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/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  */
  38 void 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 }
  61 EXPORT_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  */
  71 void 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 }
  85 EXPORT_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  */
  96 struct 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 }
 107 EXPORT_SYMBOL_GPL(timerqueue_iterate_next);