/*
   *  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.
   *
   *  This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation; either version 2 of the License, or
   *  (at your option) any later version.
   *
   *  This program is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *  GNU General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License
   *  along with this program; if not, write to the Free Software
   *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #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.
   */
  void 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.tv64 < ptr->expires.tv64)
  			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.tv64 < head->next->expires.tv64)
  		head->next = node;
  }
  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.
   */
  void 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 = rbn ?
  			rb_entry(rbn, struct timerqueue_node, node) : NULL;
  	}
  	rb_erase(&node->node, &head->head);
  	RB_CLEAR_NODE(&node->node);
  }
  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);