text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   *  kernel/sched/core.c
   *
   *  Core kernel scheduler code and related syscalls
   *
   *  Copyright (C) 1991-2002  Linus Torvalds
   */
  #include "sched.h"
  
  #include <linux/nospec.h>
  
  #include <linux/kcov.h>
  
  #include <asm/switch_to.h>
  #include <asm/tlb.h>
  
  #include "../workqueue_internal.h"
  #include "../smpboot.h"
  
  #include "pelt.h"
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/sched.h>
  
  /*
   * Export tracepoints that act as a bare tracehook (ie: have no trace event
   * associated with them) to allow external modules to probe them.
   */
  EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
  EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp);
  EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
  EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
  EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
  EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
  
  DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
  
  #if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_JUMP_LABEL)
  /*
   * Debugging: various feature bits
   *
   * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
   * sysctl_sched_features, defined in sched.h, to allow constants propagation
   * at compile time and compiler optimization based on features default.
   */
  #define SCHED_FEAT(name, enabled)	\
  	(1UL << __SCHED_FEAT_##name) * enabled |
  const_debug unsigned int sysctl_sched_features =
  #include "features.h"
  	0;
  #undef SCHED_FEAT
  #endif
  
  /*
   * Number of tasks to iterate in a single balance run.
   * Limited because this is done with IRQs disabled.
   */
  const_debug unsigned int sysctl_sched_nr_migrate = 32;
  
  /*
   * period over which we measure -rt task CPU usage in us.
   * default: 1s
   */
  unsigned int sysctl_sched_rt_period = 1000000;
  
  __read_mostly int scheduler_running;
  
  /*
   * part of the period that we allow rt tasks to run in us.
   * default: 0.95s
   */
  int sysctl_sched_rt_runtime = 950000;
  
  /*
   * __task_rq_lock - lock the rq @p resides on.
   */
  struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
  	__acquires(rq->lock)
  {
  	struct rq *rq;
  
  	lockdep_assert_held(&p->pi_lock);
  
  	for (;;) {
  		rq = task_rq(p);
  		raw_spin_lock(&rq->lock);
  		if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
  			rq_pin_lock(rq, rf);
  			return rq;
  		}
  		raw_spin_unlock(&rq->lock);
  
  		while (unlikely(task_on_rq_migrating(p)))
  			cpu_relax();
  	}
  }
  
  /*
   * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
   */
  struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
  	__acquires(p->pi_lock)
  	__acquires(rq->lock)
  {
  	struct rq *rq;
  
  	for (;;) {
  		raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
  		rq = task_rq(p);
  		raw_spin_lock(&rq->lock);
  		/*
  		 *	move_queued_task()		task_rq_lock()
  		 *
  		 *	ACQUIRE (rq->lock)
  		 *	[S] ->on_rq = MIGRATING		[L] rq = task_rq()
  		 *	WMB (__set_task_cpu())		ACQUIRE (rq->lock);
  		 *	[S] ->cpu = new_cpu		[L] task_rq()
  		 *					[L] ->on_rq
  		 *	RELEASE (rq->lock)
  		 *
  		 * If we observe the old CPU in task_rq_lock(), the acquire of
  		 * the old rq->lock will fully serialize against the stores.
  		 *
  		 * If we observe the new CPU in task_rq_lock(), the address
  		 * dependency headed by '[L] rq = task_rq()' and the acquire
  		 * will pair with the WMB to ensure we then also see migrating.
  		 */
  		if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
  			rq_pin_lock(rq, rf);
  			return rq;
  		}
  		raw_spin_unlock(&rq->lock);
  		raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
  
  		while (unlikely(task_on_rq_migrating(p)))
  			cpu_relax();
  	}
  }
  
  /*
   * RQ-clock updating methods:
   */
  
  static void update_rq_clock_task(struct rq *rq, s64 delta)
  {
  /*
   * In theory, the compile should just see 0 here, and optimize out the call
   * to sched_rt_avg_update. But I don't trust it...
   */
  	s64 __maybe_unused steal = 0, irq_delta = 0;
  
  #ifdef CONFIG_IRQ_TIME_ACCOUNTING
  	irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
  
  	/*
  	 * Since irq_time is only updated on {soft,}irq_exit, we might run into
  	 * this case when a previous update_rq_clock() happened inside a
  	 * {soft,}irq region.
  	 *
  	 * When this happens, we stop ->clock_task and only update the
  	 * prev_irq_time stamp to account for the part that fit, so that a next
  	 * update will consume the rest. This ensures ->clock_task is
  	 * monotonic.
  	 *
  	 * It does however cause some slight miss-attribution of {soft,}irq
  	 * time, a more accurate solution would be to update the irq_time using
  	 * the current rq->clock timestamp, except that would require using
  	 * atomic ops.
  	 */
  	if (irq_delta > delta)
  		irq_delta = delta;
  
  	rq->prev_irq_time += irq_delta;
  	delta -= irq_delta;
  #endif
  #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
  	if (static_key_false((&paravirt_steal_rq_enabled))) {
  		steal = paravirt_steal_clock(cpu_of(rq));
  		steal -= rq->prev_steal_time_rq;
  
  		if (unlikely(steal > delta))
  			steal = delta;
  
  		rq->prev_steal_time_rq += steal;
  		delta -= steal;
  	}
  #endif
  
  	rq->clock_task += delta;
  
  #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
  	if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
  		update_irq_load_avg(rq, irq_delta + steal);
  #endif
  	update_rq_clock_pelt(rq, delta);
  }
  
  void update_rq_clock(struct rq *rq)
  {
  	s64 delta;
  
  	lockdep_assert_held(&rq->lock);
  
  	if (rq->clock_update_flags & RQCF_ACT_SKIP)
  		return;
  
  #ifdef CONFIG_SCHED_DEBUG
  	if (sched_feat(WARN_DOUBLE_CLOCK))
  		SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
  	rq->clock_update_flags |= RQCF_UPDATED;
  #endif
  
  	delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
  	if (delta < 0)
  		return;
  	rq->clock += delta;
  	update_rq_clock_task(rq, delta);
  }
  
  
  #ifdef CONFIG_SCHED_HRTICK
  /*
   * Use HR-timers to deliver accurate preemption points.
   */
  
  static void hrtick_clear(struct rq *rq)
  {
  	if (hrtimer_active(&rq->hrtick_timer))
  		hrtimer_cancel(&rq->hrtick_timer);
  }
  
  /*
   * High-resolution timer tick.
   * Runs from hardirq context with interrupts disabled.
   */
  static enum hrtimer_restart hrtick(struct hrtimer *timer)
  {
  	struct rq *rq = container_of(timer, struct rq, hrtick_timer);
  	struct rq_flags rf;
  
  	WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
  
  	rq_lock(rq, &rf);
  	update_rq_clock(rq);
  	rq->curr->sched_class->task_tick(rq, rq->curr, 1);
  	rq_unlock(rq, &rf);
  
  	return HRTIMER_NORESTART;
  }
  
  #ifdef CONFIG_SMP
  
  static void __hrtick_restart(struct rq *rq)
  {
  	struct hrtimer *timer = &rq->hrtick_timer;
  
  	hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED_HARD);
  }
  
  /*
   * called from hardirq (IPI) context
   */
  static void __hrtick_start(void *arg)
  {
  	struct rq *rq = arg;
  	struct rq_flags rf;
  
  	rq_lock(rq, &rf);
  	__hrtick_restart(rq);
  	rq->hrtick_csd_pending = 0;
  	rq_unlock(rq, &rf);
  }
  
  /*
   * Called to set the hrtick timer state.
   *
   * called with rq->lock held and irqs disabled
   */
  void hrtick_start(struct rq *rq, u64 delay)
  {
  	struct hrtimer *timer = &rq->hrtick_timer;
  	ktime_t time;
  	s64 delta;
  
  	/*
  	 * Don't schedule slices shorter than 10000ns, that just
  	 * doesn't make sense and can cause timer DoS.
  	 */
  	delta = max_t(s64, delay, 10000LL);
  	time = ktime_add_ns(timer->base->get_time(), delta);
  
  	hrtimer_set_expires(timer, time);
  
  	if (rq == this_rq()) {
  		__hrtick_restart(rq);
  	} else if (!rq->hrtick_csd_pending) {
  		smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
  		rq->hrtick_csd_pending = 1;
  	}
  }
  
  #else
  /*
   * Called to set the hrtick timer state.
   *
   * called with rq->lock held and irqs disabled
   */
  void hrtick_start(struct rq *rq, u64 delay)
  {
  	/*
  	 * Don't schedule slices shorter than 10000ns, that just
  	 * doesn't make sense. Rely on vruntime for fairness.
  	 */
  	delay = max_t(u64, delay, 10000LL);
  	hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
  		      HRTIMER_MODE_REL_PINNED_HARD);
  }
  #endif /* CONFIG_SMP */
  
  static void hrtick_rq_init(struct rq *rq)
  {
  #ifdef CONFIG_SMP
  	rq->hrtick_csd_pending = 0;
  
  	rq->hrtick_csd.flags = 0;
  	rq->hrtick_csd.func = __hrtick_start;
  	rq->hrtick_csd.info = rq;
  #endif
  
  	hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
  	rq->hrtick_timer.function = hrtick;
  }
  #else	/* CONFIG_SCHED_HRTICK */
  static inline void hrtick_clear(struct rq *rq)
  {
  }
  
  static inline void hrtick_rq_init(struct rq *rq)
  {
  }
  #endif	/* CONFIG_SCHED_HRTICK */
  
  /*
   * cmpxchg based fetch_or, macro so it works for different integer types
   */
  #define fetch_or(ptr, mask)						\
  	({								\
  		typeof(ptr) _ptr = (ptr);				\
  		typeof(mask) _mask = (mask);				\
  		typeof(*_ptr) _old, _val = *_ptr;			\
  									\
  		for (;;) {						\
  			_old = cmpxchg(_ptr, _val, _val | _mask);	\
  			if (_old == _val)				\
  				break;					\
  			_val = _old;					\
  		}							\
  	_old;								\
  })
  
  #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
  /*
   * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
   * this avoids any races wrt polling state changes and thereby avoids
   * spurious IPIs.
   */
  static bool set_nr_and_not_polling(struct task_struct *p)
  {
  	struct thread_info *ti = task_thread_info(p);
  	return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
  }
  
  /*
   * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
   *
   * If this returns true, then the idle task promises to call
   * sched_ttwu_pending() and reschedule soon.
   */
  static bool set_nr_if_polling(struct task_struct *p)
  {
  	struct thread_info *ti = task_thread_info(p);
  	typeof(ti->flags) old, val = READ_ONCE(ti->flags);
  
  	for (;;) {
  		if (!(val & _TIF_POLLING_NRFLAG))
  			return false;
  		if (val & _TIF_NEED_RESCHED)
  			return true;
  		old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
  		if (old == val)
  			break;
  		val = old;
  	}
  	return true;
  }
  
  #else
  static bool set_nr_and_not_polling(struct task_struct *p)
  {
  	set_tsk_need_resched(p);
  	return true;
  }
  
  #ifdef CONFIG_SMP
  static bool set_nr_if_polling(struct task_struct *p)
  {
  	return false;
  }
  #endif
  #endif
  
  static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
  {
  	struct wake_q_node *node = &task->wake_q;
  
  	/*
  	 * Atomically grab the task, if ->wake_q is !nil already it means
  	 * its already queued (either by us or someone else) and will get the
  	 * wakeup due to that.
  	 *
  	 * In order to ensure that a pending wakeup will observe our pending
  	 * state, even in the failed case, an explicit smp_mb() must be used.
  	 */
  	smp_mb__before_atomic();
  	if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
  		return false;
  
  	/*
  	 * The head is context local, there can be no concurrency.
  	 */
  	*head->lastp = node;
  	head->lastp = &node->next;
  	return true;
  }
  
  /**
   * wake_q_add() - queue a wakeup for 'later' waking.
   * @head: the wake_q_head to add @task to
   * @task: the task to queue for 'later' wakeup
   *
   * Queue a task for later wakeup, most likely by the wake_up_q() call in the
   * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
   * instantly.
   *
   * This function must be used as-if it were wake_up_process(); IOW the task
   * must be ready to be woken at this location.
   */
  void wake_q_add(struct wake_q_head *head, struct task_struct *task)
  {
  	if (__wake_q_add(head, task))
  		get_task_struct(task);
  }
  
  /**
   * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
   * @head: the wake_q_head to add @task to
   * @task: the task to queue for 'later' wakeup
   *
   * Queue a task for later wakeup, most likely by the wake_up_q() call in the
   * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
   * instantly.
   *
   * This function must be used as-if it were wake_up_process(); IOW the task
   * must be ready to be woken at this location.
   *
   * This function is essentially a task-safe equivalent to wake_q_add(). Callers
   * that already hold reference to @task can call the 'safe' version and trust
   * wake_q to do the right thing depending whether or not the @task is already
   * queued for wakeup.
   */
  void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
  {
  	if (!__wake_q_add(head, task))
  		put_task_struct(task);
  }
  
  void wake_up_q(struct wake_q_head *head)
  {
  	struct wake_q_node *node = head->first;
  
  	while (node != WAKE_Q_TAIL) {
  		struct task_struct *task;
  
  		task = container_of(node, struct task_struct, wake_q);
  		BUG_ON(!task);
  		/* Task can safely be re-inserted now: */
  		node = node->next;
  		task->wake_q.next = NULL;
  
  		/*
  		 * wake_up_process() executes a full barrier, which pairs with
  		 * the queueing in wake_q_add() so as not to miss wakeups.
  		 */
  		wake_up_process(task);
  		put_task_struct(task);
  	}
  }
  
  /*
   * resched_curr - mark rq's current task 'to be rescheduled now'.
   *
   * On UP this means the setting of the need_resched flag, on SMP it
   * might also involve a cross-CPU call to trigger the scheduler on
   * the target CPU.
   */
  void resched_curr(struct rq *rq)
  {
  	struct task_struct *curr = rq->curr;
  	int cpu;
  
  	lockdep_assert_held(&rq->lock);
  
  	if (test_tsk_need_resched(curr))
  		return;
  
  	cpu = cpu_of(rq);
  
  	if (cpu == smp_processor_id()) {
  		set_tsk_need_resched(curr);
  		set_preempt_need_resched();
  		return;
  	}
  
  	if (set_nr_and_not_polling(curr))
  		smp_send_reschedule(cpu);
  	else
  		trace_sched_wake_idle_without_ipi(cpu);
  }
  
  void resched_cpu(int cpu)
  {
  	struct rq *rq = cpu_rq(cpu);
  	unsigned long flags;
  
  	raw_spin_lock_irqsave(&rq->lock, flags);
  	if (cpu_online(cpu) || cpu == smp_processor_id())
  		resched_curr(rq);
  	raw_spin_unlock_irqrestore(&rq->lock, flags);
  }
  
  #ifdef CONFIG_SMP
  #ifdef CONFIG_NO_HZ_COMMON
  /*
   * In the semi idle case, use the nearest busy CPU for migrating timers
   * from an idle CPU.  This is good for power-savings.
   *
   * We don't do similar optimization for completely idle system, as
   * selecting an idle CPU will add more delays to the timers than intended
   * (as that CPU's timer base may not be uptodate wrt jiffies etc).
   */
  int get_nohz_timer_target(void)
  {
  	int i, cpu = smp_processor_id();
  	struct sched_domain *sd;
  
  	if (!idle_cpu(cpu) && housekeeping_cpu(cpu, HK_FLAG_TIMER))
  		return cpu;
  
  	rcu_read_lock();
  	for_each_domain(cpu, sd) {
  		for_each_cpu(i, sched_domain_span(sd)) {
  			if (cpu == i)
  				continue;
  
  			if (!idle_cpu(i) && housekeeping_cpu(i, HK_FLAG_TIMER)) {
  				cpu = i;
  				goto unlock;
  			}
  		}
  	}
  
  	if (!housekeeping_cpu(cpu, HK_FLAG_TIMER))
  		cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
  unlock:
  	rcu_read_unlock();
  	return cpu;
  }
  
  /*
   * When add_timer_on() enqueues a timer into the timer wheel of an
   * idle CPU then this timer might expire before the next timer event
   * which is scheduled to wake up that CPU. In case of a completely
   * idle system the next event might even be infinite time into the
   * future. wake_up_idle_cpu() ensures that the CPU is woken up and
   * leaves the inner idle loop so the newly added timer is taken into
   * account when the CPU goes back to idle and evaluates the timer
   * wheel for the next timer event.
   */
  static void wake_up_idle_cpu(int cpu)
  {
  	struct rq *rq = cpu_rq(cpu);
  
  	if (cpu == smp_processor_id())
  		return;
  
  	if (set_nr_and_not_polling(rq->idle))
  		smp_send_reschedule(cpu);
  	else
  		trace_sched_wake_idle_without_ipi(cpu);
  }
  
  static bool wake_up_full_nohz_cpu(int cpu)
  {
  	/*
  	 * We just need the target to call irq_exit() and re-evaluate
  	 * the next tick. The nohz full kick at least implies that.
  	 * If needed we can still optimize that later with an
  	 * empty IRQ.
  	 */
  	if (cpu_is_offline(cpu))
  		return true;  /* Don't try to wake offline CPUs. */
  	if (tick_nohz_full_cpu(cpu)) {
  		if (cpu != smp_processor_id() ||
  		    tick_nohz_tick_stopped())
  			tick_nohz_full_kick_cpu(cpu);
  		return true;
  	}
  
  	return false;
  }
  
  /*
   * Wake up the specified CPU.  If the CPU is going offline, it is the
   * caller's responsibility to deal with the lost wakeup, for example,
   * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
   */
  void wake_up_nohz_cpu(int cpu)
  {
  	if (!wake_up_full_nohz_cpu(cpu))
  		wake_up_idle_cpu(cpu);
  }
  
  static inline bool got_nohz_idle_kick(void)
  {
  	int cpu = smp_processor_id();
  
  	if (!(atomic_read(nohz_flags(cpu)) & NOHZ_KICK_MASK))
  		return false;
  
  	if (idle_cpu(cpu) && !need_resched())
  		return true;
  
  	/*
  	 * We can't run Idle Load Balance on this CPU for this time so we
  	 * cancel it and clear NOHZ_BALANCE_KICK
  	 */
  	atomic_andnot(NOHZ_KICK_MASK, nohz_flags(cpu));
  	return false;
  }
  
  #else /* CONFIG_NO_HZ_COMMON */
  
  static inline bool got_nohz_idle_kick(void)
  {
  	return false;
  }
  
  #endif /* CONFIG_NO_HZ_COMMON */
  
  #ifdef CONFIG_NO_HZ_FULL
  bool sched_can_stop_tick(struct rq *rq)
  {
  	int fifo_nr_running;
  
  	/* Deadline tasks, even if single, need the tick */
  	if (rq->dl.dl_nr_running)
  		return false;
  
  	/*
  	 * If there are more than one RR tasks, we need the tick to effect the
  	 * actual RR behaviour.
  	 */
  	if (rq->rt.rr_nr_running) {
  		if (rq->rt.rr_nr_running == 1)
  			return true;
  		else
  			return false;
  	}
  
  	/*
  	 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
  	 * forced preemption between FIFO tasks.
  	 */
  	fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
  	if (fifo_nr_running)
  		return true;
  
  	/*
  	 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
  	 * if there's more than one we need the tick for involuntary
  	 * preemption.
  	 */
  	if (rq->nr_running > 1)
  		return false;
  
  	return true;
  }
  #endif /* CONFIG_NO_HZ_FULL */
  #endif /* CONFIG_SMP */
  
  #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
  			(defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
  /*
   * Iterate task_group tree rooted at *from, calling @down when first entering a
   * node and @up when leaving it for the final time.
   *
   * Caller must hold rcu_lock or sufficient equivalent.
   */
  int walk_tg_tree_from(struct task_group *from,
  			     tg_visitor down, tg_visitor up, void *data)
  {
  	struct task_group *parent, *child;
  	int ret;
  
  	parent = from;
  
  down:
  	ret = (*down)(parent, data);
  	if (ret)
  		goto out;
  	list_for_each_entry_rcu(child, &parent->children, siblings) {
  		parent = child;
  		goto down;
  
  up:
  		continue;
  	}
  	ret = (*up)(parent, data);
  	if (ret || parent == from)
  		goto out;
  
  	child = parent;
  	parent = parent->parent;
  	if (parent)
  		goto up;
  out:
  	return ret;
  }
  
  int tg_nop(struct task_group *tg, void *data)
  {
  	return 0;
  }
  #endif
  
  static void set_load_weight(struct task_struct *p, bool update_load)
  {
  	int prio = p->static_prio - MAX_RT_PRIO;
  	struct load_weight *load = &p->se.load;
  
  	/*
  	 * SCHED_IDLE tasks get minimal weight:
  	 */
  	if (task_has_idle_policy(p)) {
  		load->weight = scale_load(WEIGHT_IDLEPRIO);
  		load->inv_weight = WMULT_IDLEPRIO;
  		p->se.runnable_weight = load->weight;
  		return;
  	}
  
  	/*
  	 * SCHED_OTHER tasks have to update their load when changing their
  	 * weight
  	 */
  	if (update_load && p->sched_class == &fair_sched_class) {
  		reweight_task(p, prio);
  	} else {
  		load->weight = scale_load(sched_prio_to_weight[prio]);
  		load->inv_weight = sched_prio_to_wmult[prio];
  		p->se.runnable_weight = load->weight;
  	}
  }
  
  #ifdef CONFIG_UCLAMP_TASK
  /*
   * Serializes updates of utilization clamp values
   *
   * The (slow-path) user-space triggers utilization clamp value updates which
   * can require updates on (fast-path) scheduler's data structures used to
   * support enqueue/dequeue operations.
   * While the per-CPU rq lock protects fast-path update operations, user-space
   * requests are serialized using a mutex to reduce the risk of conflicting
   * updates or API abuses.
   */
  static DEFINE_MUTEX(uclamp_mutex);
  
  /* Max allowed minimum utilization */
  unsigned int sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE;
  
  /* Max allowed maximum utilization */
  unsigned int sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE;
  
  /* All clamps are required to be less or equal than these values */
  static struct uclamp_se uclamp_default[UCLAMP_CNT];
  
  /*
   * This static key is used to reduce the uclamp overhead in the fast path. It
   * primarily disables the call to uclamp_rq_{inc, dec}() in
   * enqueue/dequeue_task().
   *
   * This allows users to continue to enable uclamp in their kernel config with
   * minimum uclamp overhead in the fast path.
   *
   * As soon as userspace modifies any of the uclamp knobs, the static key is
   * enabled, since we have an actual users that make use of uclamp
   * functionality.
   *
   * The knobs that would enable this static key are:
   *
   *   * A task modifying its uclamp value with sched_setattr().
   *   * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
   *   * An admin modifying the cgroup cpu.uclamp.{min, max}
   */
  DEFINE_STATIC_KEY_FALSE(sched_uclamp_used);
  
  /* Integer rounded range for each bucket */
  #define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)
  
  #define for_each_clamp_id(clamp_id) \
  	for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)
  
  static inline unsigned int uclamp_bucket_id(unsigned int clamp_value)
  {
  	return clamp_value / UCLAMP_BUCKET_DELTA;
  }
  
  static inline unsigned int uclamp_bucket_base_value(unsigned int clamp_value)
  {
  	return UCLAMP_BUCKET_DELTA * uclamp_bucket_id(clamp_value);
  }
  
  static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
  {
  	if (clamp_id == UCLAMP_MIN)
  		return 0;
  	return SCHED_CAPACITY_SCALE;
  }
  
  static inline void uclamp_se_set(struct uclamp_se *uc_se,
  				 unsigned int value, bool user_defined)
  {
  	uc_se->value = value;
  	uc_se->bucket_id = uclamp_bucket_id(value);
  	uc_se->user_defined = user_defined;
  }
  
  static inline unsigned int
  uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id,
  		  unsigned int clamp_value)
  {
  	/*
  	 * Avoid blocked utilization pushing up the frequency when we go
  	 * idle (which drops the max-clamp) by retaining the last known
  	 * max-clamp.
  	 */
  	if (clamp_id == UCLAMP_MAX) {
  		rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
  		return clamp_value;
  	}
  
  	return uclamp_none(UCLAMP_MIN);
  }
  
  static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
  				     unsigned int clamp_value)
  {
  	/* Reset max-clamp retention only on idle exit */
  	if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
  		return;
  
  	WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
  }
  
  static inline
  unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
  				   unsigned int clamp_value)
  {
  	struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
  	int bucket_id = UCLAMP_BUCKETS - 1;
  
  	/*
  	 * Since both min and max clamps are max aggregated, find the
  	 * top most bucket with tasks in.
  	 */
  	for ( ; bucket_id >= 0; bucket_id--) {
  		if (!bucket[bucket_id].tasks)
  			continue;
  		return bucket[bucket_id].value;
  	}
  
  	/* No tasks -- default clamp values */
  	return uclamp_idle_value(rq, clamp_id, clamp_value);
  }
  
  static inline struct uclamp_se
  uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
  {
  	struct uclamp_se uc_req = p->uclamp_req[clamp_id];
  #ifdef CONFIG_UCLAMP_TASK_GROUP
  	struct uclamp_se uc_max;
  
  	/*
  	 * Tasks in autogroups or root task group will be
  	 * restricted by system defaults.
  	 */
  	if (task_group_is_autogroup(task_group(p)))
  		return uc_req;
  	if (task_group(p) == &root_task_group)
  		return uc_req;
  
  	uc_max = task_group(p)->uclamp[clamp_id];
  	if (uc_req.value > uc_max.value || !uc_req.user_defined)
  		return uc_max;
  #endif
  
  	return uc_req;
  }
  
  /*
   * The effective clamp bucket index of a task depends on, by increasing
   * priority:
   * - the task specific clamp value, when explicitly requested from userspace
   * - the task group effective clamp value, for tasks not either in the root
   *   group or in an autogroup
   * - the system default clamp value, defined by the sysadmin
   */
  static inline struct uclamp_se
  uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
  {
  	struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
  	struct uclamp_se uc_max = uclamp_default[clamp_id];
  
  	/* System default restrictions always apply */
  	if (unlikely(uc_req.value > uc_max.value))
  		return uc_max;
  
  	return uc_req;
  }
  
  unsigned int uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
  {
  	struct uclamp_se uc_eff;
  
  	/* Task currently refcounted: use back-annotated (effective) value */
  	if (p->uclamp[clamp_id].active)
  		return p->uclamp[clamp_id].value;
  
  	uc_eff = uclamp_eff_get(p, clamp_id);
  
  	return uc_eff.value;
  }
  
  /*
   * When a task is enqueued on a rq, the clamp bucket currently defined by the
   * task's uclamp::bucket_id is refcounted on that rq. This also immediately
   * updates the rq's clamp value if required.
   *
   * Tasks can have a task-specific value requested from user-space, track
   * within each bucket the maximum value for tasks refcounted in it.
   * This "local max aggregation" allows to track the exact "requested" value
   * for each bucket when all its RUNNABLE tasks require the same clamp.
   */
  static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
  				    enum uclamp_id clamp_id)
  {
  	struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
  	struct uclamp_se *uc_se = &p->uclamp[clamp_id];
  	struct uclamp_bucket *bucket;
  
  	lockdep_assert_held(&rq->lock);
  
  	/* Update task effective clamp */
  	p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);
  
  	bucket = &uc_rq->bucket[uc_se->bucket_id];
  	bucket->tasks++;
  	uc_se->active = true;
  
  	uclamp_idle_reset(rq, clamp_id, uc_se->value);
  
  	/*
  	 * Local max aggregation: rq buckets always track the max
  	 * "requested" clamp value of its RUNNABLE tasks.
  	 */
  	if (bucket->tasks == 1 || uc_se->value > bucket->value)
  		bucket->value = uc_se->value;
  
  	if (uc_se->value > READ_ONCE(uc_rq->value))
  		WRITE_ONCE(uc_rq->value, uc_se->value);
  }
  
  /*
   * When a task is dequeued from a rq, the clamp bucket refcounted by the task
   * is released. If this is the last task reference counting the rq's max
   * active clamp value, then the rq's clamp value is updated.
   *
   * Both refcounted tasks and rq's cached clamp values are expected to be
   * always valid. If it's detected they are not, as defensive programming,
   * enforce the expected state and warn.
   */
  static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
  				    enum uclamp_id clamp_id)
  {
  	struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
  	struct uclamp_se *uc_se = &p->uclamp[clamp_id];
  	struct uclamp_bucket *bucket;
  	unsigned int bkt_clamp;
  	unsigned int rq_clamp;
  
  	lockdep_assert_held(&rq->lock);
  
  	/*
  	 * If sched_uclamp_used was enabled after task @p was enqueued,
  	 * we could end up with unbalanced call to uclamp_rq_dec_id().
  	 *
  	 * In this case the uc_se->active flag should be false since no uclamp
  	 * accounting was performed at enqueue time and we can just return
  	 * here.
  	 *
  	 * Need to be careful of the following enqeueue/dequeue ordering
  	 * problem too
  	 *
  	 *	enqueue(taskA)
  	 *	// sched_uclamp_used gets enabled
  	 *	enqueue(taskB)
  	 *	dequeue(taskA)
  	 *	// Must not decrement bukcet->tasks here
  	 *	dequeue(taskB)
  	 *
  	 * where we could end up with stale data in uc_se and
  	 * bucket[uc_se->bucket_id].
  	 *
  	 * The following check here eliminates the possibility of such race.
  	 */
  	if (unlikely(!uc_se->active))
  		return;
  
  	bucket = &uc_rq->bucket[uc_se->bucket_id];
  
  	SCHED_WARN_ON(!bucket->tasks);
  	if (likely(bucket->tasks))
  		bucket->tasks--;
  
  	uc_se->active = false;
  
  	/*
  	 * Keep "local max aggregation" simple and accept to (possibly)
  	 * overboost some RUNNABLE tasks in the same bucket.
  	 * The rq clamp bucket value is reset to its base value whenever
  	 * there are no more RUNNABLE tasks refcounting it.
  	 */
  	if (likely(bucket->tasks))
  		return;
  
  	rq_clamp = READ_ONCE(uc_rq->value);
  	/*
  	 * Defensive programming: this should never happen. If it happens,
  	 * e.g. due to future modification, warn and fixup the expected value.
  	 */
  	SCHED_WARN_ON(bucket->value > rq_clamp);
  	if (bucket->value >= rq_clamp) {
  		bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
  		WRITE_ONCE(uc_rq->value, bkt_clamp);
  	}
  }
  
  static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
  {
  	enum uclamp_id clamp_id;
  
  	/*
  	 * Avoid any overhead until uclamp is actually used by the userspace.
  	 *
  	 * The condition is constructed such that a NOP is generated when
  	 * sched_uclamp_used is disabled.
  	 */
  	if (!static_branch_unlikely(&sched_uclamp_used))
  		return;
  
  	if (unlikely(!p->sched_class->uclamp_enabled))
  		return;
  
  	for_each_clamp_id(clamp_id)
  		uclamp_rq_inc_id(rq, p, clamp_id);
  
  	/* Reset clamp idle holding when there is one RUNNABLE task */
  	if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
  		rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
  }
  
  static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
  {
  	enum uclamp_id clamp_id;
  
  	/*
  	 * Avoid any overhead until uclamp is actually used by the userspace.
  	 *
  	 * The condition is constructed such that a NOP is generated when
  	 * sched_uclamp_used is disabled.
  	 */
  	if (!static_branch_unlikely(&sched_uclamp_used))
  		return;
  
  	if (unlikely(!p->sched_class->uclamp_enabled))
  		return;
  
  	for_each_clamp_id(clamp_id)
  		uclamp_rq_dec_id(rq, p, clamp_id);
  }
  
  static inline void
  uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id)
  {
  	struct rq_flags rf;
  	struct rq *rq;
  
  	/*
  	 * Lock the task and the rq where the task is (or was) queued.
  	 *
  	 * We might lock the (previous) rq of a !RUNNABLE task, but that's the
  	 * price to pay to safely serialize util_{min,max} updates with
  	 * enqueues, dequeues and migration operations.
  	 * This is the same locking schema used by __set_cpus_allowed_ptr().
  	 */
  	rq = task_rq_lock(p, &rf);
  
  	/*
  	 * Setting the clamp bucket is serialized by task_rq_lock().
  	 * If the task is not yet RUNNABLE and its task_struct is not
  	 * affecting a valid clamp bucket, the next time it's enqueued,
  	 * it will already see the updated clamp bucket value.
  	 */
  	if (p->uclamp[clamp_id].active) {
  		uclamp_rq_dec_id(rq, p, clamp_id);
  		uclamp_rq_inc_id(rq, p, clamp_id);
  	}
  
  	task_rq_unlock(rq, p, &rf);
  }
  
  #ifdef CONFIG_UCLAMP_TASK_GROUP
  static inline void
  uclamp_update_active_tasks(struct cgroup_subsys_state *css,
  			   unsigned int clamps)
  {
  	enum uclamp_id clamp_id;
  	struct css_task_iter it;
  	struct task_struct *p;
  
  	css_task_iter_start(css, 0, &it);
  	while ((p = css_task_iter_next(&it))) {
  		for_each_clamp_id(clamp_id) {
  			if ((0x1 << clamp_id) & clamps)
  				uclamp_update_active(p, clamp_id);
  		}
  	}
  	css_task_iter_end(&it);
  }
  
  static void cpu_util_update_eff(struct cgroup_subsys_state *css);
  static void uclamp_update_root_tg(void)
  {
  	struct task_group *tg = &root_task_group;
  
  	uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN],
  		      sysctl_sched_uclamp_util_min, false);
  	uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
  		      sysctl_sched_uclamp_util_max, false);
  
  	rcu_read_lock();
  	cpu_util_update_eff(&root_task_group.css);
  	rcu_read_unlock();
  }
  #else
  static void uclamp_update_root_tg(void) { }
  #endif
  
  int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
  				void __user *buffer, size_t *lenp,
  				loff_t *ppos)
  {
  	bool update_root_tg = false;
  	int old_min, old_max;
  	int result;
  
  	mutex_lock(&uclamp_mutex);
  	old_min = sysctl_sched_uclamp_util_min;
  	old_max = sysctl_sched_uclamp_util_max;
  
  	result = proc_dointvec(table, write, buffer, lenp, ppos);
  	if (result)
  		goto undo;
  	if (!write)
  		goto done;
  
  	if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max ||
  	    sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE) {
  		result = -EINVAL;
  		goto undo;
  	}
  
  	if (old_min != sysctl_sched_uclamp_util_min) {
  		uclamp_se_set(&uclamp_default[UCLAMP_MIN],
  			      sysctl_sched_uclamp_util_min, false);
  		update_root_tg = true;
  	}
  	if (old_max != sysctl_sched_uclamp_util_max) {
  		uclamp_se_set(&uclamp_default[UCLAMP_MAX],
  			      sysctl_sched_uclamp_util_max, false);
  		update_root_tg = true;
  	}
  
  	if (update_root_tg) {
  		static_branch_enable(&sched_uclamp_used);
  		uclamp_update_root_tg();
  	}
  
  	/*
  	 * We update all RUNNABLE tasks only when task groups are in use.
  	 * Otherwise, keep it simple and do just a lazy update at each next
  	 * task enqueue time.
  	 */
  
  	goto done;
  
  undo:
  	sysctl_sched_uclamp_util_min = old_min;
  	sysctl_sched_uclamp_util_max = old_max;
  done:
  	mutex_unlock(&uclamp_mutex);
  
  	return result;
  }
  
  static int uclamp_validate(struct task_struct *p,
  			   const struct sched_attr *attr)
  {
  	unsigned int lower_bound = p->uclamp_req[UCLAMP_MIN].value;
  	unsigned int upper_bound = p->uclamp_req[UCLAMP_MAX].value;
  
  	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN)
  		lower_bound = attr->sched_util_min;
  	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX)
  		upper_bound = attr->sched_util_max;
  
  	if (lower_bound > upper_bound)
  		return -EINVAL;
  	if (upper_bound > SCHED_CAPACITY_SCALE)
  		return -EINVAL;
  
  	/*
  	 * We have valid uclamp attributes; make sure uclamp is enabled.
  	 *
  	 * We need to do that here, because enabling static branches is a
  	 * blocking operation which obviously cannot be done while holding
  	 * scheduler locks.
  	 */
  	static_branch_enable(&sched_uclamp_used);
  
  	return 0;
  }
  
  static void __setscheduler_uclamp(struct task_struct *p,
  				  const struct sched_attr *attr)
  {
  	enum uclamp_id clamp_id;
  
  	/*
  	 * On scheduling class change, reset to default clamps for tasks
  	 * without a task-specific value.
  	 */
  	for_each_clamp_id(clamp_id) {
  		struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
  		unsigned int clamp_value = uclamp_none(clamp_id);
  
  		/* Keep using defined clamps across class changes */
  		if (uc_se->user_defined)
  			continue;
  
  		/* By default, RT tasks always get 100% boost */
  		if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
  			clamp_value = uclamp_none(UCLAMP_MAX);
  
  		uclamp_se_set(uc_se, clamp_value, false);
  	}
  
  	if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
  		return;
  
  	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
  		uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
  			      attr->sched_util_min, true);
  	}
  
  	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
  		uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
  			      attr->sched_util_max, true);
  	}
  }
  
  static void uclamp_fork(struct task_struct *p)
  {
  	enum uclamp_id clamp_id;
  
  	for_each_clamp_id(clamp_id)
  		p->uclamp[clamp_id].active = false;
  
  	if (likely(!p->sched_reset_on_fork))
  		return;
  
  	for_each_clamp_id(clamp_id) {
  		uclamp_se_set(&p->uclamp_req[clamp_id],
  			      uclamp_none(clamp_id), false);
  	}
  }
  
  static void __init init_uclamp_rq(struct rq *rq)
  {
  	enum uclamp_id clamp_id;
  	struct uclamp_rq *uc_rq = rq->uclamp;
  
  	for_each_clamp_id(clamp_id) {
  		uc_rq[clamp_id] = (struct uclamp_rq) {
  			.value = uclamp_none(clamp_id)
  		};
  	}
  
  	rq->uclamp_flags = 0;
  }
  
  static void __init init_uclamp(void)
  {
  	struct uclamp_se uc_max = {};
  	enum uclamp_id clamp_id;
  	int cpu;
  
  	mutex_init(&uclamp_mutex);
  
  	for_each_possible_cpu(cpu)
  		init_uclamp_rq(cpu_rq(cpu));
  
  	for_each_clamp_id(clamp_id) {
  		uclamp_se_set(&init_task.uclamp_req[clamp_id],
  			      uclamp_none(clamp_id), false);
  	}
  
  	/* System defaults allow max clamp values for both indexes */
  	uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false);
  	for_each_clamp_id(clamp_id) {
  		uclamp_default[clamp_id] = uc_max;
  #ifdef CONFIG_UCLAMP_TASK_GROUP
  		root_task_group.uclamp_req[clamp_id] = uc_max;
  		root_task_group.uclamp[clamp_id] = uc_max;
  #endif
  	}
  }
  
  #else /* CONFIG_UCLAMP_TASK */
  static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
  static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
  static inline int uclamp_validate(struct task_struct *p,
  				  const struct sched_attr *attr)
  {
  	return -EOPNOTSUPP;
  }
  static void __setscheduler_uclamp(struct task_struct *p,
  				  const struct sched_attr *attr) { }
  static inline void uclamp_fork(struct task_struct *p) { }
  static inline void init_uclamp(void) { }
  #endif /* CONFIG_UCLAMP_TASK */
  
  static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
  {
  	if (!(flags & ENQUEUE_NOCLOCK))
  		update_rq_clock(rq);
  
  	if (!(flags & ENQUEUE_RESTORE)) {
  		sched_info_queued(rq, p);
  		psi_enqueue(p, flags & ENQUEUE_WAKEUP);
  	}
  
  	uclamp_rq_inc(rq, p);
  	p->sched_class->enqueue_task(rq, p, flags);
  }
  
  static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
  {
  	if (!(flags & DEQUEUE_NOCLOCK))
  		update_rq_clock(rq);
  
  	if (!(flags & DEQUEUE_SAVE)) {
  		sched_info_dequeued(rq, p);
  		psi_dequeue(p, flags & DEQUEUE_SLEEP);
  	}
  
  	uclamp_rq_dec(rq, p);
  	p->sched_class->dequeue_task(rq, p, flags);
  }
  
  void activate_task(struct rq *rq, struct task_struct *p, int flags)
  {
  	if (task_contributes_to_load(p))
  		rq->nr_uninterruptible--;
  
  	enqueue_task(rq, p, flags);
  
  	p->on_rq = TASK_ON_RQ_QUEUED;
  }
  
  void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
  {
  	p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING;
  
  	if (task_contributes_to_load(p))
  		rq->nr_uninterruptible++;
  
  	dequeue_task(rq, p, flags);
  }
  
  /*
   * __normal_prio - return the priority that is based on the static prio
   */
  static inline int __normal_prio(struct task_struct *p)
  {
  	return p->static_prio;
  }
  
  /*
   * Calculate the expected normal priority: i.e. priority
   * without taking RT-inheritance into account. Might be
   * boosted by interactivity modifiers. Changes upon fork,
   * setprio syscalls, and whenever the interactivity
   * estimator recalculates.
   */
  static inline int normal_prio(struct task_struct *p)
  {
  	int prio;
  
  	if (task_has_dl_policy(p))
  		prio = MAX_DL_PRIO-1;
  	else if (task_has_rt_policy(p))
  		prio = MAX_RT_PRIO-1 - p->rt_priority;
  	else
  		prio = __normal_prio(p);
  	return prio;
  }
  
  /*
   * Calculate the current priority, i.e. the priority
   * taken into account by the scheduler. This value might
   * be boosted by RT tasks, or might be boosted by
   * interactivity modifiers. Will be RT if the task got
   * RT-boosted. If not then it returns p->normal_prio.
   */
  static int effective_prio(struct task_struct *p)
  {
  	p->normal_prio = normal_prio(p);
  	/*
  	 * If we are RT tasks or we were boosted to RT priority,
  	 * keep the priority unchanged. Otherwise, update priority
  	 * to the normal priority:
  	 */
  	if (!rt_prio(p->prio))
  		return p->normal_prio;
  	return p->prio;
  }
  
  /**
   * task_curr - is this task currently executing on a CPU?
   * @p: the task in question.
   *
   * Return: 1 if the task is currently executing. 0 otherwise.
   */
  inline int task_curr(const struct task_struct *p)
  {
  	return cpu_curr(task_cpu(p)) == p;
  }
  
  /*
   * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
   * use the balance_callback list if you want balancing.
   *
   * this means any call to check_class_changed() must be followed by a call to
   * balance_callback().
   */
  static inline void check_class_changed(struct rq *rq, struct task_struct *p,
  				       const struct sched_class *prev_class,
  				       int oldprio)
  {
  	if (prev_class != p->sched_class) {
  		if (prev_class->switched_from)
  			prev_class->switched_from(rq, p);
  
  		p->sched_class->switched_to(rq, p);
  	} else if (oldprio != p->prio || dl_task(p))
  		p->sched_class->prio_changed(rq, p, oldprio);
  }
  
  void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
  {
  	const struct sched_class *class;
  
  	if (p->sched_class == rq->curr->sched_class) {
  		rq->curr->sched_class->check_preempt_curr(rq, p, flags);
  	} else {
  		for_each_class(class) {
  			if (class == rq->curr->sched_class)
  				break;
  			if (class == p->sched_class) {
  				resched_curr(rq);
  				break;
  			}
  		}
  	}
  
  	/*
  	 * A queue event has occurred, and we're going to schedule.  In
  	 * this case, we can save a useless back to back clock update.
  	 */
  	if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
  		rq_clock_skip_update(rq);
  }
  
  #ifdef CONFIG_SMP
  
  static inline bool is_per_cpu_kthread(struct task_struct *p)
  {
  	if (!(p->flags & PF_KTHREAD))
  		return false;
  
  	if (p->nr_cpus_allowed != 1)
  		return false;
  
  	return true;
  }
  
  /*
   * Per-CPU kthreads are allowed to run on !active && online CPUs, see
   * __set_cpus_allowed_ptr() and select_fallback_rq().
   */
  static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
  {
  	if (!cpumask_test_cpu(cpu, p->cpus_ptr))
  		return false;
  
  	if (is_per_cpu_kthread(p))
  		return cpu_online(cpu);
  
  	return cpu_active(cpu);
  }
  
  /*
   * This is how migration works:
   *
   * 1) we invoke migration_cpu_stop() on the target CPU using
   *    stop_one_cpu().
   * 2) stopper starts to run (implicitly forcing the migrated thread
   *    off the CPU)
   * 3) it checks whether the migrated task is still in the wrong runqueue.
   * 4) if it's in the wrong runqueue then the migration thread removes
   *    it and puts it into the right queue.
   * 5) stopper completes and stop_one_cpu() returns and the migration
   *    is done.
   */
  
  /*
   * move_queued_task - move a queued task to new rq.
   *
   * Returns (locked) new rq. Old rq's lock is released.
   */
  static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
  				   struct task_struct *p, int new_cpu)
  {
  	lockdep_assert_held(&rq->lock);
  
  	WRITE_ONCE(p->on_rq, TASK_ON_RQ_MIGRATING);
  	dequeue_task(rq, p, DEQUEUE_NOCLOCK);
  	set_task_cpu(p, new_cpu);
  	rq_unlock(rq, rf);
  
  	rq = cpu_rq(new_cpu);
  
  	rq_lock(rq, rf);
  	BUG_ON(task_cpu(p) != new_cpu);
  	enqueue_task(rq, p, 0);
  	p->on_rq = TASK_ON_RQ_QUEUED;
  	check_preempt_curr(rq, p, 0);
  
  	return rq;
  }
  
  struct migration_arg {
  	struct task_struct *task;
  	int dest_cpu;
  };
  
  /*
   * Move (not current) task off this CPU, onto the destination CPU. We're doing
   * this because either it can't run here any more (set_cpus_allowed()
   * away from this CPU, or CPU going down), or because we're
   * attempting to rebalance this task on exec (sched_exec).
   *
   * So we race with normal scheduler movements, but that's OK, as long
   * as the task is no longer on this CPU.
   */
  static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
  				 struct task_struct *p, int dest_cpu)
  {
  	/* Affinity changed (again). */
  	if (!is_cpu_allowed(p, dest_cpu))
  		return rq;
  
  	update_rq_clock(rq);
  	rq = move_queued_task(rq, rf, p, dest_cpu);
  
  	return rq;
  }
  
  /*
   * migration_cpu_stop - this will be executed by a highprio stopper thread
   * and performs thread migration by bumping thread off CPU then
   * 'pushing' onto another runqueue.
   */
  static int migration_cpu_stop(void *data)
  {
  	struct migration_arg *arg = data;
  	struct task_struct *p = arg->task;
  	struct rq *rq = this_rq();
  	struct rq_flags rf;
  
  	/*
  	 * The original target CPU might have gone down and we might
  	 * be on another CPU but it doesn't matter.
  	 */
  	local_irq_disable();
  	/*
  	 * We need to explicitly wake pending tasks before running
  	 * __migrate_task() such that we will not miss enforcing cpus_ptr
  	 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
  	 */
  	sched_ttwu_pending();
  
  	raw_spin_lock(&p->pi_lock);
  	rq_lock(rq, &rf);
  	/*
  	 * If task_rq(p) != rq, it cannot be migrated here, because we're
  	 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
  	 * we're holding p->pi_lock.
  	 */
  	if (task_rq(p) == rq) {
  		if (task_on_rq_queued(p))
  			rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
  		else
  			p->wake_cpu = arg->dest_cpu;
  	}
  	rq_unlock(rq, &rf);
  	raw_spin_unlock(&p->pi_lock);
  
  	local_irq_enable();
  	return 0;
  }
  
  /*
   * sched_class::set_cpus_allowed must do the below, but is not required to
   * actually call this function.
   */
  void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
  {
  	cpumask_copy(&p->cpus_mask, new_mask);
  	p->nr_cpus_allowed = cpumask_weight(new_mask);
  }
  
  void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
  {
  	struct rq *rq = task_rq(p);
  	bool queued, running;
  
  	lockdep_assert_held(&p->pi_lock);
  
  	queued = task_on_rq_queued(p);
  	running = task_current(rq, p);
  
  	if (queued) {
  		/*
  		 * Because __kthread_bind() calls this on blocked tasks without
  		 * holding rq->lock.
  		 */
  		lockdep_assert_held(&rq->lock);
  		dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
  	}
  	if (running)
  		put_prev_task(rq, p);
  
  	p->sched_class->set_cpus_allowed(p, new_mask);
  
  	if (queued)
  		enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
  	if (running)
  		set_next_task(rq, p);
  }
  
  /*
   * Change a given task's CPU affinity. Migrate the thread to a
   * proper CPU and schedule it away if the CPU it's executing on
   * is removed from the allowed bitmask.
   *
   * NOTE: the caller must have a valid reference to the task, the
   * task must not exit() & deallocate itself prematurely. The
   * call is not atomic; no spinlocks may be held.
   */
  static int __set_cpus_allowed_ptr(struct task_struct *p,
  				  const struct cpumask *new_mask, bool check)
  {
  	const struct cpumask *cpu_valid_mask = cpu_active_mask;
  	unsigned int dest_cpu;
  	struct rq_flags rf;
  	struct rq *rq;
  	int ret = 0;
  
  	rq = task_rq_lock(p, &rf);
  	update_rq_clock(rq);
  
  	if (p->flags & PF_KTHREAD) {
  		/*
  		 * Kernel threads are allowed on online && !active CPUs
  		 */
  		cpu_valid_mask = cpu_online_mask;
  	}
  
  	/*
  	 * Must re-check here, to close a race against __kthread_bind(),
  	 * sched_setaffinity() is not guaranteed to observe the flag.
  	 */
  	if (check && (p->flags & PF_NO_SETAFFINITY)) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	if (cpumask_equal(&p->cpus_mask, new_mask))
  		goto out;
  
  	dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
  	if (dest_cpu >= nr_cpu_ids) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	do_set_cpus_allowed(p, new_mask);
  
  	if (p->flags & PF_KTHREAD) {
  		/*
  		 * For kernel threads that do indeed end up on online &&
  		 * !active we want to ensure they are strict per-CPU threads.
  		 */
  		WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) &&
  			!cpumask_intersects(new_mask, cpu_active_mask) &&
  			p->nr_cpus_allowed != 1);
  	}
  
  	/* Can the task run on the task's current CPU? If so, we're done */
  	if (cpumask_test_cpu(task_cpu(p), new_mask))
  		goto out;
  
  	if (task_running(rq, p) || p->state == TASK_WAKING) {
  		struct migration_arg arg = { p, dest_cpu };
  		/* Need help from migration thread: drop lock and wait. */
  		task_rq_unlock(rq, p, &rf);
  		stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
  		return 0;
  	} else if (task_on_rq_queued(p)) {
  		/*
  		 * OK, since we're going to drop the lock immediately
  		 * afterwards anyway.
  		 */
  		rq = move_queued_task(rq, &rf, p, dest_cpu);
  	}
  out:
  	task_rq_unlock(rq, p, &rf);
  
  	return ret;
  }
  
  int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
  {
  	return __set_cpus_allowed_ptr(p, new_mask, false);
  }
  EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
  
  void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
  {
  #ifdef CONFIG_SCHED_DEBUG
  	/*
  	 * We should never call set_task_cpu() on a blocked task,
  	 * ttwu() will sort out the placement.
  	 */
  	WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
  			!p->on_rq);
  
  	/*
  	 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
  	 * because schedstat_wait_{start,end} rebase migrating task's wait_start
  	 * time relying on p->on_rq.
  	 */
  	WARN_ON_ONCE(p->state == TASK_RUNNING &&
  		     p->sched_class == &fair_sched_class &&
  		     (p->on_rq && !task_on_rq_migrating(p)));
  
  #ifdef CONFIG_LOCKDEP
  	/*
  	 * The caller should hold either p->pi_lock or rq->lock, when changing
  	 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
  	 *
  	 * sched_move_task() holds both and thus holding either pins the cgroup,
  	 * see task_group().
  	 *
  	 * Furthermore, all task_rq users should acquire both locks, see
  	 * task_rq_lock().
  	 */
  	WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
  				      lockdep_is_held(&task_rq(p)->lock)));
  #endif
  	/*
  	 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
  	 */
  	WARN_ON_ONCE(!cpu_online(new_cpu));
  #endif
  
  	trace_sched_migrate_task(p, new_cpu);
  
  	if (task_cpu(p) != new_cpu) {
  		if (p->sched_class->migrate_task_rq)
  			p->sched_class->migrate_task_rq(p, new_cpu);
  		p->se.nr_migrations++;
  		rseq_migrate(p);
  		perf_event_task_migrate(p);
  	}
  
  	__set_task_cpu(p, new_cpu);
  }
  
  #ifdef CONFIG_NUMA_BALANCING
  static void __migrate_swap_task(struct task_struct *p, int cpu)
  {
  	if (task_on_rq_queued(p)) {
  		struct rq *src_rq, *dst_rq;
  		struct rq_flags srf, drf;
  
  		src_rq = task_rq(p);
  		dst_rq = cpu_rq(cpu);
  
  		rq_pin_lock(src_rq, &srf);
  		rq_pin_lock(dst_rq, &drf);
  
  		deactivate_task(src_rq, p, 0);
  		set_task_cpu(p, cpu);
  		activate_task(dst_rq, p, 0);
  		check_preempt_curr(dst_rq, p, 0);
  
  		rq_unpin_lock(dst_rq, &drf);
  		rq_unpin_lock(src_rq, &srf);
  
  	} else {
  		/*
  		 * Task isn't running anymore; make it appear like we migrated
  		 * it before it went to sleep. This means on wakeup we make the
  		 * previous CPU our target instead of where it really is.
  		 */
  		p->wake_cpu = cpu;
  	}
  }
  
  struct migration_swap_arg {
  	struct task_struct *src_task, *dst_task;
  	int src_cpu, dst_cpu;
  };
  
  static int migrate_swap_stop(void *data)
  {
  	struct migration_swap_arg *arg = data;
  	struct rq *src_rq, *dst_rq;
  	int ret = -EAGAIN;
  
  	if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
  		return -EAGAIN;
  
  	src_rq = cpu_rq(arg->src_cpu);
  	dst_rq = cpu_rq(arg->dst_cpu);
  
  	double_raw_lock(&arg->src_task->pi_lock,
  			&arg->dst_task->pi_lock);
  	double_rq_lock(src_rq, dst_rq);
  
  	if (task_cpu(arg->dst_task) != arg->dst_cpu)
  		goto unlock;
  
  	if (task_cpu(arg->src_task) != arg->src_cpu)
  		goto unlock;
  
  	if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
  		goto unlock;
  
  	if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
  		goto unlock;
  
  	__migrate_swap_task(arg->src_task, arg->dst_cpu);
  	__migrate_swap_task(arg->dst_task, arg->src_cpu);
  
  	ret = 0;
  
  unlock:
  	double_rq_unlock(src_rq, dst_rq);
  	raw_spin_unlock(&arg->dst_task->pi_lock);
  	raw_spin_unlock(&arg->src_task->pi_lock);
  
  	return ret;
  }
  
  /*
   * Cross migrate two tasks
   */
  int migrate_swap(struct task_struct *cur, struct task_struct *p,
  		int target_cpu, int curr_cpu)
  {
  	struct migration_swap_arg arg;
  	int ret = -EINVAL;
  
  	arg = (struct migration_swap_arg){
  		.src_task = cur,
  		.src_cpu = curr_cpu,
  		.dst_task = p,
  		.dst_cpu = target_cpu,
  	};
  
  	if (arg.src_cpu == arg.dst_cpu)
  		goto out;
  
  	/*
  	 * These three tests are all lockless; this is OK since all of them
  	 * will be re-checked with proper locks held further down the line.
  	 */
  	if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
  		goto out;
  
  	if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr))
  		goto out;
  
  	if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr))
  		goto out;
  
  	trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
  	ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
  
  out:
  	return ret;
  }
  #endif /* CONFIG_NUMA_BALANCING */
  
  /*
   * wait_task_inactive - wait for a thread to unschedule.
   *
   * If @match_state is nonzero, it's the @p->state value just checked and
   * not expected to change.  If it changes, i.e. @p might have woken up,
   * then return zero.  When we succeed in waiting for @p to be off its CPU,
   * we return a positive number (its total switch count).  If a second call
   * a short while later returns the same number, the caller can be sure that
   * @p has remained unscheduled the whole time.
   *
   * The caller must ensure that the task *will* unschedule sometime soon,
   * else this function might spin for a *long* time. This function can't
   * be called with interrupts off, or it may introduce deadlock with
   * smp_call_function() if an IPI is sent by the same process we are
   * waiting to become inactive.
   */
  unsigned long wait_task_inactive(struct task_struct *p, long match_state)
  {
  	int running, queued;
  	struct rq_flags rf;
  	unsigned long ncsw;
  	struct rq *rq;
  
  	for (;;) {
  		/*
  		 * We do the initial early heuristics without holding
  		 * any task-queue locks at all. We'll only try to get
  		 * the runqueue lock when things look like they will
  		 * work out!
  		 */
  		rq = task_rq(p);
  
  		/*
  		 * If the task is actively running on another CPU
  		 * still, just relax and busy-wait without holding
  		 * any locks.
  		 *
  		 * NOTE! Since we don't hold any locks, it's not
  		 * even sure that "rq" stays as the right runqueue!
  		 * But we don't care, since "task_running()" will
  		 * return false if the runqueue has changed and p
  		 * is actually now running somewhere else!
  		 */
  		while (task_running(rq, p)) {
  			if (match_state && unlikely(p->state != match_state))
  				return 0;
  			cpu_relax();
  		}
  
  		/*
  		 * Ok, time to look more closely! We need the rq
  		 * lock now, to be *sure*. If we're wrong, we'll
  		 * just go back and repeat.
  		 */
  		rq = task_rq_lock(p, &rf);
  		trace_sched_wait_task(p);
  		running = task_running(rq, p);
  		queued = task_on_rq_queued(p);
  		ncsw = 0;
  		if (!match_state || p->state == match_state)
  			ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
  		task_rq_unlock(rq, p, &rf);
  
  		/*
  		 * If it changed from the expected state, bail out now.
  		 */
  		if (unlikely(!ncsw))
  			break;
  
  		/*
  		 * Was it really running after all now that we
  		 * checked with the proper locks actually held?
  		 *
  		 * Oops. Go back and try again..
  		 */
  		if (unlikely(running)) {
  			cpu_relax();
  			continue;
  		}
  
  		/*
  		 * It's not enough that it's not actively running,
  		 * it must be off the runqueue _entirely_, and not
  		 * preempted!
  		 *
  		 * So if it was still runnable (but just not actively
  		 * running right now), it's preempted, and we should
  		 * yield - it could be a while.
  		 */
  		if (unlikely(queued)) {
  			ktime_t to = NSEC_PER_SEC / HZ;
  
  			set_current_state(TASK_UNINTERRUPTIBLE);
  			schedule_hrtimeout(&to, HRTIMER_MODE_REL);
  			continue;
  		}
  
  		/*
  		 * Ahh, all good. It wasn't running, and it wasn't
  		 * runnable, which means that it will never become
  		 * running in the future either. We're all done!
  		 */
  		break;
  	}
  
  	return ncsw;
  }
  
  /***
   * kick_process - kick a running thread to enter/exit the kernel
   * @p: the to-be-kicked thread
   *
   * Cause a process which is running on another CPU to enter
   * kernel-mode, without any delay. (to get signals handled.)
   *
   * NOTE: this function doesn't have to take the runqueue lock,
   * because all it wants to ensure is that the remote task enters
   * the kernel. If the IPI races and the task has been migrated
   * to another CPU then no harm is done and the purpose has been
   * achieved as well.
   */
  void kick_process(struct task_struct *p)
  {
  	int cpu;
  
  	preempt_disable();
  	cpu = task_cpu(p);
  	if ((cpu != smp_processor_id()) && task_curr(p))
  		smp_send_reschedule(cpu);
  	preempt_enable();
  }
  EXPORT_SYMBOL_GPL(kick_process);
  
  /*
   * ->cpus_ptr is protected by both rq->lock and p->pi_lock
   *
   * A few notes on cpu_active vs cpu_online:
   *
   *  - cpu_active must be a subset of cpu_online
   *
   *  - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
   *    see __set_cpus_allowed_ptr(). At this point the newly online
   *    CPU isn't yet part of the sched domains, and balancing will not
   *    see it.
   *
   *  - on CPU-down we clear cpu_active() to mask the sched domains and
   *    avoid the load balancer to place new tasks on the to be removed
   *    CPU. Existing tasks will remain running there and will be taken
   *    off.
   *
   * This means that fallback selection must not select !active CPUs.
   * And can assume that any active CPU must be online. Conversely
   * select_task_rq() below may allow selection of !active CPUs in order
   * to satisfy the above rules.
   */
  static int select_fallback_rq(int cpu, struct task_struct *p)
  {
  	int nid = cpu_to_node(cpu);
  	const struct cpumask *nodemask = NULL;
  	enum { cpuset, possible, fail } state = cpuset;
  	int dest_cpu;
  
  	/*
  	 * If the node that the CPU is on has been offlined, cpu_to_node()
  	 * will return -1. There is no CPU on the node, and we should
  	 * select the CPU on the other node.
  	 */
  	if (nid != -1) {
  		nodemask = cpumask_of_node(nid);
  
  		/* Look for allowed, online CPU in same node. */
  		for_each_cpu(dest_cpu, nodemask) {
  			if (!cpu_active(dest_cpu))
  				continue;
  			if (cpumask_test_cpu(dest_cpu, p->cpus_ptr))
  				return dest_cpu;
  		}
  	}
  
  	for (;;) {
  		/* Any allowed, online CPU? */
  		for_each_cpu(dest_cpu, p->cpus_ptr) {
  			if (!is_cpu_allowed(p, dest_cpu))
  				continue;
  
  			goto out;
  		}
  
  		/* No more Mr. Nice Guy. */
  		switch (state) {
  		case cpuset:
  			if (IS_ENABLED(CONFIG_CPUSETS)) {
  				cpuset_cpus_allowed_fallback(p);
  				state = possible;
  				break;
  			}
  			/* Fall-through */
  		case possible:
  			do_set_cpus_allowed(p, cpu_possible_mask);
  			state = fail;
  			break;
  
  		case fail:
  			BUG();
  			break;
  		}
  	}
  
  out:
  	if (state != cpuset) {
  		/*
  		 * Don't tell them about moving exiting tasks or
  		 * kernel threads (both mm NULL), since they never
  		 * leave kernel.
  		 */
  		if (p->mm && printk_ratelimit()) {
  			printk_deferred("process %d (%s) no longer affine to cpu%d\n",
  					task_pid_nr(p), p->comm, cpu);
  		}
  	}
  
  	return dest_cpu;
  }
  
  /*
   * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
   */
  static inline
  int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
  {
  	lockdep_assert_held(&p->pi_lock);
  
  	if (p->nr_cpus_allowed > 1)
  		cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
  	else
  		cpu = cpumask_any(p->cpus_ptr);
  
  	/*
  	 * In order not to call set_task_cpu() on a blocking task we need
  	 * to rely on ttwu() to place the task on a valid ->cpus_ptr
  	 * CPU.
  	 *
  	 * Since this is common to all placement strategies, this lives here.
  	 *
  	 * [ this allows ->select_task() to simply return task_cpu(p) and
  	 *   not worry about this generic constraint ]
  	 */
  	if (unlikely(!is_cpu_allowed(p, cpu)))
  		cpu = select_fallback_rq(task_cpu(p), p);
  
  	return cpu;
  }
  
  static void update_avg(u64 *avg, u64 sample)
  {
  	s64 diff = sample - *avg;
  	*avg += diff >> 3;
  }
  
  void sched_set_stop_task(int cpu, struct task_struct *stop)
  {
  	struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
  	struct task_struct *old_stop = cpu_rq(cpu)->stop;
  
  	if (stop) {
  		/*
  		 * Make it appear like a SCHED_FIFO task, its something
  		 * userspace knows about and won't get confused about.
  		 *
  		 * Also, it will make PI more or less work without too
  		 * much confusion -- but then, stop work should not
  		 * rely on PI working anyway.
  		 */
  		sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
  
  		stop->sched_class = &stop_sched_class;
  	}
  
  	cpu_rq(cpu)->stop = stop;
  
  	if (old_stop) {
  		/*
  		 * Reset it back to a normal scheduling class so that
  		 * it can die in pieces.
  		 */
  		old_stop->sched_class = &rt_sched_class;
  	}
  }
  
  #else
  
  static inline int __set_cpus_allowed_ptr(struct task_struct *p,
  					 const struct cpumask *new_mask, bool check)
  {
  	return set_cpus_allowed_ptr(p, new_mask);
  }
  
  #endif /* CONFIG_SMP */
  
  static void
  ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
  {
  	struct rq *rq;
  
  	if (!schedstat_enabled())
  		return;
  
  	rq = this_rq();
  
  #ifdef CONFIG_SMP
  	if (cpu == rq->cpu) {
  		__schedstat_inc(rq->ttwu_local);
  		__schedstat_inc(p->se.statistics.nr_wakeups_local);
  	} else {
  		struct sched_domain *sd;
  
  		__schedstat_inc(p->se.statistics.nr_wakeups_remote);
  		rcu_read_lock();
  		for_each_domain(rq->cpu, sd) {
  			if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
  				__schedstat_inc(sd->ttwu_wake_remote);
  				break;
  			}
  		}
  		rcu_read_unlock();
  	}
  
  	if (wake_flags & WF_MIGRATED)
  		__schedstat_inc(p->se.statistics.nr_wakeups_migrate);
  #endif /* CONFIG_SMP */
  
  	__schedstat_inc(rq->ttwu_count);
  	__schedstat_inc(p->se.statistics.nr_wakeups);
  
  	if (wake_flags & WF_SYNC)
  		__schedstat_inc(p->se.statistics.nr_wakeups_sync);
  }
  
  /*
   * Mark the task runnable and perform wakeup-preemption.
   */
  static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
  			   struct rq_flags *rf)
  {
  	check_preempt_curr(rq, p, wake_flags);
  	p->state = TASK_RUNNING;
  	trace_sched_wakeup(p);
  
  #ifdef CONFIG_SMP
  	if (p->sched_class->task_woken) {
  		/*
  		 * Our task @p is fully woken up and running; so its safe to
  		 * drop the rq->lock, hereafter rq is only used for statistics.
  		 */
  		rq_unpin_lock(rq, rf);
  		p->sched_class->task_woken(rq, p);
  		rq_repin_lock(rq, rf);
  	}
  
  	if (rq->idle_stamp) {
  		u64 delta = rq_clock(rq) - rq->idle_stamp;
  		u64 max = 2*rq->max_idle_balance_cost;
  
  		update_avg(&rq->avg_idle, delta);
  
  		if (rq->avg_idle > max)
  			rq->avg_idle = max;
  
  		rq->idle_stamp = 0;
  	}
  #endif
  }
  
  static void
  ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
  		 struct rq_flags *rf)
  {
  	int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
  
  	lockdep_assert_held(&rq->lock);
  
  #ifdef CONFIG_SMP
  	if (p->sched_contributes_to_load)
  		rq->nr_uninterruptible--;
  
  	if (wake_flags & WF_MIGRATED)
  		en_flags |= ENQUEUE_MIGRATED;
  #endif
  
  	activate_task(rq, p, en_flags);
  	ttwu_do_wakeup(rq, p, wake_flags, rf);
  }
  
  /*
   * Called in case the task @p isn't fully descheduled from its runqueue,
   * in this case we must do a remote wakeup. Its a 'light' wakeup though,
   * since all we need to do is flip p->state to TASK_RUNNING, since
   * the task is still ->on_rq.
   */
  static int ttwu_remote(struct task_struct *p, int wake_flags)
  {
  	struct rq_flags rf;
  	struct rq *rq;
  	int ret = 0;
  
  	rq = __task_rq_lock(p, &rf);
  	if (task_on_rq_queued(p)) {
  		/* check_preempt_curr() may use rq clock */
  		update_rq_clock(rq);
  		ttwu_do_wakeup(rq, p, wake_flags, &rf);
  		ret = 1;
  	}
  	__task_rq_unlock(rq, &rf);
  
  	return ret;
  }
  
  #ifdef CONFIG_SMP
  void sched_ttwu_pending(void)
  {
  	struct rq *rq = this_rq();
  	struct llist_node *llist = llist_del_all(&rq->wake_list);
  	struct task_struct *p, *t;
  	struct rq_flags rf;
  
  	if (!llist)
  		return;
  
  	rq_lock_irqsave(rq, &rf);
  	update_rq_clock(rq);
  
  	llist_for_each_entry_safe(p, t, llist, wake_entry)
  		ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
  
  	rq_unlock_irqrestore(rq, &rf);
  }
  
  void scheduler_ipi(void)
  {
  	/*
  	 * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
  	 * TIF_NEED_RESCHED remotely (for the first time) will also send
  	 * this IPI.
  	 */
  	preempt_fold_need_resched();
  
  	if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
  		return;
  
  	/*
  	 * Not all reschedule IPI handlers call irq_enter/irq_exit, since
  	 * traditionally all their work was done from the interrupt return
  	 * path. Now that we actually do some work, we need to make sure
  	 * we do call them.
  	 *
  	 * Some archs already do call them, luckily irq_enter/exit nest
  	 * properly.
  	 *
  	 * Arguably we should visit all archs and update all handlers,
  	 * however a fair share of IPIs are still resched only so this would
  	 * somewhat pessimize the simple resched case.
  	 */
  	irq_enter();
  	sched_ttwu_pending();
  
  	/*
  	 * Check if someone kicked us for doing the nohz idle load balance.
  	 */
  	if (unlikely(got_nohz_idle_kick())) {
  		this_rq()->idle_balance = 1;
  		raise_softirq_irqoff(SCHED_SOFTIRQ);
  	}
  	irq_exit();
  }
  
  static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
  {
  	struct rq *rq = cpu_rq(cpu);
  
  	p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
  
  	if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
  		if (!set_nr_if_polling(rq->idle))
  			smp_send_reschedule(cpu);
  		else
  			trace_sched_wake_idle_without_ipi(cpu);
  	}
  }
  
  void wake_up_if_idle(int cpu)
  {
  	struct rq *rq = cpu_rq(cpu);
  	struct rq_flags rf;
  
  	rcu_read_lock();
  
  	if (!is_idle_task(rcu_dereference(rq->curr)))
  		goto out;
  
  	if (set_nr_if_polling(rq->idle)) {
  		trace_sched_wake_idle_without_ipi(cpu);
  	} else {
  		rq_lock_irqsave(rq, &rf);
  		if (is_idle_task(rq->curr))
  			smp_send_reschedule(cpu);
  		/* Else CPU is not idle, do nothing here: */
  		rq_unlock_irqrestore(rq, &rf);
  	}
  
  out:
  	rcu_read_unlock();
  }
  
  bool cpus_share_cache(int this_cpu, int that_cpu)
  {
  	return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
  }
  #endif /* CONFIG_SMP */
  
  static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
  {
  	struct rq *rq = cpu_rq(cpu);
  	struct rq_flags rf;
  
  #if defined(CONFIG_SMP)
  	if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
  		sched_clock_cpu(cpu); /* Sync clocks across CPUs */
  		ttwu_queue_remote(p, cpu, wake_flags);
  		return;
  	}
  #endif
  
  	rq_lock(rq, &rf);
  	update_rq_clock(rq);
  	ttwu_do_activate(rq, p, wake_flags, &rf);
  	rq_unlock(rq, &rf);
  }
  
  /*
   * Notes on Program-Order guarantees on SMP systems.
   *
   *  MIGRATION
   *
   * The basic program-order guarantee on SMP systems is that when a task [t]
   * migrates, all its activity on its old CPU [c0] happens-before any subsequent
   * execution on its new CPU [c1].
   *
   * For migration (of runnable tasks) this is provided by the following means:
   *
   *  A) UNLOCK of the rq(c0)->lock scheduling out task t
   *  B) migration for t is required to synchronize *both* rq(c0)->lock and
   *     rq(c1)->lock (if not at the same time, then in that order).
   *  C) LOCK of the rq(c1)->lock scheduling in task
   *
   * Release/acquire chaining guarantees that B happens after A and C after B.
   * Note: the CPU doing B need not be c0 or c1
   *
   * Example:
   *
   *   CPU0            CPU1            CPU2
   *
   *   LOCK rq(0)->lock
   *   sched-out X
   *   sched-in Y
   *   UNLOCK rq(0)->lock
   *
   *                                   LOCK rq(0)->lock // orders against CPU0
   *                                   dequeue X
   *                                   UNLOCK rq(0)->lock
   *
   *                                   LOCK rq(1)->lock
   *                                   enqueue X
   *                                   UNLOCK rq(1)->lock
   *
   *                   LOCK rq(1)->lock // orders against CPU2
   *                   sched-out Z
   *                   sched-in X
   *                   UNLOCK rq(1)->lock
   *
   *
   *  BLOCKING -- aka. SLEEP + WAKEUP
   *
   * For blocking we (obviously) need to provide the same guarantee as for
   * migration. However the means are completely different as there is no lock
   * chain to provide order. Instead we do:
   *
   *   1) smp_store_release(X->on_cpu, 0)
   *   2) smp_cond_load_acquire(!X->on_cpu)
   *
   * Example:
   *
   *   CPU0 (schedule)  CPU1 (try_to_wake_up) CPU2 (schedule)
   *
   *   LOCK rq(0)->lock LOCK X->pi_lock
   *   dequeue X
   *   sched-out X
   *   smp_store_release(X->on_cpu, 0);
   *
   *                    smp_cond_load_acquire(&X->on_cpu, !VAL);
   *                    X->state = WAKING
   *                    set_task_cpu(X,2)
   *
   *                    LOCK rq(2)->lock
   *                    enqueue X
   *                    X->state = RUNNING
   *                    UNLOCK rq(2)->lock
   *
   *                                          LOCK rq(2)->lock // orders against CPU1
   *                                          sched-out Z
   *                                          sched-in X
   *                                          UNLOCK rq(2)->lock
   *
   *                    UNLOCK X->pi_lock
   *   UNLOCK rq(0)->lock
   *
   *
   * However, for wakeups there is a second guarantee we must provide, namely we
   * must ensure that CONDITION=1 done by the caller can not be reordered with
   * accesses to the task state; see try_to_wake_up() and set_current_state().
   */
  
  /**
   * try_to_wake_up - wake up a thread
   * @p: the thread to be awakened
   * @state: the mask of task states that can be woken
   * @wake_flags: wake modifier flags (WF_*)
   *
   * If (@state & @p->state) @p->state = TASK_RUNNING.
   *
   * If the task was not queued/runnable, also place it back on a runqueue.
   *
   * Atomic against schedule() which would dequeue a task, also see
   * set_current_state().
   *
   * This function executes a full memory barrier before accessing the task
   * state; see set_current_state().
   *
   * Return: %true if @p->state changes (an actual wakeup was done),
   *	   %false otherwise.
   */
  static int
  try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
  {
  	unsigned long flags;
  	int cpu, success = 0;
  
  	preempt_disable();
  	if (p == current) {
  		/*
  		 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
  		 * == smp_processor_id()'. Together this means we can special
  		 * case the whole 'p->on_rq && ttwu_remote()' case below
  		 * without taking any locks.
  		 *
  		 * In particular:
  		 *  - we rely on Program-Order guarantees for all the ordering,
  		 *  - we're serialized against set_special_state() by virtue of
  		 *    it disabling IRQs (this allows not taking ->pi_lock).
  		 */
  		if (!(p->state & state))
  			goto out;
  
  		success = 1;
  		cpu = task_cpu(p);
  		trace_sched_waking(p);
  		p->state = TASK_RUNNING;
  		trace_sched_wakeup(p);
  		goto out;
  	}
  
  	/*
  	 * If we are going to wake up a thread waiting for CONDITION we
  	 * need to ensure that CONDITION=1 done by the caller can not be
  	 * reordered with p->state check below. This pairs with mb() in
  	 * set_current_state() the waiting thread does.
  	 */
  	raw_spin_lock_irqsave(&p->pi_lock, flags);
  	smp_mb__after_spinlock();
  	if (!(p->state & state))
  		goto unlock;
  
  	trace_sched_waking(p);
  
  	/* We're going to change ->state: */
  	success = 1;
  	cpu = task_cpu(p);
  
  	/*
  	 * Ensure we load p->on_rq _after_ p->state, otherwise it would
  	 * be possible to, falsely, observe p->on_rq == 0 and get stuck
  	 * in smp_cond_load_acquire() below.
  	 *
  	 * sched_ttwu_pending()			try_to_wake_up()
  	 *   STORE p->on_rq = 1			  LOAD p->state
  	 *   UNLOCK rq->lock
  	 *
  	 * __schedule() (switch to task 'p')
  	 *   LOCK rq->lock			  smp_rmb();
  	 *   smp_mb__after_spinlock();
  	 *   UNLOCK rq->lock
  	 *
  	 * [task p]
  	 *   STORE p->state = UNINTERRUPTIBLE	  LOAD p->on_rq
  	 *
  	 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
  	 * __schedule().  See the comment for smp_mb__after_spinlock().
  	 */
  	smp_rmb();
  	if (p->on_rq && ttwu_remote(p, wake_flags))
  		goto unlock;
  
  #ifdef CONFIG_SMP
  	/*
  	 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
  	 * possible to, falsely, observe p->on_cpu == 0.
  	 *
  	 * One must be running (->on_cpu == 1) in order to remove oneself
  	 * from the runqueue.
  	 *
  	 * __schedule() (switch to task 'p')	try_to_wake_up()
  	 *   STORE p->on_cpu = 1		  LOAD p->on_rq
  	 *   UNLOCK rq->lock
  	 *
  	 * __schedule() (put 'p' to sleep)
  	 *   LOCK rq->lock			  smp_rmb();
  	 *   smp_mb__after_spinlock();
  	 *   STORE p->on_rq = 0			  LOAD p->on_cpu
  	 *
  	 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
  	 * __schedule().  See the comment for smp_mb__after_spinlock().
  	 */
  	smp_rmb();
  
  	/*
  	 * If the owning (remote) CPU is still in the middle of schedule() with
  	 * this task as prev, wait until its done referencing the task.
  	 *
  	 * Pairs with the smp_store_release() in finish_task().
  	 *
  	 * This ensures that tasks getting woken will be fully ordered against
  	 * their previous state and preserve Program Order.
  	 */
  	smp_cond_load_acquire(&p->on_cpu, !VAL);
  
  	p->sched_contributes_to_load = !!task_contributes_to_load(p);
  	p->state = TASK_WAKING;
  
  	if (p->in_iowait) {
  		delayacct_blkio_end(p);
  		atomic_dec(&task_rq(p)->nr_iowait);
  	}
  
  	cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
  	if (task_cpu(p) != cpu) {
  		wake_flags |= WF_MIGRATED;
  		psi_ttwu_dequeue(p);
  		set_task_cpu(p, cpu);
  	}
  
  #else /* CONFIG_SMP */
  
  	if (p->in_iowait) {
  		delayacct_blkio_end(p);
  		atomic_dec(&task_rq(p)->nr_iowait);
  	}
  
  #endif /* CONFIG_SMP */
  
  	ttwu_queue(p, cpu, wake_flags);
  unlock:
  	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  out:
  	if (success)
  		ttwu_stat(p, cpu, wake_flags);
  	preempt_enable();
  
  	return success;
  }
  
  /**
   * wake_up_process - Wake up a specific process
   * @p: The process to be woken up.
   *
   * Attempt to wake up the nominated process and move it to the set of runnable
   * processes.
   *
   * Return: 1 if the process was woken up, 0 if it was already running.
   *
   * This function executes a full memory barrier before accessing the task state.
   */
  int wake_up_process(struct task_struct *p)
  {
  	return try_to_wake_up(p, TASK_NORMAL, 0);
  }
  EXPORT_SYMBOL(wake_up_process);
  
  int wake_up_state(struct task_struct *p, unsigned int state)
  {
  	return try_to_wake_up(p, state, 0);
  }
  
  /*
   * Perform scheduler related setup for a newly forked process p.
   * p is forked by current.
   *
   * __sched_fork() is basic setup used by init_idle() too:
   */
  static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
  {
  	p->on_rq			= 0;
  
  	p->se.on_rq			= 0;
  	p->se.exec_start		= 0;
  	p->se.sum_exec_runtime		= 0;
  	p->se.prev_sum_exec_runtime	= 0;
  	p->se.nr_migrations		= 0;
  	p->se.vruntime			= 0;
  	INIT_LIST_HEAD(&p->se.group_node);
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  	p->se.cfs_rq			= NULL;
  #endif
  
  #ifdef CONFIG_SCHEDSTATS
  	/* Even if schedstat is disabled, there should not be garbage */
  	memset(&p->se.statistics, 0, sizeof(p->se.statistics));
  #endif
  
  	RB_CLEAR_NODE(&p->dl.rb_node);
  	init_dl_task_timer(&p->dl);
  	init_dl_inactive_task_timer(&p->dl);
  	__dl_clear_params(p);
  
  	INIT_LIST_HEAD(&p->rt.run_list);
  	p->rt.timeout		= 0;
  	p->rt.time_slice	= sched_rr_timeslice;
  	p->rt.on_rq		= 0;
  	p->rt.on_list		= 0;
  
  #ifdef CONFIG_PREEMPT_NOTIFIERS
  	INIT_HLIST_HEAD(&p->preempt_notifiers);
  #endif
  
  #ifdef CONFIG_COMPACTION
  	p->capture_control = NULL;
  #endif
  	init_numa_balancing(clone_flags, p);
  }
  
  DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
  
  #ifdef CONFIG_NUMA_BALANCING
  
  void set_numabalancing_state(bool enabled)
  {
  	if (enabled)
  		static_branch_enable(&sched_numa_balancing);
  	else
  		static_branch_disable(&sched_numa_balancing);
  }
  
  #ifdef CONFIG_PROC_SYSCTL
  int sysctl_numa_balancing(struct ctl_table *table, int write,
  			 void __user *buffer, size_t *lenp, loff_t *ppos)
  {
  	struct ctl_table t;
  	int err;
  	int state = static_branch_likely(&sched_numa_balancing);
  
  	if (write && !capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	t = *table;
  	t.data = &state;
  	err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
  	if (err < 0)
  		return err;
  	if (write)
  		set_numabalancing_state(state);
  	return err;
  }
  #endif
  #endif
  
  #ifdef CONFIG_SCHEDSTATS
  
  DEFINE_STATIC_KEY_FALSE(sched_schedstats);
  static bool __initdata __sched_schedstats = false;
  
  static void set_schedstats(bool enabled)
  {
  	if (enabled)
  		static_branch_enable(&sched_schedstats);
  	else
  		static_branch_disable(&sched_schedstats);
  }
  
  void force_schedstat_enabled(void)
  {
  	if (!schedstat_enabled()) {
  		pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
  		static_branch_enable(&sched_schedstats);
  	}
  }
  
  static int __init setup_schedstats(char *str)
  {
  	int ret = 0;
  	if (!str)
  		goto out;
  
  	/*
  	 * This code is called before jump labels have been set up, so we can't
  	 * change the static branch directly just yet.  Instead set a temporary
  	 * variable so init_schedstats() can do it later.
  	 */
  	if (!strcmp(str, "enable")) {
  		__sched_schedstats = true;
  		ret = 1;
  	} else if (!strcmp(str, "disable")) {
  		__sched_schedstats = false;
  		ret = 1;
  	}
  out:
  	if (!ret)
  		pr_warn("Unable to parse schedstats=\n");
  
  	return ret;
  }
  __setup("schedstats=", setup_schedstats);
  
  static void __init init_schedstats(void)
  {
  	set_schedstats(__sched_schedstats);
  }
  
  #ifdef CONFIG_PROC_SYSCTL
  int sysctl_schedstats(struct ctl_table *table, int write,
  			 void __user *buffer, size_t *lenp, loff_t *ppos)
  {
  	struct ctl_table t;
  	int err;
  	int state = static_branch_likely(&sched_schedstats);
  
  	if (write && !capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	t = *table;
  	t.data = &state;
  	err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
  	if (err < 0)
  		return err;
  	if (write)
  		set_schedstats(state);
  	return err;
  }
  #endif /* CONFIG_PROC_SYSCTL */
  #else  /* !CONFIG_SCHEDSTATS */
  static inline void init_schedstats(void) {}
  #endif /* CONFIG_SCHEDSTATS */
  
  /*
   * fork()/clone()-time setup:
   */
  int sched_fork(unsigned long clone_flags, struct task_struct *p)
  {
  	unsigned long flags;
  
  	__sched_fork(clone_flags, p);
  	/*
  	 * We mark the process as NEW here. This guarantees that
  	 * nobody will actually run it, and a signal or other external
  	 * event cannot wake it up and insert it on the runqueue either.
  	 */
  	p->state = TASK_NEW;
  
  	/*
  	 * Make sure we do not leak PI boosting priority to the child.
  	 */
  	p->prio = current->normal_prio;
  
  	uclamp_fork(p);
  
  	/*
  	 * Revert to default priority/policy on fork if requested.
  	 */
  	if (unlikely(p->sched_reset_on_fork)) {
  		if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
  			p->policy = SCHED_NORMAL;
  			p->static_prio = NICE_TO_PRIO(0);
  			p->rt_priority = 0;
  		} else if (PRIO_TO_NICE(p->static_prio) < 0)
  			p->static_prio = NICE_TO_PRIO(0);
  
  		p->prio = p->normal_prio = __normal_prio(p);
  		set_load_weight(p, false);
  
  		/*
  		 * We don't need the reset flag anymore after the fork. It has
  		 * fulfilled its duty:
  		 */
  		p->sched_reset_on_fork = 0;
  	}
  
  	if (dl_prio(p->prio))
  		return -EAGAIN;
  	else if (rt_prio(p->prio))
  		p->sched_class = &rt_sched_class;
  	else
  		p->sched_class = &fair_sched_class;
  
  	init_entity_runnable_average(&p->se);
  
  	/*
  	 * The child is not yet in the pid-hash so no cgroup attach races,
  	 * and the cgroup is pinned to this child due to cgroup_fork()
  	 * is ran before sched_fork().
  	 *
  	 * Silence PROVE_RCU.
  	 */
  	raw_spin_lock_irqsave(&p->pi_lock, flags);
  	rseq_migrate(p);
  	/*
  	 * We're setting the CPU for the first time, we don't migrate,
  	 * so use __set_task_cpu().
  	 */
  	__set_task_cpu(p, smp_processor_id());
  	if (p->sched_class->task_fork)
  		p->sched_class->task_fork(p);
  	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  
  #ifdef CONFIG_SCHED_INFO
  	if (likely(sched_info_on()))
  		memset(&p->sched_info, 0, sizeof(p->sched_info));
  #endif
  #if defined(CONFIG_SMP)
  	p->on_cpu = 0;
  #endif
  	init_task_preempt_count(p);
  #ifdef CONFIG_SMP
  	plist_node_init(&p->pushable_tasks, MAX_PRIO);
  	RB_CLEAR_NODE(&p->pushable_dl_tasks);
  #endif
  	return 0;
  }
  
  unsigned long to_ratio(u64 period, u64 runtime)
  {
  	if (runtime == RUNTIME_INF)
  		return BW_UNIT;
  
  	/*
  	 * Doing this here saves a lot of checks in all
  	 * the calling paths, and returning zero seems
  	 * safe for them anyway.
  	 */
  	if (period == 0)
  		return 0;
  
  	return div64_u64(runtime << BW_SHIFT, period);
  }
  
  /*
   * wake_up_new_task - wake up a newly created task for the first time.
   *
   * This function will do some initial scheduler statistics housekeeping
   * that must be done for every newly created context, then puts the task
   * on the runqueue and wakes it.
   */
  void wake_up_new_task(struct task_struct *p)
  {
  	struct rq_flags rf;
  	struct rq *rq;
  
  	raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
  	p->state = TASK_RUNNING;
  #ifdef CONFIG_SMP
  	/*
  	 * Fork balancing, do it here and not earlier because:
  	 *  - cpus_ptr can change in the fork path
  	 *  - any previously selected CPU might disappear through hotplug
  	 *
  	 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
  	 * as we're not fully set-up yet.
  	 */
  	p->recent_used_cpu = task_cpu(p);
  	rseq_migrate(p);
  	__set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
  #endif
  	rq = __task_rq_lock(p, &rf);
  	update_rq_clock(rq);
  	post_init_entity_util_avg(p);
  
  	activate_task(rq, p, ENQUEUE_NOCLOCK);
  	trace_sched_wakeup_new(p);
  	check_preempt_curr(rq, p, WF_FORK);
  #ifdef CONFIG_SMP
  	if (p->sched_class->task_woken) {
  		/*
  		 * Nothing relies on rq->lock after this, so its fine to
  		 * drop it.
  		 */
  		rq_unpin_lock(rq, &rf);
  		p->sched_class->task_woken(rq, p);
  		rq_repin_lock(rq, &rf);
  	}
  #endif
  	task_rq_unlock(rq, p, &rf);
  }
  
  #ifdef CONFIG_PREEMPT_NOTIFIERS
  
  static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
  
  void preempt_notifier_inc(void)
  {
  	static_branch_inc(&preempt_notifier_key);
  }
  EXPORT_SYMBOL_GPL(preempt_notifier_inc);
  
  void preempt_notifier_dec(void)
  {
  	static_branch_dec(&preempt_notifier_key);
  }
  EXPORT_SYMBOL_GPL(preempt_notifier_dec);
  
  /**
   * preempt_notifier_register - tell me when current is being preempted & rescheduled
   * @notifier: notifier struct to register
   */
  void preempt_notifier_register(struct preempt_notifier *notifier)
  {
  	if (!static_branch_unlikely(&preempt_notifier_key))
  		WARN(1, "registering preempt_notifier while notifiers disabled\n");
  
  	hlist_add_head(&notifier->link, &current->preempt_notifiers);
  }
  EXPORT_SYMBOL_GPL(preempt_notifier_register);
  
  /**
   * preempt_notifier_unregister - no longer interested in preemption notifications
   * @notifier: notifier struct to unregister
   *
   * This is *not* safe to call from within a preemption notifier.
   */
  void preempt_notifier_unregister(struct preempt_notifier *notifier)
  {
  	hlist_del(&notifier->link);
  }
  EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
  
  static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
  {
  	struct preempt_notifier *notifier;
  
  	hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
  		notifier->ops->sched_in(notifier, raw_smp_processor_id());
  }
  
  static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
  {
  	if (static_branch_unlikely(&preempt_notifier_key))
  		__fire_sched_in_preempt_notifiers(curr);
  }
  
  static void
  __fire_sched_out_preempt_notifiers(struct task_struct *curr,
  				   struct task_struct *next)
  {
  	struct preempt_notifier *notifier;
  
  	hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
  		notifier->ops->sched_out(notifier, next);
  }
  
  static __always_inline void
  fire_sched_out_preempt_notifiers(struct task_struct *curr,
  				 struct task_struct *next)
  {
  	if (static_branch_unlikely(&preempt_notifier_key))
  		__fire_sched_out_preempt_notifiers(curr, next);
  }
  
  #else /* !CONFIG_PREEMPT_NOTIFIERS */
  
  static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
  {
  }
  
  static inline void
  fire_sched_out_preempt_notifiers(struct task_struct *curr,
  				 struct task_struct *next)
  {
  }
  
  #endif /* CONFIG_PREEMPT_NOTIFIERS */
  
  static inline void prepare_task(struct task_struct *next)
  {
  #ifdef CONFIG_SMP
  	/*
  	 * Claim the task as running, we do this before switching to it
  	 * such that any running task will have this set.
  	 */
  	next->on_cpu = 1;
  #endif
  }
  
  static inline void finish_task(struct task_struct *prev)
  {
  #ifdef CONFIG_SMP
  	/*
  	 * After ->on_cpu is cleared, the task can be moved to a different CPU.
  	 * We must ensure this doesn't happen until the switch is completely
  	 * finished.
  	 *
  	 * In particular, the load of prev->state in finish_task_switch() must
  	 * happen before this.
  	 *
  	 * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
  	 */
  	smp_store_release(&prev->on_cpu, 0);
  #endif
  }
  
  static inline void
  prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
  {
  	/*
  	 * Since the runqueue lock will be released by the next
  	 * task (which is an invalid locking op but in the case
  	 * of the scheduler it's an obvious special-case), so we
  	 * do an early lockdep release here:
  	 */
  	rq_unpin_lock(rq, rf);
  	spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
  #ifdef CONFIG_DEBUG_SPINLOCK
  	/* this is a valid case when another task releases the spinlock */
  	rq->lock.owner = next;
  #endif
  }
  
  static inline void finish_lock_switch(struct rq *rq)
  {
  	/*
  	 * If we are tracking spinlock dependencies then we have to
  	 * fix up the runqueue lock - which gets 'carried over' from
  	 * prev into current:
  	 */
  	spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
  	raw_spin_unlock_irq(&rq->lock);
  }
  
  /*
   * NOP if the arch has not defined these:
   */
  
  #ifndef prepare_arch_switch
  # define prepare_arch_switch(next)	do { } while (0)
  #endif
  
  #ifndef finish_arch_post_lock_switch
  # define finish_arch_post_lock_switch()	do { } while (0)
  #endif
  
  /**
   * prepare_task_switch - prepare to switch tasks
   * @rq: the runqueue preparing to switch
   * @prev: the current task that is being switched out
   * @next: the task we are going to switch to.
   *
   * This is called with the rq lock held and interrupts off. It must
   * be paired with a subsequent finish_task_switch after the context
   * switch.
   *
   * prepare_task_switch sets up locking and calls architecture specific
   * hooks.
   */
  static inline void
  prepare_task_switch(struct rq *rq, struct task_struct *prev,
  		    struct task_struct *next)
  {
  	kcov_prepare_switch(prev);
  	sched_info_switch(rq, prev, next);
  	perf_event_task_sched_out(prev, next);
  	rseq_preempt(prev);
  	fire_sched_out_preempt_notifiers(prev, next);
  	prepare_task(next);
  	prepare_arch_switch(next);
  }
  
  /**
   * finish_task_switch - clean up after a task-switch
   * @prev: the thread we just switched away from.
   *
   * finish_task_switch must be called after the context switch, paired
   * with a prepare_task_switch call before the context switch.
   * finish_task_switch will reconcile locking set up by prepare_task_switch,
   * and do any other architecture-specific cleanup actions.
   *
   * Note that we may have delayed dropping an mm in context_switch(). If
   * so, we finish that here outside of the runqueue lock. (Doing it
   * with the lock held can cause deadlocks; see schedule() for
   * details.)
   *
   * The context switch have flipped the stack from under us and restored the
   * local variables which were saved when this task called schedule() in the
   * past. prev == current is still correct but we need to recalculate this_rq
   * because prev may have moved to another CPU.
   */
  static struct rq *finish_task_switch(struct task_struct *prev)
  	__releases(rq->lock)
  {
  	struct rq *rq = this_rq();
  	struct mm_struct *mm = rq->prev_mm;
  	long prev_state;
  
  	/*
  	 * The previous task will have left us with a preempt_count of 2
  	 * because it left us after:
  	 *
  	 *	schedule()
  	 *	  preempt_disable();			// 1
  	 *	  __schedule()
  	 *	    raw_spin_lock_irq(&rq->lock)	// 2
  	 *
  	 * Also, see FORK_PREEMPT_COUNT.
  	 */
  	if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
  		      "corrupted preempt_count: %s/%d/0x%x\n",
  		      current->comm, current->pid, preempt_count()))
  		preempt_count_set(FORK_PREEMPT_COUNT);
  
  	rq->prev_mm = NULL;
  
  	/*
  	 * A task struct has one reference for the use as "current".
  	 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
  	 * schedule one last time. The schedule call will never return, and
  	 * the scheduled task must drop that reference.
  	 *
  	 * We must observe prev->state before clearing prev->on_cpu (in
  	 * finish_task), otherwise a concurrent wakeup can get prev
  	 * running on another CPU and we could rave with its RUNNING -> DEAD
  	 * transition, resulting in a double drop.
  	 */
  	prev_state = prev->state;
  	vtime_task_switch(prev);
  	perf_event_task_sched_in(prev, current);
  	finish_task(prev);
  	finish_lock_switch(rq);
  	finish_arch_post_lock_switch();
  	kcov_finish_switch(current);
  
  	fire_sched_in_preempt_notifiers(current);
  	/*
  	 * When switching through a kernel thread, the loop in
  	 * membarrier_{private,global}_expedited() may have observed that
  	 * kernel thread and not issued an IPI. It is therefore possible to
  	 * schedule between user->kernel->user threads without passing though
  	 * switch_mm(). Membarrier requires a barrier after storing to
  	 * rq->curr, before returning to userspace, so provide them here:
  	 *
  	 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
  	 *   provided by mmdrop(),
  	 * - a sync_core for SYNC_CORE.
  	 */
  	if (mm) {
  		membarrier_mm_sync_core_before_usermode(mm);
  		mmdrop(mm);
  	}
  	if (unlikely(prev_state == TASK_DEAD)) {
  		if (prev->sched_class->task_dead)
  			prev->sched_class->task_dead(prev);
  
  		/*
  		 * Remove function-return probe instances associated with this
  		 * task and put them back on the free list.
  		 */
  		kprobe_flush_task(prev);
  
  		/* Task is done with its stack. */
  		put_task_stack(prev);
  
  		put_task_struct_rcu_user(prev);
  	}
  
  	tick_nohz_task_switch();
  	return rq;
  }
  
  #ifdef CONFIG_SMP
  
  /* rq->lock is NOT held, but preemption is disabled */
  static void __balance_callback(struct rq *rq)
  {
  	struct callback_head *head, *next;
  	void (*func)(struct rq *rq);
  	unsigned long flags;
  
  	raw_spin_lock_irqsave(&rq->lock, flags);
  	head = rq->balance_callback;
  	rq->balance_callback = NULL;
  	while (head) {
  		func = (void (*)(struct rq *))head->func;
  		next = head->next;
  		head->next = NULL;
  		head = next;
  
  		func(rq);
  	}
  	raw_spin_unlock_irqrestore(&rq->lock, flags);
  }
  
  static inline void balance_callback(struct rq *rq)
  {
  	if (unlikely(rq->balance_callback))
  		__balance_callback(rq);
  }
  
  #else
  
  static inline void balance_callback(struct rq *rq)
  {
  }
  
  #endif
  
  /**
   * schedule_tail - first thing a freshly forked thread must call.
   * @prev: the thread we just switched away from.
   */
  asmlinkage __visible void schedule_tail(struct task_struct *prev)
  	__releases(rq->lock)
  {
  	struct rq *rq;
  
  	/*
  	 * New tasks start with FORK_PREEMPT_COUNT, see there and
  	 * finish_task_switch() for details.
  	 *
  	 * finish_task_switch() will drop rq->lock() and lower preempt_count
  	 * and the preempt_enable() will end up enabling preemption (on
  	 * PREEMPT_COUNT kernels).
  	 */
  
  	rq = finish_task_switch(prev);
  	balance_callback(rq);
  	preempt_enable();
  
  	if (current->set_child_tid)
  		put_user(task_pid_vnr(current), current->set_child_tid);
  
  	calculate_sigpending();
  }
  
  /*
   * context_switch - switch to the new MM and the new thread's register state.
   */
  static __always_inline struct rq *
  context_switch(struct rq *rq, struct task_struct *prev,
  	       struct task_struct *next, struct rq_flags *rf)
  {
  	prepare_task_switch(rq, prev, next);
  
  	/*
  	 * For paravirt, this is coupled with an exit in switch_to to
  	 * combine the page table reload and the switch backend into
  	 * one hypercall.
  	 */
  	arch_start_context_switch(prev);
  
  	/*
  	 * kernel -> kernel   lazy + transfer active
  	 *   user -> kernel   lazy + mmgrab() active
  	 *
  	 * kernel ->   user   switch + mmdrop() active
  	 *   user ->   user   switch
  	 */
  	if (!next->mm) {                                // to kernel
  		enter_lazy_tlb(prev->active_mm, next);
  
  		next->active_mm = prev->active_mm;
  		if (prev->mm)                           // from user
  			mmgrab(prev->active_mm);
  		else
  			prev->active_mm = NULL;
  	} else {                                        // to user
  		membarrier_switch_mm(rq, prev->active_mm, next->mm);
  		/*
  		 * sys_membarrier() requires an smp_mb() between setting
  		 * rq->curr / membarrier_switch_mm() and returning to userspace.
  		 *
  		 * The below provides this either through switch_mm(), or in
  		 * case 'prev->active_mm == next->mm' through
  		 * finish_task_switch()'s mmdrop().
  		 */
  		switch_mm_irqs_off(prev->active_mm, next->mm, next);
  
  		if (!prev->mm) {                        // from kernel
  			/* will mmdrop() in finish_task_switch(). */
  			rq->prev_mm = prev->active_mm;
  			prev->active_mm = NULL;
  		}
  	}
  
  	rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
  
  	prepare_lock_switch(rq, next, rf);
  
  	/* Here we just switch the register state and the stack. */
  	switch_to(prev, next, prev);
  	barrier();
  
  	return finish_task_switch(prev);
  }
  
  /*
   * nr_running and nr_context_switches:
   *
   * externally visible scheduler statistics: current number of runnable
   * threads, total number of context switches performed since bootup.
   */
  unsigned long nr_running(void)
  {
  	unsigned long i, sum = 0;
  
  	for_each_online_cpu(i)
  		sum += cpu_rq(i)->nr_running;
  
  	return sum;
  }
  
  /*
   * Check if only the current task is running on the CPU.
   *
   * Caution: this function does not check that the caller has disabled
   * preemption, thus the result might have a time-of-check-to-time-of-use
   * race.  The caller is responsible to use it correctly, for example:
   *
   * - from a non-preemptible section (of course)
   *
   * - from a thread that is bound to a single CPU
   *
   * - in a loop with very short iterations (e.g. a polling loop)
   */
  bool single_task_running(void)
  {
  	return raw_rq()->nr_running == 1;
  }
  EXPORT_SYMBOL(single_task_running);
  
  unsigned long long nr_context_switches(void)
  {
  	int i;
  	unsigned long long sum = 0;
  
  	for_each_possible_cpu(i)
  		sum += cpu_rq(i)->nr_switches;
  
  	return sum;
  }
  
  /*
   * Consumers of these two interfaces, like for example the cpuidle menu
   * governor, are using nonsensical data. Preferring shallow idle state selection
   * for a CPU that has IO-wait which might not even end up running the task when
   * it does become runnable.
   */
  
  unsigned long nr_iowait_cpu(int cpu)
  {
  	return atomic_read(&cpu_rq(cpu)->nr_iowait);
  }
  
  /*
   * IO-wait accounting, and how its mostly bollocks (on SMP).
   *
   * The idea behind IO-wait account is to account the idle time that we could
   * have spend running if it were not for IO. That is, if we were to improve the
   * storage performance, we'd have a proportional reduction in IO-wait time.
   *
   * This all works nicely on UP, where, when a task blocks on IO, we account
   * idle time as IO-wait, because if the storage were faster, it could've been
   * running and we'd not be idle.
   *
   * This has been extended to SMP, by doing the same for each CPU. This however
   * is broken.
   *
   * Imagine for instance the case where two tasks block on one CPU, only the one
   * CPU will have IO-wait accounted, while the other has regular idle. Even
   * though, if the storage were faster, both could've ran at the same time,
   * utilising both CPUs.
   *
   * This means, that when looking globally, the current IO-wait accounting on
   * SMP is a lower bound, by reason of under accounting.
   *
   * Worse, since the numbers are provided per CPU, they are sometimes
   * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
   * associated with any one particular CPU, it can wake to another CPU than it
   * blocked on. This means the per CPU IO-wait number is meaningless.
   *
   * Task CPU affinities can make all that even more 'interesting'.
   */
  
  unsigned long nr_iowait(void)
  {
  	unsigned long i, sum = 0;
  
  	for_each_possible_cpu(i)
  		sum += nr_iowait_cpu(i);
  
  	return sum;
  }
  
  #ifdef CONFIG_SMP
  
  /*
   * sched_exec - execve() is a valuable balancing opportunity, because at
   * this point the task has the smallest effective memory and cache footprint.
   */
  void sched_exec(void)
  {
  	struct task_struct *p = current;
  	unsigned long flags;
  	int dest_cpu;
  
  	raw_spin_lock_irqsave(&p->pi_lock, flags);
  	dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
  	if (dest_cpu == smp_processor_id())
  		goto unlock;
  
  	if (likely(cpu_active(dest_cpu))) {
  		struct migration_arg arg = { p, dest_cpu };
  
  		raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  		stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
  		return;
  	}
  unlock:
  	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  }
  
  #endif
  
  DEFINE_PER_CPU(struct kernel_stat, kstat);
  DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
  
  EXPORT_PER_CPU_SYMBOL(kstat);
  EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
  
  /*
   * The function fair_sched_class.update_curr accesses the struct curr
   * and its field curr->exec_start; when called from task_sched_runtime(),
   * we observe a high rate of cache misses in practice.
   * Prefetching this data results in improved performance.
   */
  static inline void prefetch_curr_exec_start(struct task_struct *p)
  {
  #ifdef CONFIG_FAIR_GROUP_SCHED
  	struct sched_entity *curr = (&p->se)->cfs_rq->curr;
  #else
  	struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
  #endif
  	prefetch(curr);
  	prefetch(&curr->exec_start);
  }
  
  /*
   * Return accounted runtime for the task.
   * In case the task is currently running, return the runtime plus current's
   * pending runtime that have not been accounted yet.
   */
  unsigned long long task_sched_runtime(struct task_struct *p)
  {
  	struct rq_flags rf;
  	struct rq *rq;
  	u64 ns;
  
  #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
  	/*
  	 * 64-bit doesn't need locks to atomically read a 64-bit value.
  	 * So we have a optimization chance when the task's delta_exec is 0.
  	 * Reading ->on_cpu is racy, but this is ok.
  	 *
  	 * If we race with it leaving CPU, we'll take a lock. So we're correct.
  	 * If we race with it entering CPU, unaccounted time is 0. This is
  	 * indistinguishable from the read occurring a few cycles earlier.
  	 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
  	 * been accounted, so we're correct here as well.
  	 */
  	if (!p->on_cpu || !task_on_rq_queued(p))
  		return p->se.sum_exec_runtime;
  #endif
  
  	rq = task_rq_lock(p, &rf);
  	/*
  	 * Must be ->curr _and_ ->on_rq.  If dequeued, we would
  	 * project cycles that may never be accounted to this
  	 * thread, breaking clock_gettime().
  	 */
  	if (task_current(rq, p) && task_on_rq_queued(p)) {
  		prefetch_curr_exec_start(p);
  		update_rq_clock(rq);
  		p->sched_class->update_curr(rq);
  	}
  	ns = p->se.sum_exec_runtime;
  	task_rq_unlock(rq, p, &rf);
  
  	return ns;
  }
  
  /*
   * This function gets called by the timer code, with HZ frequency.
   * We call it with interrupts disabled.
   */
  void scheduler_tick(void)
  {
  	int cpu = smp_processor_id();
  	struct rq *rq = cpu_rq(cpu);
  	struct task_struct *curr = rq->curr;
  	struct rq_flags rf;
  
  	sched_clock_tick();
  
  	rq_lock(rq, &rf);
  
  	update_rq_clock(rq);
  	curr->sched_class->task_tick(rq, curr, 0);
  	calc_global_load_tick(rq);
  	psi_task_tick(rq);
  
  	rq_unlock(rq, &rf);
  
  	perf_event_task_tick();
  
  #ifdef CONFIG_SMP
  	rq->idle_balance = idle_cpu(cpu);
  	trigger_load_balance(rq);
  #endif
  }
  
  #ifdef CONFIG_NO_HZ_FULL
  
  struct tick_work {
  	int			cpu;
  	atomic_t		state;
  	struct delayed_work	work;
  };
  /* Values for ->state, see diagram below. */
  #define TICK_SCHED_REMOTE_OFFLINE	0
  #define TICK_SCHED_REMOTE_OFFLINING	1
  #define TICK_SCHED_REMOTE_RUNNING	2
  
  /*
   * State diagram for ->state:
   *
   *
   *          TICK_SCHED_REMOTE_OFFLINE
   *                    |   ^
   *                    |   |
   *                    |   | sched_tick_remote()
   *                    |   |
   *                    |   |
   *                    +--TICK_SCHED_REMOTE_OFFLINING
   *                    |   ^
   *                    |   |
   * sched_tick_start() |   | sched_tick_stop()
   *                    |   |
   *                    V   |
   *          TICK_SCHED_REMOTE_RUNNING
   *
   *
   * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
   * and sched_tick_start() are happy to leave the state in RUNNING.
   */
  
  static struct tick_work __percpu *tick_work_cpu;
  
  static void sched_tick_remote(struct work_struct *work)
  {
  	struct delayed_work *dwork = to_delayed_work(work);
  	struct tick_work *twork = container_of(dwork, struct tick_work, work);
  	int cpu = twork->cpu;
  	struct rq *rq = cpu_rq(cpu);
  	struct task_struct *curr;
  	struct rq_flags rf;
  	u64 delta;
  	int os;
  
  	/*
  	 * Handle the tick only if it appears the remote CPU is running in full
  	 * dynticks mode. The check is racy by nature, but missing a tick or
  	 * having one too much is no big deal because the scheduler tick updates
  	 * statistics and checks timeslices in a time-independent way, regardless
  	 * of when exactly it is running.
  	 */
  	if (!tick_nohz_tick_stopped_cpu(cpu))
  		goto out_requeue;
  
  	rq_lock_irq(rq, &rf);
  	curr = rq->curr;
  	if (cpu_is_offline(cpu))
  		goto out_unlock;
  
  	update_rq_clock(rq);
  
  	if (!is_idle_task(curr)) {
  		/*
  		 * Make sure the next tick runs within a reasonable
  		 * amount of time.
  		 */
  		delta = rq_clock_task(rq) - curr->se.exec_start;
  		WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
  	}
  	curr->sched_class->task_tick(rq, curr, 0);
  
  	calc_load_nohz_remote(rq);
  out_unlock:
  	rq_unlock_irq(rq, &rf);
  out_requeue:
  
  	/*
  	 * Run the remote tick once per second (1Hz). This arbitrary
  	 * frequency is large enough to avoid overload but short enough
  	 * to keep scheduler internal stats reasonably up to date.  But
  	 * first update state to reflect hotplug activity if required.
  	 */
  	os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING);
  	WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE);
  	if (os == TICK_SCHED_REMOTE_RUNNING)
  		queue_delayed_work(system_unbound_wq, dwork, HZ);
  }
  
  static void sched_tick_start(int cpu)
  {
  	int os;
  	struct tick_work *twork;
  
  	if (housekeeping_cpu(cpu, HK_FLAG_TICK))
  		return;
  
  	WARN_ON_ONCE(!tick_work_cpu);
  
  	twork = per_cpu_ptr(tick_work_cpu, cpu);
  	os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING);
  	WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING);
  	if (os == TICK_SCHED_REMOTE_OFFLINE) {
  		twork->cpu = cpu;
  		INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
  		queue_delayed_work(system_unbound_wq, &twork->work, HZ);
  	}
  }
  
  #ifdef CONFIG_HOTPLUG_CPU
  static void sched_tick_stop(int cpu)
  {
  	struct tick_work *twork;
  	int os;
  
  	if (housekeeping_cpu(cpu, HK_FLAG_TICK))
  		return;
  
  	WARN_ON_ONCE(!tick_work_cpu);
  
  	twork = per_cpu_ptr(tick_work_cpu, cpu);
  	/* There cannot be competing actions, but don't rely on stop-machine. */
  	os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING);
  	WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING);
  	/* Don't cancel, as this would mess up the state machine. */
  }
  #endif /* CONFIG_HOTPLUG_CPU */
  
  int __init sched_tick_offload_init(void)
  {
  	tick_work_cpu = alloc_percpu(struct tick_work);
  	BUG_ON(!tick_work_cpu);
  	return 0;
  }
  
  #else /* !CONFIG_NO_HZ_FULL */
  static inline void sched_tick_start(int cpu) { }
  static inline void sched_tick_stop(int cpu) { }
  #endif
  
  #if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
  				defined(CONFIG_TRACE_PREEMPT_TOGGLE))
  /*
   * If the value passed in is equal to the current preempt count
   * then we just disabled preemption. Start timing the latency.
   */
  static inline void preempt_latency_start(int val)
  {
  	if (preempt_count() == val) {
  		unsigned long ip = get_lock_parent_ip();
  #ifdef CONFIG_DEBUG_PREEMPT
  		current->preempt_disable_ip = ip;
  #endif
  		trace_preempt_off(CALLER_ADDR0, ip);
  	}
  }
  
  void preempt_count_add(int val)
  {
  #ifdef CONFIG_DEBUG_PREEMPT
  	/*
  	 * Underflow?
  	 */
  	if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
  		return;
  #endif
  	__preempt_count_add(val);
  #ifdef CONFIG_DEBUG_PREEMPT
  	/*
  	 * Spinlock count overflowing soon?
  	 */
  	DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
  				PREEMPT_MASK - 10);
  #endif
  	preempt_latency_start(val);
  }
  EXPORT_SYMBOL(preempt_count_add);
  NOKPROBE_SYMBOL(preempt_count_add);
  
  /*
   * If the value passed in equals to the current preempt count
   * then we just enabled preemption. Stop timing the latency.
   */
  static inline void preempt_latency_stop(int val)
  {
  	if (preempt_count() == val)
  		trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
  }
  
  void preempt_count_sub(int val)
  {
  #ifdef CONFIG_DEBUG_PREEMPT
  	/*
  	 * Underflow?
  	 */
  	if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
  		return;
  	/*
  	 * Is the spinlock portion underflowing?
  	 */
  	if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
  			!(preempt_count() & PREEMPT_MASK)))
  		return;
  #endif
  
  	preempt_latency_stop(val);
  	__preempt_count_sub(val);
  }
  EXPORT_SYMBOL(preempt_count_sub);
  NOKPROBE_SYMBOL(preempt_count_sub);
  
  #else
  static inline void preempt_latency_start(int val) { }
  static inline void preempt_latency_stop(int val) { }
  #endif
  
  static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
  {
  #ifdef CONFIG_DEBUG_PREEMPT
  	return p->preempt_disable_ip;
  #else
  	return 0;
  #endif
  }
  
  /*
   * Print scheduling while atomic bug:
   */
  static noinline void __schedule_bug(struct task_struct *prev)
  {
  	/* Save this before calling printk(), since that will clobber it */
  	unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
  
  	if (oops_in_progress)
  		return;
  
  	printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
  		prev->comm, prev->pid, preempt_count());
  
  	debug_show_held_locks(prev);
  	print_modules();
  	if (irqs_disabled())
  		print_irqtrace_events(prev);
  	if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
  	    && in_atomic_preempt_off()) {
  		pr_err("Preemption disabled at:");
  		print_ip_sym(preempt_disable_ip);
  		pr_cont("\n");
  	}
  	if (panic_on_warn)
  		panic("scheduling while atomic\n");
  
  	dump_stack();
  	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
  }
  
  /*
   * Various schedule()-time debugging checks and statistics:
   */
  static inline void schedule_debug(struct task_struct *prev, bool preempt)
  {
  #ifdef CONFIG_SCHED_STACK_END_CHECK
  	if (task_stack_end_corrupted(prev))
  		panic("corrupted stack end detected inside scheduler\n");
  #endif
  
  #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
  	if (!preempt && prev->state && prev->non_block_count) {
  		printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n",
  			prev->comm, prev->pid, prev->non_block_count);
  		dump_stack();
  		add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
  	}
  #endif
  
  	if (unlikely(in_atomic_preempt_off())) {
  		__schedule_bug(prev);
  		preempt_count_set(PREEMPT_DISABLED);
  	}
  	rcu_sleep_check();
  
  	profile_hit(SCHED_PROFILING, __builtin_return_address(0));
  
  	schedstat_inc(this_rq()->sched_count);
  }
  
  /*
   * Pick up the highest-prio task:
   */
  static inline struct task_struct *
  pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
  {
  	const struct sched_class *class;
  	struct task_struct *p;
  
  	/*
  	 * Optimization: we know that if all tasks are in the fair class we can
  	 * call that function directly, but only if the @prev task wasn't of a
  	 * higher scheduling class, because otherwise those loose the
  	 * opportunity to pull in more work from other CPUs.
  	 */
  	if (likely((prev->sched_class == &idle_sched_class ||
  		    prev->sched_class == &fair_sched_class) &&
  		   rq->nr_running == rq->cfs.h_nr_running)) {
  
  		p = fair_sched_class.pick_next_task(rq, prev, rf);
  		if (unlikely(p == RETRY_TASK))
  			goto restart;
  
  		/* Assumes fair_sched_class->next == idle_sched_class */
  		if (unlikely(!p))
  			p = idle_sched_class.pick_next_task(rq, prev, rf);
  
  		return p;
  	}
  
  restart:
  #ifdef CONFIG_SMP
  	/*
  	 * We must do the balancing pass before put_next_task(), such
  	 * that when we release the rq->lock the task is in the same
  	 * state as before we took rq->lock.
  	 *
  	 * We can terminate the balance pass as soon as we know there is
  	 * a runnable task of @class priority or higher.
  	 */
  	for_class_range(class, prev->sched_class, &idle_sched_class) {
  		if (class->balance(rq, prev, rf))
  			break;
  	}
  #endif
  
  	put_prev_task(rq, prev);
  
  	for_each_class(class) {
  		p = class->pick_next_task(rq, NULL, NULL);
  		if (p)
  			return p;
  	}
  
  	/* The idle class should always have a runnable task: */
  	BUG();
  }
  
  /*
   * __schedule() is the main scheduler function.
   *
   * The main means of driving the scheduler and thus entering this function are:
   *
   *   1. Explicit blocking: mutex, semaphore, waitqueue, etc.
   *
   *   2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
   *      paths. For example, see arch/x86/entry_64.S.
   *
   *      To drive preemption between tasks, the scheduler sets the flag in timer
   *      interrupt handler scheduler_tick().
   *
   *   3. Wakeups don't really cause entry into schedule(). They add a
   *      task to the run-queue and that's it.
   *
   *      Now, if the new task added to the run-queue preempts the current
   *      task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
   *      called on the nearest possible occasion:
   *
   *       - If the kernel is preemptible (CONFIG_PREEMPTION=y):
   *
   *         - in syscall or exception context, at the next outmost
   *           preempt_enable(). (this might be as soon as the wake_up()'s
   *           spin_unlock()!)
   *
   *         - in IRQ context, return from interrupt-handler to
   *           preemptible context
   *
   *       - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
   *         then at the next:
   *
   *          - cond_resched() call
   *          - explicit schedule() call
   *          - return from syscall or exception to user-space
   *          - return from interrupt-handler to user-space
   *
   * WARNING: must be called with preemption disabled!
   */
  static void __sched notrace __schedule(bool preempt)
  {
  	struct task_struct *prev, *next;
  	unsigned long *switch_count;
  	struct rq_flags rf;
  	struct rq *rq;
  	int cpu;
  
  	cpu = smp_processor_id();
  	rq = cpu_rq(cpu);
  	prev = rq->curr;
  
  	schedule_debug(prev, preempt);
  
  	if (sched_feat(HRTICK))
  		hrtick_clear(rq);
  
  	local_irq_disable();
  	rcu_note_context_switch(preempt);
  
  	/*
  	 * Make sure that signal_pending_state()->signal_pending() below
  	 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
  	 * done by the caller to avoid the race with signal_wake_up().
  	 *
  	 * The membarrier system call requires a full memory barrier
  	 * after coming from user-space, before storing to rq->curr.
  	 */
  	rq_lock(rq, &rf);
  	smp_mb__after_spinlock();
  
  	/* Promote REQ to ACT */
  	rq->clock_update_flags <<= 1;
  	update_rq_clock(rq);
  
  	switch_count = &prev->nivcsw;
  	if (!preempt && prev->state) {
  		if (signal_pending_state(prev->state, prev)) {
  			prev->state = TASK_RUNNING;
  		} else {
  			deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
  
  			if (prev->in_iowait) {
  				atomic_inc(&rq->nr_iowait);
  				delayacct_blkio_start();
  			}
  		}
  		switch_count = &prev->nvcsw;
  	}
  
  	next = pick_next_task(rq, prev, &rf);
  	clear_tsk_need_resched(prev);
  	clear_preempt_need_resched();
  
  	if (likely(prev != next)) {
  		rq->nr_switches++;
  		/*
  		 * RCU users of rcu_dereference(rq->curr) may not see
  		 * changes to task_struct made by pick_next_task().
  		 */
  		RCU_INIT_POINTER(rq->curr, next);
  		/*
  		 * The membarrier system call requires each architecture
  		 * to have a full memory barrier after updating
  		 * rq->curr, before returning to user-space.
  		 *
  		 * Here are the schemes providing that barrier on the
  		 * various architectures:
  		 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
  		 *   switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
  		 * - finish_lock_switch() for weakly-ordered
  		 *   architectures where spin_unlock is a full barrier,
  		 * - switch_to() for arm64 (weakly-ordered, spin_unlock
  		 *   is a RELEASE barrier),
  		 */
  		++*switch_count;
  
  		trace_sched_switch(preempt, prev, next);
  
  		/* Also unlocks the rq: */
  		rq = context_switch(rq, prev, next, &rf);
  	} else {
  		rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
  		rq_unlock_irq(rq, &rf);
  	}
  
  	balance_callback(rq);
  }
  
  void __noreturn do_task_dead(void)
  {
  	/* Causes final put_task_struct in finish_task_switch(): */
  	set_special_state(TASK_DEAD);
  
  	/* Tell freezer to ignore us: */
  	current->flags |= PF_NOFREEZE;
  
  	__schedule(false);
  	BUG();
  
  	/* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
  	for (;;)
  		cpu_relax();
  }
  
  static inline void sched_submit_work(struct task_struct *tsk)
  {
  	if (!tsk->state)
  		return;
  
  	/*
  	 * If a worker went to sleep, notify and ask workqueue whether
  	 * it wants to wake up a task to maintain concurrency.
  	 * As this function is called inside the schedule() context,
  	 * we disable preemption to avoid it calling schedule() again
  	 * in the possible wakeup of a kworker.
  	 */
  	if (tsk->flags & PF_WQ_WORKER) {
  		preempt_disable();
  		wq_worker_sleeping(tsk);
  		preempt_enable_no_resched();
  	}
  
  	if (tsk_is_pi_blocked(tsk))
  		return;
  
  	/*
  	 * If we are going to sleep and we have plugged IO queued,
  	 * make sure to submit it to avoid deadlocks.
  	 */
  	if (blk_needs_flush_plug(tsk))
  		blk_schedule_flush_plug(tsk);
  }
  
  static void sched_update_worker(struct task_struct *tsk)
  {
  	if (tsk->flags & PF_WQ_WORKER)
  		wq_worker_running(tsk);
  }
  
  asmlinkage __visible void __sched schedule(void)
  {
  	struct task_struct *tsk = current;
  
  	sched_submit_work(tsk);
  	do {
  		preempt_disable();
  		__schedule(false);
  		sched_preempt_enable_no_resched();
  	} while (need_resched());
  	sched_update_worker(tsk);
  }
  EXPORT_SYMBOL(schedule);
  
  /*
   * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
   * state (have scheduled out non-voluntarily) by making sure that all
   * tasks have either left the run queue or have gone into user space.
   * As idle tasks do not do either, they must not ever be preempted
   * (schedule out non-voluntarily).
   *
   * schedule_idle() is similar to schedule_preempt_disable() except that it
   * never enables preemption because it does not call sched_submit_work().
   */
  void __sched schedule_idle(void)
  {
  	/*
  	 * As this skips calling sched_submit_work(), which the idle task does
  	 * regardless because that function is a nop when the task is in a
  	 * TASK_RUNNING state, make sure this isn't used someplace that the
  	 * current task can be in any other state. Note, idle is always in the
  	 * TASK_RUNNING state.
  	 */
  	WARN_ON_ONCE(current->state);
  	do {
  		__schedule(false);
  	} while (need_resched());
  }
  
  #ifdef CONFIG_CONTEXT_TRACKING
  asmlinkage __visible void __sched schedule_user(void)
  {
  	/*
  	 * If we come here after a random call to set_need_resched(),
  	 * or we have been woken up remotely but the IPI has not yet arrived,
  	 * we haven't yet exited the RCU idle mode. Do it here manually until
  	 * we find a better solution.
  	 *
  	 * NB: There are buggy callers of this function.  Ideally we
  	 * should warn if prev_state != CONTEXT_USER, but that will trigger
  	 * too frequently to make sense yet.
  	 */
  	enum ctx_state prev_state = exception_enter();
  	schedule();
  	exception_exit(prev_state);
  }
  #endif
  
  /**
   * schedule_preempt_disabled - called with preemption disabled
   *
   * Returns with preemption disabled. Note: preempt_count must be 1
   */
  void __sched schedule_preempt_disabled(void)
  {
  	sched_preempt_enable_no_resched();
  	schedule();
  	preempt_disable();
  }
  
  static void __sched notrace preempt_schedule_common(void)
  {
  	do {
  		/*
  		 * Because the function tracer can trace preempt_count_sub()
  		 * and it also uses preempt_enable/disable_notrace(), if
  		 * NEED_RESCHED is set, the preempt_enable_notrace() called
  		 * by the function tracer will call this function again and
  		 * cause infinite recursion.
  		 *
  		 * Preemption must be disabled here before the function
  		 * tracer can trace. Break up preempt_disable() into two
  		 * calls. One to disable preemption without fear of being
  		 * traced. The other to still record the preemption latency,
  		 * which can also be traced by the function tracer.
  		 */
  		preempt_disable_notrace();
  		preempt_latency_start(1);
  		__schedule(true);
  		preempt_latency_stop(1);
  		preempt_enable_no_resched_notrace();
  
  		/*
  		 * Check again in case we missed a preemption opportunity
  		 * between schedule and now.
  		 */
  	} while (need_resched());
  }
  
  #ifdef CONFIG_PREEMPTION
  /*
   * This is the entry point to schedule() from in-kernel preemption
   * off of preempt_enable.
   */
  asmlinkage __visible void __sched notrace preempt_schedule(void)
  {
  	/*
  	 * If there is a non-zero preempt_count or interrupts are disabled,
  	 * we do not want to preempt the current task. Just return..
  	 */
  	if (likely(!preemptible()))
  		return;
  
  	preempt_schedule_common();
  }
  NOKPROBE_SYMBOL(preempt_schedule);
  EXPORT_SYMBOL(preempt_schedule);
  
  /**
   * preempt_schedule_notrace - preempt_schedule called by tracing
   *
   * The tracing infrastructure uses preempt_enable_notrace to prevent
   * recursion and tracing preempt enabling caused by the tracing
   * infrastructure itself. But as tracing can happen in areas coming
   * from userspace or just about to enter userspace, a preempt enable
   * can occur before user_exit() is called. This will cause the scheduler
   * to be called when the system is still in usermode.
   *
   * To prevent this, the preempt_enable_notrace will use this function
   * instead of preempt_schedule() to exit user context if needed before
   * calling the scheduler.
   */
  asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
  {
  	enum ctx_state prev_ctx;
  
  	if (likely(!preemptible()))
  		return;
  
  	do {
  		/*
  		 * Because the function tracer can trace preempt_count_sub()
  		 * and it also uses preempt_enable/disable_notrace(), if
  		 * NEED_RESCHED is set, the preempt_enable_notrace() called
  		 * by the function tracer will call this function again and
  		 * cause infinite recursion.
  		 *
  		 * Preemption must be disabled here before the function
  		 * tracer can trace. Break up preempt_disable() into two
  		 * calls. One to disable preemption without fear of being
  		 * traced. The other to still record the preemption latency,
  		 * which can also be traced by the function tracer.
  		 */
  		preempt_disable_notrace();
  		preempt_latency_start(1);
  		/*
  		 * Needs preempt disabled in case user_exit() is traced
  		 * and the tracer calls preempt_enable_notrace() causing
  		 * an infinite recursion.
  		 */
  		prev_ctx = exception_enter();
  		__schedule(true);
  		exception_exit(prev_ctx);
  
  		preempt_latency_stop(1);
  		preempt_enable_no_resched_notrace();
  	} while (need_resched());
  }
  EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
  
  #endif /* CONFIG_PREEMPTION */
  
  /*
   * This is the entry point to schedule() from kernel preemption
   * off of irq context.
   * Note, that this is called and return with irqs disabled. This will
   * protect us against recursive calling from irq.
   */
  asmlinkage __visible void __sched preempt_schedule_irq(void)
  {
  	enum ctx_state prev_state;
  
  	/* Catch callers which need to be fixed */
  	BUG_ON(preempt_count() || !irqs_disabled());
  
  	prev_state = exception_enter();
  
  	do {
  		preempt_disable();
  		local_irq_enable();
  		__schedule(true);
  		local_irq_disable();
  		sched_preempt_enable_no_resched();
  	} while (need_resched());
  
  	exception_exit(prev_state);
  }
  
  int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
  			  void *key)
  {
  	return try_to_wake_up(curr->private, mode, wake_flags);
  }
  EXPORT_SYMBOL(default_wake_function);
  
  #ifdef CONFIG_RT_MUTEXES
  
  static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
  {
  	if (pi_task)
  		prio = min(prio, pi_task->prio);
  
  	return prio;
  }
  
  static inline int rt_effective_prio(struct task_struct *p, int prio)
  {
  	struct task_struct *pi_task = rt_mutex_get_top_task(p);
  
  	return __rt_effective_prio(pi_task, prio);
  }
  
  /*
   * rt_mutex_setprio - set the current priority of a task
   * @p: task to boost
   * @pi_task: donor task
   *
   * This function changes the 'effective' priority of a task. It does
   * not touch ->normal_prio like __setscheduler().
   *
   * Used by the rt_mutex code to implement priority inheritance
   * logic. Call site only calls if the priority of the task changed.
   */
  void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
  {
  	int prio, oldprio, queued, running, queue_flag =
  		DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
  	const struct sched_class *prev_class;
  	struct rq_flags rf;
  	struct rq *rq;
  
  	/* XXX used to be waiter->prio, not waiter->task->prio */
  	prio = __rt_effective_prio(pi_task, p->normal_prio);
  
  	/*
  	 * If nothing changed; bail early.
  	 */
  	if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
  		return;
  
  	rq = __task_rq_lock(p, &rf);
  	update_rq_clock(rq);
  	/*
  	 * Set under pi_lock && rq->lock, such that the value can be used under
  	 * either lock.
  	 *
  	 * Note that there is loads of tricky to make this pointer cache work
  	 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
  	 * ensure a task is de-boosted (pi_task is set to NULL) before the
  	 * task is allowed to run again (and can exit). This ensures the pointer
  	 * points to a blocked task -- which guaratees the task is present.
  	 */
  	p->pi_top_task = pi_task;
  
  	/*
  	 * For FIFO/RR we only need to set prio, if that matches we're done.
  	 */
  	if (prio == p->prio && !dl_prio(prio))
  		goto out_unlock;
  
  	/*
  	 * Idle task boosting is a nono in general. There is one
  	 * exception, when PREEMPT_RT and NOHZ is active:
  	 *
  	 * The idle task calls get_next_timer_interrupt() and holds
  	 * the timer wheel base->lock on the CPU and another CPU wants
  	 * to access the timer (probably to cancel it). We can safely
  	 * ignore the boosting request, as the idle CPU runs this code
  	 * with interrupts disabled and will complete the lock
  	 * protected section without being interrupted. So there is no
  	 * real need to boost.
  	 */
  	if (unlikely(p == rq->idle)) {
  		WARN_ON(p != rq->curr);
  		WARN_ON(p->pi_blocked_on);
  		goto out_unlock;
  	}
  
  	trace_sched_pi_setprio(p, pi_task);
  	oldprio = p->prio;
  
  	if (oldprio == prio)
  		queue_flag &= ~DEQUEUE_MOVE;
  
  	prev_class = p->sched_class;
  	queued = task_on_rq_queued(p);
  	running = task_current(rq, p);
  	if (queued)
  		dequeue_task(rq, p, queue_flag);
  	if (running)
  		put_prev_task(rq, p);
  
  	/*
  	 * Boosting condition are:
  	 * 1. -rt task is running and holds mutex A
  	 *      --> -dl task blocks on mutex A
  	 *
  	 * 2. -dl task is running and holds mutex A
  	 *      --> -dl task blocks on mutex A and could preempt the
  	 *          running task
  	 */
  	if (dl_prio(prio)) {
  		if (!dl_prio(p->normal_prio) ||
  		    (pi_task && dl_prio(pi_task->prio) &&
  		     dl_entity_preempt(&pi_task->dl, &p->dl))) {
  			p->dl.dl_boosted = 1;
  			queue_flag |= ENQUEUE_REPLENISH;
  		} else
  			p->dl.dl_boosted = 0;
  		p->sched_class = &dl_sched_class;
  	} else if (rt_prio(prio)) {
  		if (dl_prio(oldprio))
  			p->dl.dl_boosted = 0;
  		if (oldprio < prio)
  			queue_flag |= ENQUEUE_HEAD;
  		p->sched_class = &rt_sched_class;
  	} else {
  		if (dl_prio(oldprio))
  			p->dl.dl_boosted = 0;
  		if (rt_prio(oldprio))
  			p->rt.timeout = 0;
  		p->sched_class = &fair_sched_class;
  	}
  
  	p->prio = prio;
  
  	if (queued)
  		enqueue_task(rq, p, queue_flag);
  	if (running)
  		set_next_task(rq, p);
  
  	check_class_changed(rq, p, prev_class, oldprio);
  out_unlock:
  	/* Avoid rq from going away on us: */
  	preempt_disable();
  	__task_rq_unlock(rq, &rf);
  
  	balance_callback(rq);
  	preempt_enable();
  }
  #else
  static inline int rt_effective_prio(struct task_struct *p, int prio)
  {
  	return prio;
  }
  #endif
  
  void set_user_nice(struct task_struct *p, long nice)
  {
  	bool queued, running;
  	int old_prio, delta;
  	struct rq_flags rf;
  	struct rq *rq;
  
  	if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
  		return;
  	/*
  	 * We have to be careful, if called from sys_setpriority(),
  	 * the task might be in the middle of scheduling on another CPU.
  	 */
  	rq = task_rq_lock(p, &rf);
  	update_rq_clock(rq);
  
  	/*
  	 * The RT priorities are set via sched_setscheduler(), but we still
  	 * allow the 'normal' nice value to be set - but as expected
  	 * it wont have any effect on scheduling until the task is
  	 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
  	 */
  	if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
  		p->static_prio = NICE_TO_PRIO(nice);
  		goto out_unlock;
  	}
  	queued = task_on_rq_queued(p);
  	running = task_current(rq, p);
  	if (queued)
  		dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
  	if (running)
  		put_prev_task(rq, p);
  
  	p->static_prio = NICE_TO_PRIO(nice);
  	set_load_weight(p, true);
  	old_prio = p->prio;
  	p->prio = effective_prio(p);
  	delta = p->prio - old_prio;
  
  	if (queued) {
  		enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
  		/*
  		 * If the task increased its priority or is running and
  		 * lowered its priority, then reschedule its CPU:
  		 */
  		if (delta < 0 || (delta > 0 && task_running(rq, p)))
  			resched_curr(rq);
  	}
  	if (running)
  		set_next_task(rq, p);
  out_unlock:
  	task_rq_unlock(rq, p, &rf);
  }
  EXPORT_SYMBOL(set_user_nice);
  
  /*
   * can_nice - check if a task can reduce its nice value
   * @p: task
   * @nice: nice value
   */
  int can_nice(const struct task_struct *p, const int nice)
  {
  	/* Convert nice value [19,-20] to rlimit style value [1,40]: */
  	int nice_rlim = nice_to_rlimit(nice);
  
  	return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
  		capable(CAP_SYS_NICE));
  }
  
  #ifdef __ARCH_WANT_SYS_NICE
  
  /*
   * sys_nice - change the priority of the current process.
   * @increment: priority increment
   *
   * sys_setpriority is a more generic, but much slower function that
   * does similar things.
   */
  SYSCALL_DEFINE1(nice, int, increment)
  {
  	long nice, retval;
  
  	/*
  	 * Setpriority might change our priority at the same moment.
  	 * We don't have to worry. Conceptually one call occurs first
  	 * and we have a single winner.
  	 */
  	increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
  	nice = task_nice(current) + increment;
  
  	nice = clamp_val(nice, MIN_NICE, MAX_NICE);
  	if (increment < 0 && !can_nice(current, nice))
  		return -EPERM;
  
  	retval = security_task_setnice(current, nice);
  	if (retval)
  		return retval;
  
  	set_user_nice(current, nice);
  	return 0;
  }
  
  #endif
  
  /**
   * task_prio - return the priority value of a given task.
   * @p: the task in question.
   *
   * Return: The priority value as seen by users in /proc.
   * RT tasks are offset by -200. Normal tasks are centered
   * around 0, value goes from -16 to +15.
   */
  int task_prio(const struct task_struct *p)
  {
  	return p->prio - MAX_RT_PRIO;
  }
  
  /**
   * idle_cpu - is a given CPU idle currently?
   * @cpu: the processor in question.
   *
   * Return: 1 if the CPU is currently idle. 0 otherwise.
   */
  int idle_cpu(int cpu)
  {
  	struct rq *rq = cpu_rq(cpu);
  
  	if (rq->curr != rq->idle)
  		return 0;
  
  	if (rq->nr_running)
  		return 0;
  
  #ifdef CONFIG_SMP
  	if (!llist_empty(&rq->wake_list))
  		return 0;
  #endif
  
  	return 1;
  }
  
  /**
   * available_idle_cpu - is a given CPU idle for enqueuing work.
   * @cpu: the CPU in question.
   *
   * Return: 1 if the CPU is currently idle. 0 otherwise.
   */
  int available_idle_cpu(int cpu)
  {
  	if (!idle_cpu(cpu))
  		return 0;
  
  	if (vcpu_is_preempted(cpu))
  		return 0;
  
  	return 1;
  }
  
  /**
   * idle_task - return the idle task for a given CPU.
   * @cpu: the processor in question.
   *
   * Return: The idle task for the CPU @cpu.
   */
  struct task_struct *idle_task(int cpu)
  {
  	return cpu_rq(cpu)->idle;
  }
  
  /**
   * find_process_by_pid - find a process with a matching PID value.
   * @pid: the pid in question.
   *
   * The task of @pid, if found. %NULL otherwise.
   */
  static struct task_struct *find_process_by_pid(pid_t pid)
  {
  	return pid ? find_task_by_vpid(pid) : current;
  }
  
  /*
   * sched_setparam() passes in -1 for its policy, to let the functions
   * it calls know not to change it.
   */
  #define SETPARAM_POLICY	-1
  
  static void __setscheduler_params(struct task_struct *p,
  		const struct sched_attr *attr)
  {
  	int policy = attr->sched_policy;
  
  	if (policy == SETPARAM_POLICY)
  		policy = p->policy;
  
  	p->policy = policy;
  
  	if (dl_policy(policy))
  		__setparam_dl(p, attr);
  	else if (fair_policy(policy))
  		p->static_prio = NICE_TO_PRIO(attr->sched_nice);
  
  	/*
  	 * __sched_setscheduler() ensures attr->sched_priority == 0 when
  	 * !rt_policy. Always setting this ensures that things like
  	 * getparam()/getattr() don't report silly values for !rt tasks.
  	 */
  	p->rt_priority = attr->sched_priority;
  	p->normal_prio = normal_prio(p);
  	set_load_weight(p, true);
  }
  
  /* Actually do priority change: must hold pi & rq lock. */
  static void __setscheduler(struct rq *rq, struct task_struct *p,
  			   const struct sched_attr *attr, bool keep_boost)
  {
  	/*
  	 * If params can't change scheduling class changes aren't allowed
  	 * either.
  	 */
  	if (attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)
  		return;
  
  	__setscheduler_params(p, attr);
  
  	/*
  	 * Keep a potential priority boosting if called from
  	 * sched_setscheduler().
  	 */
  	p->prio = normal_prio(p);
  	if (keep_boost)
  		p->prio = rt_effective_prio(p, p->prio);
  
  	if (dl_prio(p->prio))
  		p->sched_class = &dl_sched_class;
  	else if (rt_prio(p->prio))
  		p->sched_class = &rt_sched_class;
  	else
  		p->sched_class = &fair_sched_class;
  }
  
  /*
   * Check the target process has a UID that matches the current process's:
   */
  static bool check_same_owner(struct task_struct *p)
  {
  	const struct cred *cred = current_cred(), *pcred;
  	bool match;
  
  	rcu_read_lock();
  	pcred = __task_cred(p);
  	match = (uid_eq(cred->euid, pcred->euid) ||
  		 uid_eq(cred->euid, pcred->uid));
  	rcu_read_unlock();
  	return match;
  }
  
  static int __sched_setscheduler(struct task_struct *p,
  				const struct sched_attr *attr,
  				bool user, bool pi)
  {
  	int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
  		      MAX_RT_PRIO - 1 - attr->sched_priority;
  	int retval, oldprio, oldpolicy = -1, queued, running;
  	int new_effective_prio, policy = attr->sched_policy;
  	const struct sched_class *prev_class;
  	struct rq_flags rf;
  	int reset_on_fork;
  	int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
  	struct rq *rq;
  
  	/* The pi code expects interrupts enabled */
  	BUG_ON(pi && in_interrupt());
  recheck:
  	/* Double check policy once rq lock held: */
  	if (policy < 0) {
  		reset_on_fork = p->sched_reset_on_fork;
  		policy = oldpolicy = p->policy;
  	} else {
  		reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
  
  		if (!valid_policy(policy))
  			return -EINVAL;
  	}
  
  	if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
  		return -EINVAL;
  
  	/*
  	 * Valid priorities for SCHED_FIFO and SCHED_RR are
  	 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
  	 * SCHED_BATCH and SCHED_IDLE is 0.
  	 */
  	if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
  	    (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
  		return -EINVAL;
  	if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
  	    (rt_policy(policy) != (attr->sched_priority != 0)))
  		return -EINVAL;
  
  	/*
  	 * Allow unprivileged RT tasks to decrease priority:
  	 */
  	if (user && !capable(CAP_SYS_NICE)) {
  		if (fair_policy(policy)) {
  			if (attr->sched_nice < task_nice(p) &&
  			    !can_nice(p, attr->sched_nice))
  				return -EPERM;
  		}
  
  		if (rt_policy(policy)) {
  			unsigned long rlim_rtprio =
  					task_rlimit(p, RLIMIT_RTPRIO);
  
  			/* Can't set/change the rt policy: */
  			if (policy != p->policy && !rlim_rtprio)
  				return -EPERM;
  
  			/* Can't increase priority: */
  			if (attr->sched_priority > p->rt_priority &&
  			    attr->sched_priority > rlim_rtprio)
  				return -EPERM;
  		}
  
  		 /*
  		  * Can't set/change SCHED_DEADLINE policy at all for now
  		  * (safest behavior); in the future we would like to allow
  		  * unprivileged DL tasks to increase their relative deadline
  		  * or reduce their runtime (both ways reducing utilization)
  		  */
  		if (dl_policy(policy))
  			return -EPERM;
  
  		/*
  		 * Treat SCHED_IDLE as nice 20. Only allow a switch to
  		 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
  		 */
  		if (task_has_idle_policy(p) && !idle_policy(policy)) {
  			if (!can_nice(p, task_nice(p)))
  				return -EPERM;
  		}
  
  		/* Can't change other user's priorities: */
  		if (!check_same_owner(p))
  			return -EPERM;
  
  		/* Normal users shall not reset the sched_reset_on_fork flag: */
  		if (p->sched_reset_on_fork && !reset_on_fork)
  			return -EPERM;
  	}
  
  	if (user) {
  		if (attr->sched_flags & SCHED_FLAG_SUGOV)
  			return -EINVAL;
  
  		retval = security_task_setscheduler(p);
  		if (retval)
  			return retval;
  	}
  
  	/* Update task specific "requested" clamps */
  	if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
  		retval = uclamp_validate(p, attr);
  		if (retval)
  			return retval;
  	}
  
  	if (pi)
  		cpuset_read_lock();
  
  	/*
  	 * Make sure no PI-waiters arrive (or leave) while we are
  	 * changing the priority of the task:
  	 *
  	 * To be able to change p->policy safely, the appropriate
  	 * runqueue lock must be held.
  	 */
  	rq = task_rq_lock(p, &rf);
  	update_rq_clock(rq);
  
  	/*
  	 * Changing the policy of the stop threads its a very bad idea:
  	 */
  	if (p == rq->stop) {
  		retval = -EINVAL;
  		goto unlock;
  	}
  
  	/*
  	 * If not changing anything there's no need to proceed further,
  	 * but store a possible modification of reset_on_fork.
  	 */
  	if (unlikely(policy == p->policy)) {
  		if (fair_policy(policy) && attr->sched_nice != task_nice(p))
  			goto change;
  		if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
  			goto change;
  		if (dl_policy(policy) && dl_param_changed(p, attr))
  			goto change;
  		if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
  			goto change;
  
  		p->sched_reset_on_fork = reset_on_fork;
  		retval = 0;
  		goto unlock;
  	}
  change:
  
  	if (user) {
  #ifdef CONFIG_RT_GROUP_SCHED
  		/*
  		 * Do not allow realtime tasks into groups that have no runtime
  		 * assigned.
  		 */
  		if (rt_bandwidth_enabled() && rt_policy(policy) &&
  				task_group(p)->rt_bandwidth.rt_runtime == 0 &&
  				!task_group_is_autogroup(task_group(p))) {
  			retval = -EPERM;
  			goto unlock;
  		}
  #endif
  #ifdef CONFIG_SMP
  		if (dl_bandwidth_enabled() && dl_policy(policy) &&
  				!(attr->sched_flags & SCHED_FLAG_SUGOV)) {
  			cpumask_t *span = rq->rd->span;
  
  			/*
  			 * Don't allow tasks with an affinity mask smaller than
  			 * the entire root_domain to become SCHED_DEADLINE. We
  			 * will also fail if there's no bandwidth available.
  			 */
  			if (!cpumask_subset(span, p->cpus_ptr) ||
  			    rq->rd->dl_bw.bw == 0) {
  				retval = -EPERM;
  				goto unlock;
  			}
  		}
  #endif
  	}
  
  	/* Re-check policy now with rq lock held: */
  	if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
  		policy = oldpolicy = -1;
  		task_rq_unlock(rq, p, &rf);
  		if (pi)
  			cpuset_read_unlock();
  		goto recheck;
  	}
  
  	/*
  	 * If setscheduling to SCHED_DEADLINE (or changing the parameters
  	 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
  	 * is available.
  	 */
  	if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
  		retval = -EBUSY;
  		goto unlock;
  	}
  
  	p->sched_reset_on_fork = reset_on_fork;
  	oldprio = p->prio;
  
  	if (pi) {
  		/*
  		 * Take priority boosted tasks into account. If the new
  		 * effective priority is unchanged, we just store the new
  		 * normal parameters and do not touch the scheduler class and
  		 * the runqueue. This will be done when the task deboost
  		 * itself.
  		 */
  		new_effective_prio = rt_effective_prio(p, newprio);
  		if (new_effective_prio == oldprio)
  			queue_flags &= ~DEQUEUE_MOVE;
  	}
  
  	queued = task_on_rq_queued(p);
  	running = task_current(rq, p);
  	if (queued)
  		dequeue_task(rq, p, queue_flags);
  	if (running)
  		put_prev_task(rq, p);
  
  	prev_class = p->sched_class;
  
  	__setscheduler(rq, p, attr, pi);
  	__setscheduler_uclamp(p, attr);
  
  	if (queued) {
  		/*
  		 * We enqueue to tail when the priority of a task is
  		 * increased (user space view).
  		 */
  		if (oldprio < p->prio)
  			queue_flags |= ENQUEUE_HEAD;
  
  		enqueue_task(rq, p, queue_flags);
  	}
  	if (running)
  		set_next_task(rq, p);
  
  	check_class_changed(rq, p, prev_class, oldprio);
  
  	/* Avoid rq from going away on us: */
  	preempt_disable();
  	task_rq_unlock(rq, p, &rf);
  
  	if (pi) {
  		cpuset_read_unlock();
  		rt_mutex_adjust_pi(p);
  	}
  
  	/* Run balance callbacks after we've adjusted the PI chain: */
  	balance_callback(rq);
  	preempt_enable();
  
  	return 0;
  
  unlock:
  	task_rq_unlock(rq, p, &rf);
  	if (pi)
  		cpuset_read_unlock();
  	return retval;
  }
  
  static int _sched_setscheduler(struct task_struct *p, int policy,
  			       const struct sched_param *param, bool check)
  {
  	struct sched_attr attr = {
  		.sched_policy   = policy,
  		.sched_priority = param->sched_priority,
  		.sched_nice	= PRIO_TO_NICE(p->static_prio),
  	};
  
  	/* Fixup the legacy SCHED_RESET_ON_FORK hack. */
  	if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
  		attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
  		policy &= ~SCHED_RESET_ON_FORK;
  		attr.sched_policy = policy;
  	}
  
  	return __sched_setscheduler(p, &attr, check, true);
  }
  /**
   * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
   * @p: the task in question.
   * @policy: new policy.
   * @param: structure containing the new RT priority.
   *
   * Return: 0 on success. An error code otherwise.
   *
   * NOTE that the task may be already dead.
   */
  int sched_setscheduler(struct task_struct *p, int policy,
  		       const struct sched_param *param)
  {
  	return _sched_setscheduler(p, policy, param, true);
  }
  EXPORT_SYMBOL_GPL(sched_setscheduler);
  
  int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
  {
  	return __sched_setscheduler(p, attr, true, true);
  }
  EXPORT_SYMBOL_GPL(sched_setattr);
  
  int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
  {
  	return __sched_setscheduler(p, attr, false, true);
  }
  
  /**
   * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
   * @p: the task in question.
   * @policy: new policy.
   * @param: structure containing the new RT priority.
   *
   * Just like sched_setscheduler, only don't bother checking if the
   * current context has permission.  For example, this is needed in
   * stop_machine(): we create temporary high priority worker threads,
   * but our caller might not have that capability.
   *
   * Return: 0 on success. An error code otherwise.
   */
  int sched_setscheduler_nocheck(struct task_struct *p, int policy,
  			       const struct sched_param *param)
  {
  	return _sched_setscheduler(p, policy, param, false);
  }
  EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck);
  
  static int
  do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
  {
  	struct sched_param lparam;
  	struct task_struct *p;
  	int retval;
  
  	if (!param || pid < 0)
  		return -EINVAL;
  	if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
  		return -EFAULT;
  
  	rcu_read_lock();
  	retval = -ESRCH;
  	p = find_process_by_pid(pid);
  	if (likely(p))
  		get_task_struct(p);
  	rcu_read_unlock();
  
  	if (likely(p)) {
  		retval = sched_setscheduler(p, policy, &lparam);
  		put_task_struct(p);
  	}
  
  	return retval;
  }
  
  /*
   * Mimics kernel/events/core.c perf_copy_attr().
   */
  static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
  {
  	u32 size;
  	int ret;
  
  	/* Zero the full structure, so that a short copy will be nice: */
  	memset(attr, 0, sizeof(*attr));
  
  	ret = get_user(size, &uattr->size);
  	if (ret)
  		return ret;
  
  	/* ABI compatibility quirk: */
  	if (!size)
  		size = SCHED_ATTR_SIZE_VER0;
  	if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
  		goto err_size;
  
  	ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
  	if (ret) {
  		if (ret == -E2BIG)
  			goto err_size;
  		return ret;
  	}
  
  	if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&
  	    size < SCHED_ATTR_SIZE_VER1)
  		return -EINVAL;
  
  	/*
  	 * XXX: Do we want to be lenient like existing syscalls; or do we want
  	 * to be strict and return an error on out-of-bounds values?
  	 */
  	attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
  
  	return 0;
  
  err_size:
  	put_user(sizeof(*attr), &uattr->size);
  	return -E2BIG;
  }
  
  /**
   * sys_sched_setscheduler - set/change the scheduler policy and RT priority
   * @pid: the pid in question.
   * @policy: new policy.
   * @param: structure containing the new RT priority.
   *
   * Return: 0 on success. An error code otherwise.
   */
  SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
  {
  	if (policy < 0)
  		return -EINVAL;
  
  	return do_sched_setscheduler(pid, policy, param);
  }
  
  /**
   * sys_sched_setparam - set/change the RT priority of a thread
   * @pid: the pid in question.
   * @param: structure containing the new RT priority.
   *
   * Return: 0 on success. An error code otherwise.
   */
  SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
  {
  	return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
  }
  
  /**
   * sys_sched_setattr - same as above, but with extended sched_attr
   * @pid: the pid in question.
   * @uattr: structure containing the extended parameters.
   * @flags: for future extension.
   */
  SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
  			       unsigned int, flags)
  {
  	struct sched_attr attr;
  	struct task_struct *p;
  	int retval;
  
  	if (!uattr || pid < 0 || flags)
  		return -EINVAL;
  
  	retval = sched_copy_attr(uattr, &attr);
  	if (retval)
  		return retval;
  
  	if ((int)attr.sched_policy < 0)
  		return -EINVAL;
  	if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
  		attr.sched_policy = SETPARAM_POLICY;
  
  	rcu_read_lock();
  	retval = -ESRCH;
  	p = find_process_by_pid(pid);
  	if (likely(p))
  		get_task_struct(p);
  	rcu_read_unlock();
  
  	if (likely(p)) {
  		retval = sched_setattr(p, &attr);
  		put_task_struct(p);
  	}
  
  	return retval;
  }
  
  /**
   * sys_sched_getscheduler - get the policy (scheduling class) of a thread
   * @pid: the pid in question.
   *
   * Return: On success, the policy of the thread. Otherwise, a negative error
   * code.
   */
  SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
  {
  	struct task_struct *p;
  	int retval;
  
  	if (pid < 0)
  		return -EINVAL;
  
  	retval = -ESRCH;
  	rcu_read_lock();
  	p = find_process_by_pid(pid);
  	if (p) {
  		retval = security_task_getscheduler(p);
  		if (!retval)
  			retval = p->policy
  				| (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
  	}
  	rcu_read_unlock();
  	return retval;
  }
  
  /**
   * sys_sched_getparam - get the RT priority of a thread
   * @pid: the pid in question.
   * @param: structure containing the RT priority.
   *
   * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
   * code.
   */
  SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
  {
  	struct sched_param lp = { .sched_priority = 0 };
  	struct task_struct *p;
  	int retval;
  
  	if (!param || pid < 0)
  		return -EINVAL;
  
  	rcu_read_lock();
  	p = find_process_by_pid(pid);
  	retval = -ESRCH;
  	if (!p)
  		goto out_unlock;
  
  	retval = security_task_getscheduler(p);
  	if (retval)
  		goto out_unlock;
  
  	if (task_has_rt_policy(p))
  		lp.sched_priority = p->rt_priority;
  	rcu_read_unlock();
  
  	/*
  	 * This one might sleep, we cannot do it with a spinlock held ...
  	 */
  	retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
  
  	return retval;
  
  out_unlock:
  	rcu_read_unlock();
  	return retval;
  }
  
  /*
   * Copy the kernel size attribute structure (which might be larger
   * than what user-space knows about) to user-space.
   *
   * Note that all cases are valid: user-space buffer can be larger or
   * smaller than the kernel-space buffer. The usual case is that both
   * have the same size.
   */
  static int
  sched_attr_copy_to_user(struct sched_attr __user *uattr,
  			struct sched_attr *kattr,
  			unsigned int usize)
  {
  	unsigned int ksize = sizeof(*kattr);
  
  	if (!access_ok(uattr, usize))
  		return -EFAULT;
  
  	/*
  	 * sched_getattr() ABI forwards and backwards compatibility:
  	 *
  	 * If usize == ksize then we just copy everything to user-space and all is good.
  	 *
  	 * If usize < ksize then we only copy as much as user-space has space for,
  	 * this keeps ABI compatibility as well. We skip the rest.
  	 *
  	 * If usize > ksize then user-space is using a newer version of the ABI,
  	 * which part the kernel doesn't know about. Just ignore it - tooling can
  	 * detect the kernel's knowledge of attributes from the attr->size value
  	 * which is set to ksize in this case.
  	 */
  	kattr->size = min(usize, ksize);
  
  	if (copy_to_user(uattr, kattr, kattr->size))
  		return -EFAULT;
  
  	return 0;
  }
  
  /**
   * sys_sched_getattr - similar to sched_getparam, but with sched_attr
   * @pid: the pid in question.
   * @uattr: structure containing the extended parameters.
   * @usize: sizeof(attr) for fwd/bwd comp.
   * @flags: for future extension.
   */
  SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
  		unsigned int, usize, unsigned int, flags)
  {
  	struct sched_attr kattr = { };
  	struct task_struct *p;
  	int retval;
  
  	if (!uattr || pid < 0 || usize > PAGE_SIZE ||
  	    usize < SCHED_ATTR_SIZE_VER0 || flags)
  		return -EINVAL;
  
  	rcu_read_lock();
  	p = find_process_by_pid(pid);
  	retval = -ESRCH;
  	if (!p)
  		goto out_unlock;
  
  	retval = security_task_getscheduler(p);
  	if (retval)
  		goto out_unlock;
  
  	kattr.sched_policy = p->policy;
  	if (p->sched_reset_on_fork)
  		kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
  	if (task_has_dl_policy(p))
  		__getparam_dl(p, &kattr);
  	else if (task_has_rt_policy(p))
  		kattr.sched_priority = p->rt_priority;
  	else
  		kattr.sched_nice = task_nice(p);
  
  #ifdef CONFIG_UCLAMP_TASK
  	kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
  	kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
  #endif
  
  	rcu_read_unlock();
  
  	return sched_attr_copy_to_user(uattr, &kattr, usize);
  
  out_unlock:
  	rcu_read_unlock();
  	return retval;
  }
  
  long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
  {
  	cpumask_var_t cpus_allowed, new_mask;
  	struct task_struct *p;
  	int retval;
  
  	rcu_read_lock();
  
  	p = find_process_by_pid(pid);
  	if (!p) {
  		rcu_read_unlock();
  		return -ESRCH;
  	}
  
  	/* Prevent p going away */
  	get_task_struct(p);
  	rcu_read_unlock();
  
  	if (p->flags & PF_NO_SETAFFINITY) {
  		retval = -EINVAL;
  		goto out_put_task;
  	}
  	if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
  		retval = -ENOMEM;
  		goto out_put_task;
  	}
  	if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
  		retval = -ENOMEM;
  		goto out_free_cpus_allowed;
  	}
  	retval = -EPERM;
  	if (!check_same_owner(p)) {
  		rcu_read_lock();
  		if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
  			rcu_read_unlock();
  			goto out_free_new_mask;
  		}
  		rcu_read_unlock();
  	}
  
  	retval = security_task_setscheduler(p);
  	if (retval)
  		goto out_free_new_mask;
  
  
  	cpuset_cpus_allowed(p, cpus_allowed);
  	cpumask_and(new_mask, in_mask, cpus_allowed);
  
  	/*
  	 * Since bandwidth control happens on root_domain basis,
  	 * if admission test is enabled, we only admit -deadline
  	 * tasks allowed to run on all the CPUs in the task's
  	 * root_domain.
  	 */
  #ifdef CONFIG_SMP
  	if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
  		rcu_read_lock();
  		if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
  			retval = -EBUSY;
  			rcu_read_unlock();
  			goto out_free_new_mask;
  		}
  		rcu_read_unlock();
  	}
  #endif
  again:
  	retval = __set_cpus_allowed_ptr(p, new_mask, true);
  
  	if (!retval) {
  		cpuset_cpus_allowed(p, cpus_allowed);
  		if (!cpumask_subset(new_mask, cpus_allowed)) {
  			/*
  			 * We must have raced with a concurrent cpuset
  			 * update. Just reset the cpus_allowed to the
  			 * cpuset's cpus_allowed
  			 */
  			cpumask_copy(new_mask, cpus_allowed);
  			goto again;
  		}
  	}
  out_free_new_mask:
  	free_cpumask_var(new_mask);
  out_free_cpus_allowed:
  	free_cpumask_var(cpus_allowed);
  out_put_task:
  	put_task_struct(p);
  	return retval;
  }
  
  static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
  			     struct cpumask *new_mask)
  {
  	if (len < cpumask_size())
  		cpumask_clear(new_mask);
  	else if (len > cpumask_size())
  		len = cpumask_size();
  
  	return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
  }
  
  /**
   * sys_sched_setaffinity - set the CPU affinity of a process
   * @pid: pid of the process
   * @len: length in bytes of the bitmask pointed to by user_mask_ptr
   * @user_mask_ptr: user-space pointer to the new CPU mask
   *
   * Return: 0 on success. An error code otherwise.
   */
  SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
  		unsigned long __user *, user_mask_ptr)
  {
  	cpumask_var_t new_mask;
  	int retval;
  
  	if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
  		return -ENOMEM;
  
  	retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
  	if (retval == 0)
  		retval = sched_setaffinity(pid, new_mask);
  	free_cpumask_var(new_mask);
  	return retval;
  }
  
  long sched_getaffinity(pid_t pid, struct cpumask *mask)
  {
  	struct task_struct *p;
  	unsigned long flags;
  	int retval;
  
  	rcu_read_lock();
  
  	retval = -ESRCH;
  	p = find_process_by_pid(pid);
  	if (!p)
  		goto out_unlock;
  
  	retval = security_task_getscheduler(p);
  	if (retval)
  		goto out_unlock;
  
  	raw_spin_lock_irqsave(&p->pi_lock, flags);
  	cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
  	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
  
  out_unlock:
  	rcu_read_unlock();
  
  	return retval;
  }
  
  /**
   * sys_sched_getaffinity - get the CPU affinity of a process
   * @pid: pid of the process
   * @len: length in bytes of the bitmask pointed to by user_mask_ptr
   * @user_mask_ptr: user-space pointer to hold the current CPU mask
   *
   * Return: size of CPU mask copied to user_mask_ptr on success. An
   * error code otherwise.
   */
  SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
  		unsigned long __user *, user_mask_ptr)
  {
  	int ret;
  	cpumask_var_t mask;
  
  	if ((len * BITS_PER_BYTE) < nr_cpu_ids)
  		return -EINVAL;
  	if (len & (sizeof(unsigned long)-1))
  		return -EINVAL;
  
  	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
  		return -ENOMEM;
  
  	ret = sched_getaffinity(pid, mask);
  	if (ret == 0) {
  		unsigned int retlen = min(len, cpumask_size());
  
  		if (copy_to_user(user_mask_ptr, mask, retlen))
  			ret = -EFAULT;
  		else
  			ret = retlen;
  	}
  	free_cpumask_var(mask);
  
  	return ret;
  }
  
  /**
   * sys_sched_yield - yield the current processor to other threads.
   *
   * This function yields the current CPU to other tasks. If there are no
   * other threads running on this CPU then this function will return.
   *
   * Return: 0.
   */
  static void do_sched_yield(void)
  {
  	struct rq_flags rf;
  	struct rq *rq;
  
  	rq = this_rq_lock_irq(&rf);
  
  	schedstat_inc(rq->yld_count);
  	current->sched_class->yield_task(rq);
  
  	/*
  	 * Since we are going to call schedule() anyway, there's
  	 * no need to preempt or enable interrupts:
  	 */
  	preempt_disable();
  	rq_unlock(rq, &rf);
  	sched_preempt_enable_no_resched();
  
  	schedule();
  }
  
  SYSCALL_DEFINE0(sched_yield)
  {
  	do_sched_yield();
  	return 0;
  }
  
  #ifndef CONFIG_PREEMPTION
  int __sched _cond_resched(void)
  {
  	if (should_resched(0)) {
  		preempt_schedule_common();
  		return 1;
  	}
  	rcu_all_qs();
  	return 0;
  }
  EXPORT_SYMBOL(_cond_resched);
  #endif
  
  /*
   * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
   * call schedule, and on return reacquire the lock.
   *
   * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
   * operations here to prevent schedule() from being called twice (once via
   * spin_unlock(), once by hand).
   */
  int __cond_resched_lock(spinlock_t *lock)
  {
  	int resched = should_resched(PREEMPT_LOCK_OFFSET);
  	int ret = 0;
  
  	lockdep_assert_held(lock);
  
  	if (spin_needbreak(lock) || resched) {
  		spin_unlock(lock);
  		if (resched)
  			preempt_schedule_common();
  		else
  			cpu_relax();
  		ret = 1;
  		spin_lock(lock);
  	}
  	return ret;
  }
  EXPORT_SYMBOL(__cond_resched_lock);
  
  /**
   * yield - yield the current processor to other threads.
   *
   * Do not ever use this function, there's a 99% chance you're doing it wrong.
   *
   * The scheduler is at all times free to pick the calling task as the most
   * eligible task to run, if removing the yield() call from your code breaks
   * it, its already broken.
   *
   * Typical broken usage is:
   *
   * while (!event)
   *	yield();
   *
   * where one assumes that yield() will let 'the other' process run that will
   * make event true. If the current task is a SCHED_FIFO task that will never
   * happen. Never use yield() as a progress guarantee!!
   *
   * If you want to use yield() to wait for something, use wait_event().
   * If you want to use yield() to be 'nice' for others, use cond_resched().
   * If you still want to use yield(), do not!
   */
  void __sched yield(void)
  {
  	set_current_state(TASK_RUNNING);
  	do_sched_yield();
  }
  EXPORT_SYMBOL(yield);
  
  /**
   * yield_to - yield the current processor to another thread in
   * your thread group, or accelerate that thread toward the
   * processor it's on.
   * @p: target task
   * @preempt: whether task preemption is allowed or not
   *
   * It's the caller's job to ensure that the target task struct
   * can't go away on us before we can do any checks.
   *
   * Return:
   *	true (>0) if we indeed boosted the target task.
   *	false (0) if we failed to boost the target.
   *	-ESRCH if there's no task to yield to.
   */
  int __sched yield_to(struct task_struct *p, bool preempt)
  {
  	struct task_struct *curr = current;
  	struct rq *rq, *p_rq;
  	unsigned long flags;
  	int yielded = 0;
  
  	local_irq_save(flags);
  	rq = this_rq();
  
  again:
  	p_rq = task_rq(p);
  	/*
  	 * If we're the only runnable task on the rq and target rq also
  	 * has only one task, there's absolutely no point in yielding.
  	 */
  	if (rq->nr_running == 1 && p_rq->nr_running == 1) {
  		yielded = -ESRCH;
  		goto out_irq;
  	}
  
  	double_rq_lock(rq, p_rq);
  	if (task_rq(p) != p_rq) {
  		double_rq_unlock(rq, p_rq);
  		goto again;
  	}
  
  	if (!curr->sched_class->yield_to_task)
  		goto out_unlock;
  
  	if (curr->sched_class != p->sched_class)
  		goto out_unlock;
  
  	if (task_running(p_rq, p) || p->state)
  		goto out_unlock;
  
  	yielded = curr->sched_class->yield_to_task(rq, p, preempt);
  	if (yielded) {
  		schedstat_inc(rq->yld_count);
  		/*
  		 * Make p's CPU reschedule; pick_next_entity takes care of
  		 * fairness.
  		 */
  		if (preempt && rq != p_rq)
  			resched_curr(p_rq);
  	}
  
  out_unlock:
  	double_rq_unlock(rq, p_rq);
  out_irq:
  	local_irq_restore(flags);
  
  	if (yielded > 0)
  		schedule();
  
  	return yielded;
  }
  EXPORT_SYMBOL_GPL(yield_to);
  
  int io_schedule_prepare(void)
  {
  	int old_iowait = current->in_iowait;
  
  	current->in_iowait = 1;
  	blk_schedule_flush_plug(current);
  
  	return old_iowait;
  }
  
  void io_schedule_finish(int token)
  {
  	current->in_iowait = token;
  }
  
  /*
   * This task is about to go to sleep on IO. Increment rq->nr_iowait so
   * that process accounting knows that this is a task in IO wait state.
   */
  long __sched io_schedule_timeout(long timeout)
  {
  	int token;
  	long ret;
  
  	token = io_schedule_prepare();
  	ret = schedule_timeout(timeout);
  	io_schedule_finish(token);
  
  	return ret;
  }
  EXPORT_SYMBOL(io_schedule_timeout);
  
  void __sched io_schedule(void)
  {
  	int token;
  
  	token = io_schedule_prepare();
  	schedule();
  	io_schedule_finish(token);
  }
  EXPORT_SYMBOL(io_schedule);
  
  /**
   * sys_sched_get_priority_max - return maximum RT priority.
   * @policy: scheduling class.
   *
   * Return: On success, this syscall returns the maximum
   * rt_priority that can be used by a given scheduling class.
   * On failure, a negative error code is returned.
   */
  SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
  {
  	int ret = -EINVAL;
  
  	switch (policy) {
  	case SCHED_FIFO:
  	case SCHED_RR:
  		ret = MAX_USER_RT_PRIO-1;
  		break;
  	case SCHED_DEADLINE:
  	case SCHED_NORMAL:
  	case SCHED_BATCH:
  	case SCHED_IDLE:
  		ret = 0;
  		break;
  	}
  	return ret;
  }
  
  /**
   * sys_sched_get_priority_min - return minimum RT priority.
   * @policy: scheduling class.
   *
   * Return: On success, this syscall returns the minimum
   * rt_priority that can be used by a given scheduling class.
   * On failure, a negative error code is returned.
   */
  SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
  {
  	int ret = -EINVAL;
  
  	switch (policy) {
  	case SCHED_FIFO:
  	case SCHED_RR:
  		ret = 1;
  		break;
  	case SCHED_DEADLINE:
  	case SCHED_NORMAL:
  	case SCHED_BATCH:
  	case SCHED_IDLE:
  		ret = 0;
  	}
  	return ret;
  }
  
  static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
  {
  	struct task_struct *p;
  	unsigned int time_slice;
  	struct rq_flags rf;
  	struct rq *rq;
  	int retval;
  
  	if (pid < 0)
  		return -EINVAL;
  
  	retval = -ESRCH;
  	rcu_read_lock();
  	p = find_process_by_pid(pid);
  	if (!p)
  		goto out_unlock;
  
  	retval = security_task_getscheduler(p);
  	if (retval)
  		goto out_unlock;
  
  	rq = task_rq_lock(p, &rf);
  	time_slice = 0;
  	if (p->sched_class->get_rr_interval)
  		time_slice = p->sched_class->get_rr_interval(rq, p);
  	task_rq_unlock(rq, p, &rf);
  
  	rcu_read_unlock();
  	jiffies_to_timespec64(time_slice, t);
  	return 0;
  
  out_unlock:
  	rcu_read_unlock();
  	return retval;
  }
  
  /**
   * sys_sched_rr_get_interval - return the default timeslice of a process.
   * @pid: pid of the process.
   * @interval: userspace pointer to the timeslice value.
   *
   * this syscall writes the default timeslice value of a given process
   * into the user-space timespec buffer. A value of '0' means infinity.
   *
   * Return: On success, 0 and the timeslice is in @interval. Otherwise,
   * an error code.
   */
  SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
  		struct __kernel_timespec __user *, interval)
  {
  	struct timespec64 t;
  	int retval = sched_rr_get_interval(pid, &t);
  
  	if (retval == 0)
  		retval = put_timespec64(&t, interval);
  
  	return retval;
  }
  
  #ifdef CONFIG_COMPAT_32BIT_TIME
  SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
  		struct old_timespec32 __user *, interval)
  {
  	struct timespec64 t;
  	int retval = sched_rr_get_interval(pid, &t);
  
  	if (retval == 0)
  		retval = put_old_timespec32(&t, interval);
  	return retval;
  }
  #endif
  
  void sched_show_task(struct task_struct *p)
  {
  	unsigned long free = 0;
  	int ppid;
  
  	if (!try_get_task_stack(p))
  		return;
  
  	printk(KERN_INFO "%-15.15s %c", p->comm, task_state_to_char(p));
  
  	if (p->state == TASK_RUNNING)
  		printk(KERN_CONT "  running task    ");
  #ifdef CONFIG_DEBUG_STACK_USAGE
  	free = stack_not_used(p);
  #endif
  	ppid = 0;
  	rcu_read_lock();
  	if (pid_alive(p))
  		ppid = task_pid_nr(rcu_dereference(p->real_parent));
  	rcu_read_unlock();
  	printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
  		task_pid_nr(p), ppid,
  		(unsigned long)task_thread_info(p)->flags);
  
  	print_worker_info(KERN_INFO, p);
  	show_stack(p, NULL);
  	put_task_stack(p);
  }
  EXPORT_SYMBOL_GPL(sched_show_task);
  
  static inline bool
  state_filter_match(unsigned long state_filter, struct task_struct *p)
  {
  	/* no filter, everything matches */
  	if (!state_filter)
  		return true;
  
  	/* filter, but doesn't match */
  	if (!(p->state & state_filter))
  		return false;
  
  	/*
  	 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
  	 * TASK_KILLABLE).
  	 */
  	if (state_filter == TASK_UNINTERRUPTIBLE && p->state == TASK_IDLE)
  		return false;
  
  	return true;
  }
  
  
  void show_state_filter(unsigned long state_filter)
  {
  	struct task_struct *g, *p;
  
  #if BITS_PER_LONG == 32
  	printk(KERN_INFO
  		"  task                PC stack   pid father\n");
  #else
  	printk(KERN_INFO
  		"  task                        PC stack   pid father\n");
  #endif
  	rcu_read_lock();
  	for_each_process_thread(g, p) {
  		/*
  		 * reset the NMI-timeout, listing all files on a slow
  		 * console might take a lot of time:
  		 * Also, reset softlockup watchdogs on all CPUs, because
  		 * another CPU might be blocked waiting for us to process
  		 * an IPI.
  		 */
  		touch_nmi_watchdog();
  		touch_all_softlockup_watchdogs();
  		if (state_filter_match(state_filter, p))
  			sched_show_task(p);
  	}
  
  #ifdef CONFIG_SCHED_DEBUG
  	if (!state_filter)
  		sysrq_sched_debug_show();
  #endif
  	rcu_read_unlock();
  	/*
  	 * Only show locks if all tasks are dumped:
  	 */
  	if (!state_filter)
  		debug_show_all_locks();
  }
  
  /**
   * init_idle - set up an idle thread for a given CPU
   * @idle: task in question
   * @cpu: CPU the idle task belongs to
   *
   * NOTE: this function does not set the idle thread's NEED_RESCHED
   * flag, to make booting more robust.
   */
  void init_idle(struct task_struct *idle, int cpu)
  {
  	struct rq *rq = cpu_rq(cpu);
  	unsigned long flags;
  
  	__sched_fork(0, idle);
  
  	raw_spin_lock_irqsave(&idle->pi_lock, flags);
  	raw_spin_lock(&rq->lock);
  
  	idle->state = TASK_RUNNING;
  	idle->se.exec_start = sched_clock();
  	idle->flags |= PF_IDLE;
  
  	kasan_unpoison_task_stack(idle);
  
  #ifdef CONFIG_SMP
  	/*
  	 * Its possible that init_idle() gets called multiple times on a task,
  	 * in that case do_set_cpus_allowed() will not do the right thing.
  	 *
  	 * And since this is boot we can forgo the serialization.
  	 */
  	set_cpus_allowed_common(idle, cpumask_of(cpu));
  #endif
  	/*
  	 * We're having a chicken and egg problem, even though we are
  	 * holding rq->lock, the CPU isn't yet set to this CPU so the
  	 * lockdep check in task_group() will fail.
  	 *
  	 * Similar case to sched_fork(). / Alternatively we could
  	 * use task_rq_lock() here and obtain the other rq->lock.
  	 *
  	 * Silence PROVE_RCU
  	 */
  	rcu_read_lock();
  	__set_task_cpu(idle, cpu);
  	rcu_read_unlock();
  
  	rq->idle = idle;
  	rcu_assign_pointer(rq->curr, idle);
  	idle->on_rq = TASK_ON_RQ_QUEUED;
  #ifdef CONFIG_SMP
  	idle->on_cpu = 1;
  #endif
  	raw_spin_unlock(&rq->lock);
  	raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
  
  	/* Set the preempt count _outside_ the spinlocks! */
  	init_idle_preempt_count(idle, cpu);
  
  	/*
  	 * The idle tasks have their own, simple scheduling class:
  	 */
  	idle->sched_class = &idle_sched_class;
  	ftrace_graph_init_idle_task(idle, cpu);
  	vtime_init_idle(idle, cpu);
  #ifdef CONFIG_SMP
  	sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
  #endif
  }
  
  #ifdef CONFIG_SMP
  
  int cpuset_cpumask_can_shrink(const struct cpumask *cur,
  			      const struct cpumask *trial)
  {
  	int ret = 1;
  
  	if (!cpumask_weight(cur))
  		return ret;
  
  	ret = dl_cpuset_cpumask_can_shrink(cur, trial);
  
  	return ret;
  }
  
  int task_can_attach(struct task_struct *p,
  		    const struct cpumask *cs_cpus_allowed)
  {
  	int ret = 0;
  
  	/*
  	 * Kthreads which disallow setaffinity shouldn't be moved
  	 * to a new cpuset; we don't want to change their CPU
  	 * affinity and isolating such threads by their set of
  	 * allowed nodes is unnecessary.  Thus, cpusets are not
  	 * applicable for such threads.  This prevents checking for
  	 * success of set_cpus_allowed_ptr() on all attached tasks
  	 * before cpus_mask may be changed.
  	 */
  	if (p->flags & PF_NO_SETAFFINITY) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
  					      cs_cpus_allowed))
  		ret = dl_task_can_attach(p, cs_cpus_allowed);
  
  out:
  	return ret;
  }
  
  bool sched_smp_initialized __read_mostly;
  
  #ifdef CONFIG_NUMA_BALANCING
  /* Migrate current task p to target_cpu */
  int migrate_task_to(struct task_struct *p, int target_cpu)
  {
  	struct migration_arg arg = { p, target_cpu };
  	int curr_cpu = task_cpu(p);
  
  	if (curr_cpu == target_cpu)
  		return 0;
  
  	if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
  		return -EINVAL;
  
  	/* TODO: This is not properly updating schedstats */
  
  	trace_sched_move_numa(p, curr_cpu, target_cpu);
  	return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
  }
  
  /*
   * Requeue a task on a given node and accurately track the number of NUMA
   * tasks on the runqueues
   */
  void sched_setnuma(struct task_struct *p, int nid)
  {
  	bool queued, running;
  	struct rq_flags rf;
  	struct rq *rq;
  
  	rq = task_rq_lock(p, &rf);
  	queued = task_on_rq_queued(p);
  	running = task_current(rq, p);
  
  	if (queued)
  		dequeue_task(rq, p, DEQUEUE_SAVE);
  	if (running)
  		put_prev_task(rq, p);
  
  	p->numa_preferred_nid = nid;
  
  	if (queued)
  		enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
  	if (running)
  		set_next_task(rq, p);
  	task_rq_unlock(rq, p, &rf);
  }
  #endif /* CONFIG_NUMA_BALANCING */
  
  #ifdef CONFIG_HOTPLUG_CPU
  /*
   * Ensure that the idle task is using init_mm right before its CPU goes
   * offline.
   */
  void idle_task_exit(void)
  {
  	struct mm_struct *mm = current->active_mm;
  
  	BUG_ON(cpu_online(smp_processor_id()));
  	BUG_ON(current != this_rq()->idle);
  
  	if (mm != &init_mm) {
  		switch_mm(mm, &init_mm, current);
  		finish_arch_post_lock_switch();
  	}
  
  	/* finish_cpu(), as ran on the BP, will clean up the active_mm state */
  }
  
  /*
   * Since this CPU is going 'away' for a while, fold any nr_active delta
   * we might have. Assumes we're called after migrate_tasks() so that the
   * nr_active count is stable. We need to take the teardown thread which
   * is calling this into account, so we hand in adjust = 1 to the load
   * calculation.
   *
   * Also see the comment "Global load-average calculations".
   */
  static void calc_load_migrate(struct rq *rq)
  {
  	long delta = calc_load_fold_active(rq, 1);
  	if (delta)
  		atomic_long_add(delta, &calc_load_tasks);
  }
  
  static struct task_struct *__pick_migrate_task(struct rq *rq)
  {
  	const struct sched_class *class;
  	struct task_struct *next;
  
  	for_each_class(class) {
  		next = class->pick_next_task(rq, NULL, NULL);
  		if (next) {
  			next->sched_class->put_prev_task(rq, next);
  			return next;
  		}
  	}
  
  	/* The idle class should always have a runnable task */
  	BUG();
  }
  
  /*
   * Migrate all tasks from the rq, sleeping tasks will be migrated by
   * try_to_wake_up()->select_task_rq().
   *
   * Called with rq->lock held even though we'er in stop_machine() and
   * there's no concurrency possible, we hold the required locks anyway
   * because of lock validation efforts.
   */
  static void migrate_tasks(struct rq *dead_rq, struct rq_flags *rf)
  {
  	struct rq *rq = dead_rq;
  	struct task_struct *next, *stop = rq->stop;
  	struct rq_flags orf = *rf;
  	int dest_cpu;
  
  	/*
  	 * Fudge the rq selection such that the below task selection loop
  	 * doesn't get stuck on the currently eligible stop task.
  	 *
  	 * We're currently inside stop_machine() and the rq is either stuck
  	 * in the stop_machine_cpu_stop() loop, or we're executing this code,
  	 * either way we should never end up calling schedule() until we're
  	 * done here.
  	 */
  	rq->stop = NULL;
  
  	/*
  	 * put_prev_task() and pick_next_task() sched
  	 * class method both need to have an up-to-date
  	 * value of rq->clock[_task]
  	 */
  	update_rq_clock(rq);
  
  	for (;;) {
  		/*
  		 * There's this thread running, bail when that's the only
  		 * remaining thread:
  		 */
  		if (rq->nr_running == 1)
  			break;
  
  		next = __pick_migrate_task(rq);
  
  		/*
  		 * Rules for changing task_struct::cpus_mask are holding
  		 * both pi_lock and rq->lock, such that holding either
  		 * stabilizes the mask.
  		 *
  		 * Drop rq->lock is not quite as disastrous as it usually is
  		 * because !cpu_active at this point, which means load-balance
  		 * will not interfere. Also, stop-machine.
  		 */
  		rq_unlock(rq, rf);
  		raw_spin_lock(&next->pi_lock);
  		rq_relock(rq, rf);
  
  		/*
  		 * Since we're inside stop-machine, _nothing_ should have
  		 * changed the task, WARN if weird stuff happened, because in
  		 * that case the above rq->lock drop is a fail too.
  		 */
  		if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
  			raw_spin_unlock(&next->pi_lock);
  			continue;
  		}
  
  		/* Find suitable destination for @next, with force if needed. */
  		dest_cpu = select_fallback_rq(dead_rq->cpu, next);
  		rq = __migrate_task(rq, rf, next, dest_cpu);
  		if (rq != dead_rq) {
  			rq_unlock(rq, rf);
  			rq = dead_rq;
  			*rf = orf;
  			rq_relock(rq, rf);
  		}
  		raw_spin_unlock(&next->pi_lock);
  	}
  
  	rq->stop = stop;
  }
  #endif /* CONFIG_HOTPLUG_CPU */
  
  void set_rq_online(struct rq *rq)
  {
  	if (!rq->online) {
  		const struct sched_class *class;
  
  		cpumask_set_cpu(rq->cpu, rq->rd->online);
  		rq->online = 1;
  
  		for_each_class(class) {
  			if (class->rq_online)
  				class->rq_online(rq);
  		}
  	}
  }
  
  void set_rq_offline(struct rq *rq)
  {
  	if (rq->online) {
  		const struct sched_class *class;
  
  		for_each_class(class) {
  			if (class->rq_offline)
  				class->rq_offline(rq);
  		}
  
  		cpumask_clear_cpu(rq->cpu, rq->rd->online);
  		rq->online = 0;
  	}
  }
  
  /*
   * used to mark begin/end of suspend/resume:
   */
  static int num_cpus_frozen;
  
  /*
   * Update cpusets according to cpu_active mask.  If cpusets are
   * disabled, cpuset_update_active_cpus() becomes a simple wrapper
   * around partition_sched_domains().
   *
   * If we come here as part of a suspend/resume, don't touch cpusets because we
   * want to restore it back to its original state upon resume anyway.
   */
  static void cpuset_cpu_active(void)
  {
  	if (cpuhp_tasks_frozen) {
  		/*
  		 * num_cpus_frozen tracks how many CPUs are involved in suspend
  		 * resume sequence. As long as this is not the last online
  		 * operation in the resume sequence, just build a single sched
  		 * domain, ignoring cpusets.
  		 */
  		partition_sched_domains(1, NULL, NULL);
  		if (--num_cpus_frozen)
  			return;
  		/*
  		 * This is the last CPU online operation. So fall through and
  		 * restore the original sched domains by considering the
  		 * cpuset configurations.
  		 */
  		cpuset_force_rebuild();
  	}
  	cpuset_update_active_cpus();
  }
  
  static int cpuset_cpu_inactive(unsigned int cpu)
  {
  	if (!cpuhp_tasks_frozen) {
  		if (dl_cpu_busy(cpu))
  			return -EBUSY;
  		cpuset_update_active_cpus();
  	} else {
  		num_cpus_frozen++;
  		partition_sched_domains(1, NULL, NULL);
  	}
  	return 0;
  }
  
  int sched_cpu_activate(unsigned int cpu)
  {
  	struct rq *rq = cpu_rq(cpu);
  	struct rq_flags rf;
  
  #ifdef CONFIG_SCHED_SMT
  	/*
  	 * When going up, increment the number of cores with SMT present.
  	 */
  	if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
  		static_branch_inc_cpuslocked(&sched_smt_present);
  #endif
  	set_cpu_active(cpu, true);
  
  	if (sched_smp_initialized) {
  		sched_domains_numa_masks_set(cpu);
  		cpuset_cpu_active();
  	}
  
  	/*
  	 * Put the rq online, if not already. This happens:
  	 *
  	 * 1) In the early boot process, because we build the real domains
  	 *    after all CPUs have been brought up.
  	 *
  	 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
  	 *    domains.
  	 */
  	rq_lock_irqsave(rq, &rf);
  	if (rq->rd) {
  		BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
  		set_rq_online(rq);
  	}
  	rq_unlock_irqrestore(rq, &rf);
  
  	return 0;
  }
  
  int sched_cpu_deactivate(unsigned int cpu)
  {
  	int ret;
  
  	set_cpu_active(cpu, false);
  	/*
  	 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
  	 * users of this state to go away such that all new such users will
  	 * observe it.
  	 *
  	 * Do sync before park smpboot threads to take care the rcu boost case.
  	 */
  	synchronize_rcu();
  
  #ifdef CONFIG_SCHED_SMT
  	/*
  	 * When going down, decrement the number of cores with SMT present.
  	 */
  	if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
  		static_branch_dec_cpuslocked(&sched_smt_present);
  #endif
  
  	if (!sched_smp_initialized)
  		return 0;
  
  	ret = cpuset_cpu_inactive(cpu);
  	if (ret) {
  		set_cpu_active(cpu, true);
  		return ret;
  	}
  	sched_domains_numa_masks_clear(cpu);
  	return 0;
  }
  
  static void sched_rq_cpu_starting(unsigned int cpu)
  {
  	struct rq *rq = cpu_rq(cpu);
  
  	rq->calc_load_update = calc_load_update;
  	update_max_interval();
  }
  
  int sched_cpu_starting(unsigned int cpu)
  {
  	sched_rq_cpu_starting(cpu);
  	sched_tick_start(cpu);
  	return 0;
  }
  
  #ifdef CONFIG_HOTPLUG_CPU
  int sched_cpu_dying(unsigned int cpu)
  {
  	struct rq *rq = cpu_rq(cpu);
  	struct rq_flags rf;
  
  	/* Handle pending wakeups and then migrate everything off */
  	sched_ttwu_pending();
  	sched_tick_stop(cpu);
  
  	rq_lock_irqsave(rq, &rf);
  	if (rq->rd) {
  		BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
  		set_rq_offline(rq);
  	}
  	migrate_tasks(rq, &rf);
  	BUG_ON(rq->nr_running != 1);
  	rq_unlock_irqrestore(rq, &rf);
  
  	calc_load_migrate(rq);
  	update_max_interval();
  	nohz_balance_exit_idle(rq);
  	hrtick_clear(rq);
  	return 0;
  }
  #endif
  
  void __init sched_init_smp(void)
  {
  	sched_init_numa();
  
  	/*
  	 * There's no userspace yet to cause hotplug operations; hence all the
  	 * CPU masks are stable and all blatant races in the below code cannot
  	 * happen.
  	 */
  	mutex_lock(&sched_domains_mutex);
  	sched_init_domains(cpu_active_mask);
  	mutex_unlock(&sched_domains_mutex);
  
  	/* Move init over to a non-isolated CPU */
  	if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
  		BUG();
  	sched_init_granularity();
  
  	init_sched_rt_class();
  	init_sched_dl_class();
  
  	sched_smp_initialized = true;
  }
  
  static int __init migration_init(void)
  {
  	sched_cpu_starting(smp_processor_id());
  	return 0;
  }
  early_initcall(migration_init);
  
  #else
  void __init sched_init_smp(void)
  {
  	sched_init_granularity();
  }
  #endif /* CONFIG_SMP */
  
  int in_sched_functions(unsigned long addr)
  {
  	return in_lock_functions(addr) ||
  		(addr >= (unsigned long)__sched_text_start
  		&& addr < (unsigned long)__sched_text_end);
  }
  
  #ifdef CONFIG_CGROUP_SCHED
  /*
   * Default task group.
   * Every task in system belongs to this group at bootup.
   */
  struct task_group root_task_group;
  LIST_HEAD(task_groups);
  
  /* Cacheline aligned slab cache for task_group */
  static struct kmem_cache *task_group_cache __read_mostly;
  #endif
  
  DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
  DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
  
  void __init sched_init(void)
  {
  	unsigned long ptr = 0;
  	int i;
  
  	wait_bit_init();
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  	ptr += 2 * nr_cpu_ids * sizeof(void **);
  #endif
  #ifdef CONFIG_RT_GROUP_SCHED
  	ptr += 2 * nr_cpu_ids * sizeof(void **);
  #endif
  	if (ptr) {
  		ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  		root_task_group.se = (struct sched_entity **)ptr;
  		ptr += nr_cpu_ids * sizeof(void **);
  
  		root_task_group.cfs_rq = (struct cfs_rq **)ptr;
  		ptr += nr_cpu_ids * sizeof(void **);
  
  #endif /* CONFIG_FAIR_GROUP_SCHED */
  #ifdef CONFIG_RT_GROUP_SCHED
  		root_task_group.rt_se = (struct sched_rt_entity **)ptr;
  		ptr += nr_cpu_ids * sizeof(void **);
  
  		root_task_group.rt_rq = (struct rt_rq **)ptr;
  		ptr += nr_cpu_ids * sizeof(void **);
  
  #endif /* CONFIG_RT_GROUP_SCHED */
  	}
  #ifdef CONFIG_CPUMASK_OFFSTACK
  	for_each_possible_cpu(i) {
  		per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
  			cpumask_size(), GFP_KERNEL, cpu_to_node(i));
  		per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
  			cpumask_size(), GFP_KERNEL, cpu_to_node(i));
  	}
  #endif /* CONFIG_CPUMASK_OFFSTACK */
  
  	init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
  	init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime());
  
  #ifdef CONFIG_SMP
  	init_defrootdomain();
  #endif
  
  #ifdef CONFIG_RT_GROUP_SCHED
  	init_rt_bandwidth(&root_task_group.rt_bandwidth,
  			global_rt_period(), global_rt_runtime());
  #endif /* CONFIG_RT_GROUP_SCHED */
  
  #ifdef CONFIG_CGROUP_SCHED
  	task_group_cache = KMEM_CACHE(task_group, 0);
  
  	list_add(&root_task_group.list, &task_groups);
  	INIT_LIST_HEAD(&root_task_group.children);
  	INIT_LIST_HEAD(&root_task_group.siblings);
  	autogroup_init(&init_task);
  #endif /* CONFIG_CGROUP_SCHED */
  
  	for_each_possible_cpu(i) {
  		struct rq *rq;
  
  		rq = cpu_rq(i);
  		raw_spin_lock_init(&rq->lock);
  		rq->nr_running = 0;
  		rq->calc_load_active = 0;
  		rq->calc_load_update = jiffies + LOAD_FREQ;
  		init_cfs_rq(&rq->cfs);
  		init_rt_rq(&rq->rt);
  		init_dl_rq(&rq->dl);
  #ifdef CONFIG_FAIR_GROUP_SCHED
  		root_task_group.shares = ROOT_TASK_GROUP_LOAD;
  		INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
  		rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
  		/*
  		 * How much CPU bandwidth does root_task_group get?
  		 *
  		 * In case of task-groups formed thr' the cgroup filesystem, it
  		 * gets 100% of the CPU resources in the system. This overall
  		 * system CPU resource is divided among the tasks of
  		 * root_task_group and its child task-groups in a fair manner,
  		 * based on each entity's (task or task-group's) weight
  		 * (se->load.weight).
  		 *
  		 * In other words, if root_task_group has 10 tasks of weight
  		 * 1024) and two child groups A0 and A1 (of weight 1024 each),
  		 * then A0's share of the CPU resource is:
  		 *
  		 *	A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
  		 *
  		 * We achieve this by letting root_task_group's tasks sit
  		 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
  		 */
  		init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
  		init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
  #endif /* CONFIG_FAIR_GROUP_SCHED */
  
  		rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
  #ifdef CONFIG_RT_GROUP_SCHED
  		init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
  #endif
  #ifdef CONFIG_SMP
  		rq->sd = NULL;
  		rq->rd = NULL;
  		rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
  		rq->balance_callback = NULL;
  		rq->active_balance = 0;
  		rq->next_balance = jiffies;
  		rq->push_cpu = 0;
  		rq->cpu = i;
  		rq->online = 0;
  		rq->idle_stamp = 0;
  		rq->avg_idle = 2*sysctl_sched_migration_cost;
  		rq->max_idle_balance_cost = sysctl_sched_migration_cost;
  
  		INIT_LIST_HEAD(&rq->cfs_tasks);
  
  		rq_attach_root(rq, &def_root_domain);
  #ifdef CONFIG_NO_HZ_COMMON
  		rq->last_load_update_tick = jiffies;
  		rq->last_blocked_load_update_tick = jiffies;
  		atomic_set(&rq->nohz_flags, 0);
  #endif
  #endif /* CONFIG_SMP */
  		hrtick_rq_init(rq);
  		atomic_set(&rq->nr_iowait, 0);
  	}
  
  	set_load_weight(&init_task, false);
  
  	/*
  	 * The boot idle thread does lazy MMU switching as well:
  	 */
  	mmgrab(&init_mm);
  	enter_lazy_tlb(&init_mm, current);
  
  	/*
  	 * Make us the idle thread. Technically, schedule() should not be
  	 * called from this thread, however somewhere below it might be,
  	 * but because we are the idle thread, we just pick up running again
  	 * when this runqueue becomes "idle".
  	 */
  	init_idle(current, smp_processor_id());
  
  	calc_load_update = jiffies + LOAD_FREQ;
  
  #ifdef CONFIG_SMP
  	idle_thread_set_boot_cpu();
  #endif
  	init_sched_fair_class();
  
  	init_schedstats();
  
  	psi_init();
  
  	init_uclamp();
  
  	scheduler_running = 1;
  }
  
  #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
  static inline int preempt_count_equals(int preempt_offset)
  {
  	int nested = preempt_count() + rcu_preempt_depth();
  
  	return (nested == preempt_offset);
  }
  
  void __might_sleep(const char *file, int line, int preempt_offset)
  {
  	/*
  	 * Blocking primitives will set (and therefore destroy) current->state,
  	 * since we will exit with TASK_RUNNING make sure we enter with it,
  	 * otherwise we will destroy state.
  	 */
  	WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
  			"do not call blocking ops when !TASK_RUNNING; "
  			"state=%lx set at [<%p>] %pS\n",
  			current->state,
  			(void *)current->task_state_change,
  			(void *)current->task_state_change);
  
  	___might_sleep(file, line, preempt_offset);
  }
  EXPORT_SYMBOL(__might_sleep);
  
  void ___might_sleep(const char *file, int line, int preempt_offset)
  {
  	/* Ratelimiting timestamp: */
  	static unsigned long prev_jiffy;
  
  	unsigned long preempt_disable_ip;
  
  	/* WARN_ON_ONCE() by default, no rate limit required: */
  	rcu_sleep_check();
  
  	if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
  	     !is_idle_task(current) && !current->non_block_count) ||
  	    system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
  	    oops_in_progress)
  		return;
  
  	if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
  		return;
  	prev_jiffy = jiffies;
  
  	/* Save this before calling printk(), since that will clobber it: */
  	preempt_disable_ip = get_preempt_disable_ip(current);
  
  	printk(KERN_ERR
  		"BUG: sleeping function called from invalid context at %s:%d\n",
  			file, line);
  	printk(KERN_ERR
  		"in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
  			in_atomic(), irqs_disabled(), current->non_block_count,
  			current->pid, current->comm);
  
  	if (task_stack_end_corrupted(current))
  		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
  
  	debug_show_held_locks(current);
  	if (irqs_disabled())
  		print_irqtrace_events(current);
  	if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
  	    && !preempt_count_equals(preempt_offset)) {
  		pr_err("Preemption disabled at:");
  		print_ip_sym(preempt_disable_ip);
  		pr_cont("\n");
  	}
  	dump_stack();
  	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
  }
  EXPORT_SYMBOL(___might_sleep);
  
  void __cant_sleep(const char *file, int line, int preempt_offset)
  {
  	static unsigned long prev_jiffy;
  
  	if (irqs_disabled())
  		return;
  
  	if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
  		return;
  
  	if (preempt_count() > preempt_offset)
  		return;
  
  	if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
  		return;
  	prev_jiffy = jiffies;
  
  	printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
  	printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
  			in_atomic(), irqs_disabled(),
  			current->pid, current->comm);
  
  	debug_show_held_locks(current);
  	dump_stack();
  	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
  }
  EXPORT_SYMBOL_GPL(__cant_sleep);
  #endif
  
  #ifdef CONFIG_MAGIC_SYSRQ
  void normalize_rt_tasks(void)
  {
  	struct task_struct *g, *p;
  	struct sched_attr attr = {
  		.sched_policy = SCHED_NORMAL,
  	};
  
  	read_lock(&tasklist_lock);
  	for_each_process_thread(g, p) {
  		/*
  		 * Only normalize user tasks:
  		 */
  		if (p->flags & PF_KTHREAD)
  			continue;
  
  		p->se.exec_start = 0;
  		schedstat_set(p->se.statistics.wait_start,  0);
  		schedstat_set(p->se.statistics.sleep_start, 0);
  		schedstat_set(p->se.statistics.block_start, 0);
  
  		if (!dl_task(p) && !rt_task(p)) {
  			/*
  			 * Renice negative nice level userspace
  			 * tasks back to 0:
  			 */
  			if (task_nice(p) < 0)
  				set_user_nice(p, 0);
  			continue;
  		}
  
  		__sched_setscheduler(p, &attr, false, false);
  	}
  	read_unlock(&tasklist_lock);
  }
  
  #endif /* CONFIG_MAGIC_SYSRQ */
  
  #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
  /*
   * These functions are only useful for the IA64 MCA handling, or kdb.
   *
   * They can only be called when the whole system has been
   * stopped - every CPU needs to be quiescent, and no scheduling
   * activity can take place. Using them for anything else would
   * be a serious bug, and as a result, they aren't even visible
   * under any other configuration.
   */
  
  /**
   * curr_task - return the current task for a given CPU.
   * @cpu: the processor in question.
   *
   * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
   *
   * Return: The current task for @cpu.
   */
  struct task_struct *curr_task(int cpu)
  {
  	return cpu_curr(cpu);
  }
  
  #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
  
  #ifdef CONFIG_IA64
  /**
   * ia64_set_curr_task - set the current task for a given CPU.
   * @cpu: the processor in question.
   * @p: the task pointer to set.
   *
   * Description: This function must only be used when non-maskable interrupts
   * are serviced on a separate stack. It allows the architecture to switch the
   * notion of the current task on a CPU in a non-blocking manner. This function
   * must be called with all CPU's synchronized, and interrupts disabled, the
   * and caller must save the original value of the current task (see
   * curr_task() above) and restore that value before reenabling interrupts and
   * re-starting the system.
   *
   * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
   */
  void ia64_set_curr_task(int cpu, struct task_struct *p)
  {
  	cpu_curr(cpu) = p;
  }
  
  #endif
  
  #ifdef CONFIG_CGROUP_SCHED
  /* task_group_lock serializes the addition/removal of task groups */
  static DEFINE_SPINLOCK(task_group_lock);
  
  static inline void alloc_uclamp_sched_group(struct task_group *tg,
  					    struct task_group *parent)
  {
  #ifdef CONFIG_UCLAMP_TASK_GROUP
  	enum uclamp_id clamp_id;
  
  	for_each_clamp_id(clamp_id) {
  		uclamp_se_set(&tg->uclamp_req[clamp_id],
  			      uclamp_none(clamp_id), false);
  		tg->uclamp[clamp_id] = parent->uclamp[clamp_id];
  	}
  #endif
  }
  
  static void sched_free_group(struct task_group *tg)
  {
  	free_fair_sched_group(tg);
  	free_rt_sched_group(tg);
  	autogroup_free(tg);
  	kmem_cache_free(task_group_cache, tg);
  }
  
  /* allocate runqueue etc for a new task group */
  struct task_group *sched_create_group(struct task_group *parent)
  {
  	struct task_group *tg;
  
  	tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
  	if (!tg)
  		return ERR_PTR(-ENOMEM);
  
  	if (!alloc_fair_sched_group(tg, parent))
  		goto err;
  
  	if (!alloc_rt_sched_group(tg, parent))
  		goto err;
  
  	alloc_uclamp_sched_group(tg, parent);
  
  	return tg;
  
  err:
  	sched_free_group(tg);
  	return ERR_PTR(-ENOMEM);
  }
  
  void sched_online_group(struct task_group *tg, struct task_group *parent)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&task_group_lock, flags);
  	list_add_rcu(&tg->list, &task_groups);
  
  	/* Root should already exist: */
  	WARN_ON(!parent);
  
  	tg->parent = parent;
  	INIT_LIST_HEAD(&tg->children);
  	list_add_rcu(&tg->siblings, &parent->children);
  	spin_unlock_irqrestore(&task_group_lock, flags);
  
  	online_fair_sched_group(tg);
  }
  
  /* rcu callback to free various structures associated with a task group */
  static void sched_free_group_rcu(struct rcu_head *rhp)
  {
  	/* Now it should be safe to free those cfs_rqs: */
  	sched_free_group(container_of(rhp, struct task_group, rcu));
  }
  
  void sched_destroy_group(struct task_group *tg)
  {
  	/* Wait for possible concurrent references to cfs_rqs complete: */
  	call_rcu(&tg->rcu, sched_free_group_rcu);
  }
  
  void sched_offline_group(struct task_group *tg)
  {
  	unsigned long flags;
  
  	/* End participation in shares distribution: */
  	unregister_fair_sched_group(tg);
  
  	spin_lock_irqsave(&task_group_lock, flags);
  	list_del_rcu(&tg->list);
  	list_del_rcu(&tg->siblings);
  	spin_unlock_irqrestore(&task_group_lock, flags);
  }
  
  static void sched_change_group(struct task_struct *tsk, int type)
  {
  	struct task_group *tg;
  
  	/*
  	 * All callers are synchronized by task_rq_lock(); we do not use RCU
  	 * which is pointless here. Thus, we pass "true" to task_css_check()
  	 * to prevent lockdep warnings.
  	 */
  	tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
  			  struct task_group, css);
  	tg = autogroup_task_group(tsk, tg);
  	tsk->sched_task_group = tg;
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  	if (tsk->sched_class->task_change_group)
  		tsk->sched_class->task_change_group(tsk, type);
  	else
  #endif
  		set_task_rq(tsk, task_cpu(tsk));
  }
  
  /*
   * Change task's runqueue when it moves between groups.
   *
   * The caller of this function should have put the task in its new group by
   * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
   * its new group.
   */
  void sched_move_task(struct task_struct *tsk)
  {
  	int queued, running, queue_flags =
  		DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
  	struct rq_flags rf;
  	struct rq *rq;
  
  	rq = task_rq_lock(tsk, &rf);
  	update_rq_clock(rq);
  
  	running = task_current(rq, tsk);
  	queued = task_on_rq_queued(tsk);
  
  	if (queued)
  		dequeue_task(rq, tsk, queue_flags);
  	if (running)
  		put_prev_task(rq, tsk);
  
  	sched_change_group(tsk, TASK_MOVE_GROUP);
  
  	if (queued)
  		enqueue_task(rq, tsk, queue_flags);
  	if (running) {
  		set_next_task(rq, tsk);
  		/*
  		 * After changing group, the running task may have joined a
  		 * throttled one but it's still the running task. Trigger a
  		 * resched to make sure that task can still run.
  		 */
  		resched_curr(rq);
  	}
  
  	task_rq_unlock(rq, tsk, &rf);
  }
  
  static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
  {
  	return css ? container_of(css, struct task_group, css) : NULL;
  }
  
  static struct cgroup_subsys_state *
  cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
  {
  	struct task_group *parent = css_tg(parent_css);
  	struct task_group *tg;
  
  	if (!parent) {
  		/* This is early initialization for the top cgroup */
  		return &root_task_group.css;
  	}
  
  	tg = sched_create_group(parent);
  	if (IS_ERR(tg))
  		return ERR_PTR(-ENOMEM);
  
  	return &tg->css;
  }
  
  /* Expose task group only after completing cgroup initialization */
  static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
  {
  	struct task_group *tg = css_tg(css);
  	struct task_group *parent = css_tg(css->parent);
  
  	if (parent)
  		sched_online_group(tg, parent);
  
  #ifdef CONFIG_UCLAMP_TASK_GROUP
  	/* Propagate the effective uclamp value for the new group */
  	cpu_util_update_eff(css);
  #endif
  
  	return 0;
  }
  
  static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
  {
  	struct task_group *tg = css_tg(css);
  
  	sched_offline_group(tg);
  }
  
  static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
  {
  	struct task_group *tg = css_tg(css);
  
  	/*
  	 * Relies on the RCU grace period between css_released() and this.
  	 */
  	sched_free_group(tg);
  }
  
  /*
   * This is called before wake_up_new_task(), therefore we really only
   * have to set its group bits, all the other stuff does not apply.
   */
  static void cpu_cgroup_fork(struct task_struct *task)
  {
  	struct rq_flags rf;
  	struct rq *rq;
  
  	rq = task_rq_lock(task, &rf);
  
  	update_rq_clock(rq);
  	sched_change_group(task, TASK_SET_GROUP);
  
  	task_rq_unlock(rq, task, &rf);
  }
  
  static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
  {
  	struct task_struct *task;
  	struct cgroup_subsys_state *css;
  	int ret = 0;
  
  	cgroup_taskset_for_each(task, css, tset) {
  #ifdef CONFIG_RT_GROUP_SCHED
  		if (!sched_rt_can_attach(css_tg(css), task))
  			return -EINVAL;
  #endif
  		/*
  		 * Serialize against wake_up_new_task() such that if its
  		 * running, we're sure to observe its full state.
  		 */
  		raw_spin_lock_irq(&task->pi_lock);
  		/*
  		 * Avoid calling sched_move_task() before wake_up_new_task()
  		 * has happened. This would lead to problems with PELT, due to
  		 * move wanting to detach+attach while we're not attached yet.
  		 */
  		if (task->state == TASK_NEW)
  			ret = -EINVAL;
  		raw_spin_unlock_irq(&task->pi_lock);
  
  		if (ret)
  			break;
  	}
  	return ret;
  }
  
  static void cpu_cgroup_attach(struct cgroup_taskset *tset)
  {
  	struct task_struct *task;
  	struct cgroup_subsys_state *css;
  
  	cgroup_taskset_for_each(task, css, tset)
  		sched_move_task(task);
  }
  
  #ifdef CONFIG_UCLAMP_TASK_GROUP
  static void cpu_util_update_eff(struct cgroup_subsys_state *css)
  {
  	struct cgroup_subsys_state *top_css = css;
  	struct uclamp_se *uc_parent = NULL;
  	struct uclamp_se *uc_se = NULL;
  	unsigned int eff[UCLAMP_CNT];
  	enum uclamp_id clamp_id;
  	unsigned int clamps;
  
  	css_for_each_descendant_pre(css, top_css) {
  		uc_parent = css_tg(css)->parent
  			? css_tg(css)->parent->uclamp : NULL;
  
  		for_each_clamp_id(clamp_id) {
  			/* Assume effective clamps matches requested clamps */
  			eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value;
  			/* Cap effective clamps with parent's effective clamps */
  			if (uc_parent &&
  			    eff[clamp_id] > uc_parent[clamp_id].value) {
  				eff[clamp_id] = uc_parent[clamp_id].value;
  			}
  		}
  		/* Ensure protection is always capped by limit */
  		eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);
  
  		/* Propagate most restrictive effective clamps */
  		clamps = 0x0;
  		uc_se = css_tg(css)->uclamp;
  		for_each_clamp_id(clamp_id) {
  			if (eff[clamp_id] == uc_se[clamp_id].value)
  				continue;
  			uc_se[clamp_id].value = eff[clamp_id];
  			uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]);
  			clamps |= (0x1 << clamp_id);
  		}
  		if (!clamps) {
  			css = css_rightmost_descendant(css);
  			continue;
  		}
  
  		/* Immediately update descendants RUNNABLE tasks */
  		uclamp_update_active_tasks(css, clamps);
  	}
  }
  
  /*
   * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
   * C expression. Since there is no way to convert a macro argument (N) into a
   * character constant, use two levels of macros.
   */
  #define _POW10(exp) ((unsigned int)1e##exp)
  #define POW10(exp) _POW10(exp)
  
  struct uclamp_request {
  #define UCLAMP_PERCENT_SHIFT	2
  #define UCLAMP_PERCENT_SCALE	(100 * POW10(UCLAMP_PERCENT_SHIFT))
  	s64 percent;
  	u64 util;
  	int ret;
  };
  
  static inline struct uclamp_request
  capacity_from_percent(char *buf)
  {
  	struct uclamp_request req = {
  		.percent = UCLAMP_PERCENT_SCALE,
  		.util = SCHED_CAPACITY_SCALE,
  		.ret = 0,
  	};
  
  	buf = strim(buf);
  	if (strcmp(buf, "max")) {
  		req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT,
  					     &req.percent);
  		if (req.ret)
  			return req;
  		if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
  			req.ret = -ERANGE;
  			return req;
  		}
  
  		req.util = req.percent << SCHED_CAPACITY_SHIFT;
  		req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE);
  	}
  
  	return req;
  }
  
  static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf,
  				size_t nbytes, loff_t off,
  				enum uclamp_id clamp_id)
  {
  	struct uclamp_request req;
  	struct task_group *tg;
  
  	req = capacity_from_percent(buf);
  	if (req.ret)
  		return req.ret;
  
  	static_branch_enable(&sched_uclamp_used);
  
  	mutex_lock(&uclamp_mutex);
  	rcu_read_lock();
  
  	tg = css_tg(of_css(of));
  	if (tg->uclamp_req[clamp_id].value != req.util)
  		uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false);
  
  	/*
  	 * Because of not recoverable conversion rounding we keep track of the
  	 * exact requested value
  	 */
  	tg->uclamp_pct[clamp_id] = req.percent;
  
  	/* Update effective clamps to track the most restrictive value */
  	cpu_util_update_eff(of_css(of));
  
  	rcu_read_unlock();
  	mutex_unlock(&uclamp_mutex);
  
  	return nbytes;
  }
  
  static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of,
  				    char *buf, size_t nbytes,
  				    loff_t off)
  {
  	return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN);
  }
  
  static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of,
  				    char *buf, size_t nbytes,
  				    loff_t off)
  {
  	return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX);
  }
  
  static inline void cpu_uclamp_print(struct seq_file *sf,
  				    enum uclamp_id clamp_id)
  {
  	struct task_group *tg;
  	u64 util_clamp;
  	u64 percent;
  	u32 rem;
  
  	rcu_read_lock();
  	tg = css_tg(seq_css(sf));
  	util_clamp = tg->uclamp_req[clamp_id].value;
  	rcu_read_unlock();
  
  	if (util_clamp == SCHED_CAPACITY_SCALE) {
  		seq_puts(sf, "max\n");
  		return;
  	}
  
  	percent = tg->uclamp_pct[clamp_id];
  	percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem);
  	seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem);
  }
  
  static int cpu_uclamp_min_show(struct seq_file *sf, void *v)
  {
  	cpu_uclamp_print(sf, UCLAMP_MIN);
  	return 0;
  }
  
  static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
  {
  	cpu_uclamp_print(sf, UCLAMP_MAX);
  	return 0;
  }
  #endif /* CONFIG_UCLAMP_TASK_GROUP */
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
  				struct cftype *cftype, u64 shareval)
  {
  	if (shareval > scale_load_down(ULONG_MAX))
  		shareval = MAX_SHARES;
  	return sched_group_set_shares(css_tg(css), scale_load(shareval));
  }
  
  static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
  			       struct cftype *cft)
  {
  	struct task_group *tg = css_tg(css);
  
  	return (u64) scale_load_down(tg->shares);
  }
  
  #ifdef CONFIG_CFS_BANDWIDTH
  static DEFINE_MUTEX(cfs_constraints_mutex);
  
  const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
  static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
  /* More than 203 days if BW_SHIFT equals 20. */
  static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
  
  static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
  
  static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
  {
  	int i, ret = 0, runtime_enabled, runtime_was_enabled;
  	struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
  
  	if (tg == &root_task_group)
  		return -EINVAL;
  
  	/*
  	 * Ensure we have at some amount of bandwidth every period.  This is
  	 * to prevent reaching a state of large arrears when throttled via
  	 * entity_tick() resulting in prolonged exit starvation.
  	 */
  	if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
  		return -EINVAL;
  
  	/*
  	 * Likewise, bound things on the otherside by preventing insane quota
  	 * periods.  This also allows us to normalize in computing quota
  	 * feasibility.
  	 */
  	if (period > max_cfs_quota_period)
  		return -EINVAL;
  
  	/*
  	 * Bound quota to defend quota against overflow during bandwidth shift.
  	 */
  	if (quota != RUNTIME_INF && quota > max_cfs_runtime)
  		return -EINVAL;
  
  	/*
  	 * Prevent race between setting of cfs_rq->runtime_enabled and
  	 * unthrottle_offline_cfs_rqs().
  	 */
  	get_online_cpus();
  	mutex_lock(&cfs_constraints_mutex);
  	ret = __cfs_schedulable(tg, period, quota);
  	if (ret)
  		goto out_unlock;
  
  	runtime_enabled = quota != RUNTIME_INF;
  	runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
  	/*
  	 * If we need to toggle cfs_bandwidth_used, off->on must occur
  	 * before making related changes, and on->off must occur afterwards
  	 */
  	if (runtime_enabled && !runtime_was_enabled)
  		cfs_bandwidth_usage_inc();
  	raw_spin_lock_irq(&cfs_b->lock);
  	cfs_b->period = ns_to_ktime(period);
  	cfs_b->quota = quota;
  
  	__refill_cfs_bandwidth_runtime(cfs_b);
  
  	/* Restart the period timer (if active) to handle new period expiry: */
  	if (runtime_enabled)
  		start_cfs_bandwidth(cfs_b);
  
  	raw_spin_unlock_irq(&cfs_b->lock);
  
  	for_each_online_cpu(i) {
  		struct cfs_rq *cfs_rq = tg->cfs_rq[i];
  		struct rq *rq = cfs_rq->rq;
  		struct rq_flags rf;
  
  		rq_lock_irq(rq, &rf);
  		cfs_rq->runtime_enabled = runtime_enabled;
  		cfs_rq->runtime_remaining = 0;
  
  		if (cfs_rq->throttled)
  			unthrottle_cfs_rq(cfs_rq);
  		rq_unlock_irq(rq, &rf);
  	}
  	if (runtime_was_enabled && !runtime_enabled)
  		cfs_bandwidth_usage_dec();
  out_unlock:
  	mutex_unlock(&cfs_constraints_mutex);
  	put_online_cpus();
  
  	return ret;
  }
  
  static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
  {
  	u64 quota, period;
  
  	period = ktime_to_ns(tg->cfs_bandwidth.period);
  	if (cfs_quota_us < 0)
  		quota = RUNTIME_INF;
  	else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
  		quota = (u64)cfs_quota_us * NSEC_PER_USEC;
  	else
  		return -EINVAL;
  
  	return tg_set_cfs_bandwidth(tg, period, quota);
  }
  
  static long tg_get_cfs_quota(struct task_group *tg)
  {
  	u64 quota_us;
  
  	if (tg->cfs_bandwidth.quota == RUNTIME_INF)
  		return -1;
  
  	quota_us = tg->cfs_bandwidth.quota;
  	do_div(quota_us, NSEC_PER_USEC);
  
  	return quota_us;
  }
  
  static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
  {
  	u64 quota, period;
  
  	if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC)
  		return -EINVAL;
  
  	period = (u64)cfs_period_us * NSEC_PER_USEC;
  	quota = tg->cfs_bandwidth.quota;
  
  	return tg_set_cfs_bandwidth(tg, period, quota);
  }
  
  static long tg_get_cfs_period(struct task_group *tg)
  {
  	u64 cfs_period_us;
  
  	cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
  	do_div(cfs_period_us, NSEC_PER_USEC);
  
  	return cfs_period_us;
  }
  
  static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
  				  struct cftype *cft)
  {
  	return tg_get_cfs_quota(css_tg(css));
  }
  
  static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
  				   struct cftype *cftype, s64 cfs_quota_us)
  {
  	return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
  }
  
  static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
  				   struct cftype *cft)
  {
  	return tg_get_cfs_period(css_tg(css));
  }
  
  static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
  				    struct cftype *cftype, u64 cfs_period_us)
  {
  	return tg_set_cfs_period(css_tg(css), cfs_period_us);
  }
  
  struct cfs_schedulable_data {
  	struct task_group *tg;
  	u64 period, quota;
  };
  
  /*
   * normalize group quota/period to be quota/max_period
   * note: units are usecs
   */
  static u64 normalize_cfs_quota(struct task_group *tg,
  			       struct cfs_schedulable_data *d)
  {
  	u64 quota, period;
  
  	if (tg == d->tg) {
  		period = d->period;
  		quota = d->quota;
  	} else {
  		period = tg_get_cfs_period(tg);
  		quota = tg_get_cfs_quota(tg);
  	}
  
  	/* note: these should typically be equivalent */
  	if (quota == RUNTIME_INF || quota == -1)
  		return RUNTIME_INF;
  
  	return to_ratio(period, quota);
  }
  
  static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
  {
  	struct cfs_schedulable_data *d = data;
  	struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
  	s64 quota = 0, parent_quota = -1;
  
  	if (!tg->parent) {
  		quota = RUNTIME_INF;
  	} else {
  		struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
  
  		quota = normalize_cfs_quota(tg, d);
  		parent_quota = parent_b->hierarchical_quota;
  
  		/*
  		 * Ensure max(child_quota) <= parent_quota.  On cgroup2,
  		 * always take the min.  On cgroup1, only inherit when no
  		 * limit is set:
  		 */
  		if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
  			quota = min(quota, parent_quota);
  		} else {
  			if (quota == RUNTIME_INF)
  				quota = parent_quota;
  			else if (parent_quota != RUNTIME_INF && quota > parent_quota)
  				return -EINVAL;
  		}
  	}
  	cfs_b->hierarchical_quota = quota;
  
  	return 0;
  }
  
  static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
  {
  	int ret;
  	struct cfs_schedulable_data data = {
  		.tg = tg,
  		.period = period,
  		.quota = quota,
  	};
  
  	if (quota != RUNTIME_INF) {
  		do_div(data.period, NSEC_PER_USEC);
  		do_div(data.quota, NSEC_PER_USEC);
  	}
  
  	rcu_read_lock();
  	ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
  	rcu_read_unlock();
  
  	return ret;
  }
  
  static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
  {
  	struct task_group *tg = css_tg(seq_css(sf));
  	struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
  
  	seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
  	seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
  	seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
  
  	if (schedstat_enabled() && tg != &root_task_group) {
  		u64 ws = 0;
  		int i;
  
  		for_each_possible_cpu(i)
  			ws += schedstat_val(tg->se[i]->statistics.wait_sum);
  
  		seq_printf(sf, "wait_sum %llu\n", ws);
  	}
  
  	return 0;
  }
  #endif /* CONFIG_CFS_BANDWIDTH */
  #endif /* CONFIG_FAIR_GROUP_SCHED */
  
  #ifdef CONFIG_RT_GROUP_SCHED
  static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
  				struct cftype *cft, s64 val)
  {
  	return sched_group_set_rt_runtime(css_tg(css), val);
  }
  
  static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
  			       struct cftype *cft)
  {
  	return sched_group_rt_runtime(css_tg(css));
  }
  
  static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
  				    struct cftype *cftype, u64 rt_period_us)
  {
  	return sched_group_set_rt_period(css_tg(css), rt_period_us);
  }
  
  static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
  				   struct cftype *cft)
  {
  	return sched_group_rt_period(css_tg(css));
  }
  #endif /* CONFIG_RT_GROUP_SCHED */
  
  static struct cftype cpu_legacy_files[] = {
  #ifdef CONFIG_FAIR_GROUP_SCHED
  	{
  		.name = "shares",
  		.read_u64 = cpu_shares_read_u64,
  		.write_u64 = cpu_shares_write_u64,
  	},
  #endif
  #ifdef CONFIG_CFS_BANDWIDTH
  	{
  		.name = "cfs_quota_us",
  		.read_s64 = cpu_cfs_quota_read_s64,
  		.write_s64 = cpu_cfs_quota_write_s64,
  	},
  	{
  		.name = "cfs_period_us",
  		.read_u64 = cpu_cfs_period_read_u64,
  		.write_u64 = cpu_cfs_period_write_u64,
  	},
  	{
  		.name = "stat",
  		.seq_show = cpu_cfs_stat_show,
  	},
  #endif
  #ifdef CONFIG_RT_GROUP_SCHED
  	{
  		.name = "rt_runtime_us",
  		.read_s64 = cpu_rt_runtime_read,
  		.write_s64 = cpu_rt_runtime_write,
  	},
  	{
  		.name = "rt_period_us",
  		.read_u64 = cpu_rt_period_read_uint,
  		.write_u64 = cpu_rt_period_write_uint,
  	},
  #endif
  #ifdef CONFIG_UCLAMP_TASK_GROUP
  	{
  		.name = "uclamp.min",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.seq_show = cpu_uclamp_min_show,
  		.write = cpu_uclamp_min_write,
  	},
  	{
  		.name = "uclamp.max",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.seq_show = cpu_uclamp_max_show,
  		.write = cpu_uclamp_max_write,
  	},
  #endif
  	{ }	/* Terminate */
  };
  
  static int cpu_extra_stat_show(struct seq_file *sf,
  			       struct cgroup_subsys_state *css)
  {
  #ifdef CONFIG_CFS_BANDWIDTH
  	{
  		struct task_group *tg = css_tg(css);
  		struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
  		u64 throttled_usec;
  
  		throttled_usec = cfs_b->throttled_time;
  		do_div(throttled_usec, NSEC_PER_USEC);
  
  		seq_printf(sf, "nr_periods %d\n"
  			   "nr_throttled %d\n"
  			   "throttled_usec %llu\n",
  			   cfs_b->nr_periods, cfs_b->nr_throttled,
  			   throttled_usec);
  	}
  #endif
  	return 0;
  }
  
  #ifdef CONFIG_FAIR_GROUP_SCHED
  static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
  			       struct cftype *cft)
  {
  	struct task_group *tg = css_tg(css);
  	u64 weight = scale_load_down(tg->shares);
  
  	return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
  }
  
  static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
  				struct cftype *cft, u64 weight)
  {
  	/*
  	 * cgroup weight knobs should use the common MIN, DFL and MAX
  	 * values which are 1, 100 and 10000 respectively.  While it loses
  	 * a bit of range on both ends, it maps pretty well onto the shares
  	 * value used by scheduler and the round-trip conversions preserve
  	 * the original value over the entire range.
  	 */
  	if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
  		return -ERANGE;
  
  	weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
  
  	return sched_group_set_shares(css_tg(css), scale_load(weight));
  }
  
  static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
  				    struct cftype *cft)
  {
  	unsigned long weight = scale_load_down(css_tg(css)->shares);
  	int last_delta = INT_MAX;
  	int prio, delta;
  
  	/* find the closest nice value to the current weight */
  	for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
  		delta = abs(sched_prio_to_weight[prio] - weight);
  		if (delta >= last_delta)
  			break;
  		last_delta = delta;
  	}
  
  	return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
  }
  
  static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
  				     struct cftype *cft, s64 nice)
  {
  	unsigned long weight;
  	int idx;
  
  	if (nice < MIN_NICE || nice > MAX_NICE)
  		return -ERANGE;
  
  	idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
  	idx = array_index_nospec(idx, 40);
  	weight = sched_prio_to_weight[idx];
  
  	return sched_group_set_shares(css_tg(css), scale_load(weight));
  }
  #endif
  
  static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
  						  long period, long quota)
  {
  	if (quota < 0)
  		seq_puts(sf, "max");
  	else
  		seq_printf(sf, "%ld", quota);
  
  	seq_printf(sf, " %ld\n", period);
  }
  
  /* caller should put the current value in *@periodp before calling */
  static int __maybe_unused cpu_period_quota_parse(char *buf,
  						 u64 *periodp, u64 *quotap)
  {
  	char tok[21];	/* U64_MAX */
  
  	if (sscanf(buf, "%20s %llu", tok, periodp) < 1)
  		return -EINVAL;
  
  	*periodp *= NSEC_PER_USEC;
  
  	if (sscanf(tok, "%llu", quotap))
  		*quotap *= NSEC_PER_USEC;
  	else if (!strcmp(tok, "max"))
  		*quotap = RUNTIME_INF;
  	else
  		return -EINVAL;
  
  	return 0;
  }
  
  #ifdef CONFIG_CFS_BANDWIDTH
  static int cpu_max_show(struct seq_file *sf, void *v)
  {
  	struct task_group *tg = css_tg(seq_css(sf));
  
  	cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
  	return 0;
  }
  
  static ssize_t cpu_max_write(struct kernfs_open_file *of,
  			     char *buf, size_t nbytes, loff_t off)
  {
  	struct task_group *tg = css_tg(of_css(of));
  	u64 period = tg_get_cfs_period(tg);
  	u64 quota;
  	int ret;
  
  	ret = cpu_period_quota_parse(buf, &period, &quota);
  	if (!ret)
  		ret = tg_set_cfs_bandwidth(tg, period, quota);
  	return ret ?: nbytes;
  }
  #endif
  
  static struct cftype cpu_files[] = {
  #ifdef CONFIG_FAIR_GROUP_SCHED
  	{
  		.name = "weight",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.read_u64 = cpu_weight_read_u64,
  		.write_u64 = cpu_weight_write_u64,
  	},
  	{
  		.name = "weight.nice",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.read_s64 = cpu_weight_nice_read_s64,
  		.write_s64 = cpu_weight_nice_write_s64,
  	},
  #endif
  #ifdef CONFIG_CFS_BANDWIDTH
  	{
  		.name = "max",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.seq_show = cpu_max_show,
  		.write = cpu_max_write,
  	},
  #endif
  #ifdef CONFIG_UCLAMP_TASK_GROUP
  	{
  		.name = "uclamp.min",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.seq_show = cpu_uclamp_min_show,
  		.write = cpu_uclamp_min_write,
  	},
  	{
  		.name = "uclamp.max",
  		.flags = CFTYPE_NOT_ON_ROOT,
  		.seq_show = cpu_uclamp_max_show,
  		.write = cpu_uclamp_max_write,
  	},
  #endif
  	{ }	/* terminate */
  };
  
  struct cgroup_subsys cpu_cgrp_subsys = {
  	.css_alloc	= cpu_cgroup_css_alloc,
  	.css_online	= cpu_cgroup_css_online,
  	.css_released	= cpu_cgroup_css_released,
  	.css_free	= cpu_cgroup_css_free,
  	.css_extra_stat_show = cpu_extra_stat_show,
  	.fork		= cpu_cgroup_fork,
  	.can_attach	= cpu_cgroup_can_attach,
  	.attach		= cpu_cgroup_attach,
  	.legacy_cftypes	= cpu_legacy_files,
  	.dfl_cftypes	= cpu_files,
  	.early_init	= true,
  	.threaded	= true,
  };
  
  #endif	/* CONFIG_CGROUP_SCHED */
  
  void dump_cpu_task(int cpu)
  {
  	pr_info("Task dump for CPU %d:\n", cpu);
  	sched_show_task(cpu_curr(cpu));
  }
  
  /*
   * Nice levels are multiplicative, with a gentle 10% change for every
   * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
   * nice 1, it will get ~10% less CPU time than another CPU-bound task
   * that remained on nice 0.
   *
   * The "10% effect" is relative and cumulative: from _any_ nice level,
   * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
   * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
   * If a task goes up by ~10% and another task goes down by ~10% then
   * the relative distance between them is ~25%.)
   */
  const int sched_prio_to_weight[40] = {
   /* -20 */     88761,     71755,     56483,     46273,     36291,
   /* -15 */     29154,     23254,     18705,     14949,     11916,
   /* -10 */      9548,      7620,      6100,      4904,      3906,
   /*  -5 */      3121,      2501,      1991,      1586,      1277,
   /*   0 */      1024,       820,       655,       526,       423,
   /*   5 */       335,       272,       215,       172,       137,
   /*  10 */       110,        87,        70,        56,        45,
   /*  15 */        36,        29,        23,        18,        15,
  };
  
  /*
   * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
   *
   * In cases where the weight does not change often, we can use the
   * precalculated inverse to speed up arithmetics by turning divisions
   * into multiplications:
   */
  const u32 sched_prio_to_wmult[40] = {
   /* -20 */     48388,     59856,     76040,     92818,    118348,
   /* -15 */    147320,    184698,    229616,    287308,    360437,
   /* -10 */    449829,    563644,    704093,    875809,   1099582,
   /*  -5 */   1376151,   1717300,   2157191,   2708050,   3363326,
   /*   0 */   4194304,   5237765,   6557202,   8165337,  10153587,
   /*   5 */  12820798,  15790321,  19976592,  24970740,  31350126,
   /*  10 */  39045157,  49367440,  61356676,  76695844,  95443717,
   /*  15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
  };
  
  #undef CREATE_TRACE_POINTS
  