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 bool 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 < ptr->expires)
  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 < head->next->expires) {
  60                 head->next = node;
  61                 return true;
  62         }
  63         return false;
  64 }
  65 EXPORT_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  */
  75 bool 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 }
  90 EXPORT_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  */
 101 struct 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 }
 112 EXPORT_SYMBOL_GPL(timerqueue_iterate_next);