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  */
  39 void 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 }
  62 EXPORT_SYMBOL_GPL(timerqueue_add);
  63
  64 /**
  65  * timerqueue_del - Removes a timer from the timerqueue.
  66  *
  67  * @head: head of timerqueue
  68  * @node: timer node to be removed
  69  *
  70  * Removes the timer node from the timerqueue.
  71  */
  72 void timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
  73 {
  74         WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
  75
  76         /* update next pointer */
  77         if (head->next == node) {
  78                 struct rb_node *rbn = rb_next(&node->node);
  79
  80                 head->next = rbn ?
  81                         rb_entry(rbn, struct timerqueue_node, node) : NULL;
  82         }
  83         rb_erase(&node->node, &head->head);
  84         RB_CLEAR_NODE(&node->node);
  85 }
  86 EXPORT_SYMBOL_GPL(timerqueue_del);
  87
  88 /**
  89  * timerqueue_iterate_next - Returns the timer after the provided timer
  90  *
  91  * @node: Pointer to a timer.
  92  *
  93  * Provides the timer that is after the given node. This is used, when
  94  * necessary, to iterate through the list of timers in a timer list
  95  * without modifying the list.
  96  */
  97 struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
  98 {
  99         struct rb_node *next;
 100
 101         if (!node)
 102                 return NULL;
 103         next = rb_next(&node->node);
 104         if (!next)
 105                 return NULL;
 106         return container_of(next, struct timerqueue_node, node);
 107 }
 108 EXPORT_SYMBOL_GPL(timerqueue_iterate_next);