1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Generic Timer-queue
4 *
5 * Manages a simple queue of timers, ordered by expiration time.
6 * Uses rbtrees for quick list adds and expiration.
7 *
8 * NOTE: All of the following functions need to be serialized
9 * to avoid races. No locking is done by this library code.
10 */
11
12 #include <linux/bug.h>
13 #include <linux/timerqueue.h>
14 #include <linux/rbtree.h>
15 #include <linux/export.h>
16
17 /**
18 * timerqueue_add - Adds timer to timerqueue.
19 *
20 * @head: head of timerqueue
21 * @node: timer node to be added
22 *
23 * Adds the timer node to the timerqueue, sorted by the node's expires
24 * value. Returns true if the newly added timer is the first expiring timer in
25 * the queue.
26 */
timerqueue_add(struct timerqueue_head * head,struct timerqueue_node * node)27 bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
28 {
29 struct rb_node **p = &head->rb_root.rb_root.rb_node;
30 struct rb_node *parent = NULL;
31 struct timerqueue_node *ptr;
32 bool leftmost = true;
33
34 /* Make sure we don't add nodes that are already added */
35 WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
36
37 while (*p) {
38 parent = *p;
39 ptr = rb_entry(parent, struct timerqueue_node, node);
40 if (node->expires < ptr->expires) {
41 p = &(*p)->rb_left;
42 } else {
43 p = &(*p)->rb_right;
44 leftmost = false;
45 }
46 }
47 rb_link_node(&node->node, parent, p);
48 rb_insert_color_cached(&node->node, &head->rb_root, leftmost);
49
50 return leftmost;
51 }
52 EXPORT_SYMBOL_GPL(timerqueue_add);
53
54 /**
55 * timerqueue_del - Removes a timer from the timerqueue.
56 *
57 * @head: head of timerqueue
58 * @node: timer node to be removed
59 *
60 * Removes the timer node from the timerqueue. Returns true if the queue is
61 * not empty after the remove.
62 */
timerqueue_del(struct timerqueue_head * head,struct timerqueue_node * node)63 bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
64 {
65 WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
66
67 rb_erase_cached(&node->node, &head->rb_root);
68 RB_CLEAR_NODE(&node->node);
69
70 return !RB_EMPTY_ROOT(&head->rb_root.rb_root);
71 }
72 EXPORT_SYMBOL_GPL(timerqueue_del);
73
74 /**
75 * timerqueue_iterate_next - Returns the timer after the provided timer
76 *
77 * @node: Pointer to a timer.
78 *
79 * Provides the timer that is after the given node. This is used, when
80 * necessary, to iterate through the list of timers in a timer list
81 * without modifying the list.
82 */
timerqueue_iterate_next(struct timerqueue_node * node)83 struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
84 {
85 struct rb_node *next;
86
87 if (!node)
88 return NULL;
89 next = rb_next(&node->node);
90 if (!next)
91 return NULL;
92 return container_of(next, struct timerqueue_node, node);
93 }
94 EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
95
