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         WARN_ON(head != &test_head && !head->rawlock && !head->spinlock);
  60         if (head->rawlock)
  61                 WARN_ON_SMP(!raw_spin_is_locked(head->rawlock));
  62         if (head->spinlock)
  63                 WARN_ON_SMP(!spin_is_locked(head->spinlock));
  64         if (!plist_head_empty(head))
  65                 plist_check_list(&plist_first(head)->prio_list);
  66         plist_check_list(&head->node_list);
  67 }
  68
  69 #else
  70 # define plist_check_head(h)    do { } while (0)
  71 #endif
  72
  73 /**
  74  * plist_add - add @node to @head
  75  *
  76  * @node:       &struct plist_node pointer
  77  * @head:       &struct plist_head pointer
  78  */
  79 void plist_add(struct plist_node *node, struct plist_head *head)
  80 {
  81         struct plist_node *first, *iter, *prev = NULL;
  82         struct list_head *node_next = &head->node_list;
  83
  84         plist_check_head(head);
  85         WARN_ON(!plist_node_empty(node));
  86         WARN_ON(!list_empty(&node->prio_list));
  87
  88         if (plist_head_empty(head))
  89                 goto ins_node;
  90
  91         first = iter = plist_first(head);
  92
  93         do {
  94                 if (node->prio < iter->prio) {
  95                         node_next = &iter->node_list;
  96                         break;
  97                 }
  98
  99                 prev = iter;
 100                 iter = list_entry(iter->prio_list.next,
 101                                 struct plist_node, prio_list);
 102         } while (iter != first);
 103
 104         if (!prev || prev->prio != node->prio)
 105                 list_add_tail(&node->prio_list, &iter->prio_list);
 106 ins_node:
 107         list_add_tail(&node->node_list, node_next);
 108
 109         plist_check_head(head);
 110 }
 111
 112 /**
 113  * plist_del - Remove a @node from plist.
 114  *
 115  * @node:       &struct plist_node pointer - entry to be removed
 116  * @head:       &struct plist_head pointer - list head
 117  */
 118 void plist_del(struct plist_node *node, struct plist_head *head)
 119 {
 120         plist_check_head(head);
 121
 122         if (!list_empty(&node->prio_list)) {
 123                 if (node->node_list.next != &head->node_list) {
 124                         struct plist_node *next;
 125
 126                         next = list_entry(node->node_list.next,
 127                                         struct plist_node, node_list);
 128
 129                         /* add the next plist_node into prio_list */
 130                         if (list_empty(&next->prio_list))
 131                                 list_add(&next->prio_list, &node->prio_list);
 132                 }
 133                 list_del_init(&node->prio_list);
 134         }
 135
 136         list_del_init(&node->node_list);
 137
 138         plist_check_head(head);
 139 }
 140
 141 #ifdef CONFIG_DEBUG_PI_LIST
 142 #include <linux/sched.h>
 143 #include <linux/module.h>
 144 #include <linux/init.h>
 145
 146 static struct plist_node __initdata test_node[241];
 147
 148 static void __init plist_test_check(int nr_expect)
 149 {
 150         struct plist_node *first, *prio_pos, *node_pos;
 151
 152         if (plist_head_empty(&test_head)) {
 153                 BUG_ON(nr_expect != 0);
 154                 return;
 155         }
 156
 157         prio_pos = first = plist_first(&test_head);
 158         plist_for_each(node_pos, &test_head) {
 159                 if (nr_expect-- < 0)
 160                         break;
 161                 if (node_pos == first)
 162                         continue;
 163                 if (node_pos->prio == prio_pos->prio) {
 164                         BUG_ON(!list_empty(&node_pos->prio_list));
 165                         continue;
 166                 }
 167
 168                 BUG_ON(prio_pos->prio > node_pos->prio);
 169                 BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
 170                 prio_pos = node_pos;
 171         }
 172
 173         BUG_ON(nr_expect != 0);
 174         BUG_ON(prio_pos->prio_list.next != &first->prio_list);
 175 }
 176
 177 static int  __init plist_test(void)
 178 {
 179         int nr_expect = 0, i, loop;
 180         unsigned int r = local_clock();
 181
 182         printk(KERN_INFO "start plist test\n");
 183         plist_head_init(&test_head, NULL);
 184         for (i = 0; i < ARRAY_SIZE(test_node); i++)
 185                 plist_node_init(test_node + i, 0);
 186
 187         for (loop = 0; loop < 1000; loop++) {
 188                 r = r * 193939 % 47629;
 189                 i = r % ARRAY_SIZE(test_node);
 190                 if (plist_node_empty(test_node + i)) {
 191                         r = r * 193939 % 47629;
 192                         test_node[i].prio = r % 99;
 193                         plist_add(test_node + i, &test_head);
 194                         nr_expect++;
 195                 } else {
 196                         plist_del(test_node + i, &test_head);
 197                         nr_expect--;
 198                 }
 199                 plist_test_check(nr_expect);
 200         }
 201
 202         for (i = 0; i < ARRAY_SIZE(test_node); i++) {
 203                 if (plist_node_empty(test_node + i))
 204                         continue;
 205                 plist_del(test_node + i, &test_head);
 206                 nr_expect--;
 207                 plist_test_check(nr_expect);
 208         }
 209
 210         printk(KERN_INFO "end plist test\n");
 211         return 0;
 212 }
 213
 214 module_init(plist_test);
 215
 216 #endif