plist.c

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/*
 * lib/plist.c
 *
 * Descending-priority-sorted double-linked list
 *
 * (C) 2002-2003 Intel Corp
 * Inaky Perez-Gonzalez <[email protected]>.
 *
 * 2001-2005 (c) MontaVista Software, Inc.
 * Daniel Walker <[email protected]>
 *
 * (C) 2005 Thomas Gleixner <[email protected]>
 *
 * Simplifications of the original code by
 * Oleg Nesterov <[email protected]>
 *
 * Licensed under the FSF's GNU Public License v2 or later.
 *
 * Based on simple lists (include/linux/list.h).
 *
 * This file contains the add / del functions which are considered to
 * be too large to inline. See include/linux/plist.h for further
 * information.
 */

#include <linux/bug.h>
#include <linux/plist.h>
#include <linux/spinlock.h>

#ifdef CONFIG_DEBUG_PI_LIST

static struct plist_head test_head;

static void plist_check_prev_next(struct list_head *t, struct list_head *p,
                  struct list_head *n)
{
    WARN(n->prev != p || p->next != n,
            "top: %p, n: %p, p: %p\n"
            "prev: %p, n: %p, p: %p\n"
            "next: %p, n: %p, p: %p\n",
             t, t->next, t->prev,
            p, p->next, p->prev,
            n, n->next, n->prev);
}

static void plist_check_list(struct list_head *top)
{
    struct list_head *prev = top, *next = top->next;

    plist_check_prev_next(top, prev, next);
    while (next != top) {
        prev = next;
        next = prev->next;
        plist_check_prev_next(top, prev, next);
    }
}

static void plist_check_head(struct plist_head *head)
{
    if (!plist_head_empty(head))
        plist_check_list(&plist_first(head)->prio_list);
    plist_check_list(&head->node_list);
}

#else
# define plist_check_head(h)    do { } while (0)
#endif

void plist_add(struct plist_node *node, struct plist_head *head)
{
    struct plist_node *first, *iter, *prev = NULL;
    struct list_head *node_next = &head->node_list;

    plist_check_head(head);
    WARN_ON(!plist_node_empty(node));
    WARN_ON(!list_empty(&node->prio_list));

    if (plist_head_empty(head))
        goto ins_node;

    first = iter = plist_first(head);

    do {
        if (node->prio < iter->prio) {
            node_next = &iter->node_list;
            break;
        }

        prev = iter;
        iter = list_entry(iter->prio_list.next,
                struct plist_node, prio_list);
    } while (iter != first);

    if (!prev || prev->prio != node->prio)
        list_add_tail(&node->prio_list, &iter->prio_list);
ins_node:
    list_add_tail(&node->node_list, node_next);

    plist_check_head(head);
}

void plist_del(struct plist_node *node, struct plist_head *head)
{
    plist_check_head(head);

    if (!list_empty(&node->prio_list)) {
        if (node->node_list.next != &head->node_list) {
            struct plist_node *next;

            next = list_entry(node->node_list.next,
                    struct plist_node, node_list);

            /* add the next plist_node into prio_list */
            if (list_empty(&next->prio_list))
                list_add(&next->prio_list, &node->prio_list);
        }
        list_del_init(&node->prio_list);
    }

    list_del_init(&node->node_list);

    plist_check_head(head);
}

#ifdef CONFIG_DEBUG_PI_LIST
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/init.h>

static struct plist_node __initdata test_node[241];

static void __init plist_test_check(int nr_expect)
{
    struct plist_node *first, *prio_pos, *node_pos;

    if (plist_head_empty(&test_head)) {
        BUG_ON(nr_expect != 0);
        return;
    }

    prio_pos = first = plist_first(&test_head);
    plist_for_each(node_pos, &test_head) {
        if (nr_expect-- < 0)
            break;
        if (node_pos == first)
            continue;
        if (node_pos->prio == prio_pos->prio) {
            BUG_ON(!list_empty(&node_pos->prio_list));
            continue;
        }

        BUG_ON(prio_pos->prio > node_pos->prio);
        BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
        prio_pos = node_pos;
    }

    BUG_ON(nr_expect != 0);
    BUG_ON(prio_pos->prio_list.next != &first->prio_list);
}

static int  __init plist_test(void)
{
    int nr_expect = 0, i, loop;
    unsigned int r = local_clock();

    pr_debug("start plist test\n");
    plist_head_init(&test_head);
    for (i = 0; i < ARRAY_SIZE(test_node); i++)
        plist_node_init(test_node + i, 0);

    for (loop = 0; loop < 1000; loop++) {
        r = r * 193939 % 47629;
        i = r % ARRAY_SIZE(test_node);
        if (plist_node_empty(test_node + i)) {
            r = r * 193939 % 47629;
            test_node[i].prio = r % 99;
            plist_add(test_node + i, &test_head);
            nr_expect++;
        } else {
            plist_del(test_node + i, &test_head);
            nr_expect--;
        }
        plist_test_check(nr_expect);
    }

    for (i = 0; i < ARRAY_SIZE(test_node); i++) {
        if (plist_node_empty(test_node + i))
            continue;
        plist_del(test_node + i, &test_head);
        nr_expect--;
        plist_test_check(nr_expect);
    }

    pr_debug("end plist test\n");
    return 0;
}

module_init(plist_test);

#endif