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
29#ifdef CONFIG_DEBUG_PI_LIST
30
31static struct plist_head test_head;
32
33static void plist_check_prev_next(struct list_head *t, struct list_head *p,
34				  struct list_head *n)
35{
36	WARN(n->prev != p || p->next != n,
37			"top: %p, n: %p, p: %p\n"
38			"prev: %p, n: %p, p: %p\n"
39			"next: %p, n: %p, p: %p\n",
40			 t, t->next, t->prev,
41			p, p->next, p->prev,
42			n, n->next, n->prev);
43}
44
45static void plist_check_list(struct list_head *top)
46{
47	struct list_head *prev = top, *next = top->next;
48
49	plist_check_prev_next(top, prev, next);
50	while (next != top) {
51		prev = next;
52		next = prev->next;
53		plist_check_prev_next(top, prev, next);
54	}
55}
56
57static void plist_check_head(struct plist_head *head)
58{
59	if (!plist_head_empty(head))
60		plist_check_list(&plist_first(head)->prio_list);
61	plist_check_list(&head->node_list);
62}
63
64#else
65# define plist_check_head(h)	do { } while (0)
66#endif
67
68/**
69 * plist_add - add @node to @head
70 *
71 * @node:	&struct plist_node pointer
72 * @head:	&struct plist_head pointer
73 */
74void plist_add(struct plist_node *node, struct plist_head *head)
75{
76	struct plist_node *first, *iter, *prev = NULL;
77	struct list_head *node_next = &head->node_list;
78
79	plist_check_head(head);
80	WARN_ON(!plist_node_empty(node));
81	WARN_ON(!list_empty(&node->prio_list));
82
83	if (plist_head_empty(head))
84		goto ins_node;
85
86	first = iter = plist_first(head);
87
88	do {
89		if (node->prio < iter->prio) {
90			node_next = &iter->node_list;
91			break;
92		}
93
94		prev = iter;
95		iter = list_entry(iter->prio_list.next,
96				struct plist_node, prio_list);
97	} while (iter != first);
98
99	if (!prev || prev->prio != node->prio)
100		list_add_tail(&node->prio_list, &iter->prio_list);
101ins_node:
102	list_add_tail(&node->node_list, node_next);
103
104	plist_check_head(head);
105}
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 */
113void 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
136/**
137 * plist_requeue - Requeue @node at end of same-prio entries.
138 *
139 * This is essentially an optimized plist_del() followed by
140 * plist_add().  It moves an entry already in the plist to
141 * after any other same-priority entries.
142 *
143 * @node:	&struct plist_node pointer - entry to be moved
144 * @head:	&struct plist_head pointer - list head
145 */
146void plist_requeue(struct plist_node *node, struct plist_head *head)
147{
148	struct plist_node *iter;
149	struct list_head *node_next = &head->node_list;
150
151	plist_check_head(head);
152	BUG_ON(plist_head_empty(head));
153	BUG_ON(plist_node_empty(node));
154
155	if (node == plist_last(head))
156		return;
157
158	iter = plist_next(node);
159
160	if (node->prio != iter->prio)
161		return;
162
163	plist_del(node, head);
164
165	plist_for_each_continue(iter, head) {
166		if (node->prio != iter->prio) {
167			node_next = &iter->node_list;
168			break;
169		}
170	}
171	list_add_tail(&node->node_list, node_next);
172
173	plist_check_head(head);
174}
175
176#ifdef CONFIG_DEBUG_PI_LIST
177#include <linux/sched.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