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 
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  */
plist_del(struct plist_node * node,struct plist_head * head)112 void 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  */
plist_requeue(struct plist_node * node,struct plist_head * head)145 void 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 
181 static struct plist_node __initdata test_node[241];
182 
plist_test_check(int nr_expect)183 static 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 
plist_test_requeue(struct plist_node * node)212 static 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 
plist_test(void)220 static 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 
261 module_init(plist_test);
262 
263 #endif
264