// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  kernel/sched/cpudl.c
   *
   *  Global CPU deadline management
   *
   *  Author: Juri Lelli <j.lelli@sssup.it>

   */

  #include "sched.h"

  
  static inline int parent(int i)
  {
  	return (i - 1) >> 1;
  }
  
  static inline int left_child(int i)
  {
  	return (i << 1) + 1;
  }
  
  static inline int right_child(int i)
  {
  	return (i << 1) + 2;
  }

  static void cpudl_heapify_down(struct cpudl *cp, int idx)

  {
  	int l, r, largest;

  	int orig_cpu = cp->elements[idx].cpu;
  	u64 orig_dl = cp->elements[idx].dl;
  
  	if (left_child(idx) >= cp->size)
  		return;

  	/* adapted from lib/prio_heap.c */

  	while (1) {

  		u64 largest_dl;

  		l = left_child(idx);
  		r = right_child(idx);
  		largest = idx;

  		largest_dl = orig_dl;

  		if ((l < cp->size) && dl_time_before(orig_dl,
  						cp->elements[l].dl)) {

  			largest = l;

  			largest_dl = cp->elements[l].dl;
  		}
  		if ((r < cp->size) && dl_time_before(largest_dl,
  						cp->elements[r].dl))

  			largest = r;

  		if (largest == idx)
  			break;

  		/* pull largest child onto idx */
  		cp->elements[idx].cpu = cp->elements[largest].cpu;
  		cp->elements[idx].dl = cp->elements[largest].dl;
  		cp->elements[cp->elements[idx].cpu].idx = idx;

  		idx = largest;
  	}

  	/* actual push down of saved original values orig_* */
  	cp->elements[idx].cpu = orig_cpu;
  	cp->elements[idx].dl = orig_dl;
  	cp->elements[cp->elements[idx].cpu].idx = idx;

  }

  static void cpudl_heapify_up(struct cpudl *cp, int idx)

  {

  	int p;
  
  	int orig_cpu = cp->elements[idx].cpu;
  	u64 orig_dl = cp->elements[idx].dl;
  
  	if (idx == 0)
  		return;
  
  	do {
  		p = parent(idx);
  		if (dl_time_before(orig_dl, cp->elements[p].dl))
  			break;
  		/* pull parent onto idx */
  		cp->elements[idx].cpu = cp->elements[p].cpu;
  		cp->elements[idx].dl = cp->elements[p].dl;
  		cp->elements[cp->elements[idx].cpu].idx = idx;
  		idx = p;
  	} while (idx != 0);
  	/* actual push up of saved original values orig_* */
  	cp->elements[idx].cpu = orig_cpu;
  	cp->elements[idx].dl = orig_dl;
  	cp->elements[cp->elements[idx].cpu].idx = idx;

  }

  static void cpudl_heapify(struct cpudl *cp, int idx)
  {
  	if (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
  				cp->elements[idx].dl))
  		cpudl_heapify_up(cp, idx);
  	else
  		cpudl_heapify_down(cp, idx);
  }

  static inline int cpudl_maximum(struct cpudl *cp)
  {
  	return cp->elements[0].cpu;
  }
  
  /*
   * cpudl_find - find the best (later-dl) CPU in the system
   * @cp: the cpudl max-heap context
   * @p: the task
   * @later_mask: a mask to fill in with the selected CPUs (or NULL)
   *

   * Returns: int - CPUs were found

   */
  int cpudl_find(struct cpudl *cp, struct task_struct *p,
  	       struct cpumask *later_mask)
  {

  	const struct sched_dl_entity *dl_se = &p->dl;

  	if (later_mask &&

  	    cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr)) {

  		return 1;
  	} else {
  		int best_cpu = cpudl_maximum(cp);

  		WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));

  		if (cpumask_test_cpu(best_cpu, p->cpus_ptr) &&

  		    dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
  			if (later_mask)
  				cpumask_set_cpu(best_cpu, later_mask);

  			return 1;
  		}
  	}
  	return 0;

  }
  
  /*

   * cpudl_clear - remove a CPU from the cpudl max-heap

   * @cp: the cpudl max-heap context

   * @cpu: the target CPU

   *
   * Notes: assumes cpu_rq(cpu)->lock is locked
   *
   * Returns: (void)
   */

  void cpudl_clear(struct cpudl *cp, int cpu)

  {
  	int old_idx, new_cpu;
  	unsigned long flags;

  	WARN_ON(!cpu_present(cpu));

  
  	raw_spin_lock_irqsave(&cp->lock, flags);

  	old_idx = cp->elements[cpu].idx;

  	if (old_idx == IDX_INVALID) {
  		/*
  		 * Nothing to remove if old_idx was invalid.
  		 * This could happen if a rq_offline_dl is
  		 * called for a CPU without -dl tasks running.
  		 */
  	} else {

  		new_cpu = cp->elements[cp->size - 1].cpu;
  		cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
  		cp->elements[old_idx].cpu = new_cpu;
  		cp->size--;

  		cp->elements[new_cpu].idx = old_idx;
  		cp->elements[cpu].idx = IDX_INVALID;

  		cpudl_heapify(cp, old_idx);

  		cpumask_set_cpu(cpu, cp->free_cpus);

  	}

  	raw_spin_unlock_irqrestore(&cp->lock, flags);
  }
  
  /*
   * cpudl_set - update the cpudl max-heap
   * @cp: the cpudl max-heap context

   * @cpu: the target CPU
   * @dl: the new earliest deadline for this CPU

   *
   * Notes: assumes cpu_rq(cpu)->lock is locked
   *
   * Returns: (void)
   */
  void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
  {
  	int old_idx;
  	unsigned long flags;
  
  	WARN_ON(!cpu_present(cpu));

  	raw_spin_lock_irqsave(&cp->lock, flags);
  
  	old_idx = cp->elements[cpu].idx;

  	if (old_idx == IDX_INVALID) {

  		int new_idx = cp->size++;

  		cp->elements[new_idx].dl = dl;
  		cp->elements[new_idx].cpu = cpu;
  		cp->elements[cpu].idx = new_idx;
  		cpudl_heapify_up(cp, new_idx);

  		cpumask_clear_cpu(cpu, cp->free_cpus);
  	} else {

  		cp->elements[old_idx].dl = dl;
  		cpudl_heapify(cp, old_idx);

  	}

  	raw_spin_unlock_irqrestore(&cp->lock, flags);
  }
  
  /*

   * cpudl_set_freecpu - Set the cpudl.free_cpus
   * @cp: the cpudl max-heap context

   * @cpu: rd attached CPU

   */
  void cpudl_set_freecpu(struct cpudl *cp, int cpu)
  {
  	cpumask_set_cpu(cpu, cp->free_cpus);
  }
  
  /*
   * cpudl_clear_freecpu - Clear the cpudl.free_cpus
   * @cp: the cpudl max-heap context

   * @cpu: rd attached CPU

   */
  void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
  {
  	cpumask_clear_cpu(cpu, cp->free_cpus);
  }
  
  /*

   * cpudl_init - initialize the cpudl structure
   * @cp: the cpudl max-heap context
   */
  int cpudl_init(struct cpudl *cp)
  {
  	int i;

  	raw_spin_lock_init(&cp->lock);
  	cp->size = 0;

  
  	cp->elements = kcalloc(nr_cpu_ids,
  			       sizeof(struct cpudl_item),
  			       GFP_KERNEL);
  	if (!cp->elements)
  		return -ENOMEM;

  	if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {

  		kfree(cp->elements);

  		return -ENOMEM;

  	}
  
  	for_each_possible_cpu(i)
  		cp->elements[i].idx = IDX_INVALID;

  	return 0;
  }
  
  /*
   * cpudl_cleanup - clean up the cpudl structure
   * @cp: the cpudl max-heap context
   */
  void cpudl_cleanup(struct cpudl *cp)
  {

  	free_cpumask_var(cp->free_cpus);

  	kfree(cp->elements);

  }