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

  /*

   *  Generic Timer-queue

   *

   *  Manages a simple queue of timers, ordered by expiration time.

   *  Uses rbtrees for quick list adds and expiration.
   *
   *  NOTE: All of the following functions need to be serialized

   *  to avoid races. No locking is done by this library code.

   */

  #include <linux/bug.h>

  #include <linux/timerqueue.h>

  #include <linux/rbtree.h>

  #include <linux/export.h>

  
  /**

   * timerqueue_add - Adds timer to timerqueue.

   *

   * @head: head of timerqueue

   * @node: timer node to be added
   *

   * Adds the timer node to the timerqueue, sorted by the node's expires
   * value. Returns true if the newly added timer is the first expiring timer in
   * the queue.

   */

  bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)

  {
  	struct rb_node **p = &head->head.rb_node;
  	struct rb_node *parent = NULL;

  	struct timerqueue_node  *ptr;

  
  	/* Make sure we don't add nodes that are already added */
  	WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
  
  	while (*p) {
  		parent = *p;

  		ptr = rb_entry(parent, struct timerqueue_node, node);

  		if (node->expires < ptr->expires)

  			p = &(*p)->rb_left;
  		else
  			p = &(*p)->rb_right;
  	}
  	rb_link_node(&node->node, parent, p);
  	rb_insert_color(&node->node, &head->head);

  	if (!head->next || node->expires < head->next->expires) {

  		head->next = node;

  		return true;
  	}
  	return false;

  }

  EXPORT_SYMBOL_GPL(timerqueue_add);

  
  /**

   * timerqueue_del - Removes a timer from the timerqueue.

   *

   * @head: head of timerqueue

   * @node: timer node to be removed
   *

   * Removes the timer node from the timerqueue. Returns true if the queue is
   * not empty after the remove.

   */

  bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)

  {
  	WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
  
  	/* update next pointer */
  	if (head->next == node) {
  		struct rb_node *rbn = rb_next(&node->node);

  		head->next = rb_entry_safe(rbn, struct timerqueue_node, node);

  	}
  	rb_erase(&node->node, &head->head);
  	RB_CLEAR_NODE(&node->node);

  	return head->next != NULL;

  }

  EXPORT_SYMBOL_GPL(timerqueue_del);

  
  /**

   * timerqueue_iterate_next - Returns the timer after the provided timer

   *
   * @node: Pointer to a timer.
   *
   * Provides the timer that is after the given node. This is used, when
   * necessary, to iterate through the list of timers in a timer list
   * without modifying the list.
   */

  struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)

  {
  	struct rb_node *next;
  
  	if (!node)
  		return NULL;
  	next = rb_next(&node->node);
  	if (!next)
  		return NULL;

  	return container_of(next, struct timerqueue_node, node);

  }

  EXPORT_SYMBOL_GPL(timerqueue_iterate_next);