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         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
  43 static 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
  55 static 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  */
  74 void 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
  91 lt_prio:
  92         list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
  93 eq_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  */
 105 void 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 }