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); 95