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 */
timerqueue_add(struct timerqueue_head * head,struct timerqueue_node * node)40 bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
41 {
42 struct rb_node **p = &head->rb_root.rb_root.rb_node;
43 struct rb_node *parent = NULL;
44 struct timerqueue_node *ptr;
45 bool leftmost = true;
46
47 /* Make sure we don't add nodes that are already added */
48 WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
49
50 while (*p) {
51 parent = *p;
52 ptr = rb_entry(parent, struct timerqueue_node, node);
53 if (node->expires < ptr->expires) {
54 p = &(*p)->rb_left;
55 } else {
56 p = &(*p)->rb_right;
57 leftmost = false;
58 }
59 }
60 rb_link_node(&node->node, parent, p);
61 rb_insert_color_cached(&node->node, &head->rb_root, leftmost);
62
63 return leftmost;
64 }
65 EXPORT_SYMBOL_GPL(timerqueue_add);
66
67 /**
68 * timerqueue_del - Removes a timer from the timerqueue.
69 *
70 * @head: head of timerqueue
71 * @node: timer node to be removed
72 *
73 * Removes the timer node from the timerqueue. Returns true if the queue is
74 * not empty after the remove.
75 */
timerqueue_del(struct timerqueue_head * head,struct timerqueue_node * node)76 bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
77 {
78 WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
79
80 rb_erase_cached(&node->node, &head->rb_root);
81 RB_CLEAR_NODE(&node->node);
82
83 return !RB_EMPTY_ROOT(&head->rb_root.rb_root);
84 }
85 EXPORT_SYMBOL_GPL(timerqueue_del);
86
87 /**
88 * timerqueue_iterate_next - Returns the timer after the provided timer
89 *
90 * @node: Pointer to a timer.
91 *
92 * Provides the timer that is after the given node. This is used, when
93 * necessary, to iterate through the list of timers in a timer list
94 * without modifying the list.
95 */
timerqueue_iterate_next(struct timerqueue_node * node)96 struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
97 {
98 struct rb_node *next;
99
100 if (!node)
101 return NULL;
102 next = rb_next(&node->node);
103 if (!next)
104 return NULL;
105 return container_of(next, struct timerqueue_node, node);
106 }
107 EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
108