timerqueue.c 3.17 KB
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/*
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 *  Generic Timer-queue
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 *
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 *  Manages a simple queue of timers, ordered by expiration time.
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 *  Uses rbtrees for quick list adds and expiration.
 *
 *  NOTE: All of the following functions need to be serialized
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 *  to avoid races. No locking is done by this library code.
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 *
 *  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
 */

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#include <linux/bug.h>
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#include <linux/timerqueue.h>
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#include <linux/rbtree.h>
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#include <linux/export.h>
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/**
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 * timerqueue_add - Adds timer to timerqueue.
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 *
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 * @head: head of timerqueue
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 * @node: timer node to be added
 *
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 * Adds the timer node to the timerqueue, sorted by the
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 * node's expires value.
 */
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bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
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{
	struct rb_node **p = &head->head.rb_node;
	struct rb_node *parent = NULL;
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	struct timerqueue_node  *ptr;
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	/* Make sure we don't add nodes that are already added */
	WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));

	while (*p) {
		parent = *p;
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		ptr = rb_entry(parent, struct timerqueue_node, node);
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		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);

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	if (!head->next || node->expires.tv64 < head->next->expires.tv64) {
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		head->next = node;
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		return true;
	}
	return false;
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}
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EXPORT_SYMBOL_GPL(timerqueue_add);
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/**
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 * timerqueue_del - Removes a timer from the timerqueue.
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 *
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 * @head: head of timerqueue
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 * @node: timer node to be removed
 *
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 * Removes the timer node from the timerqueue.
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 */
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bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
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{
	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 ?
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			rb_entry(rbn, struct timerqueue_node, node) : NULL;
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	}
	rb_erase(&node->node, &head->head);
	RB_CLEAR_NODE(&node->node);
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	return head->next != NULL;
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}
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EXPORT_SYMBOL_GPL(timerqueue_del);
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/**
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 * timerqueue_iterate_next - Returns the timer after the provided timer
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 *
 * @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.
 */
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struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
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{
	struct rb_node *next;

	if (!node)
		return NULL;
	next = rb_next(&node->node);
	if (!next)
		return NULL;
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	return container_of(next, struct timerqueue_node, node);
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}
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EXPORT_SYMBOL_GPL(timerqueue_iterate_next);