LXR linux/lib/timerqueue.c

   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, &head->rb_root, __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, &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