LXR linux/lib/plist.c

   1/*
   2 * lib/plist.c
   3 *
   4 * Descending-priority-sorted double-linked list
   5 *
   6 * (C) 2002-2003 Intel Corp
   7 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
   8 *
   9 * 2001-2005 (c) MontaVista Software, Inc.
  10 * Daniel Walker <dwalker@mvista.com>
  11 *
  12 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
  13 *
  14 * Simplifications of the original code by
  15 * Oleg Nesterov <oleg@tv-sign.ru>
  16 *
  17 * Licensed under the FSF's GNU Public License v2 or later.
  18 *
  19 * Based on simple lists (include/linux/list.h).
  20 *
  21 * This file contains the add / del functions which are considered to
  22 * be too large to inline. See include/linux/plist.h for further
  23 * information.
  24 */
  25
  26#include <linux/plist.h>
  27#include <linux/spinlock.h>
  28
  29#ifdef CONFIG_DEBUG_PI_LIST
  30
  31static void plist_check_prev_next(struct list_head *t, struct list_head *p,
  32                                  struct list_head *n)
  33{
  34        if (n->prev != p || p->next != n) {
  35                printk("top: %p, n: %p, p: %p\n", t, t->next, t->prev);
  36                printk("prev: %p, n: %p, p: %p\n", p, p->next, p->prev);
  37                printk("next: %p, n: %p, p: %p\n", n, n->next, n->prev);
  38                WARN_ON(1);
  39        }
  40}
  41
  42static void plist_check_list(struct list_head *top)
  43{
  44        struct list_head *prev = top, *next = top->next;
  45
  46        plist_check_prev_next(top, prev, next);
  47        while (next != top) {
  48                prev = next;
  49                next = prev->next;
  50                plist_check_prev_next(top, prev, next);
  51        }
  52}
  53
  54static void plist_check_head(struct plist_head *head)
  55{
  56        WARN_ON(!head->lock);
  57        if (head->lock)
  58                WARN_ON_SMP(!spin_is_locked(head->lock));
  59        plist_check_list(&head->prio_list);
  60        plist_check_list(&head->node_list);
  61}
  62
  63#else
  64# define plist_check_head(h)    do { } while (0)
  65#endif
  66
  67/**
  68 * plist_add - add @node to @head
  69 *
  70 * @node:       &struct plist_node pointer
  71 * @head:       &struct plist_head pointer
  72 */
  73void plist_add(struct plist_node *node, struct plist_head *head)
  74{
  75        struct plist_node *iter;
  76
  77        plist_check_head(head);
  78        WARN_ON(!plist_node_empty(node));
  79
  80        list_for_each_entry(iter, &head->prio_list, plist.prio_list) {
  81                if (node->prio < iter->prio)
  82                        goto lt_prio;
  83                else if (node->prio == iter->prio) {
  84                        iter = list_entry(iter->plist.prio_list.next,
  85                                        struct plist_node, plist.prio_list);
  86                        goto eq_prio;
  87                }
  88        }
  89
  90lt_prio:
  91        list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
  92eq_prio:
  93        list_add_tail(&node->plist.node_list, &iter->plist.node_list);
  94
  95        plist_check_head(head);
  96}
  97
  98/**
  99 * plist_del - Remove a @node from plist.
 100 *
 101 * @node:       &struct plist_node pointer - entry to be removed
 102 * @head:       &struct plist_head pointer - list head
 103 */
 104void plist_del(struct plist_node *node, struct plist_head *head)
 105{
 106        plist_check_head(head);
 107
 108        if (!list_empty(&node->plist.prio_list)) {
 109                struct plist_node *next = plist_first(&node->plist);
 110
 111                list_move_tail(&next->plist.prio_list, &node->plist.prio_list);
 112                list_del_init(&node->plist.prio_list);
 113        }
 114
 115        list_del_init(&node->plist.node_list);
 116
 117        plist_check_head(head);
 118}
 119