OSCL-LXR linux-6.0.1/​kernel/​time/​tick-sched.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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
  *
  *  No idle tick implementation for low and high resolution timers
  *
  *  Started by: Thomas Gleixner and Ingo Molnar
  */
 #include <linux/cpu.h>
 #include <linux/err.h>
 #include <linux/hrtimer.h>
 #include <linux/interrupt.h>
 #include <linux/kernel_stat.h>
 #include <linux/percpu.h>
 #include <linux/nmi.h>
 #include <linux/profile.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/clock.h>
 #include <linux/sched/stat.h>
 #include <linux/sched/nohz.h>
 #include <linux/sched/loadavg.h>
 #include <linux/module.h>
 #include <linux/irq_work.h>
 #include <linux/posix-timers.h>
 #include <linux/context_tracking.h>
 #include <linux/mm.h>
 
 #include <asm/irq_regs.h>
 
 #include "tick-internal.h"
 
 #include <trace/events/timer.h>
 
 /*
  * Per-CPU nohz control structure
  */
 static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
 
 struct tick_sched *tick_get_tick_sched(int cpu)
 {
     return &per_cpu(tick_cpu_sched, cpu);
 }
 
 #if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
 /*
  * The time, when the last jiffy update happened. Write access must hold
  * jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a
  * consistent view of jiffies and last_jiffies_update.
  */
 static ktime_t last_jiffies_update;
 
 /*
  * Must be called with interrupts disabled !
  */
 static void tick_do_update_jiffies64(ktime_t now)
 {
     unsigned long ticks = 1;
     ktime_t delta, nextp;
 
     /*
      * 64bit can do a quick check without holding jiffies lock and
      * without looking at the sequence count. The smp_load_acquire()
      * pairs with the update done later in this function.
      *
      * 32bit cannot do that because the store of tick_next_period
      * consists of two 32bit stores and the first store could move it
      * to a random point in the future.
      */
     if (IS_ENABLED(CONFIG_64BIT)) {
         if (ktime_before(now, smp_load_acquire(&tick_next_period)))
             return;
     } else {
         unsigned int seq;
 
         /*
          * Avoid contention on jiffies_lock and protect the quick
          * check with the sequence count.
          */
         do {
             seq = read_seqcount_begin(&jiffies_seq);
             nextp = tick_next_period;
         } while (read_seqcount_retry(&jiffies_seq, seq));
 
         if (ktime_before(now, nextp))
             return;
     }
 
     /* Quick check failed, i.e. update is required. */
     raw_spin_lock(&jiffies_lock);
     /*
      * Reevaluate with the lock held. Another CPU might have done the
      * update already.
      */
     if (ktime_before(now, tick_next_period)) {
         raw_spin_unlock(&jiffies_lock);
         return;
     }
 
     write_seqcount_begin(&jiffies_seq);
 
     delta = ktime_sub(now, tick_next_period);
     if (unlikely(delta >= TICK_NSEC)) {
         /* Slow path for long idle sleep times */
         s64 incr = TICK_NSEC;
 
         ticks += ktime_divns(delta, incr);
 
         last_jiffies_update = ktime_add_ns(last_jiffies_update,
                            incr * ticks);
     } else {
         last_jiffies_update = ktime_add_ns(last_jiffies_update,
                            TICK_NSEC);
     }
 
     /* Advance jiffies to complete the jiffies_seq protected job */
     jiffies_64 += ticks;
 
     /*
      * Keep the tick_next_period variable up to date.
      */
     nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC);
 
     if (IS_ENABLED(CONFIG_64BIT)) {
         /*
          * Pairs with smp_load_acquire() in the lockless quick
          * check above and ensures that the update to jiffies_64 is
          * not reordered vs. the store to tick_next_period, neither
          * by the compiler nor by the CPU.
          */
         smp_store_release(&tick_next_period, nextp);
     } else {
         /*
          * A plain store is good enough on 32bit as the quick check
          * above is protected by the sequence count.
          */
         tick_next_period = nextp;
     }
 
     /*
      * Release the sequence count. calc_global_load() below is not
      * protected by it, but jiffies_lock needs to be held to prevent
      * concurrent invocations.
      */
     write_seqcount_end(&jiffies_seq);
 
     calc_global_load();
 
     raw_spin_unlock(&jiffies_lock);
     update_wall_time();
 }
 
 /*
  * Initialize and return retrieve the jiffies update.
  */
 static ktime_t tick_init_jiffy_update(void)
 {
     ktime_t period;
 
     raw_spin_lock(&jiffies_lock);
     write_seqcount_begin(&jiffies_seq);
     /* Did we start the jiffies update yet ? */
     if (last_jiffies_update == 0)
         last_jiffies_update = tick_next_period;
     period = last_jiffies_update;
     write_seqcount_end(&jiffies_seq);
     raw_spin_unlock(&jiffies_lock);
     return period;
 }
 
 #define MAX_STALLED_JIFFIES 5
 
 static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
 {
     int cpu = smp_processor_id();
 
 #ifdef CONFIG_NO_HZ_COMMON
     /*
      * Check if the do_timer duty was dropped. We don't care about
      * concurrency: This happens only when the CPU in charge went
      * into a long sleep. If two CPUs happen to assign themselves to
      * this duty, then the jiffies update is still serialized by
      * jiffies_lock.
      *
      * If nohz_full is enabled, this should not happen because the
      * tick_do_timer_cpu never relinquishes.
      */
     if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) {
 #ifdef CONFIG_NO_HZ_FULL
         WARN_ON_ONCE(tick_nohz_full_running);
 #endif
         tick_do_timer_cpu = cpu;
     }
 #endif
 
     /* Check, if the jiffies need an update */
     if (tick_do_timer_cpu == cpu)
         tick_do_update_jiffies64(now);
 
     /*
      * If jiffies update stalled for too long (timekeeper in stop_machine()
      * or VMEXIT'ed for several msecs), force an update.
      */
     if (ts->last_tick_jiffies != jiffies) {
         ts->stalled_jiffies = 0;
         ts->last_tick_jiffies = READ_ONCE(jiffies);
     } else {
         if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) {
             tick_do_update_jiffies64(now);
             ts->stalled_jiffies = 0;
             ts->last_tick_jiffies = READ_ONCE(jiffies);
         }
     }
 
     if (ts->inidle)
         ts->got_idle_tick = 1;
 }
 
 static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
 {
 #ifdef CONFIG_NO_HZ_COMMON
     /*
      * When we are idle and the tick is stopped, we have to touch
      * the watchdog as we might not schedule for a really long
      * time. This happens on complete idle SMP systems while
      * waiting on the login prompt. We also increment the "start of
      * idle" jiffy stamp so the idle accounting adjustment we do
      * when we go busy again does not account too much ticks.
      */
     if (ts->tick_stopped) {
         touch_softlockup_watchdog_sched();
         if (is_idle_task(current))
             ts->idle_jiffies++;
         /*
          * In case the current tick fired too early past its expected
          * expiration, make sure we don't bypass the next clock reprogramming
          * to the same deadline.
          */
         ts->next_tick = 0;
     }
 #endif
     update_process_times(user_mode(regs));
     profile_tick(CPU_PROFILING);
 }
 #endif
 
 #ifdef CONFIG_NO_HZ_FULL
 cpumask_var_t tick_nohz_full_mask;
 EXPORT_SYMBOL_GPL(tick_nohz_full_mask);
 bool tick_nohz_full_running;
 EXPORT_SYMBOL_GPL(tick_nohz_full_running);
 static atomic_t tick_dep_mask;
 
 static bool check_tick_dependency(atomic_t *dep)
 {
     int val = atomic_read(dep);
 
     if (val & TICK_DEP_MASK_POSIX_TIMER) {
         trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER);
         return true;
     }
 
     if (val & TICK_DEP_MASK_PERF_EVENTS) {
         trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS);
         return true;
     }
 
     if (val & TICK_DEP_MASK_SCHED) {
         trace_tick_stop(0, TICK_DEP_MASK_SCHED);
         return true;
     }
 
     if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) {
         trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE);
         return true;
     }
 
     if (val & TICK_DEP_MASK_RCU) {
         trace_tick_stop(0, TICK_DEP_MASK_RCU);
         return true;
     }
 
     return false;
 }
 
 static bool can_stop_full_tick(int cpu, struct tick_sched *ts)
 {
     lockdep_assert_irqs_disabled();
 
     if (unlikely(!cpu_online(cpu)))
         return false;
 
     if (check_tick_dependency(&tick_dep_mask))
         return false;
 
     if (check_tick_dependency(&ts->tick_dep_mask))
         return false;
 
     if (check_tick_dependency(&current->tick_dep_mask))
         return false;
 
     if (check_tick_dependency(&current->signal->tick_dep_mask))
         return false;
 
     return true;
 }
 
 static void nohz_full_kick_func(struct irq_work *work)
 {
     /* Empty, the tick restart happens on tick_nohz_irq_exit() */
 }
 
 static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) =
     IRQ_WORK_INIT_HARD(nohz_full_kick_func);
 
 /*
  * Kick this CPU if it's full dynticks in order to force it to
  * re-evaluate its dependency on the tick and restart it if necessary.
  * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
  * is NMI safe.
  */
 static void tick_nohz_full_kick(void)
 {
     if (!tick_nohz_full_cpu(smp_processor_id()))
         return;
 
     irq_work_queue(this_cpu_ptr(&nohz_full_kick_work));
 }
 
 /*
  * Kick the CPU if it's full dynticks in order to force it to
  * re-evaluate its dependency on the tick and restart it if necessary.
  */
 void tick_nohz_full_kick_cpu(int cpu)
 {
     if (!tick_nohz_full_cpu(cpu))
         return;
 
     irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
 }
 
 static void tick_nohz_kick_task(struct task_struct *tsk)
 {
     int cpu;
 
     /*
      * If the task is not running, run_posix_cpu_timers()
      * has nothing to elapse, IPI can then be spared.
      *
      * activate_task()                      STORE p->tick_dep_mask
      *   STORE p->on_rq
      * __schedule() (switch to task 'p')    smp_mb() (atomic_fetch_or())
      *   LOCK rq->lock                      LOAD p->on_rq
      *   smp_mb__after_spin_lock()
      *   tick_nohz_task_switch()
      *     LOAD p->tick_dep_mask
      */
     if (!sched_task_on_rq(tsk))
         return;
 
     /*
      * If the task concurrently migrates to another CPU,
      * we guarantee it sees the new tick dependency upon
      * schedule.
      *
      * set_task_cpu(p, cpu);
      *   STORE p->cpu = @cpu
      * __schedule() (switch to task 'p')
      *   LOCK rq->lock
      *   smp_mb__after_spin_lock()          STORE p->tick_dep_mask
      *   tick_nohz_task_switch()            smp_mb() (atomic_fetch_or())
      *      LOAD p->tick_dep_mask           LOAD p->cpu
      */
     cpu = task_cpu(tsk);
 
     preempt_disable();
     if (cpu_online(cpu))
         tick_nohz_full_kick_cpu(cpu);
     preempt_enable();
 }
 
 /*
  * Kick all full dynticks CPUs in order to force these to re-evaluate
  * their dependency on the tick and restart it if necessary.
  */
 static void tick_nohz_full_kick_all(void)
 {
     int cpu;
 
     if (!tick_nohz_full_running)
         return;
 
     preempt_disable();
     for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask)
         tick_nohz_full_kick_cpu(cpu);
     preempt_enable();
 }
 
 static void tick_nohz_dep_set_all(atomic_t *dep,
                   enum tick_dep_bits bit)
 {
     int prev;
 
     prev = atomic_fetch_or(BIT(bit), dep);
     if (!prev)
         tick_nohz_full_kick_all();
 }
 
 /*
  * Set a global tick dependency. Used by perf events that rely on freq and
  * by unstable clock.
  */
 void tick_nohz_dep_set(enum tick_dep_bits bit)
 {
     tick_nohz_dep_set_all(&tick_dep_mask, bit);
 }
 
 void tick_nohz_dep_clear(enum tick_dep_bits bit)
 {
     atomic_andnot(BIT(bit), &tick_dep_mask);
 }
 
 /*
  * Set per-CPU tick dependency. Used by scheduler and perf events in order to
  * manage events throttling.
  */
 void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit)
 {
     int prev;
     struct tick_sched *ts;
 
     ts = per_cpu_ptr(&tick_cpu_sched, cpu);
 
     prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask);
     if (!prev) {
         preempt_disable();
         /* Perf needs local kick that is NMI safe */
         if (cpu == smp_processor_id()) {
             tick_nohz_full_kick();
         } else {
             /* Remote irq work not NMI-safe */
             if (!WARN_ON_ONCE(in_nmi()))
                 tick_nohz_full_kick_cpu(cpu);
         }
         preempt_enable();
     }
 }
 EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu);
 
 void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
 {
     struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
 
     atomic_andnot(BIT(bit), &ts->tick_dep_mask);
 }
 EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu);
 
 /*
  * Set a per-task tick dependency. RCU need this. Also posix CPU timers
  * in order to elapse per task timers.
  */
 void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
 {
     if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask))
         tick_nohz_kick_task(tsk);
 }
 EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task);
 
 void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit)
 {
     atomic_andnot(BIT(bit), &tsk->tick_dep_mask);
 }
 EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task);
 
 /*
  * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
  * per process timers.
  */
 void tick_nohz_dep_set_signal(struct task_struct *tsk,
                   enum tick_dep_bits bit)
 {
     int prev;
     struct signal_struct *sig = tsk->signal;
 
     prev = atomic_fetch_or(BIT(bit), &sig->tick_dep_mask);
     if (!prev) {
         struct task_struct *t;
 
         lockdep_assert_held(&tsk->sighand->siglock);
         __for_each_thread(sig, t)
             tick_nohz_kick_task(t);
     }
 }
 
 void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit)
 {
     atomic_andnot(BIT(bit), &sig->tick_dep_mask);
 }
 
 /*
  * Re-evaluate the need for the tick as we switch the current task.
  * It might need the tick due to per task/process properties:
  * perf events, posix CPU timers, ...
  */
 void __tick_nohz_task_switch(void)
 {
     struct tick_sched *ts;
 
     if (!tick_nohz_full_cpu(smp_processor_id()))
         return;
 
     ts = this_cpu_ptr(&tick_cpu_sched);
 
     if (ts->tick_stopped) {
         if (atomic_read(&current->tick_dep_mask) ||
             atomic_read(&current->signal->tick_dep_mask))
             tick_nohz_full_kick();
     }
 }
 
 /* Get the boot-time nohz CPU list from the kernel parameters. */
 void __init tick_nohz_full_setup(cpumask_var_t cpumask)
 {
     alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
     cpumask_copy(tick_nohz_full_mask, cpumask);
     tick_nohz_full_running = true;
 }
 
 static int tick_nohz_cpu_down(unsigned int cpu)
 {
     /*
      * The tick_do_timer_cpu CPU handles housekeeping duty (unbound
      * timers, workqueues, timekeeping, ...) on behalf of full dynticks
      * CPUs. It must remain online when nohz full is enabled.
      */
     if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
         return -EBUSY;
     return 0;
 }
 
 void __init tick_nohz_init(void)
 {
     int cpu, ret;
 
     if (!tick_nohz_full_running)
         return;
 
     /*
      * Full dynticks uses irq work to drive the tick rescheduling on safe
      * locking contexts. But then we need irq work to raise its own
      * interrupts to avoid circular dependency on the tick
      */
     if (!arch_irq_work_has_interrupt()) {
         pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n");
         cpumask_clear(tick_nohz_full_mask);
         tick_nohz_full_running = false;
         return;
     }
 
     if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) &&
             !IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) {
         cpu = smp_processor_id();
 
         if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
             pr_warn("NO_HZ: Clearing %d from nohz_full range "
                 "for timekeeping\n", cpu);
             cpumask_clear_cpu(cpu, tick_nohz_full_mask);
         }
     }
 
     for_each_cpu(cpu, tick_nohz_full_mask)
         ct_cpu_track_user(cpu);
 
     ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
                     "kernel/nohz:predown", NULL,
                     tick_nohz_cpu_down);
     WARN_ON(ret < 0);
     pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
         cpumask_pr_args(tick_nohz_full_mask));
 }
 #endif
 
 /*
  * NOHZ - aka dynamic tick functionality
  */
 #ifdef CONFIG_NO_HZ_COMMON
 /*
  * NO HZ enabled ?
  */
 bool tick_nohz_enabled __read_mostly  = true;
 unsigned long tick_nohz_active  __read_mostly;
 /*
  * Enable / Disable tickless mode
  */
 static int __init setup_tick_nohz(char *str)
 {
     return (kstrtobool(str, &tick_nohz_enabled) == 0);
 }
 
 __setup("nohz=", setup_tick_nohz);
 
 bool tick_nohz_tick_stopped(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
     return ts->tick_stopped;
 }
 
 bool tick_nohz_tick_stopped_cpu(int cpu)
 {
     struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
 
     return ts->tick_stopped;
 }
 
 /**
  * tick_nohz_update_jiffies - update jiffies when idle was interrupted
  *
  * Called from interrupt entry when the CPU was idle
  *
  * In case the sched_tick was stopped on this CPU, we have to check if jiffies
  * must be updated. Otherwise an interrupt handler could use a stale jiffy
  * value. We do this unconditionally on any CPU, as we don't know whether the
  * CPU, which has the update task assigned is in a long sleep.
  */
 static void tick_nohz_update_jiffies(ktime_t now)
 {
     unsigned long flags;
 
     __this_cpu_write(tick_cpu_sched.idle_waketime, now);
 
     local_irq_save(flags);
     tick_do_update_jiffies64(now);
     local_irq_restore(flags);
 
     touch_softlockup_watchdog_sched();
 }
 
 /*
  * Updates the per-CPU time idle statistics counters
  */
 static void
 update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time)
 {
     ktime_t delta;
 
     if (ts->idle_active) {
         delta = ktime_sub(now, ts->idle_entrytime);
         if (nr_iowait_cpu(cpu) > 0)
             ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
         else
             ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
         ts->idle_entrytime = now;
     }
 
     if (last_update_time)
         *last_update_time = ktime_to_us(now);
 
 }
 
 static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
 {
     update_ts_time_stats(smp_processor_id(), ts, now, NULL);
     ts->idle_active = 0;
 
     sched_clock_idle_wakeup_event();
 }
 
 static void tick_nohz_start_idle(struct tick_sched *ts)
 {
     ts->idle_entrytime = ktime_get();
     ts->idle_active = 1;
     sched_clock_idle_sleep_event();
 }
 
 /**
  * get_cpu_idle_time_us - get the total idle time of a CPU
  * @cpu: CPU number to query
  * @last_update_time: variable to store update time in. Do not update
  * counters if NULL.
  *
  * Return the cumulative idle time (since boot) for a given
  * CPU, in microseconds.
  *
  * This time is measured via accounting rather than sampling,
  * and is as accurate as ktime_get() is.
  *
  * This function returns -1 if NOHZ is not enabled.
  */
 u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
 {
     struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
     ktime_t now, idle;
 
     if (!tick_nohz_active)
         return -1;
 
     now = ktime_get();
     if (last_update_time) {
         update_ts_time_stats(cpu, ts, now, last_update_time);
         idle = ts->idle_sleeptime;
     } else {
         if (ts->idle_active && !nr_iowait_cpu(cpu)) {
             ktime_t delta = ktime_sub(now, ts->idle_entrytime);
 
             idle = ktime_add(ts->idle_sleeptime, delta);
         } else {
             idle = ts->idle_sleeptime;
         }
     }
 
     return ktime_to_us(idle);
 
 }
 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
 
 /**
  * get_cpu_iowait_time_us - get the total iowait time of a CPU
  * @cpu: CPU number to query
  * @last_update_time: variable to store update time in. Do not update
  * counters if NULL.
  *
  * Return the cumulative iowait time (since boot) for a given
  * CPU, in microseconds.
  *
  * This time is measured via accounting rather than sampling,
  * and is as accurate as ktime_get() is.
  *
  * This function returns -1 if NOHZ is not enabled.
  */
 u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
 {
     struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
     ktime_t now, iowait;
 
     if (!tick_nohz_active)
         return -1;
 
     now = ktime_get();
     if (last_update_time) {
         update_ts_time_stats(cpu, ts, now, last_update_time);
         iowait = ts->iowait_sleeptime;
     } else {
         if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {
             ktime_t delta = ktime_sub(now, ts->idle_entrytime);
 
             iowait = ktime_add(ts->iowait_sleeptime, delta);
         } else {
             iowait = ts->iowait_sleeptime;
         }
     }
 
     return ktime_to_us(iowait);
 }
 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
 
 static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 {
     hrtimer_cancel(&ts->sched_timer);
     hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
 
     /* Forward the time to expire in the future */
     hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
 
     if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
         hrtimer_start_expires(&ts->sched_timer,
                       HRTIMER_MODE_ABS_PINNED_HARD);
     } else {
         tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
     }
 
     /*
      * Reset to make sure next tick stop doesn't get fooled by past
      * cached clock deadline.
      */
     ts->next_tick = 0;
 }
 
 static inline bool local_timer_softirq_pending(void)
 {
     return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
 }
 
 static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
 {
     u64 basemono, next_tick, delta, expires;
     unsigned long basejiff;
     unsigned int seq;
 
     /* Read jiffies and the time when jiffies were updated last */
     do {
         seq = read_seqcount_begin(&jiffies_seq);
         basemono = last_jiffies_update;
         basejiff = jiffies;
     } while (read_seqcount_retry(&jiffies_seq, seq));
     ts->last_jiffies = basejiff;
     ts->timer_expires_base = basemono;
 
     /*
      * Keep the periodic tick, when RCU, architecture or irq_work
      * requests it.
      * Aside of that check whether the local timer softirq is
      * pending. If so its a bad idea to call get_next_timer_interrupt()
      * because there is an already expired timer, so it will request
      * immediate expiry, which rearms the hardware timer with a
      * minimal delta which brings us back to this place
      * immediately. Lather, rinse and repeat...
      */
     if (rcu_needs_cpu() || arch_needs_cpu() ||
         irq_work_needs_cpu() || local_timer_softirq_pending()) {
         next_tick = basemono + TICK_NSEC;
     } else {
         /*
          * Get the next pending timer. If high resolution
          * timers are enabled this only takes the timer wheel
          * timers into account. If high resolution timers are
          * disabled this also looks at the next expiring
          * hrtimer.
          */
         next_tick = get_next_timer_interrupt(basejiff, basemono);
         ts->next_timer = next_tick;
     }
 
     /*
      * If the tick is due in the next period, keep it ticking or
      * force prod the timer.
      */
     delta = next_tick - basemono;
     if (delta <= (u64)TICK_NSEC) {
         /*
          * Tell the timer code that the base is not idle, i.e. undo
          * the effect of get_next_timer_interrupt():
          */
         timer_clear_idle();
         /*
          * We've not stopped the tick yet, and there's a timer in the
          * next period, so no point in stopping it either, bail.
          */
         if (!ts->tick_stopped) {
             ts->timer_expires = 0;
             goto out;
         }
     }
 
     /*
      * If this CPU is the one which had the do_timer() duty last, we limit
      * the sleep time to the timekeeping max_deferment value.
      * Otherwise we can sleep as long as we want.
      */
     delta = timekeeping_max_deferment();
     if (cpu != tick_do_timer_cpu &&
         (tick_do_timer_cpu != TICK_DO_TIMER_NONE || !ts->do_timer_last))
         delta = KTIME_MAX;
 
     /* Calculate the next expiry time */
     if (delta < (KTIME_MAX - basemono))
         expires = basemono + delta;
     else
         expires = KTIME_MAX;
 
     ts->timer_expires = min_t(u64, expires, next_tick);
 
 out:
     return ts->timer_expires;
 }
 
 static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
 {
     struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
     u64 basemono = ts->timer_expires_base;
     u64 expires = ts->timer_expires;
     ktime_t tick = expires;
 
     /* Make sure we won't be trying to stop it twice in a row. */
     ts->timer_expires_base = 0;
 
     /*
      * If this CPU is the one which updates jiffies, then give up
      * the assignment and let it be taken by the CPU which runs
      * the tick timer next, which might be this CPU as well. If we
      * don't drop this here the jiffies might be stale and
      * do_timer() never invoked. Keep track of the fact that it
      * was the one which had the do_timer() duty last.
      */
     if (cpu == tick_do_timer_cpu) {
         tick_do_timer_cpu = TICK_DO_TIMER_NONE;
         ts->do_timer_last = 1;
     } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
         ts->do_timer_last = 0;
     }
 
     /* Skip reprogram of event if its not changed */
     if (ts->tick_stopped && (expires == ts->next_tick)) {
         /* Sanity check: make sure clockevent is actually programmed */
         if (tick == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer))
             return;
 
         WARN_ON_ONCE(1);
         printk_once("basemono: %llu ts->next_tick: %llu dev->next_event: %llu timer->active: %d timer->expires: %llu\n",
                 basemono, ts->next_tick, dev->next_event,
                 hrtimer_active(&ts->sched_timer), hrtimer_get_expires(&ts->sched_timer));
     }
 
     /*
      * nohz_stop_sched_tick can be called several times before
      * the nohz_restart_sched_tick is called. This happens when
      * interrupts arrive which do not cause a reschedule. In the
      * first call we save the current tick time, so we can restart
      * the scheduler tick in nohz_restart_sched_tick.
      */
     if (!ts->tick_stopped) {
         calc_load_nohz_start();
         quiet_vmstat();
 
         ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
         ts->tick_stopped = 1;
         trace_tick_stop(1, TICK_DEP_MASK_NONE);
     }
 
     ts->next_tick = tick;
 
     /*
      * If the expiration time == KTIME_MAX, then we simply stop
      * the tick timer.
      */
     if (unlikely(expires == KTIME_MAX)) {
         if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
             hrtimer_cancel(&ts->sched_timer);
         else
             tick_program_event(KTIME_MAX, 1);
         return;
     }
 
     if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
         hrtimer_start(&ts->sched_timer, tick,
                   HRTIMER_MODE_ABS_PINNED_HARD);
     } else {
         hrtimer_set_expires(&ts->sched_timer, tick);
         tick_program_event(tick, 1);
     }
 }
 
 static void tick_nohz_retain_tick(struct tick_sched *ts)
 {
     ts->timer_expires_base = 0;
 }
 
 #ifdef CONFIG_NO_HZ_FULL
 static void tick_nohz_stop_sched_tick(struct tick_sched *ts, int cpu)
 {
     if (tick_nohz_next_event(ts, cpu))
         tick_nohz_stop_tick(ts, cpu);
     else
         tick_nohz_retain_tick(ts);
 }
 #endif /* CONFIG_NO_HZ_FULL */
 
 static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
 {
     /* Update jiffies first */
     tick_do_update_jiffies64(now);
 
     /*
      * Clear the timer idle flag, so we avoid IPIs on remote queueing and
      * the clock forward checks in the enqueue path:
      */
     timer_clear_idle();
 
     calc_load_nohz_stop();
     touch_softlockup_watchdog_sched();
     /*
      * Cancel the scheduled timer and restore the tick
      */
     ts->tick_stopped  = 0;
     tick_nohz_restart(ts, now);
 }
 
 static void __tick_nohz_full_update_tick(struct tick_sched *ts,
                      ktime_t now)
 {
 #ifdef CONFIG_NO_HZ_FULL
     int cpu = smp_processor_id();
 
     if (can_stop_full_tick(cpu, ts))
         tick_nohz_stop_sched_tick(ts, cpu);
     else if (ts->tick_stopped)
         tick_nohz_restart_sched_tick(ts, now);
 #endif
 }
 
 static void tick_nohz_full_update_tick(struct tick_sched *ts)
 {
     if (!tick_nohz_full_cpu(smp_processor_id()))
         return;
 
     if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
         return;
 
     __tick_nohz_full_update_tick(ts, ktime_get());
 }
 
 /*
  * A pending softirq outside an IRQ (or softirq disabled section) context
  * should be waiting for ksoftirqd to handle it. Therefore we shouldn't
  * reach here due to the need_resched() early check in can_stop_idle_tick().
  *
  * However if we are between CPUHP_AP_SMPBOOT_THREADS and CPU_TEARDOWN_CPU on the
  * cpu_down() process, softirqs can still be raised while ksoftirqd is parked,
  * triggering the below since wakep_softirqd() is ignored.
  *
  */
 static bool report_idle_softirq(void)
 {
     static int ratelimit;
     unsigned int pending = local_softirq_pending();
 
     if (likely(!pending))
         return false;
 
     /* Some softirqs claim to be safe against hotplug and ksoftirqd parking */
     if (!cpu_active(smp_processor_id())) {
         pending &= ~SOFTIRQ_HOTPLUG_SAFE_MASK;
         if (!pending)
             return false;
     }
 
     if (ratelimit < 10)
         return false;
 
     /* On RT, softirqs handling may be waiting on some lock */
     if (!local_bh_blocked())
         return false;
 
     pr_warn("NOHZ tick-stop error: local softirq work is pending, handler #%02x!!!\n",
         pending);
     ratelimit++;
 
     return true;
 }
 
 static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
 {
     /*
      * If this CPU is offline and it is the one which updates
      * jiffies, then give up the assignment and let it be taken by
      * the CPU which runs the tick timer next. If we don't drop
      * this here the jiffies might be stale and do_timer() never
      * invoked.
      */
     if (unlikely(!cpu_online(cpu))) {
         if (cpu == tick_do_timer_cpu)
             tick_do_timer_cpu = TICK_DO_TIMER_NONE;
         /*
          * Make sure the CPU doesn't get fooled by obsolete tick
          * deadline if it comes back online later.
          */
         ts->next_tick = 0;
         return false;
     }
 
     if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
         return false;
 
     if (need_resched())
         return false;
 
     if (unlikely(report_idle_softirq()))
         return false;
 
     if (tick_nohz_full_enabled()) {
         /*
          * Keep the tick alive to guarantee timekeeping progression
          * if there are full dynticks CPUs around
          */
         if (tick_do_timer_cpu == cpu)
             return false;
 
         /* Should not happen for nohz-full */
         if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
             return false;
     }
 
     return true;
 }
 
 static void __tick_nohz_idle_stop_tick(struct tick_sched *ts)
 {
     ktime_t expires;
     int cpu = smp_processor_id();
 
     /*
      * If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the
      * tick timer expiration time is known already.
      */
     if (ts->timer_expires_base)
         expires = ts->timer_expires;
     else if (can_stop_idle_tick(cpu, ts))
         expires = tick_nohz_next_event(ts, cpu);
     else
         return;
 
     ts->idle_calls++;
 
     if (expires > 0LL) {
         int was_stopped = ts->tick_stopped;
 
         tick_nohz_stop_tick(ts, cpu);
 
         ts->idle_sleeps++;
         ts->idle_expires = expires;
 
         if (!was_stopped && ts->tick_stopped) {
             ts->idle_jiffies = ts->last_jiffies;
             nohz_balance_enter_idle(cpu);
         }
     } else {
         tick_nohz_retain_tick(ts);
     }
 }
 
 /**
  * tick_nohz_idle_stop_tick - stop the idle tick from the idle task
  *
  * When the next event is more than a tick into the future, stop the idle tick
  */
 void tick_nohz_idle_stop_tick(void)
 {
     __tick_nohz_idle_stop_tick(this_cpu_ptr(&tick_cpu_sched));
 }
 
 void tick_nohz_idle_retain_tick(void)
 {
     tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched));
     /*
      * Undo the effect of get_next_timer_interrupt() called from
      * tick_nohz_next_event().
      */
     timer_clear_idle();
 }
 
 /**
  * tick_nohz_idle_enter - prepare for entering idle on the current CPU
  *
  * Called when we start the idle loop.
  */
 void tick_nohz_idle_enter(void)
 {
     struct tick_sched *ts;
 
     lockdep_assert_irqs_enabled();
 
     local_irq_disable();
 
     ts = this_cpu_ptr(&tick_cpu_sched);
 
     WARN_ON_ONCE(ts->timer_expires_base);
 
     ts->inidle = 1;
     tick_nohz_start_idle(ts);
 
     local_irq_enable();
 }
 
 /**
  * tick_nohz_irq_exit - update next tick event from interrupt exit
  *
  * When an interrupt fires while we are idle and it doesn't cause
  * a reschedule, it may still add, modify or delete a timer, enqueue
  * an RCU callback, etc...
  * So we need to re-calculate and reprogram the next tick event.
  */
 void tick_nohz_irq_exit(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
     if (ts->inidle)
         tick_nohz_start_idle(ts);
     else
         tick_nohz_full_update_tick(ts);
 }
 
 /**
  * tick_nohz_idle_got_tick - Check whether or not the tick handler has run
  */
 bool tick_nohz_idle_got_tick(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
     if (ts->got_idle_tick) {
         ts->got_idle_tick = 0;
         return true;
     }
     return false;
 }
 
 /**
  * tick_nohz_get_next_hrtimer - return the next expiration time for the hrtimer
  * or the tick, whatever that expires first. Note that, if the tick has been
  * stopped, it returns the next hrtimer.
  *
  * Called from power state control code with interrupts disabled
  */
 ktime_t tick_nohz_get_next_hrtimer(void)
 {
     return __this_cpu_read(tick_cpu_device.evtdev)->next_event;
 }
 
 /**
  * tick_nohz_get_sleep_length - return the expected length of the current sleep
  * @delta_next: duration until the next event if the tick cannot be stopped
  *
  * Called from power state control code with interrupts disabled.
  *
  * The return value of this function and/or the value returned by it through the
  * @delta_next pointer can be negative which must be taken into account by its
  * callers.
  */
 ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
 {
     struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
     int cpu = smp_processor_id();
     /*
      * The idle entry time is expected to be a sufficient approximation of
      * the current time at this point.
      */
     ktime_t now = ts->idle_entrytime;
     ktime_t next_event;
 
     WARN_ON_ONCE(!ts->inidle);
 
     *delta_next = ktime_sub(dev->next_event, now);
 
     if (!can_stop_idle_tick(cpu, ts))
         return *delta_next;
 
     next_event = tick_nohz_next_event(ts, cpu);
     if (!next_event)
         return *delta_next;
 
     /*
      * If the next highres timer to expire is earlier than next_event, the
      * idle governor needs to know that.
      */
     next_event = min_t(u64, next_event,
                hrtimer_next_event_without(&ts->sched_timer));
 
     return ktime_sub(next_event, now);
 }
 
 /**
  * tick_nohz_get_idle_calls_cpu - return the current idle calls counter value
  * for a particular CPU.
  *
  * Called from the schedutil frequency scaling governor in scheduler context.
  */
 unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
 {
     struct tick_sched *ts = tick_get_tick_sched(cpu);
 
     return ts->idle_calls;
 }
 
 /**
  * tick_nohz_get_idle_calls - return the current idle calls counter value
  *
  * Called from the schedutil frequency scaling governor in scheduler context.
  */
 unsigned long tick_nohz_get_idle_calls(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
     return ts->idle_calls;
 }
 
 static void tick_nohz_account_idle_time(struct tick_sched *ts,
                     ktime_t now)
 {
     unsigned long ticks;
 
     ts->idle_exittime = now;
 
     if (vtime_accounting_enabled_this_cpu())
         return;
     /*
      * We stopped the tick in idle. Update process times would miss the
      * time we slept as update_process_times does only a 1 tick
      * accounting. Enforce that this is accounted to idle !
      */
     ticks = jiffies - ts->idle_jiffies;
     /*
      * We might be one off. Do not randomly account a huge number of ticks!
      */
     if (ticks && ticks < LONG_MAX)
         account_idle_ticks(ticks);
 }
 
 void tick_nohz_idle_restart_tick(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
     if (ts->tick_stopped) {
         ktime_t now = ktime_get();
         tick_nohz_restart_sched_tick(ts, now);
         tick_nohz_account_idle_time(ts, now);
     }
 }
 
 static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now)
 {
     if (tick_nohz_full_cpu(smp_processor_id()))
         __tick_nohz_full_update_tick(ts, now);
     else
         tick_nohz_restart_sched_tick(ts, now);
 
     tick_nohz_account_idle_time(ts, now);
 }
 
 /**
  * tick_nohz_idle_exit - restart the idle tick from the idle task
  *
  * Restart the idle tick when the CPU is woken up from idle
  * This also exit the RCU extended quiescent state. The CPU
  * can use RCU again after this function is called.
  */
 void tick_nohz_idle_exit(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
     bool idle_active, tick_stopped;
     ktime_t now;
 
     local_irq_disable();
 
     WARN_ON_ONCE(!ts->inidle);
     WARN_ON_ONCE(ts->timer_expires_base);
 
     ts->inidle = 0;
     idle_active = ts->idle_active;
     tick_stopped = ts->tick_stopped;
 
     if (idle_active || tick_stopped)
         now = ktime_get();
 
     if (idle_active)
         tick_nohz_stop_idle(ts, now);
 
     if (tick_stopped)
         tick_nohz_idle_update_tick(ts, now);
 
     local_irq_enable();
 }
 
 /*
  * The nohz low res interrupt handler
  */
 static void tick_nohz_handler(struct clock_event_device *dev)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
     struct pt_regs *regs = get_irq_regs();
     ktime_t now = ktime_get();
 
     dev->next_event = KTIME_MAX;
 
     tick_sched_do_timer(ts, now);
     tick_sched_handle(ts, regs);
 
     if (unlikely(ts->tick_stopped)) {
         /*
          * The clockevent device is not reprogrammed, so change the
          * clock event device to ONESHOT_STOPPED to avoid spurious
          * interrupts on devices which might not be truly one shot.
          */
         tick_program_event(KTIME_MAX, 1);
         return;
     }
 
     hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
     tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
 }
 
 static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
 {
     if (!tick_nohz_enabled)
         return;
     ts->nohz_mode = mode;
     /* One update is enough */
     if (!test_and_set_bit(0, &tick_nohz_active))
         timers_update_nohz();
 }
 
 /**
  * tick_nohz_switch_to_nohz - switch to nohz mode
  */
 static void tick_nohz_switch_to_nohz(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
     ktime_t next;
 
     if (!tick_nohz_enabled)
         return;
 
     if (tick_switch_to_oneshot(tick_nohz_handler))
         return;
 
     /*
      * Recycle the hrtimer in ts, so we can share the
      * hrtimer_forward with the highres code.
      */
     hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
     /* Get the next period */
     next = tick_init_jiffy_update();
 
     hrtimer_set_expires(&ts->sched_timer, next);
     hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
     tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
     tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
 }
 
 static inline void tick_nohz_irq_enter(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
     ktime_t now;
 
     if (!ts->idle_active && !ts->tick_stopped)
         return;
     now = ktime_get();
     if (ts->idle_active)
         tick_nohz_stop_idle(ts, now);
     /*
      * If all CPUs are idle. We may need to update a stale jiffies value.
      * Note nohz_full is a special case: a timekeeper is guaranteed to stay
      * alive but it might be busy looping with interrupts disabled in some
      * rare case (typically stop machine). So we must make sure we have a
      * last resort.
      */
     if (ts->tick_stopped)
         tick_nohz_update_jiffies(now);
 }
 
 #else
 
 static inline void tick_nohz_switch_to_nohz(void) { }
 static inline void tick_nohz_irq_enter(void) { }
 static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { }
 
 #endif /* CONFIG_NO_HZ_COMMON */
 
 /*
  * Called from irq_enter to notify about the possible interruption of idle()
  */
 void tick_irq_enter(void)
 {
     tick_check_oneshot_broadcast_this_cpu();
     tick_nohz_irq_enter();
 }
 
 /*
  * High resolution timer specific code
  */
 #ifdef CONFIG_HIGH_RES_TIMERS
 /*
  * We rearm the timer until we get disabled by the idle code.
  * Called with interrupts disabled.
  */
 static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 {
     struct tick_sched *ts =
         container_of(timer, struct tick_sched, sched_timer);
     struct pt_regs *regs = get_irq_regs();
     ktime_t now = ktime_get();
 
     tick_sched_do_timer(ts, now);
 
     /*
      * Do not call, when we are not in irq context and have
      * no valid regs pointer
      */
     if (regs)
         tick_sched_handle(ts, regs);
     else
         ts->next_tick = 0;
 
     /* No need to reprogram if we are in idle or full dynticks mode */
     if (unlikely(ts->tick_stopped))
         return HRTIMER_NORESTART;
 
     hrtimer_forward(timer, now, TICK_NSEC);
 
     return HRTIMER_RESTART;
 }
 
 static int sched_skew_tick;
 
 static int __init skew_tick(char *str)
 {
     get_option(&str, &sched_skew_tick);
 
     return 0;
 }
 early_param("skew_tick", skew_tick);
 
 /**
  * tick_setup_sched_timer - setup the tick emulation timer
  */
 void tick_setup_sched_timer(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
     ktime_t now = ktime_get();
 
     /*
      * Emulate tick processing via per-CPU hrtimers:
      */
     hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
     ts->sched_timer.function = tick_sched_timer;
 
     /* Get the next period (per-CPU) */
     hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
 
     /* Offset the tick to avert jiffies_lock contention. */
     if (sched_skew_tick) {
         u64 offset = TICK_NSEC >> 1;
         do_div(offset, num_possible_cpus());
         offset *= smp_processor_id();
         hrtimer_add_expires_ns(&ts->sched_timer, offset);
     }
 
     hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
     hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
     tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
 }
 #endif /* HIGH_RES_TIMERS */
 
 #if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
 void tick_cancel_sched_timer(int cpu)
 {
     struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 
 # ifdef CONFIG_HIGH_RES_TIMERS
     if (ts->sched_timer.base)
         hrtimer_cancel(&ts->sched_timer);
 # endif
 
     memset(ts, 0, sizeof(*ts));
 }
 #endif
 
 /*
  * Async notification about clocksource changes
  */
 void tick_clock_notify(void)
 {
     int cpu;
 
     for_each_possible_cpu(cpu)
         set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
 }
 
 /*
  * Async notification about clock event changes
  */
 void tick_oneshot_notify(void)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
     set_bit(0, &ts->check_clocks);
 }
 
 /*
  * Check, if a change happened, which makes oneshot possible.
  *
  * Called cyclic from the hrtimer softirq (driven by the timer
  * softirq) allow_nohz signals, that we can switch into low-res nohz
  * mode, because high resolution timers are disabled (either compile
  * or runtime). Called with interrupts disabled.
  */
 int tick_check_oneshot_change(int allow_nohz)
 {
     struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
     if (!test_and_clear_bit(0, &ts->check_clocks))
         return 0;
 
     if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
         return 0;
 
     if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
         return 0;
 
     if (!allow_nohz)
         return 1;
 
     tick_nohz_switch_to_nohz();
     return 0;
 }

This page was automatically generated by the 2.1.0 LXR engine. The LXR team