Root/lib/timerqueue.c

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
37 * node's expires value.
38 */
39void timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
40{
41    struct rb_node **p = &head->head.rb_node;
42    struct rb_node *parent = NULL;
43    struct timerqueue_node *ptr;
44
45    /* Make sure we don't add nodes that are already added */
46    WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
47
48    while (*p) {
49        parent = *p;
50        ptr = rb_entry(parent, struct timerqueue_node, node);
51        if (node->expires.tv64 < ptr->expires.tv64)
52            p = &(*p)->rb_left;
53        else
54            p = &(*p)->rb_right;
55    }
56    rb_link_node(&node->node, parent, p);
57    rb_insert_color(&node->node, &head->head);
58
59    if (!head->next || node->expires.tv64 < head->next->expires.tv64)
60        head->next = node;
61}
62EXPORT_SYMBOL_GPL(timerqueue_add);
63
64/**
65 * timerqueue_del - Removes a timer from the timerqueue.
66 *
67 * @head: head of timerqueue
68 * @node: timer node to be removed
69 *
70 * Removes the timer node from the timerqueue.
71 */
72void timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
73{
74    WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
75
76    /* update next pointer */
77    if (head->next == node) {
78        struct rb_node *rbn = rb_next(&node->node);
79
80        head->next = rbn ?
81            rb_entry(rbn, struct timerqueue_node, node) : NULL;
82    }
83    rb_erase(&node->node, &head->head);
84    RB_CLEAR_NODE(&node->node);
85}
86EXPORT_SYMBOL_GPL(timerqueue_del);
87
88/**
89 * timerqueue_iterate_next - Returns the timer after the provided timer
90 *
91 * @node: Pointer to a timer.
92 *
93 * Provides the timer that is after the given node. This is used, when
94 * necessary, to iterate through the list of timers in a timer list
95 * without modifying the list.
96 */
97struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
98{
99    struct rb_node *next;
100
101    if (!node)
102        return NULL;
103    next = rb_next(&node->node);
104    if (!next)
105        return NULL;
106    return container_of(next, struct timerqueue_node, node);
107}
108EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
109

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