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        WARN(n->prev != p || p->next != n,
  35                        "top: %p, n: %p, p: %p\n"
  36                        "prev: %p, n: %p, p: %p\n"
  37                        "next: %p, n: %p, p: %p\n",
  38                         t, t->next, t->prev,
  39                        p, p->next, p->prev,
  40                        n, n->next, n->prev);
  41}
  42
  43static void plist_check_list(struct list_head *top)
  44{
  45        struct list_head *prev = top, *next = top->next;
  46
  47        plist_check_prev_next(top, prev, next);
  48        while (next != top) {
  49                prev = next;
  50                next = prev->next;
  51                plist_check_prev_next(top, prev, next);
  52        }
  53}
  54
  55static void plist_check_head(struct plist_head *head)
  56{
  57        WARN_ON(!head->lock);
  58        if (head->lock)
  59                WARN_ON_SMP(!spin_is_locked(head->lock));
  60        plist_check_list(&head->prio_list);
  61        plist_check_list(&head->node_list);
  62}
  63
  64#else
  65# define plist_check_head(h)    do { } while (0)
  66#endif
  67
  68/**
  69 * plist_add - add @node to @head
  70 *
  71 * @node:       &struct plist_node pointer
  72 * @head:       &struct plist_head pointer
  73 */
  74void plist_add(struct plist_node *node, struct plist_head *head)
  75{
  76        struct plist_node *iter;
  77
  78        plist_check_head(head);
  79        WARN_ON(!plist_node_empty(node));
  80
  81        list_for_each_entry(iter, &head->prio_list, plist.prio_list) {
  82                if (node->prio < iter->prio)
  83                        goto lt_prio;
  84                else if (node->prio == iter->prio) {
  85                        iter = list_entry(iter->plist.prio_list.next,
  86                                        struct plist_node, plist.prio_list);
  87                        goto eq_prio;
  88                }
  89        }
  90
  91lt_prio:
  92        list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
  93eq_prio:
  94        list_add_tail(&node->plist.node_list, &iter->plist.node_list);
  95
  96        plist_check_head(head);
  97}
  98
  99/**
 100 * plist_del - Remove a @node from plist.
 101 *
 102 * @node:       &struct plist_node pointer - entry to be removed
 103 * @head:       &struct plist_head pointer - list head
 104 */
 105void plist_del(struct plist_node *node, struct plist_head *head)
 106{
 107        plist_check_head(head);
 108
 109        if (!list_empty(&node->plist.prio_list)) {
 110                struct plist_node *next = plist_first(&node->plist);
 111
 112                list_move_tail(&next->plist.prio_list, &node->plist.prio_list);
 113                list_del_init(&node->plist.prio_list);
 114        }
 115
 116        list_del_init(&node->plist.node_list);
 117
 118        plist_check_head(head);
 119}
 120