LXR linux/lib/timerqueue.c

   1/*
   2 *  Generic Timer-queue
   3 *
   4 *  Manages a simple queue of timers, ordered by expiration time.
   5 *  Uses rbtrees for quick list adds and expiration.
   6 *
   7 *  NOTE: All of the following functions need to be serialized
   8 *  to avoid races. No locking is done by this library code.
   9 *
  10 *  This program is free software; you can redistribute it and/or modify
  11 *  it under the terms of the GNU General Public License as published by
  12 *  the Free Software Foundation; either version 2 of the License, or
  13 *  (at your option) any later version.
  14 *
  15 *  This program is distributed in the hope that it will be useful,
  16 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 *  GNU General Public License for more details.
  19 *
  20 *  You should have received a copy of the GNU General Public License
  21 *  along with this program; if not, write to the Free Software
  22 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  23 */
  24
  25#include <linux/bug.h>
  26#include <linux/timerqueue.h>
  27#include <linux/rbtree.h>
  28#include <linux/export.h>
  29
  30/**
  31 * timerqueue_add - Adds timer to timerqueue.
  32 *
  33 * @head: head of timerqueue
  34 * @node: timer node to be added
  35 *
  36 * Adds the timer node to the timerqueue, sorted by the
  37 * node's expires value.
  38 */
  39bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
  40{
  41        struct rb_node **p = &head->head.rb_node;
  42        struct rb_node *parent = NULL;
  43        struct timerqueue_node  *ptr;
  44
  45        /* Make sure we don't add nodes that are already added */
  46        WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
  47
  48        while (*p) {
  49                parent = *p;
  50                ptr = rb_entry(parent, struct timerqueue_node, node);
  51                if (node->expires.tv64 < ptr->expires.tv64)
  52                        p = &(*p)->rb_left;
  53                else
  54                        p = &(*p)->rb_right;
  55        }
  56        rb_link_node(&node->node, parent, p);
  57        rb_insert_color(&node->node, &head->head);
  58
  59        if (!head->next || node->expires.tv64 < head->next->expires.tv64) {
  60                head->next = node;
  61                return true;
  62        }
  63        return false;
  64}
  65EXPORT_SYMBOL_GPL(timerqueue_add);
  66
  67/**
  68 * timerqueue_del - Removes a timer from the timerqueue.
  69 *
  70 * @head: head of timerqueue
  71 * @node: timer node to be removed
  72 *
  73 * Removes the timer node from the timerqueue.
  74 */
  75bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
  76{
  77        WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
  78
  79        /* update next pointer */
  80        if (head->next == node) {
  81                struct rb_node *rbn = rb_next(&node->node);
  82
  83                head->next = rbn ?
  84                        rb_entry(rbn, struct timerqueue_node, node) : NULL;
  85        }
  86        rb_erase(&node->node, &head->head);
  87        RB_CLEAR_NODE(&node->node);
  88        return head->next != NULL;
  89}
  90EXPORT_SYMBOL_GPL(timerqueue_del);
  91
  92/**
  93 * timerqueue_iterate_next - Returns the timer after the provided timer
  94 *
  95 * @node: Pointer to a timer.
  96 *
  97 * Provides the timer that is after the given node. This is used, when
  98 * necessary, to iterate through the list of timers in a timer list
  99 * without modifying the list.
 100 */
 101struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
 102{
 103        struct rb_node *next;
 104
 105        if (!node)
 106                return NULL;
 107        next = rb_next(&node->node);
 108        if (!next)
 109                return NULL;
 110        return container_of(next, struct timerqueue_node, node);
 111}
 112EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
 113