/*
   * Generic entry point for the idle threads
   */
  #include <linux/sched.h>

  #include <linux/sched/idle.h>

  #include <linux/cpu.h>
  #include <linux/cpuidle.h>

  #include <linux/cpuhotplug.h>

  #include <linux/tick.h>
  #include <linux/mm.h>
  #include <linux/stackprotector.h>

  #include <linux/suspend.h>

  #include <linux/livepatch.h>

  
  #include <asm/tlb.h>
  
  #include <trace/events/power.h>

  #include "sched.h"

  /* Linker adds these: start and end of __cpuidle functions */
  extern char __cpuidle_text_start[], __cpuidle_text_end[];

  /**
   * sched_idle_set_state - Record idle state for the current CPU.
   * @idle_state: State to record.
   */
  void sched_idle_set_state(struct cpuidle_state *idle_state)
  {
  	idle_set_state(this_rq(), idle_state);
  }

  static int __read_mostly cpu_idle_force_poll;
  
  void cpu_idle_poll_ctrl(bool enable)
  {
  	if (enable) {
  		cpu_idle_force_poll++;
  	} else {
  		cpu_idle_force_poll--;
  		WARN_ON_ONCE(cpu_idle_force_poll < 0);
  	}
  }
  
  #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
  static int __init cpu_idle_poll_setup(char *__unused)
  {
  	cpu_idle_force_poll = 1;
  	return 1;
  }
  __setup("nohlt", cpu_idle_poll_setup);
  
  static int __init cpu_idle_nopoll_setup(char *__unused)
  {
  	cpu_idle_force_poll = 0;
  	return 1;
  }
  __setup("hlt", cpu_idle_nopoll_setup);
  #endif

  static noinline int __cpuidle cpu_idle_poll(void)

  {
  	rcu_idle_enter();
  	trace_cpu_idle_rcuidle(0, smp_processor_id());
  	local_irq_enable();

  	stop_critical_timings();

  	while (!tif_need_resched() &&
  		(cpu_idle_force_poll || tick_check_broadcast_expired()))

  		cpu_relax();

  	start_critical_timings();

  	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
  	rcu_idle_exit();
  	return 1;
  }
  
  /* Weak implementations for optional arch specific functions */
  void __weak arch_cpu_idle_prepare(void) { }
  void __weak arch_cpu_idle_enter(void) { }
  void __weak arch_cpu_idle_exit(void) { }
  void __weak arch_cpu_idle_dead(void) { }
  void __weak arch_cpu_idle(void)
  {
  	cpu_idle_force_poll = 1;
  	local_irq_enable();
  }

  /**
   * default_idle_call - Default CPU idle routine.
   *
   * To use when the cpuidle framework cannot be used.
   */

  void __cpuidle default_idle_call(void)

  {

  	if (current_clr_polling_and_test()) {

  		local_irq_enable();

  	} else {
  		stop_critical_timings();

  		arch_cpu_idle();

  		start_critical_timings();
  	}

  }

  static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
  		      int next_state)
  {

  	/*
  	 * The idle task must be scheduled, it is pointless to go to idle, just
  	 * update no idle residency and return.
  	 */
  	if (current_clr_polling_and_test()) {
  		dev->last_residency = 0;
  		local_irq_enable();
  		return -EBUSY;
  	}

  	/*
  	 * Enter the idle state previously returned by the governor decision.
  	 * This function will block until an interrupt occurs and will take
  	 * care of re-enabling the local interrupts
  	 */

  	return cpuidle_enter(drv, dev, next_state);

  }

  /**
   * cpuidle_idle_call - the main idle function
   *
   * NOTE: no locks or semaphores should be used here

   *
   * On archs that support TIF_POLLING_NRFLAG, is called with polling
   * set, and it returns with polling set.  If it ever stops polling, it
   * must clear the polling bit.

   */

  static void cpuidle_idle_call(void)

  {

  	struct cpuidle_device *dev = cpuidle_get_device();

  	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

  	int next_state, entered_state;

  	/*
  	 * Check if the idle task must be rescheduled. If it is the

  	 * case, exit the function after re-enabling the local irq.

  	 */

  	if (need_resched()) {

  		local_irq_enable();

  		return;

  	}

  	/*

  	 * Tell the RCU framework we are entering an idle section,
  	 * so no more rcu read side critical sections and one more
  	 * step to the grace period
  	 */

  	rcu_idle_enter();

  	if (cpuidle_not_available(drv, dev)) {
  		default_idle_call();
  		goto exit_idle;
  	}

  	/*

  	 * Suspend-to-idle ("s2idle") is a system state in which all user space

  	 * has been frozen, all I/O devices have been suspended and the only
  	 * activity happens here and in iterrupts (if any).  In that case bypass
  	 * the cpuidle governor and go stratight for the deepest idle state
  	 * available.  Possibly also suspend the local tick and the entire
  	 * timekeeping to prevent timer interrupts from kicking us out of idle
  	 * until a proper wakeup interrupt happens.
  	 */

  	if (idle_should_enter_s2idle() || dev->use_deepest_state) {
  		if (idle_should_enter_s2idle()) {

  			entered_state = cpuidle_enter_s2idle(drv, dev);

  			if (entered_state > 0) {
  				local_irq_enable();
  				goto exit_idle;
  			}

  		}

  		next_state = cpuidle_find_deepest_state(drv, dev);

  		call_cpuidle(drv, dev, next_state);

  	} else {

  		/*
  		 * Ask the cpuidle framework to choose a convenient idle state.
  		 */
  		next_state = cpuidle_select(drv, dev);

  		entered_state = call_cpuidle(drv, dev, next_state);
  		/*
  		 * Give the governor an opportunity to reflect on the outcome
  		 */

  		cpuidle_reflect(dev, entered_state);

  	}

  
  exit_idle:

  	__current_set_polling();

  	/*

  	 * It is up to the idle functions to reenable local interrupts

  	 */

  	if (WARN_ON_ONCE(irqs_disabled()))
  		local_irq_enable();
  
  	rcu_idle_exit();

  }

  /*
   * Generic idle loop implementation

   *
   * Called with polling cleared.

   */

  static void do_idle(void)

  {

  	/*
  	 * If the arch has a polling bit, we maintain an invariant:
  	 *
  	 * Our polling bit is clear if we're not scheduled (i.e. if rq->curr !=
  	 * rq->idle). This means that, if rq->idle has the polling bit set,
  	 * then setting need_resched is guaranteed to cause the CPU to
  	 * reschedule.
  	 */

  	__current_set_polling();

  	quiet_vmstat();

  	tick_nohz_idle_enter();

  	while (!need_resched()) {
  		check_pgt_cache();
  		rmb();

  		if (cpu_is_offline(smp_processor_id())) {
  			cpuhp_report_idle_dead();
  			arch_cpu_idle_dead();

  		}

  		local_irq_disable();
  		arch_cpu_idle_enter();

  
  		/*

  		 * In poll mode we reenable interrupts and spin. Also if we
  		 * detected in the wakeup from idle path that the tick
  		 * broadcast device expired for us, we don't want to go deep
  		 * idle as we know that the IPI is going to arrive right away.

  		 */

  		if (cpu_idle_force_poll || tick_check_broadcast_expired())
  			cpu_idle_poll();
  		else
  			cpuidle_idle_call();
  		arch_cpu_idle_exit();

  	}

  
  	/*
  	 * Since we fell out of the loop above, we know TIF_NEED_RESCHED must
  	 * be set, propagate it into PREEMPT_NEED_RESCHED.
  	 *
  	 * This is required because for polling idle loops we will not have had
  	 * an IPI to fold the state for us.
  	 */
  	preempt_set_need_resched();
  	tick_nohz_idle_exit();
  	__current_clr_polling();
  
  	/*
  	 * We promise to call sched_ttwu_pending() and reschedule if
  	 * need_resched() is set while polling is set. That means that clearing
  	 * polling needs to be visible before doing these things.
  	 */
  	smp_mb__after_atomic();
  
  	sched_ttwu_pending();

  	schedule_idle();

  
  	if (unlikely(klp_patch_pending(current)))
  		klp_update_patch_state(current);

  }

  bool cpu_in_idle(unsigned long pc)
  {
  	return pc >= (unsigned long)__cpuidle_text_start &&
  		pc < (unsigned long)__cpuidle_text_end;
  }

  struct idle_timer {
  	struct hrtimer timer;
  	int done;
  };
  
  static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
  {
  	struct idle_timer *it = container_of(timer, struct idle_timer, timer);
  
  	WRITE_ONCE(it->done, 1);
  	set_tsk_need_resched(current);
  
  	return HRTIMER_NORESTART;
  }
  
  void play_idle(unsigned long duration_ms)
  {
  	struct idle_timer it;
  
  	/*
  	 * Only FIFO tasks can disable the tick since they don't need the forced
  	 * preemption.
  	 */
  	WARN_ON_ONCE(current->policy != SCHED_FIFO);
  	WARN_ON_ONCE(current->nr_cpus_allowed != 1);
  	WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
  	WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
  	WARN_ON_ONCE(!duration_ms);
  
  	rcu_sleep_check();
  	preempt_disable();
  	current->flags |= PF_IDLE;
  	cpuidle_use_deepest_state(true);
  
  	it.done = 0;
  	hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  	it.timer.function = idle_inject_timer_fn;
  	hrtimer_start(&it.timer, ms_to_ktime(duration_ms), HRTIMER_MODE_REL_PINNED);
  
  	while (!READ_ONCE(it.done))
  		do_idle();
  
  	cpuidle_use_deepest_state(false);
  	current->flags &= ~PF_IDLE;
  
  	preempt_fold_need_resched();
  	preempt_enable();
  }
  EXPORT_SYMBOL_GPL(play_idle);

  void cpu_startup_entry(enum cpuhp_state state)
  {
  	/*
  	 * This #ifdef needs to die, but it's too late in the cycle to
  	 * make this generic (arm and sh have never invoked the canary
  	 * init for the non boot cpus!). Will be fixed in 3.11
  	 */
  #ifdef CONFIG_X86
  	/*
  	 * If we're the non-boot CPU, nothing set the stack canary up
  	 * for us. The boot CPU already has it initialized but no harm
  	 * in doing it again. This is a good place for updating it, as
  	 * we wont ever return from this function (so the invalid
  	 * canaries already on the stack wont ever trigger).
  	 */
  	boot_init_stack_canary();
  #endif

  	arch_cpu_idle_prepare();

  	cpuhp_online_idle(state);

  	while (1)
  		do_idle();

  }