Root/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/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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