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
30 static struct plist_head test_head;
31
plist_check_prev_next(struct list_head * t,struct list_head * p,struct list_head * n)32 static 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
plist_check_list(struct list_head * top)44 static 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
plist_check_head(struct plist_head * head)56 static 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 */
plist_add(struct plist_node * node,struct plist_head * head)73 void 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);
100 ins_node:
101 list_add_tail(&node->node_list, node_next);
102
103 plist_check_head(head);
104 }
105 EXPORT_SYMBOL_GPL(plist_add);
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 */
plist_del(struct plist_node * node,struct plist_head * head)113 void 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 EXPORT_SYMBOL_GPL(plist_del);
136
137 /**
138 * plist_requeue - Requeue @node at end of same-prio entries.
139 *
140 * This is essentially an optimized plist_del() followed by
141 * plist_add(). It moves an entry already in the plist to
142 * after any other same-priority entries.
143 *
144 * @node: &struct plist_node pointer - entry to be moved
145 * @head: &struct plist_head pointer - list head
146 */
plist_requeue(struct plist_node * node,struct plist_head * head)147 void plist_requeue(struct plist_node *node, struct plist_head *head)
148 {
149 struct plist_node *iter;
150 struct list_head *node_next = &head->node_list;
151
152 plist_check_head(head);
153 BUG_ON(plist_head_empty(head));
154 BUG_ON(plist_node_empty(node));
155
156 if (node == plist_last(head))
157 return;
158
159 iter = plist_next(node);
160
161 if (node->prio != iter->prio)
162 return;
163
164 plist_del(node, head);
165
166 plist_for_each_continue(iter, head) {
167 if (node->prio != iter->prio) {
168 node_next = &iter->node_list;
169 break;
170 }
171 }
172 list_add_tail(&node->node_list, node_next);
173
174 plist_check_head(head);
175 }
176 EXPORT_SYMBOL_GPL(plist_requeue);
177
178 #ifdef CONFIG_DEBUG_PLIST
179 #include <linux/sched.h>
180 #include <linux/sched/clock.h>
181 #include <linux/module.h>
182 #include <linux/init.h>
183
184 static struct plist_node __initdata test_node[241];
185
plist_test_check(int nr_expect)186 static void __init plist_test_check(int nr_expect)
187 {
188 struct plist_node *first, *prio_pos, *node_pos;
189
190 if (plist_head_empty(&test_head)) {
191 BUG_ON(nr_expect != 0);
192 return;
193 }
194
195 prio_pos = first = plist_first(&test_head);
196 plist_for_each(node_pos, &test_head) {
197 if (nr_expect-- < 0)
198 break;
199 if (node_pos == first)
200 continue;
201 if (node_pos->prio == prio_pos->prio) {
202 BUG_ON(!list_empty(&node_pos->prio_list));
203 continue;
204 }
205
206 BUG_ON(prio_pos->prio > node_pos->prio);
207 BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
208 prio_pos = node_pos;
209 }
210
211 BUG_ON(nr_expect != 0);
212 BUG_ON(prio_pos->prio_list.next != &first->prio_list);
213 }
214
plist_test_requeue(struct plist_node * node)215 static void __init plist_test_requeue(struct plist_node *node)
216 {
217 plist_requeue(node, &test_head);
218
219 if (node != plist_last(&test_head))
220 BUG_ON(node->prio == plist_next(node)->prio);
221 }
222
plist_test(void)223 static int __init plist_test(void)
224 {
225 int nr_expect = 0, i, loop;
226 unsigned int r = local_clock();
227
228 printk(KERN_DEBUG "start plist test\n");
229 plist_head_init(&test_head);
230 for (i = 0; i < ARRAY_SIZE(test_node); i++)
231 plist_node_init(test_node + i, 0);
232
233 for (loop = 0; loop < 1000; loop++) {
234 r = r * 193939 % 47629;
235 i = r % ARRAY_SIZE(test_node);
236 if (plist_node_empty(test_node + i)) {
237 r = r * 193939 % 47629;
238 test_node[i].prio = r % 99;
239 plist_add(test_node + i, &test_head);
240 nr_expect++;
241 } else {
242 plist_del(test_node + i, &test_head);
243 nr_expect--;
244 }
245 plist_test_check(nr_expect);
246 if (!plist_node_empty(test_node + i)) {
247 plist_test_requeue(test_node + i);
248 plist_test_check(nr_expect);
249 }
250 }
251
252 for (i = 0; i < ARRAY_SIZE(test_node); i++) {
253 if (plist_node_empty(test_node + i))
254 continue;
255 plist_del(test_node + i, &test_head);
256 nr_expect--;
257 plist_test_check(nr_expect);
258 }
259
260 printk(KERN_DEBUG "end plist test\n");
261 return 0;
262 }
263
264 module_init(plist_test);
265
266 #endif
267