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/container_of.h>
77 : #include <linux/list.h>
78 : #include <linux/types.h>
79 :
80 : #include <asm/bug.h>
81 :
82 : struct plist_head {
83 : struct list_head node_list;
84 : };
85 :
86 : struct plist_node {
87 : int prio;
88 : struct list_head prio_list;
89 : struct list_head node_list;
90 : };
91 :
92 : /**
93 : * PLIST_HEAD_INIT - static struct plist_head initializer
94 : * @head: struct plist_head variable name
95 : */
96 : #define PLIST_HEAD_INIT(head) \
97 : { \
98 : .node_list = LIST_HEAD_INIT((head).node_list) \
99 : }
100 :
101 : /**
102 : * PLIST_HEAD - declare and init plist_head
103 : * @head: name for struct plist_head variable
104 : */
105 : #define PLIST_HEAD(head) \
106 : struct plist_head head = PLIST_HEAD_INIT(head)
107 :
108 : /**
109 : * PLIST_NODE_INIT - static struct plist_node initializer
110 : * @node: struct plist_node variable name
111 : * @__prio: initial node priority
112 : */
113 : #define PLIST_NODE_INIT(node, __prio) \
114 : { \
115 : .prio = (__prio), \
116 : .prio_list = LIST_HEAD_INIT((node).prio_list), \
117 : .node_list = LIST_HEAD_INIT((node).node_list), \
118 : }
119 :
120 : /**
121 : * plist_head_init - dynamic struct plist_head initializer
122 : * @head: &struct plist_head pointer
123 : */
124 : static inline void
125 : plist_head_init(struct plist_head *head)
126 : {
127 522 : INIT_LIST_HEAD(&head->node_list);
128 : }
129 :
130 : /**
131 : * plist_node_init - Dynamic struct plist_node initializer
132 : * @node: &struct plist_node pointer
133 : * @prio: initial node priority
134 : */
135 : static inline void plist_node_init(struct plist_node *node, int prio)
136 : {
137 1 : node->prio = prio;
138 2 : INIT_LIST_HEAD(&node->prio_list);
139 2 : INIT_LIST_HEAD(&node->node_list);
140 : }
141 :
142 : extern void plist_add(struct plist_node *node, struct plist_head *head);
143 : extern void plist_del(struct plist_node *node, struct plist_head *head);
144 :
145 : extern void plist_requeue(struct plist_node *node, struct plist_head *head);
146 :
147 : /**
148 : * plist_for_each - iterate over the plist
149 : * @pos: the type * to use as a loop counter
150 : * @head: the head for your list
151 : */
152 : #define plist_for_each(pos, head) \
153 : list_for_each_entry(pos, &(head)->node_list, node_list)
154 :
155 : /**
156 : * plist_for_each_continue - continue iteration over the plist
157 : * @pos: the type * to use as a loop cursor
158 : * @head: the head for your list
159 : *
160 : * Continue to iterate over plist, continuing after the current position.
161 : */
162 : #define plist_for_each_continue(pos, head) \
163 : list_for_each_entry_continue(pos, &(head)->node_list, node_list)
164 :
165 : /**
166 : * plist_for_each_safe - iterate safely over a plist of given type
167 : * @pos: the type * to use as a loop counter
168 : * @n: another type * to use as temporary storage
169 : * @head: the head for your list
170 : *
171 : * Iterate over a plist of given type, safe against removal of list entry.
172 : */
173 : #define plist_for_each_safe(pos, n, head) \
174 : list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
175 :
176 : /**
177 : * plist_for_each_entry - iterate over list of given type
178 : * @pos: the type * to use as a loop counter
179 : * @head: the head for your list
180 : * @mem: the name of the list_head within the struct
181 : */
182 : #define plist_for_each_entry(pos, head, mem) \
183 : list_for_each_entry(pos, &(head)->node_list, mem.node_list)
184 :
185 : /**
186 : * plist_for_each_entry_continue - continue iteration over list of given type
187 : * @pos: the type * to use as a loop cursor
188 : * @head: the head for your list
189 : * @m: the name of the list_head within the struct
190 : *
191 : * Continue to iterate over list of given type, continuing after
192 : * the current position.
193 : */
194 : #define plist_for_each_entry_continue(pos, head, m) \
195 : list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
196 :
197 : /**
198 : * plist_for_each_entry_safe - iterate safely over list of given type
199 : * @pos: the type * to use as a loop counter
200 : * @n: another type * to use as temporary storage
201 : * @head: the head for your list
202 : * @m: the name of the list_head within the struct
203 : *
204 : * Iterate over list of given type, safe against removal of list entry.
205 : */
206 : #define plist_for_each_entry_safe(pos, n, head, m) \
207 : list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
208 :
209 : /**
210 : * plist_head_empty - return !0 if a plist_head is empty
211 : * @head: &struct plist_head pointer
212 : */
213 : static inline int plist_head_empty(const struct plist_head *head)
214 : {
215 6 : return list_empty(&head->node_list);
216 : }
217 :
218 : /**
219 : * plist_node_empty - return !0 if plist_node is not on a list
220 : * @node: &struct plist_node pointer
221 : */
222 : static inline int plist_node_empty(const struct plist_node *node)
223 : {
224 2 : return list_empty(&node->node_list);
225 : }
226 :
227 : /* All functions below assume the plist_head is not empty. */
228 :
229 : /**
230 : * plist_first_entry - get the struct for the first entry
231 : * @head: the &struct plist_head pointer
232 : * @type: the type of the struct this is embedded in
233 : * @member: the name of the list_head within the struct
234 : */
235 : #ifdef CONFIG_DEBUG_PLIST
236 : # define plist_first_entry(head, type, member) \
237 : ({ \
238 : WARN_ON(plist_head_empty(head)); \
239 : container_of(plist_first(head), type, member); \
240 : })
241 : #else
242 : # define plist_first_entry(head, type, member) \
243 : container_of(plist_first(head), type, member)
244 : #endif
245 :
246 : /**
247 : * plist_last_entry - get the struct for the last entry
248 : * @head: the &struct plist_head pointer
249 : * @type: the type of the struct this is embedded in
250 : * @member: the name of the list_head within the struct
251 : */
252 : #ifdef CONFIG_DEBUG_PLIST
253 : # define plist_last_entry(head, type, member) \
254 : ({ \
255 : WARN_ON(plist_head_empty(head)); \
256 : container_of(plist_last(head), type, member); \
257 : })
258 : #else
259 : # define plist_last_entry(head, type, member) \
260 : container_of(plist_last(head), type, member)
261 : #endif
262 :
263 : /**
264 : * plist_next - get the next entry in list
265 : * @pos: the type * to cursor
266 : */
267 : #define plist_next(pos) \
268 : list_next_entry(pos, node_list)
269 :
270 : /**
271 : * plist_prev - get the prev entry in list
272 : * @pos: the type * to cursor
273 : */
274 : #define plist_prev(pos) \
275 : list_prev_entry(pos, node_list)
276 :
277 : /**
278 : * plist_first - return the first node (and thus, highest priority)
279 : * @head: the &struct plist_head pointer
280 : *
281 : * Assumes the plist is _not_ empty.
282 : */
283 : static inline struct plist_node *plist_first(const struct plist_head *head)
284 : {
285 1 : return list_entry(head->node_list.next,
286 : struct plist_node, node_list);
287 : }
288 :
289 : /**
290 : * plist_last - return the last node (and thus, lowest priority)
291 : * @head: the &struct plist_head pointer
292 : *
293 : * Assumes the plist is _not_ empty.
294 : */
295 : static inline struct plist_node *plist_last(const struct plist_head *head)
296 : {
297 0 : return list_entry(head->node_list.prev,
298 : struct plist_node, node_list);
299 : }
300 :
301 : #endif
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