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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Generic Timer-queue
*
* Manages a simple queue of timers, ordered by expiration time.
* Uses rbtrees for quick list adds and expiration.
*
* NOTE: All of the following functions need to be serialized
* to avoid races. No locking is done by this library code.
*/
#include <linux/bug.h>
#include <linux/timerqueue.h>
#include <linux/rbtree.h>
#include <linux/export.h>
/**
* timerqueue_add - Adds timer to timerqueue.
*
* @head: head of timerqueue
* @node: timer node to be added
*
* Adds the timer node to the timerqueue, sorted by the node's expires
* value. Returns true if the newly added timer is the first expiring timer in
* the queue.
*/
bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
{
struct rb_node **p = &head->head.rb_node;
struct rb_node *parent = NULL;
struct timerqueue_node *ptr;
/* Make sure we don't add nodes that are already added */
WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
while (*p) {
parent = *p;
ptr = rb_entry(parent, struct timerqueue_node, node);
if (node->expires < ptr->expires)
p = &(*p)->rb_left;
else
p = &(*p)->rb_right;
}
rb_link_node(&node->node, parent, p);
rb_insert_color(&node->node, &head->head);
if (!head->next || node->expires < head->next->expires) {
head->next = node;
return true;
}
return false;
}
EXPORT_SYMBOL_GPL(timerqueue_add);
/**
* timerqueue_del - Removes a timer from the timerqueue.
*
* @head: head of timerqueue
* @node: timer node to be removed
*
* Removes the timer node from the timerqueue. Returns true if the queue is
* not empty after the remove.
*/
bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
{
WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
/* update next pointer */
if (head->next == node) {
struct rb_node *rbn = rb_next(&node->node);
head->next = rb_entry_safe(rbn, struct timerqueue_node, node);
}
rb_erase(&node->node, &head->head);
RB_CLEAR_NODE(&node->node);
return head->next != NULL;
}
EXPORT_SYMBOL_GPL(timerqueue_del);
/**
* timerqueue_iterate_next - Returns the timer after the provided timer
*
* @node: Pointer to a timer.
*
* Provides the timer that is after the given node. This is used, when
* necessary, to iterate through the list of timers in a timer list
* without modifying the list.
*/
struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
{
struct rb_node *next;
if (!node)
return NULL;
next = rb_next(&node->node);
if (!next)
return NULL;
return container_of(next, struct timerqueue_node, node);
}
EXPORT_SYMBOL_GPL(timerqueue_iterate_next);