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
81struct plist_head {
82 struct list_head node_list;
83};
84
85struct plist_node {
86 int prio;
87 struct list_head prio_list;
88 struct list_head node_list;
89};
90
91/**
92 * PLIST_HEAD_INIT - static struct plist_head initializer
93 * @head: struct plist_head variable name
94 */
95#define PLIST_HEAD_INIT(head) \
96{ \
97 .node_list = LIST_HEAD_INIT((head).node_list) \
98}
99
100/**
101 * PLIST_HEAD - declare and init plist_head
102 * @head: name for struct plist_head variable
103 */
104#define PLIST_HEAD(head) \
105 struct plist_head head = PLIST_HEAD_INIT(head)
106
107/**
108 * PLIST_NODE_INIT - static struct plist_node initializer
109 * @node: struct plist_node variable name
110 * @__prio: initial node priority
111 */
112#define PLIST_NODE_INIT(node, __prio) \
113{ \
114 .prio = (__prio), \
115 .prio_list = LIST_HEAD_INIT((node).prio_list), \
116 .node_list = LIST_HEAD_INIT((node).node_list), \
117}
118
119/**
120 * plist_head_init - dynamic struct plist_head initializer
121 * @head: &struct plist_head pointer
122 */
123static inline void
124plist_head_init(struct plist_head *head)
125{
126 INIT_LIST_HEAD(&head->node_list);
127}
128
129/**
130 * plist_node_init - Dynamic struct plist_node initializer
131 * @node: &struct plist_node pointer
132 * @prio: initial node priority
133 */
134static inline void plist_node_init(struct plist_node *node, int prio)
135{
136 node->prio = prio;
137 INIT_LIST_HEAD(&node->prio_list);
138 INIT_LIST_HEAD(&node->node_list);
139}
140
141extern void plist_add(struct plist_node *node, struct plist_head *head);
142extern void plist_del(struct plist_node *node, struct plist_head *head);
143
144extern void plist_requeue(struct plist_node *node, struct plist_head *head);
145
146/**
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
150 */
151#define plist_for_each(pos, head) \
152 list_for_each_entry(pos, &(head)->node_list, node_list)
153
154/**
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
158 *
159 * Continue to iterate over plist, continuing after the current position.
160 */
161#define plist_for_each_continue(pos, head) \
162 list_for_each_entry_continue(pos, &(head)->node_list, node_list)
163
164/**
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
169 *
170 * Iterate over a plist of given type, safe against removal of list entry.
171 */
172#define plist_for_each_safe(pos, n, head) \
173 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
174
175/**
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
180 */
181#define plist_for_each_entry(pos, head, mem) \
182 list_for_each_entry(pos, &(head)->node_list, mem.node_list)
183
184/**
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
189 *
190 * Continue to iterate over list of given type, continuing after
191 * the current position.
192 */
193#define plist_for_each_entry_continue(pos, head, m) \
194 list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
195
196/**
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
202 *
203 * Iterate over list of given type, safe against removal of list entry.
204 */
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)
207
208/**
209 * plist_head_empty - return !0 if a plist_head is empty
210 * @head: &struct plist_head pointer
211 */
212static inline int plist_head_empty(const struct plist_head *head)
213{
214 return list_empty(&head->node_list);
215}
216
217/**
218 * plist_node_empty - return !0 if plist_node is not on a list
219 * @node: &struct plist_node pointer
220 */
221static inline int plist_node_empty(const struct plist_node *node)
222{
223 return list_empty(&node->node_list);
224}
225
226/* All functions below assume the plist_head is not empty. */
227
228/**
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
233 */
234#ifdef CONFIG_DEBUG_PI_LIST
235# define plist_first_entry(head, type, member) \
236({ \
237 WARN_ON(plist_head_empty(head)); \
238 container_of(plist_first(head), type, member); \
239})
240#else
241# define plist_first_entry(head, type, member) \
242 container_of(plist_first(head), type, member)
243#endif
244
245/**
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
250 */
251#ifdef CONFIG_DEBUG_PI_LIST
252# define plist_last_entry(head, type, member) \
253({ \
254 WARN_ON(plist_head_empty(head)); \
255 container_of(plist_last(head), type, member); \
256})
257#else
258# define plist_last_entry(head, type, member) \
259 container_of(plist_last(head), type, member)
260#endif
261
262/**
263 * plist_next - get the next entry in list
264 * @pos: the type * to cursor
265 */
266#define plist_next(pos) \
267 list_next_entry(pos, node_list)
268
269/**
270 * plist_prev - get the prev entry in list
271 * @pos: the type * to cursor
272 */
273#define plist_prev(pos) \
274 list_prev_entry(pos, node_list)
275
276/**
277 * plist_first - return the first node (and thus, highest priority)
278 * @head: the &struct plist_head pointer
279 *
280 * Assumes the plist is _not_ empty.
281 */
282static inline struct plist_node *plist_first(const struct plist_head *head)
283{
284 return list_entry(head->node_list.next,
285 struct plist_node, node_list);
286}
287
288/**
289 * plist_last - return the last node (and thus, lowest priority)
290 * @head: the &struct plist_head pointer
291 *
292 * Assumes the plist is _not_ empty.
293 */
294static inline struct plist_node *plist_last(const struct plist_head *head)
295{
296 return list_entry(head->node_list.prev,
297 struct plist_node, node_list);
298}
299
300#endif
301