1/*
2 * Generic Timer-queue
3 *
4 * Manages a simple queue of timers, ordered by expiration time.
5 * Uses rbtrees for quick list adds and expiration.
6 *
7 * NOTE: All of the following functions need to be serialized
8 * to avoid races. No locking is done by this library code.
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
14 *
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 */
24
25#include <linux/bug.h>
26#include <linux/timerqueue.h>
27#include <linux/rbtree.h>
28#include <linux/export.h>
29
30/**
31 * timerqueue_add - Adds timer to timerqueue.
32 *
33 * @head: head of timerqueue
34 * @node: timer node to be added
35 *
36 * Adds the timer node to the timerqueue, sorted by the node's expires
37 * value. Returns true if the newly added timer is the first expiring timer in
38 * the queue.
39 */
40bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
41{
42 struct rb_node **p = &head->head.rb_node;
43 struct rb_node *parent = NULL;
44 struct timerqueue_node *ptr;
45
46 /* Make sure we don't add nodes that are already added */
47 WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
48
49 while (*p) {
50 parent = *p;
51 ptr = rb_entry(parent, struct timerqueue_node, node);
52 if (node->expires < ptr->expires)
53 p = &(*p)->rb_left;
54 else
55 p = &(*p)->rb_right;
56 }
57 rb_link_node(&node->node, parent, p);
58 rb_insert_color(&node->node, &head->head);
59
60 if (!head->next || node->expires < head->next->expires) {
61 head->next = node;
62 return true;
63 }
64 return false;
65}
66EXPORT_SYMBOL_GPL(timerqueue_add);
67
68/**
69 * timerqueue_del - Removes a timer from the timerqueue.
70 *
71 * @head: head of timerqueue
72 * @node: timer node to be removed
73 *
74 * Removes the timer node from the timerqueue. Returns true if the queue is
75 * not empty after the remove.
76 */
77bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
78{
79 WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
80
81 /* update next pointer */
82 if (head->next == node) {
83 struct rb_node *rbn = rb_next(&node->node);
84
85 head->next = rb_entry_safe(rbn, struct timerqueue_node, node);
86 }
87 rb_erase(&node->node, &head->head);
88 RB_CLEAR_NODE(&node->node);
89 return head->next != NULL;
90}
91EXPORT_SYMBOL_GPL(timerqueue_del);
92
93/**
94 * timerqueue_iterate_next - Returns the timer after the provided timer
95 *
96 * @node: Pointer to a timer.
97 *
98 * Provides the timer that is after the given node. This is used, when
99 * necessary, to iterate through the list of timers in a timer list
100 * without modifying the list.
101 */
102struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
103{
104 struct rb_node *next;
105
106 if (!node)
107 return NULL;
108 next = rb_next(&node->node);
109 if (!next)
110 return NULL;
111 return container_of(next, struct timerqueue_node, node);
112}
113EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
114