timerqueue.c

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    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);

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FreeBSD/Linux Kernel Cross Reference sys/lib/timerqueue.c

FreeBSD/Linux Kernel Cross Reference
sys/lib/timerqueue.c