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Linux/lib/plist.c

  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 
 31 static struct plist_head test_head;
 32 
 33 static 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 
 45 static 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 
 57 static 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  */
 74 void 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);
101 ins_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  */
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 
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  */
146 void 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 
181 static struct plist_node __initdata test_node[241];
182 
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 
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 
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 

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