Line data Source code
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
122 1028 : plist_head_init(struct plist_head *head)
123 : {
124 1028 : 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 : */
132 1147 : static inline void plist_node_init(struct plist_node *node, int prio)
133 : {
134 1147 : node->prio = prio;
135 1147 : INIT_LIST_HEAD(&node->prio_list);
136 1147 : 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 : */
210 176 : static inline int plist_head_empty(const struct plist_head *head)
211 : {
212 176 : 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 : */
219 509 : static inline int plist_node_empty(const struct plist_node *node)
220 : {
221 509 : 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 : */
280 0 : static inline struct plist_node *plist_first(const struct plist_head *head)
281 : {
282 0 : 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 : */
292 0 : static inline struct plist_node *plist_last(const struct plist_head *head)
293 : {
294 0 : return list_entry(head->node_list.prev,
295 : struct plist_node, node_list);
296 : }
297 :
298 : #endif
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