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-rw-r--r--lib/timerqueue.c118
1 files changed, 118 insertions, 0 deletions
diff --git a/lib/timerqueue.c b/lib/timerqueue.c
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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 libary 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/timerqueue.h>
26#include <linux/rbtree.h>
27
28/**
29 * timerqueue_add - Adds timer to timerqueue.
30 *
31 * @head: head of timerqueue
32 * @node: timer node to be added
33 *
34 * Adds the timer node to the timerqueue, sorted by the
35 * node's expires value.
36 */
37void timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
38{
39 struct rb_node **p = &head->head.rb_node;
40 struct rb_node *parent = NULL;
41 struct timerqueue_node *ptr;
42
43 /* Make sure we don't add nodes that are already added */
44 WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
45
46 while (*p) {
47 parent = *p;
48 ptr = rb_entry(parent, struct timerqueue_node, node);
49 if (node->expires.tv64 < ptr->expires.tv64)
50 p = &(*p)->rb_left;
51 else
52 p = &(*p)->rb_right;
53 }
54 rb_link_node(&node->node, parent, p);
55 rb_insert_color(&node->node, &head->head);
56
57 if (!head->next || node->expires.tv64 < head->next->expires.tv64)
58 head->next = node;
59}
60
61/**
62 * timerqueue_del - Removes a timer from the timerqueue.
63 *
64 * @head: head of timerqueue
65 * @node: timer node to be removed
66 *
67 * Removes the timer node from the timerqueue.
68 */
69void timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
70{
71 WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
72
73 /* update next pointer */
74 if (head->next == node) {
75 struct rb_node *rbn = rb_next(&node->node);
76
77 head->next = rbn ?
78 rb_entry(rbn, struct timerqueue_node, node) : NULL;
79 }
80 rb_erase(&node->node, &head->head);
81 RB_CLEAR_NODE(&node->node);
82}
83
84
85/**
86 * timerqueue_getnext - Returns the timer with the earlies expiration time
87 *
88 * @head: head of timerqueue
89 *
90 * Returns a pointer to the timer node that has the
91 * earliest expiration time.
92 */
93struct timerqueue_node *timerqueue_getnext(struct timerqueue_head *head)
94{
95 return head->next;
96}
97
98
99/**
100 * timerqueue_iterate_next - Returns the timer after the provided timer
101 *
102 * @node: Pointer to a timer.
103 *
104 * Provides the timer that is after the given node. This is used, when
105 * necessary, to iterate through the list of timers in a timer list
106 * without modifying the list.
107 */
108struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
109{
110 struct rb_node *next;
111
112 if (!node)
113 return NULL;
114 next = rb_next(&node->node);
115 if (!next)
116 return NULL;
117 return container_of(next, struct timerqueue_node, node);
118}