Loading...
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * lib/plist.c
4 *
5 * Descending-priority-sorted double-linked list
6 *
7 * (C) 2002-2003 Intel Corp
8 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
9 *
10 * 2001-2005 (c) MontaVista Software, Inc.
11 * Daniel Walker <dwalker@mvista.com>
12 *
13 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
14 *
15 * Simplifications of the original code by
16 * Oleg Nesterov <oleg@tv-sign.ru>
17 *
18 * Based on simple lists (include/linux/list.h).
19 *
20 * This file contains the add / del functions which are considered to
21 * be too large to inline. See include/linux/plist.h for further
22 * information.
23 */
24
25#include <linux/bug.h>
26#include <linux/plist.h>
27
28#ifdef CONFIG_DEBUG_PLIST
29
30static struct plist_head test_head;
31
32static void plist_check_prev_next(struct list_head *t, struct list_head *p,
33 struct list_head *n)
34{
35 WARN(n->prev != p || p->next != n,
36 "top: %p, n: %p, p: %p\n"
37 "prev: %p, n: %p, p: %p\n"
38 "next: %p, n: %p, p: %p\n",
39 t, t->next, t->prev,
40 p, p->next, p->prev,
41 n, n->next, n->prev);
42}
43
44static void plist_check_list(struct list_head *top)
45{
46 struct list_head *prev = top, *next = top->next;
47
48 plist_check_prev_next(top, prev, next);
49 while (next != top) {
50 prev = next;
51 next = prev->next;
52 plist_check_prev_next(top, prev, next);
53 }
54}
55
56static void plist_check_head(struct plist_head *head)
57{
58 if (!plist_head_empty(head))
59 plist_check_list(&plist_first(head)->prio_list);
60 plist_check_list(&head->node_list);
61}
62
63#else
64# define plist_check_head(h) do { } while (0)
65#endif
66
67/**
68 * plist_add - add @node to @head
69 *
70 * @node: &struct plist_node pointer
71 * @head: &struct plist_head pointer
72 */
73void plist_add(struct plist_node *node, struct plist_head *head)
74{
75 struct plist_node *first, *iter, *prev = NULL;
76 struct list_head *node_next = &head->node_list;
77
78 plist_check_head(head);
79 WARN_ON(!plist_node_empty(node));
80 WARN_ON(!list_empty(&node->prio_list));
81
82 if (plist_head_empty(head))
83 goto ins_node;
84
85 first = iter = plist_first(head);
86
87 do {
88 if (node->prio < iter->prio) {
89 node_next = &iter->node_list;
90 break;
91 }
92
93 prev = iter;
94 iter = list_entry(iter->prio_list.next,
95 struct plist_node, prio_list);
96 } while (iter != first);
97
98 if (!prev || prev->prio != node->prio)
99 list_add_tail(&node->prio_list, &iter->prio_list);
100ins_node:
101 list_add_tail(&node->node_list, node_next);
102
103 plist_check_head(head);
104}
105
106/**
107 * plist_del - Remove a @node from plist.
108 *
109 * @node: &struct plist_node pointer - entry to be removed
110 * @head: &struct plist_head pointer - list head
111 */
112void plist_del(struct plist_node *node, struct plist_head *head)
113{
114 plist_check_head(head);
115
116 if (!list_empty(&node->prio_list)) {
117 if (node->node_list.next != &head->node_list) {
118 struct plist_node *next;
119
120 next = list_entry(node->node_list.next,
121 struct plist_node, node_list);
122
123 /* add the next plist_node into prio_list */
124 if (list_empty(&next->prio_list))
125 list_add(&next->prio_list, &node->prio_list);
126 }
127 list_del_init(&node->prio_list);
128 }
129
130 list_del_init(&node->node_list);
131
132 plist_check_head(head);
133}
134
135/**
136 * plist_requeue - Requeue @node at end of same-prio entries.
137 *
138 * This is essentially an optimized plist_del() followed by
139 * plist_add(). It moves an entry already in the plist to
140 * after any other same-priority entries.
141 *
142 * @node: &struct plist_node pointer - entry to be moved
143 * @head: &struct plist_head pointer - list head
144 */
145void plist_requeue(struct plist_node *node, struct plist_head *head)
146{
147 struct plist_node *iter;
148 struct list_head *node_next = &head->node_list;
149
150 plist_check_head(head);
151 BUG_ON(plist_head_empty(head));
152 BUG_ON(plist_node_empty(node));
153
154 if (node == plist_last(head))
155 return;
156
157 iter = plist_next(node);
158
159 if (node->prio != iter->prio)
160 return;
161
162 plist_del(node, head);
163
164 plist_for_each_continue(iter, head) {
165 if (node->prio != iter->prio) {
166 node_next = &iter->node_list;
167 break;
168 }
169 }
170 list_add_tail(&node->node_list, node_next);
171
172 plist_check_head(head);
173}
174
175#ifdef CONFIG_DEBUG_PLIST
176#include <linux/sched.h>
177#include <linux/sched/clock.h>
178#include <linux/module.h>
179#include <linux/init.h>
180
181static struct plist_node __initdata test_node[241];
182
183static void __init plist_test_check(int nr_expect)
184{
185 struct plist_node *first, *prio_pos, *node_pos;
186
187 if (plist_head_empty(&test_head)) {
188 BUG_ON(nr_expect != 0);
189 return;
190 }
191
192 prio_pos = first = plist_first(&test_head);
193 plist_for_each(node_pos, &test_head) {
194 if (nr_expect-- < 0)
195 break;
196 if (node_pos == first)
197 continue;
198 if (node_pos->prio == prio_pos->prio) {
199 BUG_ON(!list_empty(&node_pos->prio_list));
200 continue;
201 }
202
203 BUG_ON(prio_pos->prio > node_pos->prio);
204 BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
205 prio_pos = node_pos;
206 }
207
208 BUG_ON(nr_expect != 0);
209 BUG_ON(prio_pos->prio_list.next != &first->prio_list);
210}
211
212static void __init plist_test_requeue(struct plist_node *node)
213{
214 plist_requeue(node, &test_head);
215
216 if (node != plist_last(&test_head))
217 BUG_ON(node->prio == plist_next(node)->prio);
218}
219
220static int __init plist_test(void)
221{
222 int nr_expect = 0, i, loop;
223 unsigned int r = local_clock();
224
225 printk(KERN_DEBUG "start plist test\n");
226 plist_head_init(&test_head);
227 for (i = 0; i < ARRAY_SIZE(test_node); i++)
228 plist_node_init(test_node + i, 0);
229
230 for (loop = 0; loop < 1000; loop++) {
231 r = r * 193939 % 47629;
232 i = r % ARRAY_SIZE(test_node);
233 if (plist_node_empty(test_node + i)) {
234 r = r * 193939 % 47629;
235 test_node[i].prio = r % 99;
236 plist_add(test_node + i, &test_head);
237 nr_expect++;
238 } else {
239 plist_del(test_node + i, &test_head);
240 nr_expect--;
241 }
242 plist_test_check(nr_expect);
243 if (!plist_node_empty(test_node + i)) {
244 plist_test_requeue(test_node + i);
245 plist_test_check(nr_expect);
246 }
247 }
248
249 for (i = 0; i < ARRAY_SIZE(test_node); i++) {
250 if (plist_node_empty(test_node + i))
251 continue;
252 plist_del(test_node + i, &test_head);
253 nr_expect--;
254 plist_test_check(nr_expect);
255 }
256
257 printk(KERN_DEBUG "end plist test\n");
258 return 0;
259}
260
261module_init(plist_test);
262
263#endif