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2 * Descending-priority-sorted double-linked list
4 * (C) 2002-2003 Intel Corp
5 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
7 * 2001-2005 (c) MontaVista Software, Inc.
8 * Daniel Walker <dwalker@mvista.com>
10 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
12 * Simplifications of the original code by
13 * Oleg Nesterov <oleg@tv-sign.ru>
15 * Licensed under the FSF's GNU Public License v2 or later.
17 * Based on simple lists (include/linux/list.h).
19 * This is a priority-sorted list of nodes; each node has a
20 * priority from INT_MIN (highest) to INT_MAX (lowest).
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.
26 * This list is really a list of lists:
28 * - The tier 1 list is the prio_list, different priority nodes.
30 * - The tier 2 list is the node_list, serialized nodes.
32 * Simple ASCII art explanation:
34 * pl:prio_list (only for plist_node)
38 * ||------------------------------------|
39 * ||->|pl|<->|pl|<--------------->|pl|<-|
40 * | |10| |21| |21| |21| |40| (prio)
41 * | | | | | | | | | | |
42 * | | | | | | | | | | |
43 * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
44 * |-------------------------------------------|
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.
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
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
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.
69 * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
72 * No locking is done, up to the caller.
75 #ifndef _LINUX_PLIST_H_
76 #define _LINUX_PLIST_H_
78 #include <linux/kernel.h>
79 #include <linux/list.h>
82 struct list_head node_list
;
87 struct list_head prio_list
;
88 struct list_head node_list
;
92 * PLIST_HEAD_INIT - static struct plist_head initializer
93 * @head: struct plist_head variable name
95 #define PLIST_HEAD_INIT(head) \
97 .node_list = LIST_HEAD_INIT((head).node_list) \
101 * PLIST_HEAD - declare and init plist_head
102 * @head: name for struct plist_head variable
104 #define PLIST_HEAD(head) \
105 struct plist_head head = PLIST_HEAD_INIT(head)
108 * PLIST_NODE_INIT - static struct plist_node initializer
109 * @node: struct plist_node variable name
110 * @__prio: initial node priority
112 #define PLIST_NODE_INIT(node, __prio) \
115 .prio_list = LIST_HEAD_INIT((node).prio_list), \
116 .node_list = LIST_HEAD_INIT((node).node_list), \
120 * plist_head_init - dynamic struct plist_head initializer
121 * @head: &struct plist_head pointer
124 plist_head_init(struct plist_head
*head
)
126 INIT_LIST_HEAD(&head
->node_list
);
130 * plist_node_init - Dynamic struct plist_node initializer
131 * @node: &struct plist_node pointer
132 * @prio: initial node priority
134 static inline void plist_node_init(struct plist_node
*node
, int prio
)
137 INIT_LIST_HEAD(&node
->prio_list
);
138 INIT_LIST_HEAD(&node
->node_list
);
141 extern void plist_add(struct plist_node
*node
, struct plist_head
*head
);
142 extern void plist_del(struct plist_node
*node
, struct plist_head
*head
);
144 extern void plist_requeue(struct plist_node
*node
, struct plist_head
*head
);
147 * plist_for_each - iterate over the plist
148 * @pos: the type * to use as a loop counter
149 * @head: the head for your list
151 #define plist_for_each(pos, head) \
152 list_for_each_entry(pos, &(head)->node_list, node_list)
155 * plist_for_each_continue - continue iteration over the plist
156 * @pos: the type * to use as a loop cursor
157 * @head: the head for your list
159 * Continue to iterate over plist, continuing after the current position.
161 #define plist_for_each_continue(pos, head) \
162 list_for_each_entry_continue(pos, &(head)->node_list, node_list)
165 * plist_for_each_safe - iterate safely over a plist of given type
166 * @pos: the type * to use as a loop counter
167 * @n: another type * to use as temporary storage
168 * @head: the head for your list
170 * Iterate over a plist of given type, safe against removal of list entry.
172 #define plist_for_each_safe(pos, n, head) \
173 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
176 * plist_for_each_entry - iterate over list of given type
177 * @pos: the type * to use as a loop counter
178 * @head: the head for your list
179 * @mem: the name of the list_head within the struct
181 #define plist_for_each_entry(pos, head, mem) \
182 list_for_each_entry(pos, &(head)->node_list, mem.node_list)
185 * plist_for_each_entry_continue - continue iteration over list of given type
186 * @pos: the type * to use as a loop cursor
187 * @head: the head for your list
188 * @m: the name of the list_head within the struct
190 * Continue to iterate over list of given type, continuing after
191 * the current position.
193 #define plist_for_each_entry_continue(pos, head, m) \
194 list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
197 * plist_for_each_entry_safe - iterate safely over list of given type
198 * @pos: the type * to use as a loop counter
199 * @n: another type * to use as temporary storage
200 * @head: the head for your list
201 * @m: the name of the list_head within the struct
203 * Iterate over list of given type, safe against removal of list entry.
205 #define plist_for_each_entry_safe(pos, n, head, m) \
206 list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
209 * plist_head_empty - return !0 if a plist_head is empty
210 * @head: &struct plist_head pointer
212 static inline int plist_head_empty(const struct plist_head
*head
)
214 return list_empty(&head
->node_list
);
218 * plist_node_empty - return !0 if plist_node is not on a list
219 * @node: &struct plist_node pointer
221 static inline int plist_node_empty(const struct plist_node
*node
)
223 return list_empty(&node
->node_list
);
226 /* All functions below assume the plist_head is not empty. */
229 * plist_first_entry - get the struct for the first entry
230 * @head: the &struct plist_head pointer
231 * @type: the type of the struct this is embedded in
232 * @member: the name of the list_head within the struct
234 #ifdef CONFIG_DEBUG_PI_LIST
235 # define plist_first_entry(head, type, member) \
237 WARN_ON(plist_head_empty(head)); \
238 container_of(plist_first(head), type, member); \
241 # define plist_first_entry(head, type, member) \
242 container_of(plist_first(head), type, member)
246 * plist_last_entry - get the struct for the last 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_head within the struct
251 #ifdef CONFIG_DEBUG_PI_LIST
252 # define plist_last_entry(head, type, member) \
254 WARN_ON(plist_head_empty(head)); \
255 container_of(plist_last(head), type, member); \
258 # define plist_last_entry(head, type, member) \
259 container_of(plist_last(head), type, member)
263 * plist_next - get the next entry in list
264 * @pos: the type * to cursor
266 #define plist_next(pos) \
267 list_next_entry(pos, node_list)
270 * plist_prev - get the prev entry in list
271 * @pos: the type * to cursor
273 #define plist_prev(pos) \
274 list_prev_entry(pos, node_list)
277 * plist_first - return the first node (and thus, highest priority)
278 * @head: the &struct plist_head pointer
280 * Assumes the plist is _not_ empty.
282 static inline struct plist_node
*plist_first(const struct plist_head
*head
)
284 return list_entry(head
->node_list
.next
,
285 struct plist_node
, node_list
);
289 * plist_last - return the last node (and thus, lowest priority)
290 * @head: the &struct plist_head pointer
292 * Assumes the plist is _not_ empty.
294 static inline struct plist_node
*plist_last(const struct plist_head
*head
)
296 return list_entry(head
->node_list
.prev
,
297 struct plist_node
, node_list
);