTIME/TAI/BOOTTIME have to be updated. Otherwise the
          * next tick will take care of that.
          *
          * If high resolution mode is active then the next expiring timer
          * must be reevaluated and the clock event device reprogrammed if
          * necessary.
          *
          * In the NOHZ case the update of the offset and the reevaluation
          * of the next expiring timer is enough. The return from the SMP
          * function call will take care of the reprogramming in case the
          * CPU was in a NOHZ idle sleep.
          */
         if (!hrtimer_hres_active(base) && !tick_nohz_active)
                 return;
 
         raw_spin_lock(&base->lock);
         hrtimer_update_base(base);
         if (hrtimer_hres_active(base))
                 hrtimer_force_reprogram(base, 0);
         else
                 hrtimer_update_next_event(base);
         raw_spin_unlock(&base->lock);
 }
 
 /*
  * When a timer is enqueued and expires earlier than the already enqueued
  * timers, we have to check, whether it expires earlier than the timer for
  * which the clock event device was armed.
  *
  * Called with interrupts disabled and base->cpu_base.lock held
  */
 static void hrtimer_reprogram(struct hrtimer *timer, bool reprogram)
 {
         struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
         struct hrtimer_clock_base *base = timer->base;
         ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
 
         WARN_ON_ONCE(hrtimer_get_expires_tv64(timer) < 0);
 
         /*
          * CLOCK_REALTIME timer might be requested with an absolute
          * expiry time which is less than base->offset. Set it to 0.
          */
         if (expires < 0)
                 expires = 0;
 
         if (timer->is_soft) {
                 /*
                  * soft hrtimer could be started on a remote CPU. In this
                  * case softirq_expires_next needs to be updated on the
                  * remote CPU. The soft hrtimer will not expire before the
                  * first hard hrtimer on the remote CPU -
                  * hrtimer_check_target() prevents this case.
                  */
                 struct hrtimer_cpu_base *timer_cpu_base = base->cpu_base;
 
                 if (timer_cpu_base->softirq_activated)
                         return;
 
                 if (!ktime_before(expires, timer_cpu_base->softirq_expires_next))
                         return;
 
                 timer_cpu_base->softirq_next_timer = timer;
                 timer_cpu_base->softirq_expires_next = expires;
 
                 if (!ktime_before(expires, timer_cpu_base->expires_next) ||
                     !reprogram)
                         return;
         }
 
         /*
          * If the timer is not on the current cpu, we cannot reprogram
          * the other cpus clock event device.
          */
         if (base->cpu_base != cpu_base)
                 return;
 
         if (expires >= cpu_base->expires_next)
                 return;
 
         /*
          * If the hrtimer interrupt is running, then it will reevaluate the
          * clock bases and reprogram the clock event device.
          */
         if (cpu_base->in_hrtirq)
                 return;
 
         cpu_base->next_timer = timer;
 
         __hrtimer_reprogram(cpu_base, timer, expires);
 }
 
 static bool update_needs_ipi(struct hrtimer_cpu_base *cpu_base,
                              unsigned int active)
 {
         struct hrtimer_clock_base *base;
         unsigned int seq;
         ktime_t expires;
 
         /*
          * Update the base offsets unconditionally so the following
          * checks whether the SMP function call is required works.
          *
          * The update is safe even when the remote CPU is in the hrtimer
          * interrupt or the hrtimer soft interrupt and expiring affected
          * bases. Either it will see the update before handling a base or
          * it will see it when it finishes the processing and reevaluates
          * the next expiring timer.
          */
         seq = cpu_base->clock_was_set_seq;
         hrtimer_update_base(cpu_base);
 
         /*
          * If the sequence did not change over the update then the
          * remote CPU already handled it.
          */
         if (seq == cpu_base->clock_was_set_seq)
                 return false;
 
         /*
          * If the remote CPU is currently handling an hrtimer interrupt, it
          * will reevaluate the first expiring timer of all clock bases
          * before reprogramming. Nothing to do here.
          */
         if (cpu_base->in_hrtirq)
                 return false;
 
         /*
          * Walk the affected clock bases and check whether the first expiring
          * timer in a clock base is moving ahead of the first expiring timer of
          * @cpu_base. If so, the IPI must be invoked because per CPU clock
          * event devices cannot be remotely reprogrammed.
          */
         active &= cpu_base->active_bases;
 
         for_each_active_base(base, cpu_base, active) {
                 struct timerqueue_node *next;
 
                 next = timerqueue_getnext(&base->active);
                 expires = ktime_sub(next->expires, base->offset);
                 if (expires < cpu_base->expires_next)
                         return true;
 
                 /* Extra check for softirq clock bases */
                 if (base->clockid < HRTIMER_BASE_MONOTONIC_SOFT)
                         continue;
                 if (cpu_base->softirq_activated)
                         continue;
                 if (expires < cpu_base->softirq_expires_next)
                         return true;
         }
         return false;
 }
 
 /*
  * Clock was set. This might affect CLOCK_REALTIME, CLOCK_TAI and
  * CLOCK_BOOTTIME (for late sleep time injection).
  *
  * This requires to update the offsets for these clocks
  * vs. CLOCK_MONOTONIC. When high resolution timers are enabled, then this
  * also requires to eventually reprogram the per CPU clock event devices
  * when the change moves an affected timer ahead of the first expiring
  * timer on that CPU. Obviously remote per CPU clock event devices cannot
  * be reprogrammed. The other reason why an IPI has to be sent is when the
  * system is in !HIGH_RES and NOHZ mode. The NOHZ mode updates the offsets
  * in the tick, which obviously might be stopped, so this has to bring out
  * the remote CPU which might sleep in idle to get this sorted.
  */
 void clock_was_set(unsigned int bases)
 {
         struct hrtimer_cpu_base *cpu_base = raw_cpu_ptr(&hrtimer_bases);
         cpumask_var_t mask;
         int cpu;
 
         if (!hrtimer_hres_active(cpu_base) && !tick_nohz_active)
                 goto out_timerfd;
 
         if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) {
                 on_each_cpu(retrigger_next_event, NULL, 1);
                 goto out_timerfd;
         }
 
         /* Avoid interrupting CPUs if possible */
         cpus_read_lock();
         for_each_online_cpu(cpu) {
                 unsigned long flags;
 
                 cpu_base = &per_cpu(hrtimer_bases, cpu);
                 raw_spin_lock_irqsave(&cpu_base->lock, flags);
 
                 if (update_needs_ipi(cpu_base, bases))
                         cpumask_set_cpu(cpu, mask);
 
                 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
         }
 
         preempt_disable();
         smp_call_function_many(mask, retrigger_next_event, NULL, 1);
         preempt_enable();
         cpus_read_unlock();
         free_cpumask_var(mask);
 
 out_timerfd:
         timerfd_clock_was_set();
 }
 
 static void clock_was_set_work(struct work_struct *work)
 {
         clock_was_set(CLOCK_SET_WALL);
 }
 
 static DECLARE_WORK(hrtimer_work, clock_was_set_work);
 
 /*
  * Called from timekeeping code to reprogram the hrtimer interrupt device
  * on all cpus and to notify timerfd.
  */
 void clock_was_set_delayed(void)
 {
         schedule_work(&hrtimer_work);
 }
 
 /*
  * Called during resume either directly from via timekeeping_resume()
  * or in the case of s2idle from tick_unfreeze() to ensure that the
  * hrtimers are up to date.
  */
 void hrtimers_resume_local(void)
 {
         lockdep_assert_irqs_disabled();
         /* Retrigger on the local CPU */
         retrigger_next_event(NULL);
 }
 
 /*
  * Counterpart to lock_hrtimer_base above:
  */
 static inline
 void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
         __releases(&timer->base->cpu_base->lock)
 {
         raw_spin_unlock_irqrestore(&timer->base->cpu_base->lock, *flags);
 }
 
 /**
  * hrtimer_forward() - forward the timer expiry
  * @timer:      hrtimer to forward
  * @now:        forward past this time
  * @interval:   the interval to forward
  *
  * Forward the timer expiry so it will expire in the future.
  *
  * .. note::
  *  This only updates the timer expiry value and does not requeue the timer.
  *
  * There is also a variant of the function hrtimer_forward_now().
  *
  * Context: Can be safely called from the callback function of @timer. If called
  *          from other contexts @timer must neither be enqueued nor running the
  *          callback and the caller needs to take care of serialization.
  *
  * Return: The number of overruns are returned.
  */
 u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
 {
         u64 orun = 1;
         ktime_t delta;
 
         delta = ktime_sub(now, hrtimer_get_expires(timer));
 
         if (delta < 0)
                 return 0;
 
         if (WARN_ON(timer->state & HRTIMER_STATE_ENQUEUED))
                 return 0;
 
         if (interval < hrtimer_resolution)
                 interval = hrtimer_resolution;
 
         if (unlikely(delta >= interval)) {
                 s64 incr = ktime_to_ns(interval);
 
                 orun = ktime_divns(delta, incr);
                 hrtimer_add_expires_ns(timer, incr * orun);
                 if (hrtimer_get_expires_tv64(timer) > now)
                         return orun;
                 /*
                  * This (and the ktime_add() below) is the
                  * correction for exact:
                  */
                 orun++;
         }
         hrtimer_add_expires(timer, interval);
 
         return orun;
 }
 EXPORT_SYMBOL_GPL(hrtimer_forward);
 
 /*
  * enqueue_hrtimer - internal function to (re)start a timer
  *
  * The timer is inserted in expiry order. Insertion into the
  * red black tree is O(log(n)). Must hold the base lock.
  *
  * Returns 1 when the new timer is the leftmost timer in the tree.
  */
 static int enqueue_hrtimer(struct hrtimer *timer,
                            struct hrtimer_clock_base *base,
                            enum hrtimer_mode mode)
 {
         debug_activate(timer, mode);
         WARN_ON_ONCE(!base->cpu_base->online);
 
         base->cpu_base->active_bases |= 1 << base->index;
 
         /* Pairs with the lockless read in hrtimer_is_queued() */
         WRITE_ONCE(timer->state, HRTIMER_STATE_ENQUEUED);
 
         return timerqueue_add(&base->active, &timer->node);
 }
 
 /*
  * __remove_hrtimer - internal function to remove a timer
  *
  * Caller must hold the base lock.
  *
  * High resolution timer mode reprograms the clock event device when the
  * timer is the one which expires next. The caller can disable this by setting
  * reprogram to zero. This is useful, when the context does a reprogramming
  * anyway (e.g. timer interrupt)
  */
 static void __remove_hrtimer(struct hrtimer *timer,
                              struct hrtimer_clock_base *base,
                              u8 newstate, int reprogram)
 {
         struct hrtimer_cpu_base *cpu_base = base->cpu_base;
         u8 state = timer->state;
 
         /* Pairs with the lockless read in hrtimer_is_queued() */
         WRITE_ONCE(timer->state, newstate);
         if (!(state & HRTIMER_STATE_ENQUEUED))
                 return;
 
         if (!timerqueue_del(&base->active, &timer->node))
                 cpu_base->active_bases &= ~(1 << base->index);
 
         /*
          * Note: If reprogram is false we do not update
          * cpu_base->next_timer. This happens when we remove the first
          * timer on a remote cpu. No harm as we never dereference
          * cpu_base->next_timer. So the worst thing what can happen is
          * an superfluous call to hrtimer_force_reprogram() on the
          * remote cpu later on if the same timer gets enqueued again.
          */
         if (reprogram && timer == cpu_base->next_timer)
                 hrtimer_force_reprogram(cpu_base, 1);
 }
 
 /*
  * remove hrtimer, called with base lock held
  */
 static inline int
 remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base,
                bool restart, bool keep_local)
 {
         u8 state = timer->state;
 
         if (state & HRTIMER_STATE_ENQUEUED) {
                 bool reprogram;
 
                 /*
                  * Remove the timer and force reprogramming when high
                  * resolution mode is active and the timer is on the current
                  * CPU. If we remove a timer on another CPU, reprogramming is
                  * skipped. The interrupt event on this CPU is fired and
                  * reprogramming happens in the interrupt handler. This is a
                  * rare case and less expensive than a smp call.
                  */
                 debug_deactivate(timer);
                 reprogram = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
 
                 /*
                  * If the timer is not restarted then reprogramming is
                  * required if the timer is local. If it is local and about
                  * to be restarted, avoid programming it twice (on removal
                  * and a moment later when it's requeued).
                  */
                 if (!restart)
                         state = HRTIMER_STATE_INACTIVE;
                 else
                         reprogram &= !keep_local;
 
                 __remove_hrtimer(timer, base, state, reprogram);
                 return 1;
         }
         return 0;
 }
 
 static inline ktime_t hrtimer_update_lowres(struct hrtimer *timer, ktime_t tim,
                                             const enum hrtimer_mode mode)
 {
 #ifdef CONFIG_TIME_LOW_RES
         /*
          * CONFIG_TIME_LOW_RES indicates that the system has no way to return
          * granular time values. For relative timers we add hrtimer_resolution
          * (i.e. one jiffie) to prevent short timeouts.
          */
         timer->is_rel = mode & HRTIMER_MODE_REL;
         if (timer->is_rel)
                 tim = ktime_add_safe(tim, hrtimer_resolution);
 #endif
         return tim;
 }
 
 static void
 hrtimer_update_softirq_timer(struct hrtimer_cpu_base *cpu_base, bool reprogram)
 {
         ktime_t expires;
 
         /*
          * Find the next SOFT expiration.
          */
         expires = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
 
         /*
          * reprogramming needs to be triggered, even if the next soft
          * hrtimer expires at the same time than the next hard
          * hrtimer. cpu_base->softirq_expires_next needs to be updated!
          */
         if (expires == KTIME_MAX)
                 return;
 
         /*
          * cpu_base->*next_timer is recomputed by __hrtimer_get_next_event()
          * cpu_base->*expires_next is only set by hrtimer_reprogram()
          */
         hrtimer_reprogram(cpu_base->softirq_next_timer, reprogram);
 }
 
 static int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
                                     u64 delta_ns, const enum hrtimer_mode mode,
                                     struct hrtimer_clock_base *base)
 {
         struct hrtimer_clock_base *new_base;
         bool force_local, first;
 
         /*
          * If the timer is on the local cpu base and is the first expiring
          * timer then this might end up reprogramming the hardware twice
          * (on removal and on enqueue). To avoid that by prevent the
          * reprogram on removal, keep the timer local to the current CPU
          * and enforce reprogramming after it is queued no matter whether
          * it is the new first expiring timer again or not.
          */
         force_local = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
         force_local &= base->cpu_base->next_timer == timer;
 
         /*
          * Remove an active timer from the queue. In case it is not queued
          * on the current CPU, make sure that remove_hrtimer() updates the
          * remote data correctly.
          *
          * If it's on the current CPU and the first expiring timer, then
          * skip reprogramming, keep the timer local and enforce
          * reprogramming later if it was the first expiring timer.  This
          * avoids programming the underlying clock event twice (once at
          * removal and once after enqueue).
          */
         remove_hrtimer(timer, base, true, force_local);
 
         if (mode & HRTIMER_MODE_REL)
                 tim = ktime_add_safe(tim, base->get_time());
 
         tim = hrtimer_update_lowres(timer, tim, mode);
 
         hrtimer_set_expires_range_ns(timer, tim, delta_ns);
 
         /* Switch the timer base, if necessary: */
         if (!force_local) {
                 new_base = switch_hrtimer_base(timer, base,
                                                mode & HRTIMER_MODE_PINNED);
         } else {
                 new_base = base;
         }
 
         first = enqueue_hrtimer(timer, new_base, mode);
         if (!force_local)
                 return first;
 
         /*
          * Timer was forced to stay on the current CPU to avoid
          * reprogramming on removal and enqueue. Force reprogram the
          * hardware by evaluating the new first expiring timer.
          */
         hrtimer_force_reprogram(new_base->cpu_base, 1);
         return 0;
 }
 
 /**
  * hrtimer_start_range_ns - (re)start an hrtimer
  * @timer:      the timer to be added
  * @tim:        expiry time
  * @delta_ns:   "slack" range for the timer
  * @mode:       timer mode: absolute (HRTIMER_MODE_ABS) or
  *              relative (HRTIMER_MODE_REL), and pinned (HRTIMER_MODE_PINNED);
  *              softirq based mode is considered for debug purpose only!
  */
 void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
                             u64 delta_ns, const enum hrtimer_mode mode)
 {
         struct hrtimer_clock_base *base;
         unsigned long flags;
 
         if (WARN_ON_ONCE(!timer->function))
                 return;
         /*
          * Check whether the HRTIMER_MODE_SOFT bit and hrtimer.is_soft
          * match on CONFIG_PREEMPT_RT = n. With PREEMPT_RT check the hard
          * expiry mode because unmarked timers are moved to softirq expiry.
          */
         if (!IS_ENABLED(CONFIG_PREEMPT_RT))
                 WARN_ON_ONCE(!(mode & HRTIMER_MODE_SOFT) ^ !timer->is_soft);
         else
                 WARN_ON_ONCE(!(mode & HRTIMER_MODE_HARD) ^ !timer->is_hard);
 
         base = lock_hrtimer_base(timer, &flags);
 
         if (__hrtimer_start_range_ns(timer, tim, delta_ns, mode, base))
                 hrtimer_reprogram(timer, true);
 
         unlock_hrtimer_base(timer, &flags);
 }
 EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);
 
 /**
  * hrtimer_try_to_cancel - try to deactivate a timer
  * @timer:      hrtimer to stop
  *
  * Returns:
  *
  *  *  0 when the timer was not active
  *  *  1 when the timer was active
  *  * -1 when the timer is currently executing the callback function and
  *    cannot be stopped
  */
 int hrtimer_try_to_cancel(struct hrtimer *timer)
 {
         struct hrtimer_clock_base *base;
         unsigned long flags;
         int ret = -1;
 
         /*
          * Check lockless first. If the timer is not active (neither
          * enqueued nor running the callback, nothing to do here.  The
          * base lock does not serialize against a concurrent enqueue,
          * so we can avoid taking it.
          */
         if (!hrtimer_active(timer))
                 return 0;
 
         base = lock_hrtimer_base(timer, &flags);
 
         if (!hrtimer_callback_running(timer))
                 ret = remove_hrtimer(timer, base, false, false);
 
         unlock_hrtimer_base(timer, &flags);
 
         return ret;
 
 }
 EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);
 
 #ifdef CONFIG_PREEMPT_RT
 static void hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base)
 {
         spin_lock_init(&base->softirq_expiry_lock);
 }
 
 static void hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base)
 {
         spin_lock(&base->softirq_expiry_lock);
 }
 
 static void hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base)
 {
         spin_unlock(&base->softirq_expiry_lock);
 }
 
 /*
  * The counterpart to hrtimer_cancel_wait_running().
  *
  * If there is a waiter for cpu_base->expiry_lock, then it was waiting for
  * the timer callback to finish. Drop expiry_lock and reacquire it. That
  * allows the waiter to acquire the lock and make progress.
  */
 static void hrtimer_sync_wait_running(struct hrtimer_cpu_base *cpu_base,
                                       unsigned long flags)
 {
         if (atomic_read(&cpu_base->timer_waiters)) {
                 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
                 spin_unlock(&cpu_base->softirq_expiry_lock);
                 spin_lock(&cpu_base->softirq_expiry_lock);
                 raw_spin_lock_irq(&cpu_base->lock);
         }
 }
 
 /*
  * This function is called on PREEMPT_RT kernels when the fast path
  * deletion of a timer failed because the timer callback function was
  * running.
  *
  * This prevents priority inversion: if the soft irq thread is preempted
  * in the middle of a timer callback, then calling del_timer_sync() can
  * lead to two issues:
  *
  *  - If the caller is on a remote CPU then it has to spin wait for the timer
  *    handler to complete. This can result in unbound priority inversion.
  *
  *  - If the caller originates from the task which preempted the timer
  *    handler on the same CPU, then spin waiting for the timer handler to
  *    complete is never going to end.
  */
 void hrtimer_cancel_wait_running(const struct hrtimer *timer)
 {
         /* Lockless read. Prevent the compiler from reloading it below */
         struct hrtimer_clock_base *base = READ_ONCE(timer->base);
 
         /*
          * Just relax if the timer expires in hard interrupt context or if
          * it is currently on the migration base.
          */
         if (!timer->is_soft || is_migration_base(base)) {
                 cpu_relax();
                 return;
         }
 
         /*
          * Mark the base as contended and grab the expiry lock, which is
          * held by the softirq across the timer callback. Drop the lock
          * immediately so the softirq can expire the next timer. In theory
          * the timer could already be running again, but that's more than
          * unlikely and just causes another wait loop.
          */
         atomic_inc(&base->cpu_base->timer_waiters);
         spin_lock_bh(&base->cpu_base->softirq_expiry_lock);
         atomic_dec(&base->cpu_base->timer_waiters);
         spin_unlock_bh(&base->cpu_base->softirq_expiry_lock);
 }
 #else
 static inline void
 hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base) { }
 static inline void
 hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base) { }
 static inline void
 hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base) { }
 static inline void hrtimer_sync_wait_running(struct hrtimer_cpu_base *base,
                                              unsigned long flags) { }
 #endif
 
 /**
  * hrtimer_cancel - cancel a timer and wait for the handler to finish.
  * @timer:      the timer to be cancelled
  *
  * Returns:
  *  0 when the timer was not active
  *  1 when the timer was active
  */
 int hrtimer_cancel(struct hrtimer *timer)
 {
         int ret;
 
         do {
                 ret = hrtimer_try_to_cancel(timer);
 
                 if (ret < 0)
                         hrtimer_cancel_wait_running(timer);
         } while (ret < 0);
         return ret;
 }
 EXPORT_SYMBOL_GPL(hrtimer_cancel);
 
 /**
  * __hrtimer_get_remaining - get remaining time for the timer
  * @timer:      the timer to read
  * @adjust:     adjust relative timers when CONFIG_TIME_LOW_RES=y
  */
 ktime_t __hrtimer_get_remaining(const struct hrtimer *timer, bool adjust)
 {
         unsigned long flags;
         ktime_t rem;
 
         lock_hrtimer_base(timer, &flags);
         if (IS_ENABLED(CONFIG_TIME_LOW_RES) && adjust)
                 rem = hrtimer_expires_remaining_adjusted(timer);
         else
                 rem = hrtimer_expires_remaining(timer);
         unlock_hrtimer_base(timer, &flags);
 
         return rem;
 }
 EXPORT_SYMBOL_GPL(__hrtimer_get_remaining);
 
 #ifdef CONFIG_NO_HZ_COMMON
 /**
  * hrtimer_get_next_event - get the time until next expiry event
  *
  * Returns the next expiry time or KTIME_MAX if no timer is pending.
  */
 u64 hrtimer_get_next_event(void)
 {
         struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
         u64 expires = KTIME_MAX;
         unsigned long flags;
 
         raw_spin_lock_irqsave(&cpu_base->lock, flags);
 
         if (!hrtimer_hres_active(cpu_base))
                 expires = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL);
 
         raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 
         return expires;
 }
 
 /**
  * hrtimer_next_event_without - time until next expiry event w/o one timer
  * @exclude:    timer to exclude
  *
  * Returns the next expiry time over all timers except for the @exclude one or
  * KTIME_MAX if none of them is pending.
  */
 u64 hrtimer_next_event_without(const struct hrtimer *exclude)
 {
         struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
         u64 expires = KTIME_MAX;
         unsigned long flags;
 
         raw_spin_lock_irqsave(&cpu_base->lock, flags);
 
         if (hrtimer_hres_active(cpu_base)) {
                 unsigned int active;
 
                 if (!cpu_base->softirq_activated) {
                         active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
                         expires = __hrtimer_next_event_base(cpu_base, exclude,
                                                             active, KTIME_MAX);
                 }
                 active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
                 expires = __hrtimer_next_event_base(cpu_base, exclude, active,
                                                     expires);
         }
 
         raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 
         return expires;
 }
 #endif
 
 static inline int hrtimer_clockid_to_base(clockid_t clock_id)
 {
         if (likely(clock_id < MAX_CLOCKS)) {
                 int base = hrtimer_clock_to_base_table[clock_id];
 
                 if (likely(base != HRTIMER_MAX_CLOCK_BASES))
                         return base;
         }
         WARN(1, "Invalid clockid %d. Using MONOTONIC\n", clock_id);
         return HRTIMER_BASE_MONOTONIC;
 }
 
 static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
                            enum hrtimer_mode mode)
 {
         bool softtimer = !!(mode & HRTIMER_MODE_SOFT);
         struct hrtimer_cpu_base *cpu_base;
         int base;
 
         /*
          * On PREEMPT_RT enabled kernels hrtimers which are not explicitly
          * marked for hard interrupt expiry mode are moved into soft
          * interrupt context for latency reasons and because the callbacks
          * can invoke functions which might sleep on RT, e.g. spin_lock().
          */
         if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(mode & HRTIMER_MODE_HARD))
                 softtimer = true;
 
         memset(timer, 0, sizeof(struct hrtimer));
 
         cpu_base = raw_cpu_ptr(&hrtimer_bases);
 
         /*
          * POSIX magic: Relative CLOCK_REALTIME timers are not affected by
          * clock modifications, so they needs to become CLOCK_MONOTONIC to
          * ensure POSIX compliance.
          */
         if (clock_id == CLOCK_REALTIME && mode & HRTIMER_MODE_REL)
                 clock_id = CLOCK_MONOTONIC;
 
         base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
         base += hrtimer_clockid_to_base(clock_id);
         timer->is_soft = softtimer;
         timer->is_hard = !!(mode & HRTIMER_MODE_HARD);
         timer->base = &cpu_base->clock_base[base];
         timerqueue_init(&timer->node);
 }
 
 /**
  * hrtimer_init - initialize a timer to the given clock
  * @timer:      the timer to be initialized
  * @clock_id:   the clock to be used
  * @mode:       The modes which are relevant for initialization:
  *              HRTIMER_MODE_ABS, HRTIMER_MODE_REL, HRTIMER_MODE_ABS_SOFT,
  *              HRTIMER_MODE_REL_SOFT
  *
  *              The PINNED variants of the above can be handed in,
  *              but the PINNED bit is ignored as pinning happens
  *              when the hrtimer is started
  */
 void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
                   enum hrtimer_mode mode)
 {
         debug_init(timer, clock_id, mode);
         __hrtimer_init(timer, clock_id, mode);
 }
 EXPORT_SYMBOL_GPL(hrtimer_init);
 
 /*
  * A timer is active, when it is enqueued into the rbtree or the
  * callback function is running or it's in the state of being migrated
  * to another cpu.
  *
  * It is important for this function to not return a false negative.
  */
 bool hrtimer_active(const struct hrtimer *timer)
 {
         struct hrtimer_clock_base *base;
         unsigned int seq;
 
         do {
                 base = READ_ONCE(timer->base);
                 seq = raw_read_seqcount_begin(&base->seq);
 
                 if (timer->state != HRTIMER_STATE_INACTIVE ||
                     base->running == timer)
                         return true;
 
         } while (read_seqcount_retry(&base->seq, seq) ||
                  base != READ_ONCE(timer->base));
 
         return false;
 }
 EXPORT_SYMBOL_GPL(hrtimer_active);
 
 /*
  * The write_seqcount_barrier()s in __run_hrtimer() split the thing into 3
  * distinct sections:
  *
  *  - queued:   the timer is queued
  *  - callback: the timer is being ran
  *  - post:     the timer is inactive or (re)queued
  *
  * On the read side we ensure we observe timer->state and cpu_base->running
  * from the same section, if anything changed while we looked at it, we retry.
  * This includes timer->base changing because sequence numbers alone are
  * insufficient for that.
  *
  * The sequence numbers are required because otherwise we could still observe
  * a false negative if the read side got smeared over multiple consecutive
  * __run_hrtimer() invocations.
  */
 
 static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
                           struct hrtimer_clock_base *base,
                           struct hrtimer *timer, ktime_t *now,
                           unsigned long flags) __must_hold(&cpu_base->lock)
 {
         enum hrtimer_restart (*fn)(struct hrtimer *);
         bool expires_in_hardirq;
         int restart;
 
         lockdep_assert_held(&cpu_base->lock);
 
         debug_deactivate(timer);
         base->running = timer;
 
         /*
          * Separate the ->running assignment from the ->state assignment.
          *
          * As with a regular write barrier, this ensures the read side in
          * hrtimer_active() cannot observe base->running == NULL &&
          * timer->state == INACTIVE.
          */
         raw_write_seqcount_barrier(&base->seq);
 
         __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
         fn = timer->function;
 
         /*
          * Clear the 'is relative' flag for the TIME_LOW_RES case. If the
          * timer is restarted with a period then it becomes an absolute
          * timer. If its not restarted it does not matter.
          */
         if (IS_ENABLED(CONFIG_TIME_LOW_RES))
                 timer->is_rel = false;
 
         /*
          * The timer is marked as running in the CPU base, so it is
          * protected against migration to a different CPU even if the lock
          * is dropped.
          */
         raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
         trace_hrtimer_expire_entry(timer, now);
         expires_in_hardirq = lockdep_hrtimer_enter(timer);
 
         restart = fn(timer);
 
         lockdep_hrtimer_exit(expires_in_hardirq);
         trace_hrtimer_expire_exit(timer);
         raw_spin_lock_irq(&cpu_base->lock);
 
         /*
          * Note: We clear the running state after enqueue_hrtimer and
          * we do not reprogram the event hardware. Happens either in
          * hrtimer_start_range_ns() or in hrtimer_interrupt()
          *
          * Note: Because we dropped the cpu_base->lock above,
          * hrtimer_start_range_ns() can have popped in and enqueued the timer
          * for us already.
          */
         if (restart != HRTIMER_NORESTART &&
             !(timer->state & HRTIMER_STATE_ENQUEUED))
                 enqueue_hrtimer(timer, base, HRTIMER_MODE_ABS);
 
         /*
          * Separate the ->running assignment from the ->state assignment.
          *
          * As with a regular write barrier, this ensures the read side in
          * hrtimer_active() cannot observe base->running.timer == NULL &&
          * timer->state == INACTIVE.
          */
         raw_write_seqcount_barrier(&base->seq);
 
         WARN_ON_ONCE(base->running != timer);
         base->running = NULL;
 }
 
 static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
                                  unsigned long flags, unsigned int active_mask)
 {
         struct hrtimer_clock_base *base;
         unsigned int active = cpu_base->active_bases & active_mask;
 
         for_each_active_base(base, cpu_base, active) {
                 struct timerqueue_node *node;
                 ktime_t basenow;
 
                 basenow = ktime_add(now, base->offset);
 
                 while ((node = timerqueue_getnext(&base->active))) {
                         struct hrtimer *timer;
 
                         timer = container_of(node, struct hrtimer, node);
 
                         /*
                          * The immediate goal for using the softexpires is
                          * minimizing wakeups, not running timers at the
                          * earliest interrupt after their soft expiration.
                          * This allows us to avoid using a Priority Search
                          * Tree, which can answer a stabbing query for
                          * overlapping intervals and instead use the simple
                          * BST we already have.
                          * We don't add extra wakeups by delaying timers that
                          * are right-of a not yet expired timer, because that
                          * timer will have to trigger a wakeup anyway.
                          */
                         if (basenow < hrtimer_get_softexpires_tv64(timer))
                                 break;
 
                         __run_hrtimer(cpu_base, base, timer, &basenow, flags);
                         if (active_mask == HRTIMER_ACTIVE_SOFT)
                                 hrtimer_sync_wait_running(cpu_base, flags);
                 }
         }
 }
 
 static __latent_entropy void hrtimer_run_softirq(struct softirq_action *h)
 {
         struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
         unsigned long flags;
         ktime_t now;
 
         hrtimer_cpu_base_lock_expiry(cpu_base);
         raw_spin_lock_irqsave(&cpu_base->lock, flags);
 
         now = hrtimer_update_base(cpu_base);
         __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_SOFT);
 
         cpu_base->softirq_activated = 0;
         hrtimer_update_softirq_timer(cpu_base, true);
 
         raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
         hrtimer_cpu_base_unlock_expiry(cpu_base);
 }
 
 #ifdef CONFIG_HIGH_RES_TIMERS
 
 /*
  * High resolution timer interrupt
  * Called with interrupts disabled
  */
 void hrtimer_interrupt(struct clock_event_device *dev)
 {
         struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
         ktime_t expires_next, now, entry_time, delta;
         unsigned long flags;
         int retries = 0;
 
         BUG_ON(!cpu_base->hres_active);
         cpu_base->nr_events++;
         dev->next_event = KTIME_MAX;
 
         raw_spin_lock_irqsave(&cpu_base->lock, flags);
         entry_time = now = hrtimer_update_base(cpu_base);
 retry:
         cpu_base->in_hrtirq = 1;
         /*
          * We set expires_next to KTIME_MAX here with cpu_base->lock
          * held to prevent that a timer is enqueued in our queue via
          * the migration code. This does not affect enqueueing of
          * timers which run their callback and need to be requeued on
          * this CPU.
          */
         cpu_base->expires_next = KTIME_MAX;
 
         if (!ktime_before(now, cpu_base->softirq_expires_next)) {
                 cpu_base->softirq_expires_next = KTIME_MAX;
                 cpu_base->softirq_activated = 1;
                 raise_softirq_irqoff(HRTIMER_SOFTIRQ);
         }
 
         __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
 
         /* Reevaluate the clock bases for the [soft] next expiry */
         expires_next = hrtimer_update_next_event(cpu_base);
         /*
          * Store the new expiry value so the migration code can verify
          * against it.
          */
         cpu_base->expires_next = expires_next;
         cpu_base->in_hrtirq = 0;
         raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 
         /* Reprogramming necessary ? */
         if (!tick_program_event(expires_next, 0)) {
                 cpu_base->hang_detected = 0;
                 return;
         }
 
         /*
          * The next timer was already expired due to:
          * - tracing
          * - long lasting callbacks
          * - being scheduled away when running in a VM
          *
          * We need to prevent that we loop forever in the hrtimer
          * interrupt routine. We give it 3 attempts to avoid
          * overreacting on some spurious event.
          *
          * Acquire base lock for updating the offsets and retrieving
          * the current time.
          */
         raw_spin_lock_irqsave(&cpu_base->lock, flags);
         now = hrtimer_update_base(cpu_base);
         cpu_base->nr_retries++;
         if (++retries < 3)
                 goto retry;
         /*
          * Give the system a chance to do something else than looping
          * here. We stored the entry time, so we know exactly how long
          * we spent here. We schedule the next event this amount of
          * time away.
          */
         cpu_base->nr_hangs++;
         cpu_base->hang_detected = 1;
         raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 
         delta = ktime_sub(now, entry_time);
         if ((unsigned int)delta > cpu_base->max_hang_time)
                 cpu_base->max_hang_time = (unsigned int) delta;
         /*
          * Limit it to a sensible value as we enforce a longer
          * delay. Give the CPU at least 100ms to catch up.
          */
         if (delta > 100 * NSEC_PER_MSEC)
                 expires_next = ktime_add_ns(now, 100 * NSEC_PER_MSEC);
         else
                 expires_next = ktime_add(now, delta);
         tick_program_event(expires_next, 1);
         pr_warn_once("hrtimer: interrupt took %llu ns\n", ktime_to_ns(delta));
 }
 #endif /* !CONFIG_HIGH_RES_TIMERS */
 
 /*
  * Called from run_local_timers in hardirq context every jiffy
  */
 void hrtimer_run_queues(void)
 {
         struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
         unsigned long flags;
         ktime_t now;
 
         if (hrtimer_hres_active(cpu_base))
                 return;
 
         /*
          * This _is_ ugly: We have to check periodically, whether we
          * can switch to highres and / or nohz mode. The clocksource
          * switch happens with xtime_lock held. Notification from
          * there only sets the check bit in the tick_oneshot code,
          * otherwise we might deadlock vs. xtime_lock.
          */
         if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())) {
                 hrtimer_switch_to_hres();
                 return;
         }
 
         raw_spin_lock_irqsave(&cpu_base->lock, flags);
         now = hrtimer_update_base(cpu_base);
 
         if (!ktime_before(now, cpu_base->softirq_expires_next)) {
                 cpu_base->softirq_expires_next = KTIME_MAX;
                 cpu_base->softirq_activated = 1;
                 raise_softirq_irqoff(HRTIMER_SOFTIRQ);
         }
 
         __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
         raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
 }
 
 /*
  * Sleep related functions:
  */
 static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
 {
         struct hrtimer_sleeper *t =
                 container_of(timer, struct hrtimer_sleeper, timer);
         struct task_struct *task = t->task;
 
         t->task = NULL;
         if (task)
                 wake_up_process(task);
 
         return HRTIMER_NORESTART;
 }
 
 /**
  * hrtimer_sleeper_start_expires - Start a hrtimer sleeper timer
  * @sl:         sleeper to be started
  * @mode:       timer mode abs/rel
  *
  * Wrapper around hrtimer_start_expires() for hrtimer_sleeper based timers
  * to allow PREEMPT_RT to tweak the delivery mode (soft/hardirq context)
  */
 void hrtimer_sleeper_start_expires(struct hrtimer_sleeper *sl,
                                    enum hrtimer_mode mode)
 {
         /*
          * Make the enqueue delivery mode check work on RT. If the sleeper
          * was initialized for hard interrupt delivery, force the mode bit.
          * This is a special case for hrtimer_sleepers because
          * hrtimer_init_sleeper() determines the delivery mode on RT so the
          * fiddling with this decision is avoided at the call sites.
          */
         if (IS_ENABLED(CONFIG_PREEMPT_RT) && sl->timer.is_hard)
                 mode |= HRTIMER_MODE_HARD;
 
         hrtimer_start_expires(&sl->timer, mode);
 }
 EXPORT_SYMBOL_GPL(hrtimer_sleeper_start_expires);
 
 static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
                                    clockid_t clock_id, enum hrtimer_mode mode)
 {
         /*
          * On PREEMPT_RT enabled kernels hrtimers which are not explicitly
          * marked for hard interrupt expiry mode are moved into soft
          * interrupt context either for latency reasons or because the
          * hrtimer callback takes regular spinlocks or invokes other
          * functions which are not suitable for hard interrupt context on
          * PREEMPT_RT.
          *
          * The hrtimer_sleeper callback is RT compatible in hard interrupt
          * context, but there is a latency concern: Untrusted userspace can
          * spawn many threads which arm timers for the same expiry time on
          * the same CPU. That causes a latency spike due to the wakeup of
          * a gazillion threads.
          *
          * OTOH, privileged real-time user space applications rely on the
          * low latency of hard interrupt wakeups. If the current task is in
          * a real-time scheduling class, mark the mode for hard interrupt
          * expiry.
          */
         if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
                 if (task_is_realtime(current) && !(mode & HRTIMER_MODE_SOFT))
                         mode |= HRTIMER_MODE_HARD;
         }
 
         __hrtimer_init(&sl->timer, clock_id, mode);
         sl->timer.function = hrtimer_wakeup;
         sl->task = current;
 }
 
 /**
  * hrtimer_init_sleeper - initialize sleeper to the given clock
  * @sl:         sleeper to be initialized
  * @clock_id:   the clock to be used
  * @mode:       timer mode abs/rel
  */
 void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, clockid_t clock_id,
                           enum hrtimer_mode mode)
 {
         debug_init(&sl->timer, clock_id, mode);
         __hrtimer_init_sleeper(sl, clock_id, mode);
 
 }
 EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);
 
 int nanosleep_copyout(struct restart_block *restart, struct timespec64 *ts)
 {
         switch(restart->nanosleep.type) {
 #ifdef CONFIG_COMPAT_32BIT_TIME
         case TT_COMPAT:
                 if (put_old_timespec32(ts, restart->nanosleep.compat_rmtp))
                         return -EFAULT;
                 break;
 #endif
         case TT_NATIVE:
                 if (put_timespec64(ts, restart->nanosleep.rmtp))
                         return -EFAULT;
                 break;
         default:
                 BUG();
         }
         return -ERESTART_RESTARTBLOCK;
 }
 
 static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
 {
         struct restart_block *restart;
 
         do {
                 set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
                 hrtimer_sleeper_start_expires(t, mode);
 
                 if (likely(t->task))
                         schedule();
 
                 hrtimer_cancel(&t->timer);
                 mode = HRTIMER_MODE_ABS;
 
         } while (t->task && !signal_pending(current));
 
         __set_current_state(TASK_RUNNING);
 
         if (!t->task)
                 return 0;
 
         restart = &current->restart_block;
         if (restart->nanosleep.type != TT_NONE) {
                 ktime_t rem = hrtimer_expires_remaining(&t->timer);
                 struct timespec64 rmt;
 
                 if (rem <= 0)
                         return 0;
                 rmt = ktime_to_timespec64(rem);
 
                 return nanosleep_copyout(restart, &rmt);
         }
         return -ERESTART_RESTARTBLOCK;
 }
 
 static long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
 {
         struct hrtimer_sleeper t;
         int ret;
 
         hrtimer_init_sleeper_on_stack(&t, restart->nanosleep.clockid,
                                       HRTIMER_MODE_ABS);
         hrtimer_set_expires_tv64(&t.timer, restart->nanosleep.expires);
         ret = do_nanosleep(&t, HRTIMER_MODE_ABS);
         destroy_hrtimer_on_stack(&t.timer);
         return ret;
 }
 
 long hrtimer_nanosleep(ktime_t rqtp, const enum hrtimer_mode mode,
                        const clockid_t clockid)
 {
         struct restart_block *restart;
         struct hrtimer_sleeper t;
         int ret = 0;
         u64 slack;
 
         slack = current->timer_slack_ns;
         if (rt_task(current))
                 slack = 0;
 
         hrtimer_init_sleeper_on_stack(&t, clockid, mode);
         hrtimer_set_expires_range_ns(&t.timer, rqtp, slack);
         ret = do_nanosleep(&t, mode);
         if (ret != -ERESTART_RESTARTBLOCK)
                 goto out;
 
         /* Absolute timers do not update the rmtp value and restart: */
         if (mode == HRTIMER_MODE_ABS) {
                 ret = -ERESTARTNOHAND;
                 goto out;
         }
 
         restart = &current->restart_block;
         restart->nanosleep.clockid = t.timer.base->clockid;
         restart->nanosleep.expires = hrtimer_get_expires_tv64(&t.timer);
         set_restart_fn(restart, hrtimer_nanosleep_restart);
 out:
         destroy_hrtimer_on_stack(&t.timer);
         return ret;
 }
 
 #ifdef CONFIG_64BIT
 
 SYSCALL_DEFINE2(nanosleep, struct __kernel_timespec __user *, rqtp,
                 struct __kernel_timespec __user *, rmtp)
 {
         struct timespec64 tu;
 
         if (get_timespec64(&tu, rqtp))
                 return -EFAULT;
 
         if (!timespec64_valid(&tu))
                 return -EINVAL;
 
         current->restart_block.fn = do_no_restart_syscall;
         current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;
         current->restart_block.nanosleep.rmtp = rmtp;
         return hrtimer_nanosleep(timespec64_to_ktime(tu), HRTIMER_MODE_REL,
                                  CLOCK_MONOTONIC);
 }
 
 #endif
 
 #ifdef CONFIG_COMPAT_32BIT_TIME
 
 SYSCALL_DEFINE2(nanosleep_time32, struct old_timespec32 __user *, rqtp,
                        struct old_timespec32 __user *, rmtp)
 {
         struct timespec64 tu;
 
         if (get_old_timespec32(&tu, rqtp))
                 return -EFAULT;
 
         if (!timespec64_valid(&tu))
                 return -EINVAL;
 
         current->restart_block.fn = do_no_restart_syscall;
         current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
         current->restart_block.nanosleep.compat_rmtp = rmtp;
         return hrtimer_nanosleep(timespec64_to_ktime(tu), HRTIMER_MODE_REL,
                                  CLOCK_MONOTONIC);
 }
 #endif
 
 /*
  * Functions related to boot-time initialization:
  */
 int hrtimers_prepare_cpu(unsigned int cpu)
 {
         struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
         int i;
 
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
                 struct hrtimer_clock_base *clock_b = &cpu_base->clock_base[i];
 
                 clock_b->cpu_base = cpu_base;
                 seqcount_raw_spinlock_init(&clock_b->seq, &cpu_base->lock);
                 timerqueue_init_head(&clock_b->active);
         }
 
         cpu_base->cpu = cpu;
         cpu_base->active_bases = 0;
         cpu_base->hres_active = 0;
         cpu_base->hang_detected = 0;
         cpu_base->next_timer = NULL;
         cpu_base->softirq_next_timer = NULL;
         cpu_base->expires_next = KTIME_MAX;
         cpu_base->softirq_expires_next = KTIME_MAX;
         cpu_base->online = 1;
         hrtimer_cpu_base_init_expiry_lock(cpu_base);
         return 0;
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
 
 static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
                                 struct hrtimer_clock_base *new_base)
 {
         struct hrtimer *timer;
         struct timerqueue_node *node;
 
         while ((node = timerqueue_getnext(&old_base->active))) {
                 timer = container_of(node, struct hrtimer, node);
                 BUG_ON(hrtimer_callback_running(timer));
                 debug_deactivate(timer);
 
                 /*
                  * Mark it as ENQUEUED not INACTIVE otherwise the
                  * timer could be seen as !active and just vanish away
                  * under us on another CPU
                  */
                 __remove_hrtimer(timer, old_base, HRTIMER_STATE_ENQUEUED, 0);
                 timer->base = new_base;
                 /*
                  * Enqueue the timers on the new cpu. This does not
                  * reprogram the event device in case the timer
                  * expires before the earliest on this CPU, but we run
                  * hrtimer_interrupt after we migrated everything to
                  * sort out already expired timers and reprogram the
                  * event device.
                  */
                 enqueue_hrtimer(timer, new_base, HRTIMER_MODE_ABS);
         }
 }
 
 int hrtimers_cpu_dying(unsigned int dying_cpu)
 {
         int i, ncpu = cpumask_any_and(cpu_active_mask, housekeeping_cpumask(HK_TYPE_TIMER));
         struct hrtimer_cpu_base *old_base, *new_base;
 
         old_base = this_cpu_ptr(&hrtimer_bases);
         new_base = &per_cpu(hrtimer_bases, ncpu);
 
         /*
          * The caller is globally serialized and nobody else
          * takes two locks at once, deadlock is not possible.
          */
         raw_spin_lock(&old_base->lock);
         raw_spin_lock_nested(&new_base->lock, SINGLE_DEPTH_NESTING);
 
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
                 migrate_hrtimer_list(&old_base->clock_base[i],
                                      &new_base->clock_base[i]);
         }
 
         /*
          * The migration might have changed the first expiring softirq
          * timer on this CPU. Update it.
          */
         __hrtimer_get_next_event(new_base, HRTIMER_ACTIVE_SOFT);
         /* Tell the other CPU to retrigger the next event */
         smp_call_function_single(ncpu, retrigger_next_event, NULL, 0);
 
         raw_spin_unlock(&new_base->lock);
         old_base->online = 0;
         raw_spin_unlock(&old_base->lock);
 
         return 0;
 }
 
 #endif /* CONFIG_HOTPLUG_CPU */
 
 void __init hrtimers_init(void)
 {
         hrtimers_prepare_cpu(smp_processor_id());
         open_softirq(HRTIMER_SOFTIRQ, hrtimer_run_softirq);
 }
 
 /**
  * schedule_hrtimeout_range_clock - sleep until timeout
  * @expires:    timeout value (ktime_t)
  * @delta:      slack in expires timeout (ktime_t) for SCHED_OTHER tasks
  * @mode:       timer mode
  * @clock_id:   timer clock to be used
  */
 int __sched
 schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta,
                                const enum hrtimer_mode mode, clockid_t clock_id)
 {
         struct hrtimer_sleeper t;
 
         /*
          * Optimize when a zero timeout value is given. It does not
          * matter whether this is an absolute or a relative time.
          */
         if (expires && *expires == 0) {
                 __set_current_state(TASK_RUNNING);
                 return 0;
         }
 
         /*
          * A NULL parameter means "infinite"
          */
         if (!expires) {
                 schedule();
                 return -EINTR;
         }
 
         /*
          * Override any slack passed by the user if under
          * rt contraints.
          */
         if (rt_task(current))
                 delta = 0;
 
         hrtimer_init_sleeper_on_stack(&t, clock_id, mode);
         hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
         hrtimer_sleeper_start_expires(&t, mode);
 
         if (likely(t.task))
                 schedule();
 
         hrtimer_cancel(&t.timer);
         destroy_hrtimer_on_stack(&t.timer);
 
         __set_current_state(TASK_RUNNING);
 
         return !t.task ? 0 : -EINTR;
 }
 EXPORT_SYMBOL_GPL(schedule_hrtimeout_range_clock);
 
 /**
  * schedule_hrtimeout_range - sleep until timeout
  * @expires:    timeout value (ktime_t)
  * @delta:      slack in expires timeout (ktime_t) for SCHED_OTHER tasks
  * @mode:       timer mode
  *
  * Make the current task sleep until the given expiry time has
  * elapsed. The routine will return immediately unless
  * the current task state has been set (see set_current_state()).
  *
  * The @delta argument gives the kernel the freedom to schedule the
  * actual wakeup to a time that is both power and performance friendly
  * for regular (non RT/DL) tasks.
  * The kernel give the normal best effort behavior for "@expires+@delta",
  * but may decide to fire the timer earlier, but no earlier than @expires.
  *
  * You can set the task state as follows -
  *
  * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
  * pass before the routine returns unless the current task is explicitly
  * woken up, (e.g. by wake_up_process()).
  *
  * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
  * delivered to the current task or the current task is explicitly woken
  * up.
  *
  * The current task state is guaranteed to be TASK_RUNNING when this
  * routine returns.
  *
  * Returns 0 when the timer has expired. If the task was woken before the
  * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
  * by an explicit wakeup, it returns -EINTR.
  */
 int __sched schedule_hrtimeout_range(ktime_t *expires, u64 delta,
                                      const enum hrtimer_mode mode)
 {
         return schedule_hrtimeout_range_clock(expires, delta, mode,
                                               CLOCK_MONOTONIC);
 }
 EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);
 
 /**
  * schedule_hrtimeout - sleep until timeout
  * @expires:    timeout value (ktime_t)
  * @mode:       timer mode
  *
  * Make the current task sleep until the given expiry time has
  * elapsed. The routine will return immediately unless
  * the current task state has been set (see set_current_state()).
  *
  * You can set the task state as follows -
  *
  * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
  * pass before the routine returns unless the current task is explicitly
  * woken up, (e.g. by wake_up_process()).
  *
  * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
  * delivered to the current task or the current task is explicitly woken
  * up.
  *
  * The current task state is guaranteed to be TASK_RUNNING when this
  * routine returns.
  *
  * Returns 0 when the timer has expired. If the task was woken before the
  * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
  * by an explicit wakeup, it returns -EINTR.
  */
 int __sched schedule_hrtimeout(ktime_t *expires,
                                const enum hrtimer_mode mode)
 {
         return schedule_hrtimeout_range(expires, 0, mode);
 }
 EXPORT_SYMBOL_GPL(schedule_hrtimeout);
 

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