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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 * pl:prio_list (only for plist_node)
35 * nl:node_list
36 * HEAD| NODE(S)
37 * |
38 * ||------------------------------------|
39 * ||->|pl|<->|pl|<--------------->|pl|<-|
40 * | |10| |21| |21| |21| |40| (prio)
41 * | | | | | | | | | | |
42 * | | | | | | | | | | |
43 * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
44 * |-------------------------------------------|
45 *
46 * The nodes on the prio_list list are sorted by priority to simplify
47 * the insertion of new nodes. There are no nodes with duplicate
48 * priorites on the list.
49 *
50 * The nodes on the node_list are ordered by priority and can contain
51 * entries which have the same priority. Those entries are ordered
52 * FIFO
53 *
54 * Addition means: look for the prio_list node in the prio_list
55 * for the priority of the node and insert it before the node_list
56 * entry of the next prio_list node. If it is the first node of
57 * that priority, add it to the prio_list in the right position and
58 * insert it into the serialized node_list list
59 *
60 * Removal means remove it from the node_list and remove it from
61 * the prio_list if the node_list list_head is non empty. In case
62 * of removal from the prio_list it must be checked whether other
63 * entries of the same priority are on the list or not. If there
64 * is another entry of the same priority then this entry has to
65 * replace the removed entry on the prio_list. If the entry which
66 * is removed is the only entry of this priority then a simple
67 * remove from both list is sufficient.
68 *
69 * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
70 * is lowest priority.
71 *
72 * No locking is done, up to the caller.
73 *
74 */
75 #ifndef _LINUX_PLIST_H_
76 #define _LINUX_PLIST_H_
77
78 #include <linux/kernel.h>
79 #include <linux/list.h>
80 #include <linux/spinlock_types.h>
81
82 struct plist_head {
83 struct list_head node_list;
84 #ifdef CONFIG_DEBUG_PI_LIST
85 raw_spinlock_t *rawlock;
86 spinlock_t *spinlock;
87 #endif
88 };
89
90 struct plist_node {
91 int prio;
92 struct list_head prio_list;
93 struct list_head node_list;
94 };
95
96 #ifdef CONFIG_DEBUG_PI_LIST
97 # define PLIST_HEAD_LOCK_INIT(_lock) .spinlock = _lock
98 # define PLIST_HEAD_LOCK_INIT_RAW(_lock) .rawlock = _lock
99 #else
100 # define PLIST_HEAD_LOCK_INIT(_lock)
101 # define PLIST_HEAD_LOCK_INIT_RAW(_lock)
102 #endif
103
104 #define _PLIST_HEAD_INIT(head) \
105 .node_list = LIST_HEAD_INIT((head).node_list)
106
107 /**
108 * PLIST_HEAD_INIT - static struct plist_head initializer
109 * @head: struct plist_head variable name
110 * @_lock: lock to initialize for this list
111 */
112 #define PLIST_HEAD_INIT(head, _lock) \
113 { \
114 _PLIST_HEAD_INIT(head), \
115 PLIST_HEAD_LOCK_INIT(&(_lock)) \
116 }
117
118 /**
119 * PLIST_HEAD_INIT_RAW - static struct plist_head initializer
120 * @head: struct plist_head variable name
121 * @_lock: lock to initialize for this list
122 */
123 #define PLIST_HEAD_INIT_RAW(head, _lock) \
124 { \
125 _PLIST_HEAD_INIT(head), \
126 PLIST_HEAD_LOCK_INIT_RAW(&(_lock)) \
127 }
128
129 /**
130 * PLIST_NODE_INIT - static struct plist_node initializer
131 * @node: struct plist_node variable name
132 * @__prio: initial node priority
133 */
134 #define PLIST_NODE_INIT(node, __prio) \
135 { \
136 .prio = (__prio), \
137 .prio_list = LIST_HEAD_INIT((node).prio_list), \
138 .node_list = LIST_HEAD_INIT((node).node_list), \
139 }
140
141 /**
142 * plist_head_init - dynamic struct plist_head initializer
143 * @head: &struct plist_head pointer
144 * @lock: spinlock protecting the list (debugging)
145 */
146 static inline void
147 plist_head_init(struct plist_head *head, spinlock_t *lock)
148 {
149 INIT_LIST_HEAD(&head->node_list);
150 #ifdef CONFIG_DEBUG_PI_LIST
151 head->spinlock = lock;
152 head->rawlock = NULL;
153 #endif
154 }
155
156 /**
157 * plist_head_init_raw - dynamic struct plist_head initializer
158 * @head: &struct plist_head pointer
159 * @lock: raw_spinlock protecting the list (debugging)
160 */
161 static inline void
162 plist_head_init_raw(struct plist_head *head, raw_spinlock_t *lock)
163 {
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 INIT_LIST_HEAD(&node->prio_list);
180 INIT_LIST_HEAD(&node->node_list);
181 }
182
183 extern void plist_add(struct plist_node *node, struct plist_head *head);
184 extern void plist_del(struct plist_node *node, struct plist_head *head);
185
186 /**
187 * plist_for_each - iterate over the plist
188 * @pos: the type * to use as a loop counter
189 * @head: the head for your list
190 */
191 #define plist_for_each(pos, head) \
192 list_for_each_entry(pos, &(head)->node_list, node_list)
193
194 /**
195 * plist_for_each_safe - iterate safely over a plist of given type
196 * @pos: the type * to use as a loop counter
197 * @n: another type * to use as temporary storage
198 * @head: the head for your list
199 *
200 * Iterate over a plist of given type, safe against removal of list entry.
201 */
202 #define plist_for_each_safe(pos, n, head) \
203 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
204
205 /**
206 * plist_for_each_entry - iterate over list of given type
207 * @pos: the type * to use as a loop counter
208 * @head: the head for your list
209 * @mem: the name of the list_struct within the struct
210 */
211 #define plist_for_each_entry(pos, head, mem) \
212 list_for_each_entry(pos, &(head)->node_list, mem.node_list)
213
214 /**
215 * plist_for_each_entry_safe - iterate safely over list of given type
216 * @pos: the type * to use as a loop counter
217 * @n: another type * to use as temporary storage
218 * @head: the head for your list
219 * @m: the name of the list_struct within the struct
220 *
221 * Iterate over list of given type, safe against removal of list entry.
222 */
223 #define plist_for_each_entry_safe(pos, n, head, m) \
224 list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
225
226 /**
227 * plist_head_empty - return !0 if a plist_head is empty
228 * @head: &struct plist_head pointer
229 */
230 static inline int plist_head_empty(const struct plist_head *head)
231 {
232 return list_empty(&head->node_list);
233 }
234
235 /**
236 * plist_node_empty - return !0 if plist_node is not on a list
237 * @node: &struct plist_node pointer
238 */
239 static inline int plist_node_empty(const struct plist_node *node)
240 {
241 return list_empty(&node->node_list);
242 }
243
244 /* All functions below assume the plist_head is not empty. */
245
246 /**
247 * plist_first_entry - get the struct for the first entry
248 * @head: the &struct plist_head pointer
249 * @type: the type of the struct this is embedded in
250 * @member: the name of the list_struct within the struct
251 */
252 #ifdef CONFIG_DEBUG_PI_LIST
253 # define plist_first_entry(head, type, member) \
254 ({ \
255 WARN_ON(plist_head_empty(head)); \
256 container_of(plist_first(head), type, member); \
257 })
258 #else
259 # define plist_first_entry(head, type, member) \
260 container_of(plist_first(head), type, member)
261 #endif
262
263 /**
264 * plist_last_entry - get the struct for the last entry
265 * @head: the &struct plist_head pointer
266 * @type: the type of the struct this is embedded in
267 * @member: the name of the list_struct within the struct
268 */
269 #ifdef CONFIG_DEBUG_PI_LIST
270 # define plist_last_entry(head, type, member) \
271 ({ \
272 WARN_ON(plist_head_empty(head)); \
273 container_of(plist_last(head), type, member); \
274 })
275 #else
276 # define plist_last_entry(head, type, member) \
277 container_of(plist_last(head), type, member)
278 #endif
279
280 /**
281 * plist_first - return the first node (and thus, highest priority)
282 * @head: the &struct plist_head pointer
283 *
284 * Assumes the plist is _not_ empty.
285 */
286 static inline struct plist_node *plist_first(const struct plist_head *head)
287 {
288 return list_entry(head->node_list.next,
289 struct plist_node, node_list);
290 }
291
292 /**
293 * plist_last - return the last node (and thus, lowest priority)
294 * @head: the &struct plist_head pointer
295 *
296 * Assumes the plist is _not_ empty.
297 */
298 static inline struct plist_node *plist_last(const struct plist_head *head)
299 {
300 return list_entry(head->node_list.prev,
301 struct plist_node, node_list);
302 }
303
304 #endif