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
  31 static 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
  42 static 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
  54 static 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  */
  73 void 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
  90 lt_prio:
  91         list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
  92 eq_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  */
 104 void 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 }