4 #include <linux/types.h>
5 #include <linux/stddef.h>
6 #include <linux/poison.h>
7 #include <linux/const.h>
8 #include <linux/kernel.h>
11 * Simple doubly linked list implementation.
13 * Some of the internal functions ("__xxx") are useful when
14 * manipulating whole lists rather than single entries, as
15 * sometimes we already know the next/prev entries and we can
16 * generate better code by using them directly rather than
17 * using the generic single-entry routines.
20 #define LIST_HEAD_INIT(name) { &(name), &(name) }
22 #define LIST_HEAD(name) \
23 struct list_head name = LIST_HEAD_INIT(name)
25 static inline void INIT_LIST_HEAD(struct list_head *list)
27 WRITE_ONCE(list->next, list);
32 * Insert a new entry between two known consecutive entries.
34 * This is only for internal list manipulation where we know
35 * the prev/next entries already!
37 #ifndef CONFIG_DEBUG_LIST
38 static inline void __list_add(struct list_head *new,
39 struct list_head *prev,
40 struct list_head *next)
45 WRITE_ONCE(prev->next, new);
48 extern void __list_add(struct list_head *new,
49 struct list_head *prev,
50 struct list_head *next);
54 * list_add - add a new entry
55 * @new: new entry to be added
56 * @head: list head to add it after
58 * Insert a new entry after the specified head.
59 * This is good for implementing stacks.
61 static inline void list_add(struct list_head *new, struct list_head *head)
63 __list_add(new, head, head->next);
68 * list_add_tail - add a new entry
69 * @new: new entry to be added
70 * @head: list head to add it before
72 * Insert a new entry before the specified head.
73 * This is useful for implementing queues.
75 static inline void list_add_tail(struct list_head *new, struct list_head *head)
77 __list_add(new, head->prev, head);
81 * Delete a list entry by making the prev/next entries
82 * point to each other.
84 * This is only for internal list manipulation where we know
85 * the prev/next entries already!
87 static inline void __list_del(struct list_head * prev, struct list_head * next)
90 WRITE_ONCE(prev->next, next);
94 * list_del - deletes entry from list.
95 * @entry: the element to delete from the list.
96 * Note: list_empty() on entry does not return true after this, the entry is
97 * in an undefined state.
99 #ifndef CONFIG_DEBUG_LIST
100 static inline void __list_del_entry(struct list_head *entry)
102 __list_del(entry->prev, entry->next);
105 static inline void list_del(struct list_head *entry)
107 __list_del(entry->prev, entry->next);
108 entry->next = LIST_POISON1;
109 entry->prev = LIST_POISON2;
112 extern void __list_del_entry(struct list_head *entry);
113 extern void list_del(struct list_head *entry);
116 #ifdef CONFIG_DEBUG_LIST
118 * See devm_memremap_pages() which wants DEBUG_LIST=y to assert if one
119 * of the pages it allocates is ever passed to list_add()
121 extern void list_force_poison(struct list_head *entry);
123 /* fallback to the less strict LIST_POISON* definitions */
124 #define list_force_poison list_del
128 * list_replace - replace old entry by new one
129 * @old : the element to be replaced
130 * @new : the new element to insert
132 * If @old was empty, it will be overwritten.
134 static inline void list_replace(struct list_head *old,
135 struct list_head *new)
137 new->next = old->next;
138 new->next->prev = new;
139 new->prev = old->prev;
140 new->prev->next = new;
143 static inline void list_replace_init(struct list_head *old,
144 struct list_head *new)
146 list_replace(old, new);
151 * list_del_init - deletes entry from list and reinitialize it.
152 * @entry: the element to delete from the list.
154 static inline void list_del_init(struct list_head *entry)
156 __list_del_entry(entry);
157 INIT_LIST_HEAD(entry);
161 * list_move - delete from one list and add as another's head
162 * @list: the entry to move
163 * @head: the head that will precede our entry
165 static inline void list_move(struct list_head *list, struct list_head *head)
167 __list_del_entry(list);
168 list_add(list, head);
172 * list_move_tail - delete from one list and add as another's tail
173 * @list: the entry to move
174 * @head: the head that will follow our entry
176 static inline void list_move_tail(struct list_head *list,
177 struct list_head *head)
179 __list_del_entry(list);
180 list_add_tail(list, head);
184 * list_is_last - tests whether @list is the last entry in list @head
185 * @list: the entry to test
186 * @head: the head of the list
188 static inline int list_is_last(const struct list_head *list,
189 const struct list_head *head)
191 return list->next == head;
195 * list_empty - tests whether a list is empty
196 * @head: the list to test.
198 static inline int list_empty(const struct list_head *head)
200 return READ_ONCE(head->next) == head;
204 * list_empty_careful - tests whether a list is empty and not being modified
205 * @head: the list to test
208 * tests whether a list is empty _and_ checks that no other CPU might be
209 * in the process of modifying either member (next or prev)
211 * NOTE: using list_empty_careful() without synchronization
212 * can only be safe if the only activity that can happen
213 * to the list entry is list_del_init(). Eg. it cannot be used
214 * if another CPU could re-list_add() it.
216 static inline int list_empty_careful(const struct list_head *head)
218 struct list_head *next = head->next;
219 return (next == head) && (next == head->prev);
223 * list_rotate_left - rotate the list to the left
224 * @head: the head of the list
226 static inline void list_rotate_left(struct list_head *head)
228 struct list_head *first;
230 if (!list_empty(head)) {
232 list_move_tail(first, head);
237 * list_is_singular - tests whether a list has just one entry.
238 * @head: the list to test.
240 static inline int list_is_singular(const struct list_head *head)
242 return !list_empty(head) && (head->next == head->prev);
245 static inline void __list_cut_position(struct list_head *list,
246 struct list_head *head, struct list_head *entry)
248 struct list_head *new_first = entry->next;
249 list->next = head->next;
250 list->next->prev = list;
253 head->next = new_first;
254 new_first->prev = head;
258 * list_cut_position - cut a list into two
259 * @list: a new list to add all removed entries
260 * @head: a list with entries
261 * @entry: an entry within head, could be the head itself
262 * and if so we won't cut the list
264 * This helper moves the initial part of @head, up to and
265 * including @entry, from @head to @list. You should
266 * pass on @entry an element you know is on @head. @list
267 * should be an empty list or a list you do not care about
271 static inline void list_cut_position(struct list_head *list,
272 struct list_head *head, struct list_head *entry)
274 if (list_empty(head))
276 if (list_is_singular(head) &&
277 (head->next != entry && head != entry))
280 INIT_LIST_HEAD(list);
282 __list_cut_position(list, head, entry);
285 static inline void __list_splice(const struct list_head *list,
286 struct list_head *prev,
287 struct list_head *next)
289 struct list_head *first = list->next;
290 struct list_head *last = list->prev;
300 * list_splice - join two lists, this is designed for stacks
301 * @list: the new list to add.
302 * @head: the place to add it in the first list.
304 static inline void list_splice(const struct list_head *list,
305 struct list_head *head)
307 if (!list_empty(list))
308 __list_splice(list, head, head->next);
312 * list_splice_tail - join two lists, each list being a queue
313 * @list: the new list to add.
314 * @head: the place to add it in the first list.
316 static inline void list_splice_tail(struct list_head *list,
317 struct list_head *head)
319 if (!list_empty(list))
320 __list_splice(list, head->prev, head);
324 * list_splice_init - join two lists and reinitialise the emptied list.
325 * @list: the new list to add.
326 * @head: the place to add it in the first list.
328 * The list at @list is reinitialised
330 static inline void list_splice_init(struct list_head *list,
331 struct list_head *head)
333 if (!list_empty(list)) {
334 __list_splice(list, head, head->next);
335 INIT_LIST_HEAD(list);
340 * list_splice_tail_init - join two lists and reinitialise the emptied list
341 * @list: the new list to add.
342 * @head: the place to add it in the first list.
344 * Each of the lists is a queue.
345 * The list at @list is reinitialised
347 static inline void list_splice_tail_init(struct list_head *list,
348 struct list_head *head)
350 if (!list_empty(list)) {
351 __list_splice(list, head->prev, head);
352 INIT_LIST_HEAD(list);
357 * list_entry - get the struct for this entry
358 * @ptr: the &struct list_head pointer.
359 * @type: the type of the struct this is embedded in.
360 * @member: the name of the list_head within the struct.
362 #define list_entry(ptr, type, member) \
363 container_of(ptr, type, member)
366 * list_first_entry - get the first element from a list
367 * @ptr: the list head to take the element from.
368 * @type: the type of the struct this is embedded in.
369 * @member: the name of the list_head within the struct.
371 * Note, that list is expected to be not empty.
373 #define list_first_entry(ptr, type, member) \
374 list_entry((ptr)->next, type, member)
377 * list_last_entry - get the last element from a list
378 * @ptr: the list head to take the element from.
379 * @type: the type of the struct this is embedded in.
380 * @member: the name of the list_head within the struct.
382 * Note, that list is expected to be not empty.
384 #define list_last_entry(ptr, type, member) \
385 list_entry((ptr)->prev, type, member)
388 * list_first_entry_or_null - get the first element from a list
389 * @ptr: the list head to take the element from.
390 * @type: the type of the struct this is embedded in.
391 * @member: the name of the list_head within the struct.
393 * Note that if the list is empty, it returns NULL.
395 #define list_first_entry_or_null(ptr, type, member) \
396 (!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)
399 * list_next_entry - get the next element in list
400 * @pos: the type * to cursor
401 * @member: the name of the list_head within the struct.
403 #define list_next_entry(pos, member) \
404 list_entry((pos)->member.next, typeof(*(pos)), member)
407 * list_prev_entry - get the prev element in list
408 * @pos: the type * to cursor
409 * @member: the name of the list_head within the struct.
411 #define list_prev_entry(pos, member) \
412 list_entry((pos)->member.prev, typeof(*(pos)), member)
415 * list_for_each - iterate over a list
416 * @pos: the &struct list_head to use as a loop cursor.
417 * @head: the head for your list.
419 #define list_for_each(pos, head) \
420 for (pos = (head)->next; pos != (head); pos = pos->next)
423 * list_for_each_prev - iterate over a list backwards
424 * @pos: the &struct list_head to use as a loop cursor.
425 * @head: the head for your list.
427 #define list_for_each_prev(pos, head) \
428 for (pos = (head)->prev; pos != (head); pos = pos->prev)
431 * list_for_each_safe - iterate over a list safe against removal of list entry
432 * @pos: the &struct list_head to use as a loop cursor.
433 * @n: another &struct list_head to use as temporary storage
434 * @head: the head for your list.
436 #define list_for_each_safe(pos, n, head) \
437 for (pos = (head)->next, n = pos->next; pos != (head); \
438 pos = n, n = pos->next)
441 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
442 * @pos: the &struct list_head to use as a loop cursor.
443 * @n: another &struct list_head to use as temporary storage
444 * @head: the head for your list.
446 #define list_for_each_prev_safe(pos, n, head) \
447 for (pos = (head)->prev, n = pos->prev; \
449 pos = n, n = pos->prev)
452 * list_for_each_entry - iterate over list of given type
453 * @pos: the type * to use as a loop cursor.
454 * @head: the head for your list.
455 * @member: the name of the list_head within the struct.
457 #define list_for_each_entry(pos, head, member) \
458 for (pos = list_first_entry(head, typeof(*pos), member); \
459 &pos->member != (head); \
460 pos = list_next_entry(pos, member))
463 * list_for_each_entry_reverse - iterate backwards over list of given type.
464 * @pos: the type * to use as a loop cursor.
465 * @head: the head for your list.
466 * @member: the name of the list_head within the struct.
468 #define list_for_each_entry_reverse(pos, head, member) \
469 for (pos = list_last_entry(head, typeof(*pos), member); \
470 &pos->member != (head); \
471 pos = list_prev_entry(pos, member))
474 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
475 * @pos: the type * to use as a start point
476 * @head: the head of the list
477 * @member: the name of the list_head within the struct.
479 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
481 #define list_prepare_entry(pos, head, member) \
482 ((pos) ? : list_entry(head, typeof(*pos), member))
485 * list_for_each_entry_continue - continue iteration over list of given type
486 * @pos: the type * to use as a loop cursor.
487 * @head: the head for your list.
488 * @member: the name of the list_head within the struct.
490 * Continue to iterate over list of given type, continuing after
491 * the current position.
493 #define list_for_each_entry_continue(pos, head, member) \
494 for (pos = list_next_entry(pos, member); \
495 &pos->member != (head); \
496 pos = list_next_entry(pos, member))
499 * list_for_each_entry_continue_reverse - iterate backwards from the given point
500 * @pos: the type * to use as a loop cursor.
501 * @head: the head for your list.
502 * @member: the name of the list_head within the struct.
504 * Start to iterate over list of given type backwards, continuing after
505 * the current position.
507 #define list_for_each_entry_continue_reverse(pos, head, member) \
508 for (pos = list_prev_entry(pos, member); \
509 &pos->member != (head); \
510 pos = list_prev_entry(pos, member))
513 * list_for_each_entry_from - iterate over list of given type from the current point
514 * @pos: the type * to use as a loop cursor.
515 * @head: the head for your list.
516 * @member: the name of the list_head within the struct.
518 * Iterate over list of given type, continuing from current position.
520 #define list_for_each_entry_from(pos, head, member) \
521 for (; &pos->member != (head); \
522 pos = list_next_entry(pos, member))
525 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
526 * @pos: the type * to use as a loop cursor.
527 * @n: another type * to use as temporary storage
528 * @head: the head for your list.
529 * @member: the name of the list_head within the struct.
531 #define list_for_each_entry_safe(pos, n, head, member) \
532 for (pos = list_first_entry(head, typeof(*pos), member), \
533 n = list_next_entry(pos, member); \
534 &pos->member != (head); \
535 pos = n, n = list_next_entry(n, member))
538 * list_for_each_entry_safe_continue - continue list iteration safe against removal
539 * @pos: the type * to use as a loop cursor.
540 * @n: another type * to use as temporary storage
541 * @head: the head for your list.
542 * @member: the name of the list_head within the struct.
544 * Iterate over list of given type, continuing after current point,
545 * safe against removal of list entry.
547 #define list_for_each_entry_safe_continue(pos, n, head, member) \
548 for (pos = list_next_entry(pos, member), \
549 n = list_next_entry(pos, member); \
550 &pos->member != (head); \
551 pos = n, n = list_next_entry(n, member))
554 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
555 * @pos: the type * to use as a loop cursor.
556 * @n: another type * to use as temporary storage
557 * @head: the head for your list.
558 * @member: the name of the list_head within the struct.
560 * Iterate over list of given type from current point, safe against
561 * removal of list entry.
563 #define list_for_each_entry_safe_from(pos, n, head, member) \
564 for (n = list_next_entry(pos, member); \
565 &pos->member != (head); \
566 pos = n, n = list_next_entry(n, member))
569 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
570 * @pos: the type * to use as a loop cursor.
571 * @n: another type * to use as temporary storage
572 * @head: the head for your list.
573 * @member: the name of the list_head within the struct.
575 * Iterate backwards over list of given type, safe against removal
578 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
579 for (pos = list_last_entry(head, typeof(*pos), member), \
580 n = list_prev_entry(pos, member); \
581 &pos->member != (head); \
582 pos = n, n = list_prev_entry(n, member))
585 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
586 * @pos: the loop cursor used in the list_for_each_entry_safe loop
587 * @n: temporary storage used in list_for_each_entry_safe
588 * @member: the name of the list_head within the struct.
590 * list_safe_reset_next is not safe to use in general if the list may be
591 * modified concurrently (eg. the lock is dropped in the loop body). An
592 * exception to this is if the cursor element (pos) is pinned in the list,
593 * and list_safe_reset_next is called after re-taking the lock and before
594 * completing the current iteration of the loop body.
596 #define list_safe_reset_next(pos, n, member) \
597 n = list_next_entry(pos, member)
600 * Double linked lists with a single pointer list head.
601 * Mostly useful for hash tables where the two pointer list head is
603 * You lose the ability to access the tail in O(1).
606 #define HLIST_HEAD_INIT { .first = NULL }
607 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
608 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
609 static inline void INIT_HLIST_NODE(struct hlist_node *h)
615 static inline int hlist_unhashed(const struct hlist_node *h)
620 static inline int hlist_empty(const struct hlist_head *h)
622 return !READ_ONCE(h->first);
625 static inline void __hlist_del(struct hlist_node *n)
627 struct hlist_node *next = n->next;
628 struct hlist_node **pprev = n->pprev;
630 WRITE_ONCE(*pprev, next);
635 static inline void hlist_del(struct hlist_node *n)
638 n->next = LIST_POISON1;
639 n->pprev = LIST_POISON2;
642 static inline void hlist_del_init(struct hlist_node *n)
644 if (!hlist_unhashed(n)) {
650 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
652 struct hlist_node *first = h->first;
655 first->pprev = &n->next;
656 WRITE_ONCE(h->first, n);
657 n->pprev = &h->first;
660 /* next must be != NULL */
661 static inline void hlist_add_before(struct hlist_node *n,
662 struct hlist_node *next)
664 n->pprev = next->pprev;
666 next->pprev = &n->next;
667 WRITE_ONCE(*(n->pprev), n);
670 static inline void hlist_add_behind(struct hlist_node *n,
671 struct hlist_node *prev)
673 n->next = prev->next;
674 WRITE_ONCE(prev->next, n);
675 n->pprev = &prev->next;
678 n->next->pprev = &n->next;
681 /* after that we'll appear to be on some hlist and hlist_del will work */
682 static inline void hlist_add_fake(struct hlist_node *n)
687 static inline bool hlist_fake(struct hlist_node *h)
689 return h->pprev == &h->next;
693 * Move a list from one list head to another. Fixup the pprev
694 * reference of the first entry if it exists.
696 static inline void hlist_move_list(struct hlist_head *old,
697 struct hlist_head *new)
699 new->first = old->first;
701 new->first->pprev = &new->first;
705 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
707 #define hlist_for_each(pos, head) \
708 for (pos = (head)->first; pos ; pos = pos->next)
710 #define hlist_for_each_safe(pos, n, head) \
711 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
714 #define hlist_entry_safe(ptr, type, member) \
715 ({ typeof(ptr) ____ptr = (ptr); \
716 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
720 * hlist_for_each_entry - iterate over list of given type
721 * @pos: the type * to use as a loop cursor.
722 * @head: the head for your list.
723 * @member: the name of the hlist_node within the struct.
725 #define hlist_for_each_entry(pos, head, member) \
726 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
728 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
731 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
732 * @pos: the type * to use as a loop cursor.
733 * @member: the name of the hlist_node within the struct.
735 #define hlist_for_each_entry_continue(pos, member) \
736 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
738 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
741 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
742 * @pos: the type * to use as a loop cursor.
743 * @member: the name of the hlist_node within the struct.
745 #define hlist_for_each_entry_from(pos, member) \
747 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
750 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
751 * @pos: the type * to use as a loop cursor.
752 * @n: another &struct hlist_node to use as temporary storage
753 * @head: the head for your list.
754 * @member: the name of the hlist_node within the struct.
756 #define hlist_for_each_entry_safe(pos, n, head, member) \
757 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
758 pos && ({ n = pos->member.next; 1; }); \
759 pos = hlist_entry_safe(n, typeof(*pos), member))