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
20 static 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 */
35 bool 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, &head->rb_root, __timerqueue_less);
41 }
42 EXPORT_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 */
53 bool 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, &head->rb_root);
58 RB_CLEAR_NODE(&node->node);
59
60 return !RB_EMPTY_ROOT(&head->rb_root.rb_root);
61 }
62 EXPORT_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 */
73 struct 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 }
84 EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
85
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