/*
   * Deadline Scheduling Class (SCHED_DEADLINE)
   *
   * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
   *
   * Tasks that periodically executes their instances for less than their
   * runtime won't miss any of their deadlines.
   * Tasks that are not periodic or sporadic or that tries to execute more
   * than their reserved bandwidth will be slowed down (and may potentially
   * miss some of their deadlines), and won't affect any other task.
   *
   * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,

   *                    Juri Lelli <juri.lelli@gmail.com>,

   *                    Michael Trimarchi <michael@amarulasolutions.com>,
   *                    Fabio Checconi <fchecconi@gmail.com>
   */
  #include "sched.h"

  #include <linux/slab.h>

  struct dl_bandwidth def_dl_bandwidth;

  static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
  {
  	return container_of(dl_se, struct task_struct, dl);
  }
  
  static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
  {
  	return container_of(dl_rq, struct rq, dl);
  }
  
  static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
  {
  	struct task_struct *p = dl_task_of(dl_se);
  	struct rq *rq = task_rq(p);
  
  	return &rq->dl;
  }
  
  static inline int on_dl_rq(struct sched_dl_entity *dl_se)
  {
  	return !RB_EMPTY_NODE(&dl_se->rb_node);
  }
  
  static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
  {
  	struct sched_dl_entity *dl_se = &p->dl;
  
  	return dl_rq->rb_leftmost == &dl_se->rb_node;
  }

  void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
  {
  	raw_spin_lock_init(&dl_b->dl_runtime_lock);
  	dl_b->dl_period = period;
  	dl_b->dl_runtime = runtime;
  }

  void init_dl_bw(struct dl_bw *dl_b)
  {
  	raw_spin_lock_init(&dl_b->lock);
  	raw_spin_lock(&def_dl_bandwidth.dl_runtime_lock);

  	if (global_rt_runtime() == RUNTIME_INF)

  		dl_b->bw = -1;
  	else

  		dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());

  	raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
  	dl_b->total_bw = 0;
  }

  void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
  {
  	dl_rq->rb_root = RB_ROOT;

  
  #ifdef CONFIG_SMP
  	/* zero means no -deadline tasks */
  	dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
  
  	dl_rq->dl_nr_migratory = 0;
  	dl_rq->overloaded = 0;
  	dl_rq->pushable_dl_tasks_root = RB_ROOT;

  #else
  	init_dl_bw(&dl_rq->dl_bw);

  #endif
  }
  
  #ifdef CONFIG_SMP
  
  static inline int dl_overloaded(struct rq *rq)
  {
  	return atomic_read(&rq->rd->dlo_count);
  }
  
  static inline void dl_set_overload(struct rq *rq)
  {
  	if (!rq->online)
  		return;
  
  	cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
  	/*
  	 * Must be visible before the overload count is
  	 * set (as in sched_rt.c).
  	 *
  	 * Matched by the barrier in pull_dl_task().
  	 */
  	smp_wmb();
  	atomic_inc(&rq->rd->dlo_count);
  }
  
  static inline void dl_clear_overload(struct rq *rq)
  {
  	if (!rq->online)
  		return;
  
  	atomic_dec(&rq->rd->dlo_count);
  	cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
  }
  
  static void update_dl_migration(struct dl_rq *dl_rq)
  {

  	if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_running > 1) {

  		if (!dl_rq->overloaded) {
  			dl_set_overload(rq_of_dl_rq(dl_rq));
  			dl_rq->overloaded = 1;
  		}
  	} else if (dl_rq->overloaded) {
  		dl_clear_overload(rq_of_dl_rq(dl_rq));
  		dl_rq->overloaded = 0;
  	}
  }
  
  static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
  {
  	struct task_struct *p = dl_task_of(dl_se);

  	if (p->nr_cpus_allowed > 1)
  		dl_rq->dl_nr_migratory++;
  
  	update_dl_migration(dl_rq);
  }
  
  static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
  {
  	struct task_struct *p = dl_task_of(dl_se);

  	if (p->nr_cpus_allowed > 1)
  		dl_rq->dl_nr_migratory--;
  
  	update_dl_migration(dl_rq);
  }
  
  /*
   * The list of pushable -deadline task is not a plist, like in
   * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
   */
  static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
  {
  	struct dl_rq *dl_rq = &rq->dl;
  	struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node;
  	struct rb_node *parent = NULL;
  	struct task_struct *entry;
  	int leftmost = 1;
  
  	BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
  
  	while (*link) {
  		parent = *link;
  		entry = rb_entry(parent, struct task_struct,
  				 pushable_dl_tasks);
  		if (dl_entity_preempt(&p->dl, &entry->dl))
  			link = &parent->rb_left;
  		else {
  			link = &parent->rb_right;
  			leftmost = 0;
  		}
  	}
  
  	if (leftmost)
  		dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;
  
  	rb_link_node(&p->pushable_dl_tasks, parent, link);
  	rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);

  }

  static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
  {
  	struct dl_rq *dl_rq = &rq->dl;
  
  	if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
  		return;
  
  	if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
  		struct rb_node *next_node;
  
  		next_node = rb_next(&p->pushable_dl_tasks);
  		dl_rq->pushable_dl_tasks_leftmost = next_node;
  	}
  
  	rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
  	RB_CLEAR_NODE(&p->pushable_dl_tasks);
  }
  
  static inline int has_pushable_dl_tasks(struct rq *rq)
  {
  	return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root);
  }
  
  static int push_dl_task(struct rq *rq);

  static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
  {
  	return dl_task(prev);
  }
  
  static inline void set_post_schedule(struct rq *rq)
  {
  	rq->post_schedule = has_pushable_dl_tasks(rq);
  }

  #else
  
  static inline
  void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
  {
  }
  
  static inline
  void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
  {
  }
  
  static inline
  void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
  {
  }
  
  static inline
  void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
  {
  }

  static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
  {
  	return false;
  }
  
  static inline int pull_dl_task(struct rq *rq)
  {
  	return 0;
  }
  
  static inline void set_post_schedule(struct rq *rq)
  {
  }

  #endif /* CONFIG_SMP */

  static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
  static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
  static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
  				  int flags);
  
  /*
   * We are being explicitly informed that a new instance is starting,
   * and this means that:
   *  - the absolute deadline of the entity has to be placed at
   *    current time + relative deadline;
   *  - the runtime of the entity has to be set to the maximum value.
   *
   * The capability of specifying such event is useful whenever a -deadline
   * entity wants to (try to!) synchronize its behaviour with the scheduler's
   * one, and to (try to!) reconcile itself with its own scheduling
   * parameters.
   */

  static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
  				       struct sched_dl_entity *pi_se)

  {
  	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
  	struct rq *rq = rq_of_dl_rq(dl_rq);
  
  	WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
  
  	/*
  	 * We use the regular wall clock time to set deadlines in the
  	 * future; in fact, we must consider execution overheads (time
  	 * spent on hardirq context, etc.).
  	 */

  	dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
  	dl_se->runtime = pi_se->dl_runtime;

  	dl_se->dl_new = 0;
  }
  
  /*
   * Pure Earliest Deadline First (EDF) scheduling does not deal with the
   * possibility of a entity lasting more than what it declared, and thus
   * exhausting its runtime.
   *
   * Here we are interested in making runtime overrun possible, but we do
   * not want a entity which is misbehaving to affect the scheduling of all
   * other entities.
   * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
   * is used, in order to confine each entity within its own bandwidth.
   *
   * This function deals exactly with that, and ensures that when the runtime
   * of a entity is replenished, its deadline is also postponed. That ensures
   * the overrunning entity can't interfere with other entity in the system and
   * can't make them miss their deadlines. Reasons why this kind of overruns
   * could happen are, typically, a entity voluntarily trying to overcome its
   * runtime, or it just underestimated it during sched_setscheduler_ex().
   */

  static void replenish_dl_entity(struct sched_dl_entity *dl_se,
  				struct sched_dl_entity *pi_se)

  {
  	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
  	struct rq *rq = rq_of_dl_rq(dl_rq);

  	BUG_ON(pi_se->dl_runtime <= 0);
  
  	/*
  	 * This could be the case for a !-dl task that is boosted.
  	 * Just go with full inherited parameters.
  	 */
  	if (dl_se->dl_deadline == 0) {
  		dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
  		dl_se->runtime = pi_se->dl_runtime;
  	}

  	/*
  	 * We keep moving the deadline away until we get some
  	 * available runtime for the entity. This ensures correct
  	 * handling of situations where the runtime overrun is
  	 * arbitrary large.
  	 */
  	while (dl_se->runtime <= 0) {

  		dl_se->deadline += pi_se->dl_period;
  		dl_se->runtime += pi_se->dl_runtime;

  	}
  
  	/*
  	 * At this point, the deadline really should be "in
  	 * the future" with respect to rq->clock. If it's
  	 * not, we are, for some reason, lagging too much!
  	 * Anyway, after having warn userspace abut that,
  	 * we still try to keep the things running by
  	 * resetting the deadline and the budget of the
  	 * entity.
  	 */
  	if (dl_time_before(dl_se->deadline, rq_clock(rq))) {

  		printk_deferred_once("sched: DL replenish lagged to much
  ");

  		dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
  		dl_se->runtime = pi_se->dl_runtime;

  	}
  }
  
  /*
   * Here we check if --at time t-- an entity (which is probably being
   * [re]activated or, in general, enqueued) can use its remaining runtime
   * and its current deadline _without_ exceeding the bandwidth it is
   * assigned (function returns true if it can't). We are in fact applying
   * one of the CBS rules: when a task wakes up, if the residual runtime
   * over residual deadline fits within the allocated bandwidth, then we
   * can keep the current (absolute) deadline and residual budget without
   * disrupting the schedulability of the system. Otherwise, we should
   * refill the runtime and set the deadline a period in the future,
   * because keeping the current (absolute) deadline of the task would

   * result in breaking guarantees promised to other tasks (refer to
   * Documentation/scheduler/sched-deadline.txt for more informations).

   *
   * This function returns true if:
   *

   *   runtime / (deadline - t) > dl_runtime / dl_period ,

   *
   * IOW we can't recycle current parameters.

   *
   * Notice that the bandwidth check is done against the period. For
   * task with deadline equal to period this is the same of using
   * dl_deadline instead of dl_period in the equation above.

   */

  static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
  			       struct sched_dl_entity *pi_se, u64 t)

  {
  	u64 left, right;
  
  	/*
  	 * left and right are the two sides of the equation above,
  	 * after a bit of shuffling to use multiplications instead
  	 * of divisions.
  	 *
  	 * Note that none of the time values involved in the two
  	 * multiplications are absolute: dl_deadline and dl_runtime
  	 * are the relative deadline and the maximum runtime of each
  	 * instance, runtime is the runtime left for the last instance
  	 * and (deadline - t), since t is rq->clock, is the time left
  	 * to the (absolute) deadline. Even if overflowing the u64 type
  	 * is very unlikely to occur in both cases, here we scale down
  	 * as we want to avoid that risk at all. Scaling down by 10
  	 * means that we reduce granularity to 1us. We are fine with it,
  	 * since this is only a true/false check and, anyway, thinking
  	 * of anything below microseconds resolution is actually fiction
  	 * (but still we want to give the user that illusion >;).
  	 */

  	left = (pi_se->dl_period >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
  	right = ((dl_se->deadline - t) >> DL_SCALE) *
  		(pi_se->dl_runtime >> DL_SCALE);

  
  	return dl_time_before(right, left);
  }
  
  /*
   * When a -deadline entity is queued back on the runqueue, its runtime and
   * deadline might need updating.
   *
   * The policy here is that we update the deadline of the entity only if:
   *  - the current deadline is in the past,
   *  - using the remaining runtime with the current deadline would make
   *    the entity exceed its bandwidth.
   */

  static void update_dl_entity(struct sched_dl_entity *dl_se,
  			     struct sched_dl_entity *pi_se)

  {
  	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
  	struct rq *rq = rq_of_dl_rq(dl_rq);
  
  	/*
  	 * The arrival of a new instance needs special treatment, i.e.,
  	 * the actual scheduling parameters have to be "renewed".
  	 */
  	if (dl_se->dl_new) {

  		setup_new_dl_entity(dl_se, pi_se);

  		return;
  	}
  
  	if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||

  	    dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
  		dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
  		dl_se->runtime = pi_se->dl_runtime;

  	}
  }
  
  /*
   * If the entity depleted all its runtime, and if we want it to sleep
   * while waiting for some new execution time to become available, we
   * set the bandwidth enforcement timer to the replenishment instant
   * and try to activate it.
   *
   * Notice that it is important for the caller to know if the timer
   * actually started or not (i.e., the replenishment instant is in
   * the future or in the past).
   */

  static int start_dl_timer(struct sched_dl_entity *dl_se, bool boosted)

  {
  	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
  	struct rq *rq = rq_of_dl_rq(dl_rq);
  	ktime_t now, act;
  	ktime_t soft, hard;
  	unsigned long range;
  	s64 delta;

  	if (boosted)
  		return 0;

  	/*
  	 * We want the timer to fire at the deadline, but considering
  	 * that it is actually coming from rq->clock and not from
  	 * hrtimer's time base reading.
  	 */
  	act = ns_to_ktime(dl_se->deadline);
  	now = hrtimer_cb_get_time(&dl_se->dl_timer);
  	delta = ktime_to_ns(now) - rq_clock(rq);
  	act = ktime_add_ns(act, delta);
  
  	/*
  	 * If the expiry time already passed, e.g., because the value
  	 * chosen as the deadline is too small, don't even try to
  	 * start the timer in the past!
  	 */
  	if (ktime_us_delta(act, now) < 0)
  		return 0;
  
  	hrtimer_set_expires(&dl_se->dl_timer, act);
  
  	soft = hrtimer_get_softexpires(&dl_se->dl_timer);
  	hard = hrtimer_get_expires(&dl_se->dl_timer);
  	range = ktime_to_ns(ktime_sub(hard, soft));
  	__hrtimer_start_range_ns(&dl_se->dl_timer, soft,
  				 range, HRTIMER_MODE_ABS, 0);
  
  	return hrtimer_active(&dl_se->dl_timer);
  }
  
  /*
   * This is the bandwidth enforcement timer callback. If here, we know
   * a task is not on its dl_rq, since the fact that the timer was running
   * means the task is throttled and needs a runtime replenishment.
   *
   * However, what we actually do depends on the fact the task is active,
   * (it is on its rq) or has been removed from there by a call to
   * dequeue_task_dl(). In the former case we must issue the runtime
   * replenishment and add the task back to the dl_rq; in the latter, we just
   * do nothing but clearing dl_throttled, so that runtime and deadline
   * updating (and the queueing back to dl_rq) will be done by the
   * next call to enqueue_task_dl().
   */
  static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
  {
  	struct sched_dl_entity *dl_se = container_of(timer,
  						     struct sched_dl_entity,
  						     dl_timer);
  	struct task_struct *p = dl_task_of(dl_se);

  	struct rq *rq;
  again:
  	rq = task_rq(p);

  	raw_spin_lock(&rq->lock);

  	if (rq != task_rq(p)) {
  		/* Task was moved, retrying. */
  		raw_spin_unlock(&rq->lock);
  		goto again;
  	}

  	/*
  	 * We need to take care of a possible races here. In fact, the
  	 * task might have changed its scheduling policy to something
  	 * different from SCHED_DEADLINE or changed its reservation

  	 * parameters (through sched_setattr()).

  	 */
  	if (!dl_task(p) || dl_se->dl_new)
  		goto unlock;
  
  	sched_clock_tick();
  	update_rq_clock(rq);
  	dl_se->dl_throttled = 0;

  	dl_se->dl_yielded = 0;

  	if (p->on_rq) {
  		enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
  		if (task_has_dl_policy(rq->curr))
  			check_preempt_curr_dl(rq, p, 0);
  		else
  			resched_task(rq->curr);

  #ifdef CONFIG_SMP
  		/*
  		 * Queueing this task back might have overloaded rq,
  		 * check if we need to kick someone away.
  		 */
  		if (has_pushable_dl_tasks(rq))
  			push_dl_task(rq);
  #endif

  	}
  unlock:
  	raw_spin_unlock(&rq->lock);
  
  	return HRTIMER_NORESTART;
  }
  
  void init_dl_task_timer(struct sched_dl_entity *dl_se)
  {
  	struct hrtimer *timer = &dl_se->dl_timer;
  
  	if (hrtimer_active(timer)) {
  		hrtimer_try_to_cancel(timer);
  		return;
  	}
  
  	hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  	timer->function = dl_task_timer;
  }
  
  static
  int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
  {
  	int dmiss = dl_time_before(dl_se->deadline, rq_clock(rq));
  	int rorun = dl_se->runtime <= 0;
  
  	if (!rorun && !dmiss)
  		return 0;
  
  	/*
  	 * If we are beyond our current deadline and we are still
  	 * executing, then we have already used some of the runtime of
  	 * the next instance. Thus, if we do not account that, we are
  	 * stealing bandwidth from the system at each deadline miss!
  	 */
  	if (dmiss) {
  		dl_se->runtime = rorun ? dl_se->runtime : 0;
  		dl_se->runtime -= rq_clock(rq) - dl_se->deadline;
  	}
  
  	return 1;
  }

  extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);

  /*
   * Update the current task's runtime statistics (provided it is still
   * a -deadline task and has not been removed from the dl_rq).
   */
  static void update_curr_dl(struct rq *rq)
  {
  	struct task_struct *curr = rq->curr;
  	struct sched_dl_entity *dl_se = &curr->dl;
  	u64 delta_exec;
  
  	if (!dl_task(curr) || !on_dl_rq(dl_se))
  		return;
  
  	/*
  	 * Consumed budget is computed considering the time as
  	 * observed by schedulable tasks (excluding time spent
  	 * in hardirq context, etc.). Deadlines are instead
  	 * computed using hard walltime. This seems to be the more
  	 * natural solution, but the full ramifications of this
  	 * approach need further study.
  	 */
  	delta_exec = rq_clock_task(rq) - curr->se.exec_start;

  	if (unlikely((s64)delta_exec <= 0))
  		return;

  
  	schedstat_set(curr->se.statistics.exec_max,
  		      max(curr->se.statistics.exec_max, delta_exec));
  
  	curr->se.sum_exec_runtime += delta_exec;
  	account_group_exec_runtime(curr, delta_exec);
  
  	curr->se.exec_start = rq_clock_task(rq);
  	cpuacct_charge(curr, delta_exec);

  	sched_rt_avg_update(rq, delta_exec);

  	dl_se->runtime -= delta_exec;
  	if (dl_runtime_exceeded(rq, dl_se)) {
  		__dequeue_task_dl(rq, curr, 0);

  		if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))

  			dl_se->dl_throttled = 1;
  		else
  			enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
  
  		if (!is_leftmost(curr, &rq->dl))
  			resched_task(curr);
  	}

  
  	/*
  	 * Because -- for now -- we share the rt bandwidth, we need to
  	 * account our runtime there too, otherwise actual rt tasks
  	 * would be able to exceed the shared quota.
  	 *
  	 * Account to the root rt group for now.
  	 *
  	 * The solution we're working towards is having the RT groups scheduled
  	 * using deadline servers -- however there's a few nasties to figure
  	 * out before that can happen.
  	 */
  	if (rt_bandwidth_enabled()) {
  		struct rt_rq *rt_rq = &rq->rt;
  
  		raw_spin_lock(&rt_rq->rt_runtime_lock);

  		/*
  		 * We'll let actual RT tasks worry about the overflow here, we

  		 * have our own CBS to keep us inline; only account when RT
  		 * bandwidth is relevant.

  		 */

  		if (sched_rt_bandwidth_account(rt_rq))
  			rt_rq->rt_time += delta_exec;

  		raw_spin_unlock(&rt_rq->rt_runtime_lock);
  	}

  }

  #ifdef CONFIG_SMP
  
  static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu);
  
  static inline u64 next_deadline(struct rq *rq)
  {
  	struct task_struct *next = pick_next_earliest_dl_task(rq, rq->cpu);
  
  	if (next && dl_prio(next->prio))
  		return next->dl.deadline;
  	else
  		return 0;
  }
  
  static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
  {
  	struct rq *rq = rq_of_dl_rq(dl_rq);
  
  	if (dl_rq->earliest_dl.curr == 0 ||
  	    dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
  		/*
  		 * If the dl_rq had no -deadline tasks, or if the new task
  		 * has shorter deadline than the current one on dl_rq, we
  		 * know that the previous earliest becomes our next earliest,
  		 * as the new task becomes the earliest itself.
  		 */
  		dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr;
  		dl_rq->earliest_dl.curr = deadline;

  		cpudl_set(&rq->rd->cpudl, rq->cpu, deadline, 1);

  	} else if (dl_rq->earliest_dl.next == 0 ||
  		   dl_time_before(deadline, dl_rq->earliest_dl.next)) {
  		/*
  		 * On the other hand, if the new -deadline task has a
  		 * a later deadline than the earliest one on dl_rq, but
  		 * it is earlier than the next (if any), we must
  		 * recompute the next-earliest.
  		 */
  		dl_rq->earliest_dl.next = next_deadline(rq);
  	}
  }
  
  static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
  {
  	struct rq *rq = rq_of_dl_rq(dl_rq);
  
  	/*
  	 * Since we may have removed our earliest (and/or next earliest)
  	 * task we must recompute them.
  	 */
  	if (!dl_rq->dl_nr_running) {
  		dl_rq->earliest_dl.curr = 0;
  		dl_rq->earliest_dl.next = 0;

  		cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);

  	} else {
  		struct rb_node *leftmost = dl_rq->rb_leftmost;
  		struct sched_dl_entity *entry;
  
  		entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
  		dl_rq->earliest_dl.curr = entry->deadline;
  		dl_rq->earliest_dl.next = next_deadline(rq);

  		cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline, 1);

  	}
  }
  
  #else
  
  static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
  static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
  
  #endif /* CONFIG_SMP */
  
  static inline
  void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
  {
  	int prio = dl_task_of(dl_se)->prio;
  	u64 deadline = dl_se->deadline;
  
  	WARN_ON(!dl_prio(prio));
  	dl_rq->dl_nr_running++;

  	add_nr_running(rq_of_dl_rq(dl_rq), 1);

  
  	inc_dl_deadline(dl_rq, deadline);
  	inc_dl_migration(dl_se, dl_rq);
  }
  
  static inline
  void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
  {
  	int prio = dl_task_of(dl_se)->prio;
  
  	WARN_ON(!dl_prio(prio));
  	WARN_ON(!dl_rq->dl_nr_running);
  	dl_rq->dl_nr_running--;

  	sub_nr_running(rq_of_dl_rq(dl_rq), 1);

  
  	dec_dl_deadline(dl_rq, dl_se->deadline);
  	dec_dl_migration(dl_se, dl_rq);
  }

  static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
  {
  	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
  	struct rb_node **link = &dl_rq->rb_root.rb_node;
  	struct rb_node *parent = NULL;
  	struct sched_dl_entity *entry;
  	int leftmost = 1;
  
  	BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
  
  	while (*link) {
  		parent = *link;
  		entry = rb_entry(parent, struct sched_dl_entity, rb_node);
  		if (dl_time_before(dl_se->deadline, entry->deadline))
  			link = &parent->rb_left;
  		else {
  			link = &parent->rb_right;
  			leftmost = 0;
  		}
  	}
  
  	if (leftmost)
  		dl_rq->rb_leftmost = &dl_se->rb_node;
  
  	rb_link_node(&dl_se->rb_node, parent, link);
  	rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);

  	inc_dl_tasks(dl_se, dl_rq);

  }
  
  static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
  {
  	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
  
  	if (RB_EMPTY_NODE(&dl_se->rb_node))
  		return;
  
  	if (dl_rq->rb_leftmost == &dl_se->rb_node) {
  		struct rb_node *next_node;
  
  		next_node = rb_next(&dl_se->rb_node);
  		dl_rq->rb_leftmost = next_node;
  	}
  
  	rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
  	RB_CLEAR_NODE(&dl_se->rb_node);

  	dec_dl_tasks(dl_se, dl_rq);

  }
  
  static void

  enqueue_dl_entity(struct sched_dl_entity *dl_se,
  		  struct sched_dl_entity *pi_se, int flags)

  {
  	BUG_ON(on_dl_rq(dl_se));
  
  	/*
  	 * If this is a wakeup or a new instance, the scheduling
  	 * parameters of the task might need updating. Otherwise,
  	 * we want a replenishment of its runtime.
  	 */
  	if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH)

  		replenish_dl_entity(dl_se, pi_se);

  	else

  		update_dl_entity(dl_se, pi_se);

  
  	__enqueue_dl_entity(dl_se);
  }
  
  static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
  {
  	__dequeue_dl_entity(dl_se);
  }
  
  static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
  {

  	struct task_struct *pi_task = rt_mutex_get_top_task(p);
  	struct sched_dl_entity *pi_se = &p->dl;
  
  	/*
  	 * Use the scheduling parameters of the top pi-waiter
  	 * task if we have one and its (relative) deadline is
  	 * smaller than our one... OTW we keep our runtime and
  	 * deadline.
  	 */
  	if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio))
  		pi_se = &pi_task->dl;

  	/*
  	 * If p is throttled, we do nothing. In fact, if it exhausted
  	 * its budget it needs a replenishment and, since it now is on
  	 * its rq, the bandwidth timer callback (which clearly has not
  	 * run yet) will take care of this.
  	 */
  	if (p->dl.dl_throttled)
  		return;

  	enqueue_dl_entity(&p->dl, pi_se, flags);

  
  	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
  		enqueue_pushable_dl_task(rq, p);

  }
  
  static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
  {
  	dequeue_dl_entity(&p->dl);

  	dequeue_pushable_dl_task(rq, p);

  }
  
  static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
  {
  	update_curr_dl(rq);
  	__dequeue_task_dl(rq, p, flags);

  }
  
  /*
   * Yield task semantic for -deadline tasks is:
   *
   *   get off from the CPU until our next instance, with
   *   a new runtime. This is of little use now, since we
   *   don't have a bandwidth reclaiming mechanism. Anyway,
   *   bandwidth reclaiming is planned for the future, and
   *   yield_task_dl will indicate that some spare budget
   *   is available for other task instances to use it.
   */
  static void yield_task_dl(struct rq *rq)
  {
  	struct task_struct *p = rq->curr;
  
  	/*
  	 * We make the task go to sleep until its current deadline by
  	 * forcing its runtime to zero. This way, update_curr_dl() stops
  	 * it and the bandwidth timer will wake it up and will give it

  	 * new scheduling parameters (thanks to dl_yielded=1).

  	 */
  	if (p->dl.runtime > 0) {

  		rq->curr->dl.dl_yielded = 1;

  		p->dl.runtime = 0;
  	}
  	update_curr_dl(rq);
  }

  #ifdef CONFIG_SMP
  
  static int find_later_rq(struct task_struct *task);

  
  static int
  select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
  {
  	struct task_struct *curr;
  	struct rq *rq;
  
  	if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
  		goto out;
  
  	rq = cpu_rq(cpu);
  
  	rcu_read_lock();
  	curr = ACCESS_ONCE(rq->curr); /* unlocked access */
  
  	/*
  	 * If we are dealing with a -deadline task, we must
  	 * decide where to wake it up.
  	 * If it has a later deadline and the current task
  	 * on this rq can't move (provided the waking task
  	 * can!) we prefer to send it somewhere else. On the
  	 * other hand, if it has a shorter deadline, we
  	 * try to make it stay here, it might be important.
  	 */
  	if (unlikely(dl_task(curr)) &&
  	    (curr->nr_cpus_allowed < 2 ||
  	     !dl_entity_preempt(&p->dl, &curr->dl)) &&
  	    (p->nr_cpus_allowed > 1)) {
  		int target = find_later_rq(p);
  
  		if (target != -1)
  			cpu = target;
  	}
  	rcu_read_unlock();
  
  out:
  	return cpu;
  }
  
  static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
  {
  	/*
  	 * Current can't be migrated, useless to reschedule,
  	 * let's hope p can move out.
  	 */
  	if (rq->curr->nr_cpus_allowed == 1 ||

  	    cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)

  		return;
  
  	/*
  	 * p is migratable, so let's not schedule it and
  	 * see if it is pushed or pulled somewhere else.
  	 */
  	if (p->nr_cpus_allowed != 1 &&

  	    cpudl_find(&rq->rd->cpudl, p, NULL) != -1)

  		return;
  
  	resched_task(rq->curr);
  }

  static int pull_dl_task(struct rq *this_rq);

  #endif /* CONFIG_SMP */

  /*
   * Only called when both the current and waking task are -deadline
   * tasks.
   */
  static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
  				  int flags)
  {

  	if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {

  		resched_task(rq->curr);

  		return;
  	}
  
  #ifdef CONFIG_SMP
  	/*
  	 * In the unlikely case current and p have the same deadline
  	 * let us try to decide what's the best thing to do...
  	 */

  	if ((p->dl.deadline == rq->curr->dl.deadline) &&
  	    !test_tsk_need_resched(rq->curr))

  		check_preempt_equal_dl(rq, p);
  #endif /* CONFIG_SMP */

  }
  
  #ifdef CONFIG_SCHED_HRTICK
  static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
  {
  	s64 delta = p->dl.dl_runtime - p->dl.runtime;
  
  	if (delta > 10000)
  		hrtick_start(rq, p->dl.runtime);
  }
  #endif
  
  static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
  						   struct dl_rq *dl_rq)
  {
  	struct rb_node *left = dl_rq->rb_leftmost;
  
  	if (!left)
  		return NULL;
  
  	return rb_entry(left, struct sched_dl_entity, rb_node);
  }

  struct task_struct *pick_next_task_dl(struct rq *rq, struct task_struct *prev)

  {
  	struct sched_dl_entity *dl_se;
  	struct task_struct *p;
  	struct dl_rq *dl_rq;
  
  	dl_rq = &rq->dl;

  	if (need_pull_dl_task(rq, prev)) {

  		pull_dl_task(rq);

  		/*
  		 * pull_rt_task() can drop (and re-acquire) rq->lock; this
  		 * means a stop task can slip in, in which case we need to
  		 * re-start task selection.
  		 */
  		if (rq->stop && rq->stop->on_rq)
  			return RETRY_TASK;
  	}

  	/*
  	 * When prev is DL, we may throttle it in put_prev_task().
  	 * So, we update time before we check for dl_nr_running.
  	 */
  	if (prev->sched_class == &dl_sched_class)
  		update_curr_dl(rq);

  	if (unlikely(!dl_rq->dl_nr_running))
  		return NULL;

  	put_prev_task(rq, prev);

  	dl_se = pick_next_dl_entity(rq, dl_rq);
  	BUG_ON(!dl_se);
  
  	p = dl_task_of(dl_se);
  	p->se.exec_start = rq_clock_task(rq);

  
  	/* Running task will never be pushed. */

         dequeue_pushable_dl_task(rq, p);

  #ifdef CONFIG_SCHED_HRTICK
  	if (hrtick_enabled(rq))
  		start_hrtick_dl(rq, p);
  #endif

  	set_post_schedule(rq);

  	return p;
  }
  
  static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
  {
  	update_curr_dl(rq);

  
  	if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
  		enqueue_pushable_dl_task(rq, p);

  }
  
  static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
  {
  	update_curr_dl(rq);
  
  #ifdef CONFIG_SCHED_HRTICK
  	if (hrtick_enabled(rq) && queued && p->dl.runtime > 0)
  		start_hrtick_dl(rq, p);
  #endif
  }
  
  static void task_fork_dl(struct task_struct *p)
  {
  	/*
  	 * SCHED_DEADLINE tasks cannot fork and this is achieved through
  	 * sched_fork()
  	 */
  }
  
  static void task_dead_dl(struct task_struct *p)
  {
  	struct hrtimer *timer = &p->dl.dl_timer;

  	struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
  
  	/*
  	 * Since we are TASK_DEAD we won't slip out of the domain!
  	 */
  	raw_spin_lock_irq(&dl_b->lock);
  	dl_b->total_bw -= p->dl.dl_bw;
  	raw_spin_unlock_irq(&dl_b->lock);

  	hrtimer_cancel(timer);

  }
  
  static void set_curr_task_dl(struct rq *rq)
  {
  	struct task_struct *p = rq->curr;
  
  	p->se.exec_start = rq_clock_task(rq);

  
  	/* You can't push away the running task */
  	dequeue_pushable_dl_task(rq, p);
  }
  
  #ifdef CONFIG_SMP
  
  /* Only try algorithms three times */
  #define DL_MAX_TRIES 3
  
  static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
  {
  	if (!task_running(rq, p) &&
  	    (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
  	    (p->nr_cpus_allowed > 1))
  		return 1;
  
  	return 0;
  }
  
  /* Returns the second earliest -deadline task, NULL otherwise */
  static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu)
  {
  	struct rb_node *next_node = rq->dl.rb_leftmost;
  	struct sched_dl_entity *dl_se;
  	struct task_struct *p = NULL;
  
  next_node:
  	next_node = rb_next(next_node);
  	if (next_node) {
  		dl_se = rb_entry(next_node, struct sched_dl_entity, rb_node);
  		p = dl_task_of(dl_se);
  
  		if (pick_dl_task(rq, p, cpu))
  			return p;
  
  		goto next_node;
  	}
  
  	return NULL;
  }

  static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
  
  static int find_later_rq(struct task_struct *task)
  {
  	struct sched_domain *sd;
  	struct cpumask *later_mask = __get_cpu_var(local_cpu_mask_dl);
  	int this_cpu = smp_processor_id();
  	int best_cpu, cpu = task_cpu(task);
  
  	/* Make sure the mask is initialized first */
  	if (unlikely(!later_mask))
  		return -1;
  
  	if (task->nr_cpus_allowed == 1)
  		return -1;

  	best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
  			task, later_mask);

  	if (best_cpu == -1)
  		return -1;
  
  	/*
  	 * If we are here, some target has been found,
  	 * the most suitable of which is cached in best_cpu.
  	 * This is, among the runqueues where the current tasks
  	 * have later deadlines than the task's one, the rq
  	 * with the latest possible one.
  	 *
  	 * Now we check how well this matches with task's
  	 * affinity and system topology.
  	 *
  	 * The last cpu where the task run is our first
  	 * guess, since it is most likely cache-hot there.
  	 */
  	if (cpumask_test_cpu(cpu, later_mask))
  		return cpu;
  	/*
  	 * Check if this_cpu is to be skipped (i.e., it is
  	 * not in the mask) or not.
  	 */
  	if (!cpumask_test_cpu(this_cpu, later_mask))
  		this_cpu = -1;
  
  	rcu_read_lock();
  	for_each_domain(cpu, sd) {
  		if (sd->flags & SD_WAKE_AFFINE) {
  
  			/*
  			 * If possible, preempting this_cpu is
  			 * cheaper than migrating.
  			 */
  			if (this_cpu != -1 &&
  			    cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
  				rcu_read_unlock();
  				return this_cpu;
  			}
  
  			/*
  			 * Last chance: if best_cpu is valid and is
  			 * in the mask, that becomes our choice.
  			 */
  			if (best_cpu < nr_cpu_ids &&
  			    cpumask_test_cpu(best_cpu, sched_domain_span(sd))) {
  				rcu_read_unlock();
  				return best_cpu;
  			}
  		}
  	}
  	rcu_read_unlock();
  
  	/*
  	 * At this point, all our guesses failed, we just return
  	 * 'something', and let the caller sort the things out.
  	 */
  	if (this_cpu != -1)
  		return this_cpu;
  
  	cpu = cpumask_any(later_mask);
  	if (cpu < nr_cpu_ids)
  		return cpu;
  
  	return -1;
  }
  
  /* Locks the rq it finds */
  static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
  {
  	struct rq *later_rq = NULL;
  	int tries;
  	int cpu;
  
  	for (tries = 0; tries < DL_MAX_TRIES; tries++) {
  		cpu = find_later_rq(task);
  
  		if ((cpu == -1) || (cpu == rq->cpu))
  			break;
  
  		later_rq = cpu_rq(cpu);
  
  		/* Retry if something changed. */
  		if (double_lock_balance(rq, later_rq)) {
  			if (unlikely(task_rq(task) != rq ||
  				     !cpumask_test_cpu(later_rq->cpu,
  				                       &task->cpus_allowed) ||
  				     task_running(rq, task) || !task->on_rq)) {
  				double_unlock_balance(rq, later_rq);
  				later_rq = NULL;
  				break;
  			}
  		}
  
  		/*
  		 * If the rq we found has no -deadline task, or
  		 * its earliest one has a later deadline than our
  		 * task, the rq is a good one.
  		 */
  		if (!later_rq->dl.dl_nr_running ||
  		    dl_time_before(task->dl.deadline,
  				   later_rq->dl.earliest_dl.curr))
  			break;
  
  		/* Otherwise we try again. */
  		double_unlock_balance(rq, later_rq);
  		later_rq = NULL;
  	}
  
  	return later_rq;
  }
  
  static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
  {
  	struct task_struct *p;
  
  	if (!has_pushable_dl_tasks(rq))
  		return NULL;
  
  	p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
  		     struct task_struct, pushable_dl_tasks);
  
  	BUG_ON(rq->cpu != task_cpu(p));
  	BUG_ON(task_current(rq, p));
  	BUG_ON(p->nr_cpus_allowed <= 1);

  	BUG_ON(!p->on_rq);

  	BUG_ON(!dl_task(p));
  
  	return p;
  }
  
  /*
   * See if the non running -deadline tasks on this rq
   * can be sent to some other CPU where they can preempt
   * and start executing.
   */
  static int push_dl_task(struct rq *rq)
  {
  	struct task_struct *next_task;
  	struct rq *later_rq;
  
  	if (!rq->dl.overloaded)
  		return 0;
  
  	next_task = pick_next_pushable_dl_task(rq);
  	if (!next_task)
  		return 0;
  
  retry:
  	if (unlikely(next_task == rq->curr)) {
  		WARN_ON(1);
  		return 0;
  	}
  
  	/*
  	 * If next_task preempts rq->curr, and rq->curr
  	 * can move away, it makes sense to just reschedule
  	 * without going further in pushing next_task.
  	 */
  	if (dl_task(rq->curr) &&
  	    dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
  	    rq->curr->nr_cpus_allowed > 1) {
  		resched_task(rq->curr);
  		return 0;
  	}
  
  	/* We might release rq lock */
  	get_task_struct(next_task);
  
  	/* Will lock the rq it'll find */
  	later_rq = find_lock_later_rq(next_task, rq);
  	if (!later_rq) {
  		struct task_struct *task;
  
  		/*
  		 * We must check all this again, since
  		 * find_lock_later_rq releases rq->lock and it is
  		 * then possible that next_task has migrated.
  		 */
  		task = pick_next_pushable_dl_task(rq);
  		if (task_cpu(next_task) == rq->cpu && task == next_task) {
  			/*
  			 * The task is still there. We don't try
  			 * again, some other cpu will pull it when ready.
  			 */
  			dequeue_pushable_dl_task(rq, next_task);
  			goto out;
  		}
  
  		if (!task)
  			/* No more tasks */
  			goto out;
  
  		put_task_struct(next_task);
  		next_task = task;
  		goto retry;
  	}
  
  	deactivate_task(rq, next_task, 0);
  	set_task_cpu(next_task, later_rq->cpu);
  	activate_task(later_rq, next_task, 0);
  
  	resched_task(later_rq->curr);
  
  	double_unlock_balance(rq, later_rq);
  
  out:
  	put_task_struct(next_task);
  
  	return 1;
  }
  
  static void push_dl_tasks(struct rq *rq)
  {
  	/* Terminates as it moves a -deadline task */
  	while (push_dl_task(rq))
  		;

  }

  static int pull_dl_task(struct rq *this_rq)
  {
  	int this_cpu = this_rq->cpu, ret = 0, cpu;
  	struct task_struct *p;
  	struct rq *src_rq;
  	u64 dmin = LONG_MAX;
  
  	if (likely(!dl_overloaded(this_rq)))
  		return 0;
  
  	/*
  	 * Match the barrier from dl_set_overloaded; this guarantees that if we
  	 * see overloaded we must also see the dlo_mask bit.
  	 */
  	smp_rmb();
  
  	for_each_cpu(cpu, this_rq->rd->dlo_mask) {
  		if (this_cpu == cpu)
  			continue;
  
  		src_rq = cpu_rq(cpu);
  
  		/*
  		 * It looks racy, abd it is! However, as in sched_rt.c,
  		 * we are fine with this.
  		 */
  		if (this_rq->dl.dl_nr_running &&
  		    dl_time_before(this_rq->dl.earliest_dl.curr,
  				   src_rq->dl.earliest_dl.next))
  			continue;
  
  		/* Might drop this_rq->lock */
  		double_lock_balance(this_rq, src_rq);
  
  		/*
  		 * If there are no more pullable tasks on the
  		 * rq, we're done with it.
  		 */
  		if (src_rq->dl.dl_nr_running <= 1)
  			goto skip;
  
  		p = pick_next_earliest_dl_task(src_rq, this_cpu);
  
  		/*
  		 * We found a task to be pulled if:
  		 *  - it preempts our current (if there's one),
  		 *  - it will preempt the last one we pulled (if any).
  		 */
  		if (p && dl_time_before(p->dl.deadline, dmin) &&
  		    (!this_rq->dl.dl_nr_running ||
  		     dl_time_before(p->dl.deadline,
  				    this_rq->dl.earliest_dl.curr))) {
  			WARN_ON(p == src_rq->curr);

  			WARN_ON(!p->on_rq);

  
  			/*
  			 * Then we pull iff p has actually an earlier
  			 * deadline than the current task of its runqueue.
  			 */
  			if (dl_time_before(p->dl.deadline,
  					   src_rq->curr->dl.deadline))
  				goto skip;
  
  			ret = 1;
  
  			deactivate_task(src_rq, p, 0);
  			set_task_cpu(p, this_cpu);
  			activate_task(this_rq, p, 0);
  			dmin = p->dl.deadline;
  
  			/* Is there any other task even earlier? */
  		}
  skip:
  		double_unlock_balance(this_rq, src_rq);
  	}
  
  	return ret;
  }

  static void post_schedule_dl(struct rq *rq)
  {
  	push_dl_tasks(rq);
  }
  
  /*
   * Since the task is not running and a reschedule is not going to happen
   * anytime soon on its runqueue, we try pushing it away now.
   */
  static void task_woken_dl(struct rq *rq, struct task_struct *p)
  {
  	if (!task_running(rq, p) &&
  	    !test_tsk_need_resched(rq->curr) &&
  	    has_pushable_dl_tasks(rq) &&
  	    p->nr_cpus_allowed > 1 &&
  	    dl_task(rq->curr) &&
  	    (rq->curr->nr_cpus_allowed < 2 ||
  	     dl_entity_preempt(&rq->curr->dl, &p->dl))) {
  		push_dl_tasks(rq);
  	}
  }
  
  static void set_cpus_allowed_dl(struct task_struct *p,
  				const struct cpumask *new_mask)
  {
  	struct rq *rq;
  	int weight;
  
  	BUG_ON(!dl_task(p));
  
  	/*
  	 * Update only if the task is actually running (i.e.,
  	 * it is on the rq AND it is not throttled).
  	 */
  	if (!on_dl_rq(&p->dl))
  		return;
  
  	weight = cpumask_weight(new_mask);
  
  	/*
  	 * Only update if the process changes its state from whether it
  	 * can migrate or not.
  	 */
  	if ((p->nr_cpus_allowed > 1) == (weight > 1))
  		return;
  
  	rq = task_rq(p);
  
  	/*
  	 * The process used to be able to migrate OR it can now migrate
  	 */
  	if (weight <= 1) {
  		if (!task_current(rq, p))
  			dequeue_pushable_dl_task(rq, p);
  		BUG_ON(!rq->dl.dl_nr_migratory);
  		rq->dl.dl_nr_migratory--;
  	} else {
  		if (!task_current(rq, p))
  			enqueue_pushable_dl_task(rq, p);
  		rq->dl.dl_nr_migratory++;
  	}
  
  	update_dl_migration(&rq->dl);
  }
  
  /* Assumes rq->lock is held */
  static void rq_online_dl(struct rq *rq)
  {
  	if (rq->dl.overloaded)
  		dl_set_overload(rq);

  
  	if (rq->dl.dl_nr_running > 0)
  		cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr, 1);

  }
  
  /* Assumes rq->lock is held */
  static void rq_offline_dl(struct rq *rq)
  {
  	if (rq->dl.overloaded)
  		dl_clear_overload(rq);

  
  	cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);

  }
  
  void init_sched_dl_class(void)
  {
  	unsigned int i;
  
  	for_each_possible_cpu(i)
  		zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
  					GFP_KERNEL, cpu_to_node(i));
  }
  
  #endif /* CONFIG_SMP */

  static void switched_from_dl(struct rq *rq, struct task_struct *p)
  {

  	if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy))

  		hrtimer_try_to_cancel(&p->dl.dl_timer);

  
  #ifdef CONFIG_SMP
  	/*
  	 * Since this might be the only -deadline task on the rq,
  	 * this is the right place to try to pull some other one
  	 * from an overloaded cpu, if any.
  	 */
  	if (!rq->dl.dl_nr_running)
  		pull_dl_task(rq);
  #endif

  }

  /*
   * When switching to -deadline, we may overload the rq, then
   * we try to push someone off, if possible.
   */

  static void switched_to_dl(struct rq *rq, struct task_struct *p)
  {

  	int check_resched = 1;

  	/*
  	 * If p is throttled, don't consider the possibility
  	 * of preempting rq->curr, the check will be done right
  	 * after its runtime will get replenished.
  	 */
  	if (unlikely(p->dl.dl_throttled))
  		return;

  	if (p->on_rq && rq->curr != p) {

  #ifdef CONFIG_SMP
  		if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
  			/* Only reschedule if pushing failed */
  			check_resched = 0;
  #endif /* CONFIG_SMP */
  		if (check_resched && task_has_dl_policy(rq->curr))

  			check_preempt_curr_dl(rq, p, 0);

  	}
  }

  /*
   * If the scheduling parameters of a -deadline task changed,
   * a push or pull operation might be needed.
   */

  static void prio_changed_dl(struct rq *rq, struct task_struct *p,
  			    int oldprio)
  {

  	if (p->on_rq || rq->curr == p) {

  #ifdef CONFIG_SMP

  		/*
  		 * This might be too much, but unfortunately
  		 * we don't have the old deadline value, and
  		 * we can't argue if the task is increasing
  		 * or lowering its prio, so...
  		 */
  		if (!rq->dl.overloaded)
  			pull_dl_task(rq);
  
  		/*
  		 * If we now have a earlier deadline task than p,
  		 * then reschedule, provided p is still on this
  		 * runqueue.
  		 */
  		if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline) &&
  		    rq->curr == p)
  			resched_task(p);
  #else
  		/*
  		 * Again, we don't know if p has a earlier
  		 * or later deadline, so let's blindly set a
  		 * (maybe not needed) rescheduling point.
  		 */
  		resched_task(p);
  #endif /* CONFIG_SMP */
  	} else
  		switched_to_dl(rq, p);

  }

  
  const struct sched_class dl_sched_class = {
  	.next			= &rt_sched_class,
  	.enqueue_task		= enqueue_task_dl,
  	.dequeue_task		= dequeue_task_dl,
  	.yield_task		= yield_task_dl,
  
  	.check_preempt_curr	= check_preempt_curr_dl,
  
  	.pick_next_task		= pick_next_task_dl,
  	.put_prev_task		= put_prev_task_dl,
  
  #ifdef CONFIG_SMP
  	.select_task_rq		= select_task_rq_dl,

  	.set_cpus_allowed       = set_cpus_allowed_dl,
  	.rq_online              = rq_online_dl,
  	.rq_offline             = rq_offline_dl,

  	.post_schedule		= post_schedule_dl,
  	.task_woken		= task_woken_dl,

  #endif
  
  	.set_curr_task		= set_curr_task_dl,
  	.task_tick		= task_tick_dl,
  	.task_fork              = task_fork_dl,
  	.task_dead		= task_dead_dl,
  
  	.prio_changed           = prio_changed_dl,
  	.switched_from		= switched_from_dl,
  	.switched_to		= switched_to_dl,
  };