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#define __node_2_tq(_n) \
18 rb_entry((_n), struct timerqueue_node, node)
19
20static inline bool __timerqueue_less(struct rb_node *a, const struct rb_node *b)
21{
22 return __node_2_tq(a)->expires < __node_2_tq(b)->expires;
23}
24
25/**
26 * timerqueue_add - Adds timer to timerqueue.
27 *
28 * @head: head of timerqueue
29 * @node: timer node to be added
30 *
31 * Adds the timer node to the timerqueue, sorted by the node's expires
32 * value. Returns true if the newly added timer is the first expiring timer in
33 * the queue.
34 */
35bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
36{
37 /* Make sure we don't add nodes that are already added */
38 WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
39
40 return rb_add_cached(node: &node->node, tree: &head->rb_root, less: __timerqueue_less);
41}
42EXPORT_SYMBOL_GPL(timerqueue_add);
43
44/**
45 * timerqueue_del - Removes a timer from the timerqueue.
46 *
47 * @head: head of timerqueue
48 * @node: timer node to be removed
49 *
50 * Removes the timer node from the timerqueue. Returns true if the queue is
51 * not empty after the remove.
52 */
53bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
54{
55 WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
56
57 rb_erase_cached(node: &node->node, root: &head->rb_root);
58 RB_CLEAR_NODE(&node->node);
59
60 return !RB_EMPTY_ROOT(&head->rb_root.rb_root);
61}
62EXPORT_SYMBOL_GPL(timerqueue_del);
63
64/**
65 * timerqueue_iterate_next - Returns the timer after the provided timer
66 *
67 * @node: Pointer to a timer.
68 *
69 * Provides the timer that is after the given node. This is used, when
70 * necessary, to iterate through the list of timers in a timer list
71 * without modifying the list.
72 */
73struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
74{
75 struct rb_node *next;
76
77 if (!node)
78 return NULL;
79 next = rb_next(&node->node);
80 if (!next)
81 return NULL;
82 return container_of(next, struct timerqueue_node, node);
83}
84EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
85