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 libary 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/timerqueue.h>
  26#include <linux/rbtree.h>
  27#include <linux/module.h>
  28
  29/**
  30 * timerqueue_add - Adds timer to timerqueue.
  31 *
  32 * @head: head of timerqueue
  33 * @node: timer node to be added
  34 *
  35 * Adds the timer node to the timerqueue, sorted by the
  36 * node's expires value.
  37 */
  38void timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
  39{
  40        struct rb_node **p = &head->head.rb_node;
  41        struct rb_node *parent = NULL;
  42        struct timerqueue_node  *ptr;
  43
  44        /* Make sure we don't add nodes that are already added */
  45        WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
  46
  47        while (*p) {
  48                parent = *p;
  49                ptr = rb_entry(parent, struct timerqueue_node, node);
  50                if (node->expires.tv64 < ptr->expires.tv64)
  51                        p = &(*p)->rb_left;
  52                else
  53                        p = &(*p)->rb_right;
  54        }
  55        rb_link_node(&node->node, parent, p);
  56        rb_insert_color(&node->node, &head->head);
  57
  58        if (!head->next || node->expires.tv64 < head->next->expires.tv64)
  59                head->next = node;
  60}
  61EXPORT_SYMBOL_GPL(timerqueue_add);
  62
  63/**
  64 * timerqueue_del - Removes a timer from the timerqueue.
  65 *
  66 * @head: head of timerqueue
  67 * @node: timer node to be removed
  68 *
  69 * Removes the timer node from the timerqueue.
  70 */
  71void timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
  72{
  73        WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
  74
  75        /* update next pointer */
  76        if (head->next == node) {
  77                struct rb_node *rbn = rb_next(&node->node);
  78
  79                head->next = rbn ?
  80                        rb_entry(rbn, struct timerqueue_node, node) : NULL;
  81        }
  82        rb_erase(&node->node, &head->head);
  83        RB_CLEAR_NODE(&node->node);
  84}
  85EXPORT_SYMBOL_GPL(timerqueue_del);
  86
  87/**
  88 * timerqueue_iterate_next - Returns the timer after the provided timer
  89 *
  90 * @node: Pointer to a timer.
  91 *
  92 * Provides the timer that is after the given node. This is used, when
  93 * necessary, to iterate through the list of timers in a timer list
  94 * without modifying the list.
  95 */
  96struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
  97{
  98        struct rb_node *next;
  99
 100        if (!node)
 101                return NULL;
 102        next = rb_next(&node->node);
 103        if (!next)
 104                return NULL;
 105        return container_of(next, struct timerqueue_node, node);
 106}
 107EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
 108