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1 /*
2 * Descending-priority-sorted double-linked list
3 *
4 * (C) 2002-2003 Intel Corp
5 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
6 *
7 * 2001-2005 (c) MontaVista Software, Inc.
8 * Daniel Walker <dwalker@mvista.com>
9 *
10 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
11 *
12 * Simplifications of the original code by
13 * Oleg Nesterov <oleg@tv-sign.ru>
14 *
15 * Licensed under the FSF's GNU Public License v2 or later.
16 *
17 * Based on simple lists (include/linux/list.h).
18 *
19 * This is a priority-sorted list of nodes; each node has a
20 * priority from INT_MIN (highest) to INT_MAX (lowest).
21 *
22 * Addition is O(K), removal is O(1), change of priority of a node is
23 * O(K) and K is the number of RT priority levels used in the system.
24 * (1 <= K <= 99)
25 *
26 * This list is really a list of lists:
27 *
28 * - The tier 1 list is the prio_list, different priority nodes.
29 *
30 * - The tier 2 list is the node_list, serialized nodes.
31 *
32 * Simple ASCII art explanation:
33 *
34 * |HEAD |
35 * | |
36 * |prio_list.prev|<------------------------------------|
37 * |prio_list.next|<->|pl|<->|pl|<--------------->|pl|<-|
38 * |10 | |10| |21| |21| |21| |40| (prio)
39 * | | | | | | | | | | | |
40 * | | | | | | | | | | | |
41 * |node_list.next|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
42 * |node_list.prev|<------------------------------------|
43 *
44 * The nodes on the prio_list list are sorted by priority to simplify
45 * the insertion of new nodes. There are no nodes with duplicate
46 * priorites on the list.
47 *
48 * The nodes on the node_list are ordered by priority and can contain
49 * entries which have the same priority. Those entries are ordered
50 * FIFO
51 *
52 * Addition means: look for the prio_list node in the prio_list
53 * for the priority of the node and insert it before the node_list
54 * entry of the next prio_list node. If it is the first node of
55 * that priority, add it to the prio_list in the right position and
56 * insert it into the serialized node_list list
57 *
58 * Removal means remove it from the node_list and remove it from
59 * the prio_list if the node_list list_head is non empty. In case
60 * of removal from the prio_list it must be checked whether other
61 * entries of the same priority are on the list or not. If there
62 * is another entry of the same priority then this entry has to
63 * replace the removed entry on the prio_list. If the entry which
64 * is removed is the only entry of this priority then a simple
65 * remove from both list is sufficient.
66 *
67 * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
68 * is lowest priority.
69 *
70 * No locking is done, up to the caller.
71 *
72 */
73 #ifndef _LINUX_PLIST_H_
74 #define _LINUX_PLIST_H_
75
76 #include <linux/kernel.h>
77 #include <linux/list.h>
78 #include <linux/spinlock_types.h>
79
80 struct plist_head {
81 struct list_head prio_list;
82 struct list_head node_list;
83 #ifdef CONFIG_DEBUG_PI_LIST
84 raw_spinlock_t *rawlock;
85 spinlock_t *spinlock;
86 #endif
87 };
88
89 struct plist_node {
90 int prio;
91 struct plist_head plist;
92 };
93
94 #ifdef CONFIG_DEBUG_PI_LIST
95 # define PLIST_HEAD_LOCK_INIT(_lock) .spinlock = _lock
96 # define PLIST_HEAD_LOCK_INIT_RAW(_lock) .rawlock = _lock
97 #else
98 # define PLIST_HEAD_LOCK_INIT(_lock)
99 # define PLIST_HEAD_LOCK_INIT_RAW(_lock)
100 #endif
101
102 #define _PLIST_HEAD_INIT(head) \
103 .prio_list = LIST_HEAD_INIT((head).prio_list), \
104 .node_list = LIST_HEAD_INIT((head).node_list)
105
106 /**
107 * PLIST_HEAD_INIT - static struct plist_head initializer
108 * @head: struct plist_head variable name
109 * @_lock: lock to initialize for this list
110 */
111 #define PLIST_HEAD_INIT(head, _lock) \
112 { \
113 _PLIST_HEAD_INIT(head), \
114 PLIST_HEAD_LOCK_INIT(&(_lock)) \
115 }
116
117 /**
118 * PLIST_HEAD_INIT_RAW - static struct plist_head initializer
119 * @head: struct plist_head variable name
120 * @_lock: lock to initialize for this list
121 */
122 #define PLIST_HEAD_INIT_RAW(head, _lock) \
123 { \
124 _PLIST_HEAD_INIT(head), \
125 PLIST_HEAD_LOCK_INIT_RAW(&(_lock)) \
126 }
127
128 /**
129 * PLIST_NODE_INIT - static struct plist_node initializer
130 * @node: struct plist_node variable name
131 * @__prio: initial node priority
132 */
133 #define PLIST_NODE_INIT(node, __prio) \
134 { \
135 .prio = (__prio), \
136 .plist = { _PLIST_HEAD_INIT((node).plist) }, \
137 }
138
139 /**
140 * plist_head_init - dynamic struct plist_head initializer
141 * @head: &struct plist_head pointer
142 * @lock: spinlock protecting the list (debugging)
143 */
144 static inline void
145 plist_head_init(struct plist_head *head, spinlock_t *lock)
146 {
147 INIT_LIST_HEAD(&head->prio_list);
148 INIT_LIST_HEAD(&head->node_list);
149 #ifdef CONFIG_DEBUG_PI_LIST
150 head->spinlock = lock;
151 head->rawlock = NULL;
152 #endif
153 }
154
155 /**
156 * plist_head_init_raw - dynamic struct plist_head initializer
157 * @head: &struct plist_head pointer
158 * @lock: raw_spinlock protecting the list (debugging)
159 */
160 static inline void
161 plist_head_init_raw(struct plist_head *head, raw_spinlock_t *lock)
162 {
163 INIT_LIST_HEAD(&head->prio_list);
164 INIT_LIST_HEAD(&head->node_list);
165 #ifdef CONFIG_DEBUG_PI_LIST
166 head->rawlock = lock;
167 head->spinlock = NULL;
168 #endif
169 }
170
171 /**
172 * plist_node_init - Dynamic struct plist_node initializer
173 * @node: &struct plist_node pointer
174 * @prio: initial node priority
175 */
176 static inline void plist_node_init(struct plist_node *node, int prio)
177 {
178 node->prio = prio;
179 plist_head_init(&node->plist, NULL);
180 }
181
182 extern void plist_add(struct plist_node *node, struct plist_head *head);
183 extern void plist_del(struct plist_node *node, struct plist_head *head);
184
185 /**
186 * plist_for_each - iterate over the plist
187 * @pos: the type * to use as a loop counter
188 * @head: the head for your list
189 */
190 #define plist_for_each(pos, head) \
191 list_for_each_entry(pos, &(head)->node_list, plist.node_list)
192
193 /**
194 * plist_for_each_safe - iterate safely over a plist of given type
195 * @pos: the type * to use as a loop counter
196 * @n: another type * to use as temporary storage
197 * @head: the head for your list
198 *
199 * Iterate over a plist of given type, safe against removal of list entry.
200 */
201 #define plist_for_each_safe(pos, n, head) \
202 list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list)
203
204 /**
205 * plist_for_each_entry - iterate over list of given type
206 * @pos: the type * to use as a loop counter
207 * @head: the head for your list
208 * @mem: the name of the list_struct within the struct
209 */
210 #define plist_for_each_entry(pos, head, mem) \
211 list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list)
212
213 /**
214 * plist_for_each_entry_safe - iterate safely over list of given type
215 * @pos: the type * to use as a loop counter
216 * @n: another type * to use as temporary storage
217 * @head: the head for your list
218 * @m: the name of the list_struct within the struct
219 *
220 * Iterate over list of given type, safe against removal of list entry.
221 */
222 #define plist_for_each_entry_safe(pos, n, head, m) \
223 list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list)
224
225 /**
226 * plist_head_empty - return !0 if a plist_head is empty
227 * @head: &struct plist_head pointer
228 */
229 static inline int plist_head_empty(const struct plist_head *head)
230 {
231 return list_empty(&head->node_list);
232 }
233
234 /**
235 * plist_node_empty - return !0 if plist_node is not on a list
236 * @node: &struct plist_node pointer
237 */
238 static inline int plist_node_empty(const struct plist_node *node)
239 {
240 return plist_head_empty(&node->plist);
241 }
242
243 /* All functions below assume the plist_head is not empty. */
244
245 /**
246 * plist_first_entry - get the struct for the first entry
247 * @head: the &struct plist_head pointer
248 * @type: the type of the struct this is embedded in
249 * @member: the name of the list_struct within the struct
250 */
251 #ifdef CONFIG_DEBUG_PI_LIST
252 # define plist_first_entry(head, type, member) \
253 ({ \
254 WARN_ON(plist_head_empty(head)); \
255 container_of(plist_first(head), type, member); \
256 })
257 #else
258 # define plist_first_entry(head, type, member) \
259 container_of(plist_first(head), type, member)
260 #endif
261
262 /**
263 * plist_last_entry - get the struct for the last entry
264 * @head: the &struct plist_head pointer
265 * @type: the type of the struct this is embedded in
266 * @member: the name of the list_struct within the struct
267 */
268 #ifdef CONFIG_DEBUG_PI_LIST
269 # define plist_last_entry(head, type, member) \
270 ({ \
271 WARN_ON(plist_head_empty(head)); \
272 container_of(plist_last(head), type, member); \
273 })
274 #else
275 # define plist_last_entry(head, type, member) \
276 container_of(plist_last(head), type, member)
277 #endif
278
279 /**
280 * plist_first - return the first node (and thus, highest priority)
281 * @head: the &struct plist_head pointer
282 *
283 * Assumes the plist is _not_ empty.
284 */
285 static inline struct plist_node *plist_first(const struct plist_head *head)
286 {
287 return list_entry(head->node_list.next,
288 struct plist_node, plist.node_list);
289 }
290
291 /**
292 * plist_last - return the last node (and thus, lowest priority)
293 * @head: the &struct plist_head pointer
294 *
295 * Assumes the plist is _not_ empty.
296 */
297 static inline struct plist_node *plist_last(const struct plist_head *head)
298 {
299 return list_entry(head->node_list.prev,
300 struct plist_node, plist.node_list);
301 }
302
303 #endif