// 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->rb_root.rb_root.rb_node;

  	struct rb_node *parent = NULL;

  	struct timerqueue_node *ptr;
  	bool leftmost = true;

  
  	/* 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;

  			leftmost = false;
  		}

  	}
  	rb_link_node(&node->node, parent, p);

  	rb_insert_color_cached(&node->node, &head->rb_root, leftmost);

  	return leftmost;

  }

  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));

  	rb_erase_cached(&node->node, &head->rb_root);

  	RB_CLEAR_NODE(&node->node);

  
  	return !RB_EMPTY_ROOT(&head->rb_root.rb_root);

  }

  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);