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Linux/lib/plist.c

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  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 /**
138  * plist_requeue - Requeue @node at end of same-prio entries.
139  *
140  * This is essentially an optimized plist_del() followed by
141  * plist_add().  It moves an entry already in the plist to
142  * after any other same-priority entries.
143  *
144  * @node:       &struct plist_node pointer - entry to be moved
145  * @head:       &struct plist_head pointer - list head
146  */
147 void plist_requeue(struct plist_node *node, struct plist_head *head)
148 {
149         struct plist_node *iter;
150         struct list_head *node_next = &head->node_list;
151 
152         plist_check_head(head);
153         BUG_ON(plist_head_empty(head));
154         BUG_ON(plist_node_empty(node));
155 
156         if (node == plist_last(head))
157                 return;
158 
159         iter = plist_next(node);
160 
161         if (node->prio != iter->prio)
162                 return;
163 
164         plist_del(node, head);
165 
166         plist_for_each_continue(iter, head) {
167                 if (node->prio != iter->prio) {
168                         node_next = &iter->node_list;
169                         break;
170                 }
171         }
172         list_add_tail(&node->node_list, node_next);
173 
174         plist_check_head(head);
175 }
176 
177 #ifdef CONFIG_DEBUG_PI_LIST
178 #include <linux/sched.h>
179 #include <linux/module.h>
180 #include <linux/init.h>
181 
182 static struct plist_node __initdata test_node[241];
183 
184 static void __init plist_test_check(int nr_expect)
185 {
186         struct plist_node *first, *prio_pos, *node_pos;
187 
188         if (plist_head_empty(&test_head)) {
189                 BUG_ON(nr_expect != 0);
190                 return;
191         }
192 
193         prio_pos = first = plist_first(&test_head);
194         plist_for_each(node_pos, &test_head) {
195                 if (nr_expect-- < 0)
196                         break;
197                 if (node_pos == first)
198                         continue;
199                 if (node_pos->prio == prio_pos->prio) {
200                         BUG_ON(!list_empty(&node_pos->prio_list));
201                         continue;
202                 }
203 
204                 BUG_ON(prio_pos->prio > node_pos->prio);
205                 BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
206                 prio_pos = node_pos;
207         }
208 
209         BUG_ON(nr_expect != 0);
210         BUG_ON(prio_pos->prio_list.next != &first->prio_list);
211 }
212 
213 static void __init plist_test_requeue(struct plist_node *node)
214 {
215         plist_requeue(node, &test_head);
216 
217         if (node != plist_last(&test_head))
218                 BUG_ON(node->prio == plist_next(node)->prio);
219 }
220 
221 static int  __init plist_test(void)
222 {
223         int nr_expect = 0, i, loop;
224         unsigned int r = local_clock();
225 
226         pr_debug("start plist test\n");
227         plist_head_init(&test_head);
228         for (i = 0; i < ARRAY_SIZE(test_node); i++)
229                 plist_node_init(test_node + i, 0);
230 
231         for (loop = 0; loop < 1000; loop++) {
232                 r = r * 193939 % 47629;
233                 i = r % ARRAY_SIZE(test_node);
234                 if (plist_node_empty(test_node + i)) {
235                         r = r * 193939 % 47629;
236                         test_node[i].prio = r % 99;
237                         plist_add(test_node + i, &test_head);
238                         nr_expect++;
239                 } else {
240                         plist_del(test_node + i, &test_head);
241                         nr_expect--;
242                 }
243                 plist_test_check(nr_expect);
244                 if (!plist_node_empty(test_node + i)) {
245                         plist_test_requeue(test_node + i);
246                         plist_test_check(nr_expect);
247                 }
248         }
249 
250         for (i = 0; i < ARRAY_SIZE(test_node); i++) {
251                 if (plist_node_empty(test_node + i))
252                         continue;
253                 plist_del(test_node + i, &test_head);
254                 nr_expect--;
255                 plist_test_check(nr_expect);
256         }
257 
258         pr_debug("end plist test\n");
259         return 0;
260 }
261 
262 module_init(plist_test);
263 
264 #endif
265 

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