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 // 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/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)
 {
     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)
 {
     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 inline int hrtimer_hres_active(void)
 {
     return __hrtimer_hres_active(this_cpu_ptr(&hrtimer_bases));
 }
 
 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();
     /* "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)
 {
     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.
  * Returns the number of overruns.
  *
  * 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.
  *
  * Note: This only updates the timer expiry value and does not requeue
  * the timer.
  */
 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);
 
     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;
 
     /*
      * 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));
 }
 
 /* called with interrupts disabled */
 static inline void __hrtimer_peek_ahead_timers(void)
 {
     struct tick_device *td;
 
     if (!hrtimer_hres_active())
         return;
 
     td = this_cpu_ptr(&tick_cpu_device);
     if (td && td->evtdev)
         hrtimer_interrupt(td->evtdev);
 }
 
 #else /* CONFIG_HIGH_RES_TIMERS */
 
 static inline void __hrtimer_peek_ahead_timers(void) { }
 
 #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);
         hrtimer_sleeper_start_expires(t, mode);
 
         if (likely(t->task))
             freezable_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 (dl_task(current) || 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.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.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;
     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_dead_cpu(unsigned int scpu)
 {
     struct hrtimer_cpu_base *old_base, *new_base;
     int i;
 
     BUG_ON(cpu_online(scpu));
     tick_cancel_sched_timer(scpu);
 
     /*
      * this BH disable ensures that raise_softirq_irqoff() does
      * not wakeup ksoftirqd (and acquire the pi-lock) while
      * holding the cpu_base lock
      */
     local_bh_disable();
     local_irq_disable();
     old_base = &per_cpu(hrtimer_bases, scpu);
     new_base = this_cpu_ptr(&hrtimer_bases);
     /*
      * The caller is globally serialized and nobody else
      * takes two locks at once, deadlock is not possible.
      */
     raw_spin_lock(&new_base->lock);
     raw_spin_lock_nested(&old_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_update_softirq_timer(new_base, false);
 
     raw_spin_unlock(&old_base->lock);
     raw_spin_unlock(&new_base->lock);
 
     /* Check, if we got expired work to do */
     __hrtimer_peek_ahead_timers();
     local_irq_enable();
     local_bh_enable();
     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)
  * @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;
     }
 
     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)
  * @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.
  * 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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