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
264