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
29#ifdef CONFIG_DEBUG_PI_LIST
30
31static struct plist_head test_head;
32
33static 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
45static 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
57static 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 */
74void 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);
101ins_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 */
113void 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/**
137 * plist_requeue - Requeue @node at end of same-prio entries.
138 *
139 * This is essentially an optimized plist_del() followed by
140 * plist_add(). It moves an entry already in the plist to
141 * after any other same-priority entries.
142 *
143 * @node: &struct plist_node pointer - entry to be moved
144 * @head: &struct plist_head pointer - list head
145 */
146void plist_requeue(struct plist_node *node, struct plist_head *head)
147{
148 struct plist_node *iter;
149 struct list_head *node_next = &head->node_list;
150
151 plist_check_head(head);
152 BUG_ON(plist_head_empty(head));
153 BUG_ON(plist_node_empty(node));
154
155 if (node == plist_last(head))
156 return;
157
158 iter = plist_next(node);
159
160 if (node->prio != iter->prio)
161 return;
162
163 plist_del(node, head);
164
165 plist_for_each_continue(iter, head) {
166 if (node->prio != iter->prio) {
167 node_next = &iter->node_list;
168 break;
169 }
170 }
171 list_add_tail(&node->node_list, node_next);
172
173 plist_check_head(head);
174}
175
176#ifdef CONFIG_DEBUG_PI_LIST
177#include <linux/sched.h>
178#include <linux/sched/clock.h>
179#include <linux/module.h>
180#include <linux/init.h>
181
182static struct plist_node __initdata test_node[241];
183
184static void __init plist_test_check(int nr_expect)
185{
186 struct plist_node *first, *prio_pos, *node_pos;
187
188 if (plist_head_empty(&test_head)) {
189 BUG_ON(nr_expect != 0);
190 return;
191 }
192
193 prio_pos = first = plist_first(&test_head);
194 plist_for_each(node_pos, &test_head) {
195 if (nr_expect-- < 0)
196 break;
197 if (node_pos == first)
198 continue;
199 if (node_pos->prio == prio_pos->prio) {
200 BUG_ON(!list_empty(&node_pos->prio_list));
201 continue;
202 }
203
204 BUG_ON(prio_pos->prio > node_pos->prio);
205 BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
206 prio_pos = node_pos;
207 }
208
209 BUG_ON(nr_expect != 0);
210 BUG_ON(prio_pos->prio_list.next != &first->prio_list);
211}
212
213static void __init plist_test_requeue(struct plist_node *node)
214{
215 plist_requeue(node, &test_head);
216
217 if (node != plist_last(&test_head))
218 BUG_ON(node->prio == plist_next(node)->prio);
219}
220
221static int __init plist_test(void)
222{
223 int nr_expect = 0, i, loop;
224 unsigned int r = local_clock();
225
226 printk(KERN_DEBUG "start plist test\n");
227 plist_head_init(&test_head);
228 for (i = 0; i < ARRAY_SIZE(test_node); i++)
229 plist_node_init(test_node + i, 0);
230
231 for (loop = 0; loop < 1000; loop++) {
232 r = r * 193939 % 47629;
233 i = r % ARRAY_SIZE(test_node);
234 if (plist_node_empty(test_node + i)) {
235 r = r * 193939 % 47629;
236 test_node[i].prio = r % 99;
237 plist_add(test_node + i, &test_head);
238 nr_expect++;
239 } else {
240 plist_del(test_node + i, &test_head);
241 nr_expect--;
242 }
243 plist_test_check(nr_expect);
244 if (!plist_node_empty(test_node + i)) {
245 plist_test_requeue(test_node + i);
246 plist_test_check(nr_expect);
247 }
248 }
249
250 for (i = 0; i < ARRAY_SIZE(test_node); i++) {
251 if (plist_node_empty(test_node + i))
252 continue;
253 plist_del(test_node + i, &test_head);
254 nr_expect--;
255 plist_test_check(nr_expect);
256 }
257
258 printk(KERN_DEBUG "end plist test\n");
259 return 0;
260}
261
262module_init(plist_test);
263
264#endif
265