1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * Descending-priority-sorted double-linked list
4 *
5 * (C) 2002-2003 Intel Corp
6 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
7 *
8 * 2001-2005 (c) MontaVista Software, Inc.
9 * Daniel Walker <dwalker@mvista.com>
10 *
11 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
12 *
13 * Simplifications of the original code by
14 * Oleg Nesterov <oleg@tv-sign.ru>
15 *
16 * Based on simple lists (include/linux/list.h).
17 *
18 * This is a priority-sorted list of nodes; each node has a
19 * priority from INT_MIN (highest) to INT_MAX (lowest).
20 *
21 * Addition is O(K), removal is O(1), change of priority of a node is
22 * O(K) and K is the number of RT priority levels used in the system.
23 * (1 <= K <= 99)
24 *
25 * This list is really a list of lists:
26 *
27 * - The tier 1 list is the prio_list, different priority nodes.
28 *
29 * - The tier 2 list is the node_list, serialized nodes.
30 *
31 * Simple ASCII art explanation:
32 *
33 * pl:prio_list (only for plist_node)
34 * nl:node_list
35 * HEAD| NODE(S)
36 * |
37 * ||------------------------------------|
38 * ||->|pl|<->|pl|<--------------->|pl|<-|
39 * | |10| |21| |21| |21| |40| (prio)
40 * | | | | | | | | | | |
41 * | | | | | | | | | | |
42 * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
43 * |-------------------------------------------|
44 *
45 * The nodes on the prio_list list are sorted by priority to simplify
46 * the insertion of new nodes. There are no nodes with duplicate
47 * priorites on the list.
48 *
49 * The nodes on the node_list are ordered by priority and can contain
50 * entries which have the same priority. Those entries are ordered
51 * FIFO
52 *
53 * Addition means: look for the prio_list node in the prio_list
54 * for the priority of the node and insert it before the node_list
55 * entry of the next prio_list node. If it is the first node of
56 * that priority, add it to the prio_list in the right position and
57 * insert it into the serialized node_list list
58 *
59 * Removal means remove it from the node_list and remove it from
60 * the prio_list if the node_list list_head is non empty. In case
61 * of removal from the prio_list it must be checked whether other
62 * entries of the same priority are on the list or not. If there
63 * is another entry of the same priority then this entry has to
64 * replace the removed entry on the prio_list. If the entry which
65 * is removed is the only entry of this priority then a simple
66 * remove from both list is sufficient.
67 *
68 * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
69 * is lowest priority.
70 *
71 * No locking is done, up to the caller.
72 */
73 #ifndef _LINUX_PLIST_H_
74 #define _LINUX_PLIST_H_
75
76 #include <linux/kernel.h>
77 #include <linux/list.h>
78
79 struct plist_head {
80 struct list_head node_list;
81 };
82
83 struct plist_node {
84 int prio;
85 struct list_head prio_list;
86 struct list_head node_list;
87 };
88
89 /**
90 * PLIST_HEAD_INIT - static struct plist_head initializer
91 * @head: struct plist_head variable name
92 */
93 #define PLIST_HEAD_INIT(head) \
94 { \
95 .node_list = LIST_HEAD_INIT((head).node_list) \
96 }
97
98 /**
99 * PLIST_HEAD - declare and init plist_head
100 * @head: name for struct plist_head variable
101 */
102 #define PLIST_HEAD(head) \
103 struct plist_head head = PLIST_HEAD_INIT(head)
104
105 /**
106 * PLIST_NODE_INIT - static struct plist_node initializer
107 * @node: struct plist_node variable name
108 * @__prio: initial node priority
109 */
110 #define PLIST_NODE_INIT(node, __prio) \
111 { \
112 .prio = (__prio), \
113 .prio_list = LIST_HEAD_INIT((node).prio_list), \
114 .node_list = LIST_HEAD_INIT((node).node_list), \
115 }
116
117 /**
118 * plist_head_init - dynamic struct plist_head initializer
119 * @head: &struct plist_head pointer
120 */
121 static inline void
plist_head_init(struct plist_head * head)122 plist_head_init(struct plist_head *head)
123 {
124 INIT_LIST_HEAD(&head->node_list);
125 }
126
127 /**
128 * plist_node_init - Dynamic struct plist_node initializer
129 * @node: &struct plist_node pointer
130 * @prio: initial node priority
131 */
plist_node_init(struct plist_node * node,int prio)132 static inline void plist_node_init(struct plist_node *node, int prio)
133 {
134 node->prio = prio;
135 INIT_LIST_HEAD(&node->prio_list);
136 INIT_LIST_HEAD(&node->node_list);
137 }
138
139 extern void plist_add(struct plist_node *node, struct plist_head *head);
140 extern void plist_del(struct plist_node *node, struct plist_head *head);
141
142 extern void plist_requeue(struct plist_node *node, struct plist_head *head);
143
144 /**
145 * plist_for_each - iterate over the plist
146 * @pos: the type * to use as a loop counter
147 * @head: the head for your list
148 */
149 #define plist_for_each(pos, head) \
150 list_for_each_entry(pos, &(head)->node_list, node_list)
151
152 /**
153 * plist_for_each_continue - continue iteration over the plist
154 * @pos: the type * to use as a loop cursor
155 * @head: the head for your list
156 *
157 * Continue to iterate over plist, continuing after the current position.
158 */
159 #define plist_for_each_continue(pos, head) \
160 list_for_each_entry_continue(pos, &(head)->node_list, node_list)
161
162 /**
163 * plist_for_each_safe - iterate safely over a plist of given type
164 * @pos: the type * to use as a loop counter
165 * @n: another type * to use as temporary storage
166 * @head: the head for your list
167 *
168 * Iterate over a plist of given type, safe against removal of list entry.
169 */
170 #define plist_for_each_safe(pos, n, head) \
171 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
172
173 /**
174 * plist_for_each_entry - iterate over list of given type
175 * @pos: the type * to use as a loop counter
176 * @head: the head for your list
177 * @mem: the name of the list_head within the struct
178 */
179 #define plist_for_each_entry(pos, head, mem) \
180 list_for_each_entry(pos, &(head)->node_list, mem.node_list)
181
182 /**
183 * plist_for_each_entry_continue - continue iteration over list of given type
184 * @pos: the type * to use as a loop cursor
185 * @head: the head for your list
186 * @m: the name of the list_head within the struct
187 *
188 * Continue to iterate over list of given type, continuing after
189 * the current position.
190 */
191 #define plist_for_each_entry_continue(pos, head, m) \
192 list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
193
194 /**
195 * plist_for_each_entry_safe - iterate safely over list 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 * @m: the name of the list_head within the struct
200 *
201 * Iterate over list of given type, safe against removal of list entry.
202 */
203 #define plist_for_each_entry_safe(pos, n, head, m) \
204 list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
205
206 /**
207 * plist_head_empty - return !0 if a plist_head is empty
208 * @head: &struct plist_head pointer
209 */
plist_head_empty(const struct plist_head * head)210 static inline int plist_head_empty(const struct plist_head *head)
211 {
212 return list_empty(&head->node_list);
213 }
214
215 /**
216 * plist_node_empty - return !0 if plist_node is not on a list
217 * @node: &struct plist_node pointer
218 */
plist_node_empty(const struct plist_node * node)219 static inline int plist_node_empty(const struct plist_node *node)
220 {
221 return list_empty(&node->node_list);
222 }
223
224 /* All functions below assume the plist_head is not empty. */
225
226 /**
227 * plist_first_entry - get the struct for the first entry
228 * @head: the &struct plist_head pointer
229 * @type: the type of the struct this is embedded in
230 * @member: the name of the list_head within the struct
231 */
232 #ifdef CONFIG_DEBUG_PLIST
233 # define plist_first_entry(head, type, member) \
234 ({ \
235 WARN_ON(plist_head_empty(head)); \
236 container_of(plist_first(head), type, member); \
237 })
238 #else
239 # define plist_first_entry(head, type, member) \
240 container_of(plist_first(head), type, member)
241 #endif
242
243 /**
244 * plist_last_entry - get the struct for the last entry
245 * @head: the &struct plist_head pointer
246 * @type: the type of the struct this is embedded in
247 * @member: the name of the list_head within the struct
248 */
249 #ifdef CONFIG_DEBUG_PLIST
250 # define plist_last_entry(head, type, member) \
251 ({ \
252 WARN_ON(plist_head_empty(head)); \
253 container_of(plist_last(head), type, member); \
254 })
255 #else
256 # define plist_last_entry(head, type, member) \
257 container_of(plist_last(head), type, member)
258 #endif
259
260 /**
261 * plist_next - get the next entry in list
262 * @pos: the type * to cursor
263 */
264 #define plist_next(pos) \
265 list_next_entry(pos, node_list)
266
267 /**
268 * plist_prev - get the prev entry in list
269 * @pos: the type * to cursor
270 */
271 #define plist_prev(pos) \
272 list_prev_entry(pos, node_list)
273
274 /**
275 * plist_first - return the first node (and thus, highest priority)
276 * @head: the &struct plist_head pointer
277 *
278 * Assumes the plist is _not_ empty.
279 */
plist_first(const struct plist_head * head)280 static inline struct plist_node *plist_first(const struct plist_head *head)
281 {
282 return list_entry(head->node_list.next,
283 struct plist_node, node_list);
284 }
285
286 /**
287 * plist_last - return the last node (and thus, lowest priority)
288 * @head: the &struct plist_head pointer
289 *
290 * Assumes the plist is _not_ empty.
291 */
plist_last(const struct plist_head * head)292 static inline struct plist_node *plist_last(const struct plist_head *head)
293 {
294 return list_entry(head->node_list.prev,
295 struct plist_node, node_list);
296 }
297
298 #endif
299
