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 struct plist_head test_head;
  32
  33 static void plist_check_prev_next(struct list_head *t, struct list_head *p,
  34                                   struct list_head *n)
  35 {
  36         WARN(n->prev != p || p->next != n,
  37                         "top: %p, n: %p, p: %p\n"
  38                         "prev: %p, n: %p, p: %p\n"
  39                         "next: %p, n: %p, p: %p\n",
  40                          t, t->next, t->prev,
  41                         p, p->next, p->prev,
  42                         n, n->next, n->prev);
  43 }
  44
  45 static void plist_check_list(struct list_head *top)
  46 {
  47         struct list_head *prev = top, *next = top->next;
  48
  49         plist_check_prev_next(top, prev, next);
  50         while (next != top) {
  51                 prev = next;
  52                 next = prev->next;
  53                 plist_check_prev_next(top, prev, next);
  54         }
  55 }
  56
  57 static void plist_check_head(struct plist_head *head)
  58 {
  59         if (!plist_head_empty(head))
  60                 plist_check_list(&plist_first(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 *first, *iter, *prev = NULL;
  77         struct list_head *node_next = &head->node_list;
  78
  79         plist_check_head(head);
  80         WARN_ON(!plist_node_empty(node));
  81         WARN_ON(!list_empty(&node->prio_list));
  82
  83         if (plist_head_empty(head))
  84                 goto ins_node;
  85
  86         first = iter = plist_first(head);
  87
  88         do {
  89                 if (node->prio < iter->prio) {
  90                         node_next = &iter->node_list;
  91                         break;
  92                 }
  93
  94                 prev = iter;
  95                 iter = list_entry(iter->prio_list.next,
  96                                 struct plist_node, prio_list);
  97         } while (iter != first);
  98
  99         if (!prev || prev->prio != node->prio)
 100                 list_add_tail(&node->prio_list, &iter->prio_list);
 101 ins_node:
 102         list_add_tail(&node->node_list, node_next);
 103
 104         plist_check_head(head);
 105 }
 106
 107 /**
 108  * plist_del - Remove a @node from plist.
 109  *
 110  * @node:       &struct plist_node pointer - entry to be removed
 111  * @head:       &struct plist_head pointer - list head
 112  */
 113 void plist_del(struct plist_node *node, struct plist_head *head)
 114 {
 115         plist_check_head(head);
 116
 117         if (!list_empty(&node->prio_list)) {
 118                 if (node->node_list.next != &head->node_list) {
 119                         struct plist_node *next;
 120
 121                         next = list_entry(node->node_list.next,
 122                                         struct plist_node, node_list);
 123
 124                         /* add the next plist_node into prio_list */
 125                         if (list_empty(&next->prio_list))
 126                                 list_add(&next->prio_list, &node->prio_list);
 127                 }
 128                 list_del_init(&node->prio_list);
 129         }
 130
 131         list_del_init(&node->node_list);
 132
 133         plist_check_head(head);
 134 }
 135
 136 #ifdef CONFIG_DEBUG_PI_LIST
 137 #include <linux/sched.h>
 138 #include <linux/module.h>
 139 #include <linux/init.h>
 140
 141 static struct plist_node __initdata test_node[241];
 142
 143 static void __init plist_test_check(int nr_expect)
 144 {
 145         struct plist_node *first, *prio_pos, *node_pos;
 146
 147         if (plist_head_empty(&test_head)) {
 148                 BUG_ON(nr_expect != 0);
 149                 return;
 150         }
 151
 152         prio_pos = first = plist_first(&test_head);
 153         plist_for_each(node_pos, &test_head) {
 154                 if (nr_expect-- < 0)
 155                         break;
 156                 if (node_pos == first)
 157                         continue;
 158                 if (node_pos->prio == prio_pos->prio) {
 159                         BUG_ON(!list_empty(&node_pos->prio_list));
 160                         continue;
 161                 }
 162
 163                 BUG_ON(prio_pos->prio > node_pos->prio);
 164                 BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
 165                 prio_pos = node_pos;
 166         }
 167
 168         BUG_ON(nr_expect != 0);
 169         BUG_ON(prio_pos->prio_list.next != &first->prio_list);
 170 }
 171
 172 static int  __init plist_test(void)
 173 {
 174         int nr_expect = 0, i, loop;
 175         unsigned int r = local_clock();
 176
 177         printk(KERN_INFO "start plist test\n");
 178         plist_head_init(&test_head);
 179         for (i = 0; i < ARRAY_SIZE(test_node); i++)
 180                 plist_node_init(test_node + i, 0);
 181
 182         for (loop = 0; loop < 1000; loop++) {
 183                 r = r * 193939 % 47629;
 184                 i = r % ARRAY_SIZE(test_node);
 185                 if (plist_node_empty(test_node + i)) {
 186                         r = r * 193939 % 47629;
 187                         test_node[i].prio = r % 99;
 188                         plist_add(test_node + i, &test_head);
 189                         nr_expect++;
 190                 } else {
 191                         plist_del(test_node + i, &test_head);
 192                         nr_expect--;
 193                 }
 194                 plist_test_check(nr_expect);
 195         }
 196
 197         for (i = 0; i < ARRAY_SIZE(test_node); i++) {
 198                 if (plist_node_empty(test_node + i))
 199                         continue;
 200                 plist_del(test_node + i, &test_head);
 201                 nr_expect--;
 202                 plist_test_check(nr_expect);
 203         }
 204
 205         printk(KERN_INFO "end plist test\n");
 206         return 0;
 207 }
 208
 209 module_init(plist_test);
 210
 211 #endif