// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * lib/plist.c
   *
   * Descending-priority-sorted double-linked list
   *
   * (C) 2002-2003 Intel Corp
   * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
   *
   * 2001-2005 (c) MontaVista Software, Inc.
   * Daniel Walker <dwalker@mvista.com>
   *
   * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
   *
   * Simplifications of the original code by
   * Oleg Nesterov <oleg@tv-sign.ru>
   *

   * Based on simple lists (include/linux/list.h).
   *
   * This file contains the add / del functions which are considered to
   * be too large to inline. See include/linux/plist.h for further
   * information.
   */

  #include <linux/bug.h>

  #include <linux/plist.h>

  #ifdef CONFIG_DEBUG_PLIST

  static struct plist_head test_head;

  static void plist_check_prev_next(struct list_head *t, struct list_head *p,
  				  struct list_head *n)
  {

  	WARN(n->prev != p || p->next != n,
  			"top: %p, n: %p, p: %p
  "
  			"prev: %p, n: %p, p: %p
  "
  			"next: %p, n: %p, p: %p
  ",
  			 t, t->next, t->prev,
  			p, p->next, p->prev,
  			n, n->next, n->prev);

  }
  
  static void plist_check_list(struct list_head *top)
  {
  	struct list_head *prev = top, *next = top->next;
  
  	plist_check_prev_next(top, prev, next);
  	while (next != top) {
  		prev = next;
  		next = prev->next;
  		plist_check_prev_next(top, prev, next);
  	}
  }
  
  static void plist_check_head(struct plist_head *head)
  {

  	if (!plist_head_empty(head))
  		plist_check_list(&plist_first(head)->prio_list);

  	plist_check_list(&head->node_list);
  }
  
  #else
  # define plist_check_head(h)	do { } while (0)
  #endif
  
  /**
   * plist_add - add @node to @head
   *
   * @node:	&struct plist_node pointer
   * @head:	&struct plist_head pointer
   */
  void plist_add(struct plist_node *node, struct plist_head *head)
  {

  	struct plist_node *first, *iter, *prev = NULL;
  	struct list_head *node_next = &head->node_list;

  
  	plist_check_head(head);
  	WARN_ON(!plist_node_empty(node));

  	WARN_ON(!list_empty(&node->prio_list));

  	if (plist_head_empty(head))
  		goto ins_node;
  
  	first = iter = plist_first(head);
  
  	do {
  		if (node->prio < iter->prio) {
  			node_next = &iter->node_list;
  			break;

  		}

  		prev = iter;
  		iter = list_entry(iter->prio_list.next,
  				struct plist_node, prio_list);
  	} while (iter != first);
  
  	if (!prev || prev->prio != node->prio)
  		list_add_tail(&node->prio_list, &iter->prio_list);
  ins_node:
  	list_add_tail(&node->node_list, node_next);

  
  	plist_check_head(head);
  }
  
  /**
   * plist_del - Remove a @node from plist.
   *
   * @node:	&struct plist_node pointer - entry to be removed
   * @head:	&struct plist_head pointer - list head
   */
  void plist_del(struct plist_node *node, struct plist_head *head)
  {
  	plist_check_head(head);

  	if (!list_empty(&node->prio_list)) {
  		if (node->node_list.next != &head->node_list) {
  			struct plist_node *next;
  
  			next = list_entry(node->node_list.next,
  					struct plist_node, node_list);

  			/* add the next plist_node into prio_list */
  			if (list_empty(&next->prio_list))
  				list_add(&next->prio_list, &node->prio_list);
  		}
  		list_del_init(&node->prio_list);

  	}

  	list_del_init(&node->node_list);

  
  	plist_check_head(head);
  }

  /**
   * plist_requeue - Requeue @node at end of same-prio entries.
   *
   * This is essentially an optimized plist_del() followed by
   * plist_add().  It moves an entry already in the plist to
   * after any other same-priority entries.
   *
   * @node:	&struct plist_node pointer - entry to be moved
   * @head:	&struct plist_head pointer - list head
   */
  void plist_requeue(struct plist_node *node, struct plist_head *head)
  {
  	struct plist_node *iter;
  	struct list_head *node_next = &head->node_list;
  
  	plist_check_head(head);
  	BUG_ON(plist_head_empty(head));
  	BUG_ON(plist_node_empty(node));
  
  	if (node == plist_last(head))
  		return;
  
  	iter = plist_next(node);
  
  	if (node->prio != iter->prio)
  		return;
  
  	plist_del(node, head);
  
  	plist_for_each_continue(iter, head) {
  		if (node->prio != iter->prio) {
  			node_next = &iter->node_list;
  			break;
  		}
  	}
  	list_add_tail(&node->node_list, node_next);
  
  	plist_check_head(head);
  }

  #ifdef CONFIG_DEBUG_PLIST

  #include <linux/sched.h>

  #include <linux/sched/clock.h>

  #include <linux/module.h>
  #include <linux/init.h>
  
  static struct plist_node __initdata test_node[241];
  
  static void __init plist_test_check(int nr_expect)
  {
  	struct plist_node *first, *prio_pos, *node_pos;
  
  	if (plist_head_empty(&test_head)) {
  		BUG_ON(nr_expect != 0);
  		return;
  	}
  
  	prio_pos = first = plist_first(&test_head);
  	plist_for_each(node_pos, &test_head) {
  		if (nr_expect-- < 0)
  			break;
  		if (node_pos == first)
  			continue;
  		if (node_pos->prio == prio_pos->prio) {
  			BUG_ON(!list_empty(&node_pos->prio_list));
  			continue;
  		}
  
  		BUG_ON(prio_pos->prio > node_pos->prio);
  		BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
  		prio_pos = node_pos;
  	}
  
  	BUG_ON(nr_expect != 0);
  	BUG_ON(prio_pos->prio_list.next != &first->prio_list);
  }

  static void __init plist_test_requeue(struct plist_node *node)
  {
  	plist_requeue(node, &test_head);
  
  	if (node != plist_last(&test_head))
  		BUG_ON(node->prio == plist_next(node)->prio);
  }

  static int  __init plist_test(void)
  {
  	int nr_expect = 0, i, loop;
  	unsigned int r = local_clock();

  	printk(KERN_DEBUG "start plist test
  ");

  	plist_head_init(&test_head);

  	for (i = 0; i < ARRAY_SIZE(test_node); i++)
  		plist_node_init(test_node + i, 0);
  
  	for (loop = 0; loop < 1000; loop++) {
  		r = r * 193939 % 47629;
  		i = r % ARRAY_SIZE(test_node);
  		if (plist_node_empty(test_node + i)) {
  			r = r * 193939 % 47629;
  			test_node[i].prio = r % 99;
  			plist_add(test_node + i, &test_head);
  			nr_expect++;
  		} else {
  			plist_del(test_node + i, &test_head);
  			nr_expect--;
  		}
  		plist_test_check(nr_expect);

  		if (!plist_node_empty(test_node + i)) {
  			plist_test_requeue(test_node + i);
  			plist_test_check(nr_expect);
  		}

  	}
  
  	for (i = 0; i < ARRAY_SIZE(test_node); i++) {
  		if (plist_node_empty(test_node + i))
  			continue;
  		plist_del(test_node + i, &test_head);
  		nr_expect--;
  		plist_test_check(nr_expect);
  	}

  	printk(KERN_DEBUG "end plist test
  ");

  	return 0;
  }
  
  module_init(plist_test);
  
  #endif