| 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 | */ |
| 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 | */ |
| 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 | */ |
| 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); |