linux/lib/plist.c
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   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/bug.h>
  27#include <linux/plist.h>
  28#include <linux/spinlock.h>
  29
  30#ifdef CONFIG_DEBUG_PI_LIST
  31
  32static struct plist_head test_head;
  33
  34static void plist_check_prev_next(struct list_head *t, struct list_head *p,
  35                                  struct list_head *n)
  36{
  37        WARN(n->prev != p || p->next != n,
  38                        "top: %p, n: %p, p: %p\n"
  39                        "prev: %p, n: %p, p: %p\n"
  40                        "next: %p, n: %p, p: %p\n",
  41                         t, t->next, t->prev,
  42                        p, p->next, p->prev,
  43                        n, n->next, n->prev);
  44}
  45
  46static void plist_check_list(struct list_head *top)
  47{
  48        struct list_head *prev = top, *next = top->next;
  49
  50        plist_check_prev_next(top, prev, next);
  51        while (next != top) {
  52                prev = next;
  53                next = prev->next;
  54                plist_check_prev_next(top, prev, next);
  55        }
  56}
  57
  58static void plist_check_head(struct plist_head *head)
  59{
  60        if (!plist_head_empty(head))
  61                plist_check_list(&plist_first(head)->prio_list);
  62        plist_check_list(&head->node_list);
  63}
  64
  65#else
  66# define plist_check_head(h)    do { } while (0)
  67#endif
  68
  69/**
  70 * plist_add - add @node to @head
  71 *
  72 * @node:       &struct plist_node pointer
  73 * @head:       &struct plist_head pointer
  74 */
  75void plist_add(struct plist_node *node, struct plist_head *head)
  76{
  77        struct plist_node *first, *iter, *prev = NULL;
  78        struct list_head *node_next = &head->node_list;
  79
  80        plist_check_head(head);
  81        WARN_ON(!plist_node_empty(node));
  82        WARN_ON(!list_empty(&node->prio_list));
  83
  84        if (plist_head_empty(head))
  85                goto ins_node;
  86
  87        first = iter = plist_first(head);
  88
  89        do {
  90                if (node->prio < iter->prio) {
  91                        node_next = &iter->node_list;
  92                        break;
  93                }
  94
  95                prev = iter;
  96                iter = list_entry(iter->prio_list.next,
  97                                struct plist_node, prio_list);
  98        } while (iter != first);
  99
 100        if (!prev || prev->prio != node->prio)
 101                list_add_tail(&node->prio_list, &iter->prio_list);
 102ins_node:
 103        list_add_tail(&node->node_list, node_next);
 104
 105        plist_check_head(head);
 106}
 107
 108/**
 109 * plist_del - Remove a @node from plist.
 110 *
 111 * @node:       &struct plist_node pointer - entry to be removed
 112 * @head:       &struct plist_head pointer - list head
 113 */
 114void plist_del(struct plist_node *node, struct plist_head *head)
 115{
 116        plist_check_head(head);
 117
 118        if (!list_empty(&node->prio_list)) {
 119                if (node->node_list.next != &head->node_list) {
 120                        struct plist_node *next;
 121
 122                        next = list_entry(node->node_list.next,
 123                                        struct plist_node, node_list);
 124
 125                        /* add the next plist_node into prio_list */
 126                        if (list_empty(&next->prio_list))
 127                                list_add(&next->prio_list, &node->prio_list);
 128                }
 129                list_del_init(&node->prio_list);
 130        }
 131
 132        list_del_init(&node->node_list);
 133
 134        plist_check_head(head);
 135}
 136
 137#ifdef CONFIG_DEBUG_PI_LIST
 138#include <linux/sched.h>
 139#include <linux/module.h>
 140#include <linux/init.h>
 141
 142static struct plist_node __initdata test_node[241];
 143
 144static void __init plist_test_check(int nr_expect)
 145{
 146        struct plist_node *first, *prio_pos, *node_pos;
 147
 148        if (plist_head_empty(&test_head)) {
 149                BUG_ON(nr_expect != 0);
 150                return;
 151        }
 152
 153        prio_pos = first = plist_first(&test_head);
 154        plist_for_each(node_pos, &test_head) {
 155                if (nr_expect-- < 0)
 156                        break;
 157                if (node_pos == first)
 158                        continue;
 159                if (node_pos->prio == prio_pos->prio) {
 160                        BUG_ON(!list_empty(&node_pos->prio_list));
 161                        continue;
 162                }
 163
 164                BUG_ON(prio_pos->prio > node_pos->prio);
 165                BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
 166                prio_pos = node_pos;
 167        }
 168
 169        BUG_ON(nr_expect != 0);
 170        BUG_ON(prio_pos->prio_list.next != &first->prio_list);
 171}
 172
 173static int  __init plist_test(void)
 174{
 175        int nr_expect = 0, i, loop;
 176        unsigned int r = local_clock();
 177
 178        pr_debug("start plist test\n");
 179        plist_head_init(&test_head);
 180        for (i = 0; i < ARRAY_SIZE(test_node); i++)
 181                plist_node_init(test_node + i, 0);
 182
 183        for (loop = 0; loop < 1000; loop++) {
 184                r = r * 193939 % 47629;
 185                i = r % ARRAY_SIZE(test_node);
 186                if (plist_node_empty(test_node + i)) {
 187                        r = r * 193939 % 47629;
 188                        test_node[i].prio = r % 99;
 189                        plist_add(test_node + i, &test_head);
 190                        nr_expect++;
 191                } else {
 192                        plist_del(test_node + i, &test_head);
 193                        nr_expect--;
 194                }
 195                plist_test_check(nr_expect);
 196        }
 197
 198        for (i = 0; i < ARRAY_SIZE(test_node); i++) {
 199                if (plist_node_empty(test_node + i))
 200                        continue;
 201                plist_del(test_node + i, &test_head);
 202                nr_expect--;
 203                plist_test_check(nr_expect);
 204        }
 205
 206        pr_debug("end plist test\n");
 207        return 0;
 208}
 209
 210module_init(plist_test);
 211
 212#endif
 213
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