1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2
3 #ifndef _LINUX_LIST_H
4 #define _LINUX_LIST_H
5
6 #ifndef offsetof
7 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
8 #endif
9
10 #define container_of(ptr, type, member) ({ \
11 const typeof(((type *)0)->member) * __mptr = (ptr); \
12 (type *)((char *)__mptr - offsetof(type, member)); \
13 })
14
15 /*
16 * These are non-NULL pointers that will result in page faults
17 * under normal circumstances, used to verify that nobody uses
18 * non-initialized list entries.
19 */
20 #define LIST_POISON1 ((void *) 0x00100100)
21 #define LIST_POISON2 ((void *) 0x00200200)
22
23 /**
24 * Simple doubly linked list implementation.
25 *
26 * Some of the internal functions ("__xxx") are useful when
27 * manipulating whole lists rather than single entries, as
28 * sometimes we already know the next/prev entries and we can
29 * generate better code by using them directly rather than
30 * using the generic single-entry routines.
31 */
32 struct list_head {
33 struct list_head *next, *prev;
34 };
35
36 #define LIST_HEAD_INIT(name) { &(name), &(name) }
37
38 #define LIST_HEAD(name) \
39 struct list_head name = LIST_HEAD_INIT(name)
40
41 #define INIT_LIST_HEAD(ptr) do { \
42 (ptr)->next = (ptr); (ptr)->prev = (ptr); \
43 } while (0)
44
45 /*
46 * Insert a new entry between two known consecutive entries.
47 *
48 * This is only for internal list manipulation where we know
49 * the prev/next entries already!
50 */
__list_add(struct list_head * new,struct list_head * prev,struct list_head * next)51 static inline void __list_add(struct list_head *new,
52 struct list_head *prev,
53 struct list_head *next)
54 {
55 next->prev = new;
56 new->next = next;
57 new->prev = prev;
58 prev->next = new;
59 }
60
61 /**
62 * list_add - add a new entry
63 * @new: new entry to be added
64 * @head: list head to add it after
65 *
66 * Insert a new entry after the specified head.
67 * This is good for implementing stacks.
68 */
list_add(struct list_head * new,struct list_head * head)69 static inline void list_add(struct list_head *new, struct list_head *head)
70 {
71 __list_add(new, head, head->next);
72 }
73
74 /**
75 * list_add_tail - add a new entry
76 * @new: new entry to be added
77 * @head: list head to add it before
78 *
79 * Insert a new entry before the specified head.
80 * This is useful for implementing queues.
81 */
list_add_tail(struct list_head * new,struct list_head * head)82 static inline void list_add_tail(struct list_head *new, struct list_head *head)
83 {
84 __list_add(new, head->prev, head);
85 }
86
87 /*
88 * Delete a list entry by making the prev/next entries
89 * point to each other.
90 *
91 * This is only for internal list manipulation where we know
92 * the prev/next entries already!
93 */
__list_del(struct list_head * prev,struct list_head * next)94 static inline void __list_del(struct list_head *prev, struct list_head *next)
95 {
96 next->prev = prev;
97 prev->next = next;
98 }
99
100 /**
101 * list_del - deletes entry from list.
102 * @entry: the element to delete from the list.
103 * Note: list_empty on entry does not return true after this, the entry is
104 * in an undefined state.
105 */
list_del(struct list_head * entry)106 static inline void list_del(struct list_head *entry)
107 {
108 __list_del(entry->prev, entry->next);
109 entry->next = LIST_POISON1;
110 entry->prev = LIST_POISON2;
111 }
112
113 /**
114 * list_del_init - deletes entry from list and reinitialize it.
115 * @entry: the element to delete from the list.
116 */
list_del_init(struct list_head * entry)117 static inline void list_del_init(struct list_head *entry)
118 {
119 __list_del(entry->prev, entry->next);
120 INIT_LIST_HEAD(entry);
121 }
122
123 /**
124 * list_move - delete from one list and add as another's head
125 * @list: the entry to move
126 * @head: the head that will precede our entry
127 */
list_move(struct list_head * list,struct list_head * head)128 static inline void list_move(struct list_head *list, struct list_head *head)
129 {
130 __list_del(list->prev, list->next);
131 list_add(list, head);
132 }
133
134 /**
135 * list_move_tail - delete from one list and add as another's tail
136 * @list: the entry to move
137 * @head: the head that will follow our entry
138 */
list_move_tail(struct list_head * list,struct list_head * head)139 static inline void list_move_tail(struct list_head *list,
140 struct list_head *head)
141 {
142 __list_del(list->prev, list->next);
143 list_add_tail(list, head);
144 }
145
146 /**
147 * list_empty - tests whether a list is empty
148 * @head: the list to test.
149 */
list_empty(const struct list_head * head)150 static inline int list_empty(const struct list_head *head)
151 {
152 return head->next == head;
153 }
154
__list_splice(struct list_head * list,struct list_head * head)155 static inline void __list_splice(struct list_head *list,
156 struct list_head *head)
157 {
158 struct list_head *first = list->next;
159 struct list_head *last = list->prev;
160 struct list_head *at = head->next;
161
162 first->prev = head;
163 head->next = first;
164
165 last->next = at;
166 at->prev = last;
167 }
168
169 /**
170 * list_splice - join two lists
171 * @list: the new list to add.
172 * @head: the place to add it in the first list.
173 */
list_splice(struct list_head * list,struct list_head * head)174 static inline void list_splice(struct list_head *list, struct list_head *head)
175 {
176 if (!list_empty(list))
177 __list_splice(list, head);
178 }
179
180 /**
181 * list_splice_init - join two lists and reinitialise the emptied list.
182 * @list: the new list to add.
183 * @head: the place to add it in the first list.
184 *
185 * The list at @list is reinitialised
186 */
list_splice_init(struct list_head * list,struct list_head * head)187 static inline void list_splice_init(struct list_head *list,
188 struct list_head *head)
189 {
190 if (!list_empty(list)) {
191 __list_splice(list, head);
192 INIT_LIST_HEAD(list);
193 }
194 }
195
196 /**
197 * list_entry - get the struct for this entry
198 * @ptr: the &struct list_head pointer.
199 * @type: the type of the struct this is embedded in.
200 * @member: the name of the list_struct within the struct.
201 */
202 #define list_entry(ptr, type, member) \
203 container_of(ptr, type, member)
204
205 /**
206 * list_for_each - iterate over a list
207 * @pos: the &struct list_head to use as a loop counter.
208 * @head: the head for your list.
209 */
210
211 #define list_for_each(pos, head) \
212 for (pos = (head)->next; pos != (head); \
213 pos = pos->next)
214
215 /**
216 * __list_for_each - iterate over a list
217 * @pos: the &struct list_head to use as a loop counter.
218 * @head: the head for your list.
219 *
220 * This variant differs from list_for_each() in that it's the
221 * simplest possible list iteration code, no prefetching is done.
222 * Use this for code that knows the list to be very short (empty
223 * or 1 entry) most of the time.
224 */
225 #define __list_for_each(pos, head) \
226 for (pos = (head)->next; pos != (head); pos = pos->next)
227
228 /**
229 * list_for_each_prev - iterate over a list backwards
230 * @pos: the &struct list_head to use as a loop counter.
231 * @head: the head for your list.
232 */
233 #define list_for_each_prev(pos, head) \
234 for (pos = (head)->prev; prefetch(pos->prev), pos != (head); \
235 pos = pos->prev)
236
237 /**
238 * list_for_each_safe - iterate over a list safe against removal of list entry
239 * @pos: the &struct list_head to use as a loop counter.
240 * @n: another &struct list_head to use as temporary storage
241 * @head: the head for your list.
242 */
243 #define list_for_each_safe(pos, n, head) \
244 for (pos = (head)->next, n = pos->next; pos != (head); \
245 pos = n, n = pos->next)
246
247 /**
248 * list_for_each_entry - iterate over list of given type
249 * @pos: the type * to use as a loop counter.
250 * @head: the head for your list.
251 * @member: the name of the list_struct within the struct.
252 */
253 #define list_for_each_entry(pos, head, member) \
254 for (pos = list_entry((head)->next, typeof(*pos), member); \
255 &pos->member != (head); \
256 pos = list_entry(pos->member.next, typeof(*pos), member))
257
258 /**
259 * list_for_each_entry_reverse - iterate backwards over list of given type.
260 * @pos: the type * to use as a loop counter.
261 * @head: the head for your list.
262 * @member: the name of the list_struct within the struct.
263 */
264 #define list_for_each_entry_reverse(pos, head, member) \
265 for (pos = list_entry((head)->prev, typeof(*pos), member); \
266 &pos->member != (head); \
267 pos = list_entry(pos->member.prev, typeof(*pos), member))
268
269 /**
270 * list_prepare_entry - prepare a pos entry for use as a start point in
271 * list_for_each_entry_continue
272 * @pos: the type * to use as a start point
273 * @head: the head of the list
274 * @member: the name of the list_struct within the struct.
275 */
276 #define list_prepare_entry(pos, head, member) \
277 ((pos) ? : list_entry(head, typeof(*pos), member))
278
279 /**
280 * list_for_each_entry_continue - iterate over list of given type
281 * continuing after existing point
282 * @pos: the type * to use as a loop counter.
283 * @head: the head for your list.
284 * @member: the name of the list_struct within the struct.
285 */
286 #define list_for_each_entry_continue(pos, head, member) \
287 for (pos = list_entry(pos->member.next, typeof(*pos), member); \
288 &pos->member != (head); \
289 pos = list_entry(pos->member.next, typeof(*pos), member))
290
291 /**
292 * list_for_each_entry_safe - iterate over list of given type safe against
293 * removal of list entry
294 * @pos: the type * to use as a loop counter.
295 * @n: another type * to use as temporary storage
296 * @head: the head for your list.
297 * @member: the name of the list_struct within the struct.
298 */
299 #define list_for_each_entry_safe(pos, n, head, member) \
300 for (pos = list_entry((head)->next, typeof(*pos), member), \
301 n = list_entry(pos->member.next, typeof(*pos), member); \
302 &pos->member != (head); \
303 pos = n, n = list_entry(n->member.next, typeof(*n), member))
304
305 /**
306 * list_for_each_entry_safe_continue - iterate over list of given type
307 * continuing after existing point safe against removal of list entry
308 * @pos: the type * to use as a loop counter.
309 * @n: another type * to use as temporary storage
310 * @head: the head for your list.
311 * @member: the name of the list_struct within the struct.
312 */
313 #define list_for_each_entry_safe_continue(pos, n, head, member) \
314 for (pos = list_entry(pos->member.next, typeof(*pos), member), \
315 n = list_entry(pos->member.next, typeof(*pos), member); \
316 &pos->member != (head); \
317 pos = n, n = list_entry(n->member.next, typeof(*n), member))
318
319 /**
320 * list_for_each_entry_safe_reverse - iterate backwards over list of given
321 * type safe against removal of list entry
322 * @pos: the type * to use as a loop counter.
323 * @n: another type * to use as temporary storage
324 * @head: the head for your list.
325 * @member: the name of the list_struct within the struct.
326 */
327 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
328 for (pos = list_entry((head)->prev, typeof(*pos), member), \
329 n = list_entry(pos->member.prev, typeof(*pos), member); \
330 &pos->member != (head); \
331 pos = n, n = list_entry(n->member.prev, typeof(*n), member))
332
333 #endif
334