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/container_of.h>
77 #include <linux/list.h>
78 #include <linux/plist_types.h>
79
80 #include <asm/bug.h>
81
82 /**
83 * PLIST_HEAD_INIT - static struct plist_head initializer
84 * @head: struct plist_head variable name
85 */
86 #define PLIST_HEAD_INIT(head) \
87 { \
88 .node_list = LIST_HEAD_INIT((head).node_list) \
89 }
90
91 /**
92 * PLIST_HEAD - declare and init plist_head
93 * @head: name for struct plist_head variable
94 */
95 #define PLIST_HEAD(head) \
96 struct plist_head head = PLIST_HEAD_INIT(head)
97
98 /**
99 * PLIST_NODE_INIT - static struct plist_node initializer
100 * @node: struct plist_node variable name
101 * @__prio: initial node priority
102 */
103 #define PLIST_NODE_INIT(node, __prio) \
104 { \
105 .prio = (__prio), \
106 .prio_list = LIST_HEAD_INIT((node).prio_list), \
107 .node_list = LIST_HEAD_INIT((node).node_list), \
108 }
109
110 /**
111 * plist_head_init - dynamic struct plist_head initializer
112 * @head: &struct plist_head pointer
113 */
114 static inline void
115 plist_head_init(struct plist_head *head)
116 {
117 INIT_LIST_HEAD(&head->node_list);
118 }
119
120 /**
121 * plist_node_init - Dynamic struct plist_node initializer
122 * @node: &struct plist_node pointer
123 * @prio: initial node priority
124 */
125 static inline void plist_node_init(struct plist_node *node, int prio)
126 {
127 node->prio = prio;
128 INIT_LIST_HEAD(&node->prio_list);
129 INIT_LIST_HEAD(&node->node_list);
130 }
131
132 extern void plist_add(struct plist_node *node, struct plist_head *head);
133 extern void plist_del(struct plist_node *node, struct plist_head *head);
134
135 extern void plist_requeue(struct plist_node *node, struct plist_head *head);
136
137 /**
138 * plist_for_each - iterate over the plist
139 * @pos: the type * to use as a loop counter
140 * @head: the head for your list
141 */
142 #define plist_for_each(pos, head) \
143 list_for_each_entry(pos, &(head)->node_list, node_list)
144
145 /**
146 * plist_for_each_continue - continue iteration over the plist
147 * @pos: the type * to use as a loop cursor
148 * @head: the head for your list
149 *
150 * Continue to iterate over plist, continuing after the current position.
151 */
152 #define plist_for_each_continue(pos, head) \
153 list_for_each_entry_continue(pos, &(head)->node_list, node_list)
154
155 /**
156 * plist_for_each_safe - iterate safely over a plist of given type
157 * @pos: the type * to use as a loop counter
158 * @n: another type * to use as temporary storage
159 * @head: the head for your list
160 *
161 * Iterate over a plist of given type, safe against removal of list entry.
162 */
163 #define plist_for_each_safe(pos, n, head) \
164 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
165
166 /**
167 * plist_for_each_entry - iterate over list of given type
168 * @pos: the type * to use as a loop counter
169 * @head: the head for your list
170 * @mem: the name of the list_head within the struct
171 */
172 #define plist_for_each_entry(pos, head, mem) \
173 list_for_each_entry(pos, &(head)->node_list, mem.node_list)
174
175 /**
176 * plist_for_each_entry_continue - continue iteration over list of given type
177 * @pos: the type * to use as a loop cursor
178 * @head: the head for your list
179 * @m: the name of the list_head within the struct
180 *
181 * Continue to iterate over list of given type, continuing after
182 * the current position.
183 */
184 #define plist_for_each_entry_continue(pos, head, m) \
185 list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
186
187 /**
188 * plist_for_each_entry_safe - iterate safely over list of given type
189 * @pos: the type * to use as a loop counter
190 * @n: another type * to use as temporary storage
191 * @head: the head for your list
192 * @m: the name of the list_head within the struct
193 *
194 * Iterate over list of given type, safe against removal of list entry.
195 */
196 #define plist_for_each_entry_safe(pos, n, head, m) \
197 list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
198
199 /**
200 * plist_head_empty - return !0 if a plist_head is empty
201 * @head: &struct plist_head pointer
202 */
203 static inline int plist_head_empty(const struct plist_head *head)
204 {
205 return list_empty(&head->node_list);
206 }
207
208 /**
209 * plist_node_empty - return !0 if plist_node is not on a list
210 * @node: &struct plist_node pointer
211 */
212 static inline int plist_node_empty(const struct plist_node *node)
213 {
214 return list_empty(&node->node_list);
215 }
216
217 /* All functions below assume the plist_head is not empty. */
218
219 /**
220 * plist_first_entry - get the struct for the first entry
221 * @head: the &struct plist_head pointer
222 * @type: the type of the struct this is embedded in
223 * @member: the name of the list_head within the struct
224 */
225 #ifdef CONFIG_DEBUG_PLIST
226 # define plist_first_entry(head, type, member) \
227 ({ \
228 WARN_ON(plist_head_empty(head)); \
229 container_of(plist_first(head), type, member); \
230 })
231 #else
232 # define plist_first_entry(head, type, member) \
233 container_of(plist_first(head), type, member)
234 #endif
235
236 /**
237 * plist_last_entry - get the struct for the last entry
238 * @head: the &struct plist_head pointer
239 * @type: the type of the struct this is embedded in
240 * @member: the name of the list_head within the struct
241 */
242 #ifdef CONFIG_DEBUG_PLIST
243 # define plist_last_entry(head, type, member) \
244 ({ \
245 WARN_ON(plist_head_empty(head)); \
246 container_of(plist_last(head), type, member); \
247 })
248 #else
249 # define plist_last_entry(head, type, member) \
250 container_of(plist_last(head), type, member)
251 #endif
252
253 /**
254 * plist_next - get the next entry in list
255 * @pos: the type * to cursor
256 */
257 #define plist_next(pos) \
258 list_next_entry(pos, node_list)
259
260 /**
261 * plist_prev - get the prev entry in list
262 * @pos: the type * to cursor
263 */
264 #define plist_prev(pos) \
265 list_prev_entry(pos, node_list)
266
267 /**
268 * plist_first - return the first node (and thus, highest priority)
269 * @head: the &struct plist_head pointer
270 *
271 * Assumes the plist is _not_ empty.
272 */
273 static inline struct plist_node *plist_first(const struct plist_head *head)
274 {
275 return list_entry(head->node_list.next,
276 struct plist_node, node_list);
277 }
278
279 /**
280 * plist_last - return the last node (and thus, lowest priority)
281 * @head: the &struct plist_head pointer
282 *
283 * Assumes the plist is _not_ empty.
284 */
285 static inline struct plist_node *plist_last(const struct plist_head *head)
286 {
287 return list_entry(head->node_list.prev,
288 struct plist_node, node_list);
289 }
290
291 #endif
292
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