xref: /openbmc/linux/lib/plist.c (revision ca79522c)
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 #include <linux/spinlock.h>
29 
30 #ifdef CONFIG_DEBUG_PI_LIST
31 
32 static struct plist_head test_head;
33 
34 static void plist_check_prev_next(struct list_head *t, struct list_head *p,
35 				  struct list_head *n)
36 {
37 	WARN(n->prev != p || p->next != n,
38 			"top: %p, n: %p, p: %p\n"
39 			"prev: %p, n: %p, p: %p\n"
40 			"next: %p, n: %p, p: %p\n",
41 			 t, t->next, t->prev,
42 			p, p->next, p->prev,
43 			n, n->next, n->prev);
44 }
45 
46 static void plist_check_list(struct list_head *top)
47 {
48 	struct list_head *prev = top, *next = top->next;
49 
50 	plist_check_prev_next(top, prev, next);
51 	while (next != top) {
52 		prev = next;
53 		next = prev->next;
54 		plist_check_prev_next(top, prev, next);
55 	}
56 }
57 
58 static void plist_check_head(struct plist_head *head)
59 {
60 	if (!plist_head_empty(head))
61 		plist_check_list(&plist_first(head)->prio_list);
62 	plist_check_list(&head->node_list);
63 }
64 
65 #else
66 # define plist_check_head(h)	do { } while (0)
67 #endif
68 
69 /**
70  * plist_add - add @node to @head
71  *
72  * @node:	&struct plist_node pointer
73  * @head:	&struct plist_head pointer
74  */
75 void plist_add(struct plist_node *node, struct plist_head *head)
76 {
77 	struct plist_node *first, *iter, *prev = NULL;
78 	struct list_head *node_next = &head->node_list;
79 
80 	plist_check_head(head);
81 	WARN_ON(!plist_node_empty(node));
82 	WARN_ON(!list_empty(&node->prio_list));
83 
84 	if (plist_head_empty(head))
85 		goto ins_node;
86 
87 	first = iter = plist_first(head);
88 
89 	do {
90 		if (node->prio < iter->prio) {
91 			node_next = &iter->node_list;
92 			break;
93 		}
94 
95 		prev = iter;
96 		iter = list_entry(iter->prio_list.next,
97 				struct plist_node, prio_list);
98 	} while (iter != first);
99 
100 	if (!prev || prev->prio != node->prio)
101 		list_add_tail(&node->prio_list, &iter->prio_list);
102 ins_node:
103 	list_add_tail(&node->node_list, node_next);
104 
105 	plist_check_head(head);
106 }
107 
108 /**
109  * plist_del - Remove a @node from plist.
110  *
111  * @node:	&struct plist_node pointer - entry to be removed
112  * @head:	&struct plist_head pointer - list head
113  */
114 void plist_del(struct plist_node *node, struct plist_head *head)
115 {
116 	plist_check_head(head);
117 
118 	if (!list_empty(&node->prio_list)) {
119 		if (node->node_list.next != &head->node_list) {
120 			struct plist_node *next;
121 
122 			next = list_entry(node->node_list.next,
123 					struct plist_node, node_list);
124 
125 			/* add the next plist_node into prio_list */
126 			if (list_empty(&next->prio_list))
127 				list_add(&next->prio_list, &node->prio_list);
128 		}
129 		list_del_init(&node->prio_list);
130 	}
131 
132 	list_del_init(&node->node_list);
133 
134 	plist_check_head(head);
135 }
136 
137 #ifdef CONFIG_DEBUG_PI_LIST
138 #include <linux/sched.h>
139 #include <linux/module.h>
140 #include <linux/init.h>
141 
142 static struct plist_node __initdata test_node[241];
143 
144 static void __init plist_test_check(int nr_expect)
145 {
146 	struct plist_node *first, *prio_pos, *node_pos;
147 
148 	if (plist_head_empty(&test_head)) {
149 		BUG_ON(nr_expect != 0);
150 		return;
151 	}
152 
153 	prio_pos = first = plist_first(&test_head);
154 	plist_for_each(node_pos, &test_head) {
155 		if (nr_expect-- < 0)
156 			break;
157 		if (node_pos == first)
158 			continue;
159 		if (node_pos->prio == prio_pos->prio) {
160 			BUG_ON(!list_empty(&node_pos->prio_list));
161 			continue;
162 		}
163 
164 		BUG_ON(prio_pos->prio > node_pos->prio);
165 		BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
166 		prio_pos = node_pos;
167 	}
168 
169 	BUG_ON(nr_expect != 0);
170 	BUG_ON(prio_pos->prio_list.next != &first->prio_list);
171 }
172 
173 static int  __init plist_test(void)
174 {
175 	int nr_expect = 0, i, loop;
176 	unsigned int r = local_clock();
177 
178 	pr_debug("start plist test\n");
179 	plist_head_init(&test_head);
180 	for (i = 0; i < ARRAY_SIZE(test_node); i++)
181 		plist_node_init(test_node + i, 0);
182 
183 	for (loop = 0; loop < 1000; loop++) {
184 		r = r * 193939 % 47629;
185 		i = r % ARRAY_SIZE(test_node);
186 		if (plist_node_empty(test_node + i)) {
187 			r = r * 193939 % 47629;
188 			test_node[i].prio = r % 99;
189 			plist_add(test_node + i, &test_head);
190 			nr_expect++;
191 		} else {
192 			plist_del(test_node + i, &test_head);
193 			nr_expect--;
194 		}
195 		plist_test_check(nr_expect);
196 	}
197 
198 	for (i = 0; i < ARRAY_SIZE(test_node); i++) {
199 		if (plist_node_empty(test_node + i))
200 			continue;
201 		plist_del(test_node + i, &test_head);
202 		nr_expect--;
203 		plist_test_check(nr_expect);
204 	}
205 
206 	pr_debug("end plist test\n");
207 	return 0;
208 }
209 
210 module_init(plist_test);
211 
212 #endif
213