1 /* SPDX-License-Identifier: GPL-2.0 */
5 #include <linux/types.h>
6 #include <linux/stddef.h>
7 #include <linux/poison.h>
8 #include <linux/const.h>
9 #include <linux/kernel.h>
12 * Simple doubly linked list implementation.
14 * Some of the internal functions ("__xxx") are useful when
15 * manipulating whole lists rather than single entries, as
16 * sometimes we already know the next/prev entries and we can
17 * generate better code by using them directly rather than
18 * using the generic single-entry routines.
21 #define LIST_HEAD_INIT(name) { &(name), &(name) }
23 #define LIST_HEAD(name) \
24 struct list_head name = LIST_HEAD_INIT(name)
26 static inline void INIT_LIST_HEAD(struct list_head *list)
28 WRITE_ONCE(list->next, list);
32 #ifdef CONFIG_DEBUG_LIST
33 extern bool __list_add_valid(struct list_head *new,
34 struct list_head *prev,
35 struct list_head *next);
36 extern bool __list_del_entry_valid(struct list_head *entry);
38 static inline bool __list_add_valid(struct list_head *new,
39 struct list_head *prev,
40 struct list_head *next)
44 static inline bool __list_del_entry_valid(struct list_head *entry)
51 * Insert a new entry between two known consecutive entries.
53 * This is only for internal list manipulation where we know
54 * the prev/next entries already!
56 static inline void __list_add(struct list_head *new,
57 struct list_head *prev,
58 struct list_head *next)
60 if (!__list_add_valid(new, prev, next))
66 WRITE_ONCE(prev->next, new);
70 * list_add - add a new entry
71 * @new: new entry to be added
72 * @head: list head to add it after
74 * Insert a new entry after the specified head.
75 * This is good for implementing stacks.
77 static inline void list_add(struct list_head *new, struct list_head *head)
79 __list_add(new, head, head->next);
84 * list_add_tail - add a new entry
85 * @new: new entry to be added
86 * @head: list head to add it before
88 * Insert a new entry before the specified head.
89 * This is useful for implementing queues.
91 static inline void list_add_tail(struct list_head *new, struct list_head *head)
93 __list_add(new, head->prev, head);
97 * Delete a list entry by making the prev/next entries
98 * point to each other.
100 * This is only for internal list manipulation where we know
101 * the prev/next entries already!
103 static inline void __list_del(struct list_head * prev, struct list_head * next)
106 WRITE_ONCE(prev->next, next);
110 * Delete a list entry and clear the 'prev' pointer.
112 * This is a special-purpose list clearing method used in the networking code
113 * for lists allocated as per-cpu, where we don't want to incur the extra
114 * WRITE_ONCE() overhead of a regular list_del_init(). The code that uses this
115 * needs to check the node 'prev' pointer instead of calling list_empty().
117 static inline void __list_del_clearprev(struct list_head *entry)
119 __list_del(entry->prev, entry->next);
124 * list_del - deletes entry from list.
125 * @entry: the element to delete from the list.
126 * Note: list_empty() on entry does not return true after this, the entry is
127 * in an undefined state.
129 static inline void __list_del_entry(struct list_head *entry)
131 if (!__list_del_entry_valid(entry))
134 __list_del(entry->prev, entry->next);
137 static inline void list_del(struct list_head *entry)
139 __list_del_entry(entry);
140 entry->next = LIST_POISON1;
141 entry->prev = LIST_POISON2;
145 * list_replace - replace old entry by new one
146 * @old : the element to be replaced
147 * @new : the new element to insert
149 * If @old was empty, it will be overwritten.
151 static inline void list_replace(struct list_head *old,
152 struct list_head *new)
154 new->next = old->next;
155 new->next->prev = new;
156 new->prev = old->prev;
157 new->prev->next = new;
160 static inline void list_replace_init(struct list_head *old,
161 struct list_head *new)
163 list_replace(old, new);
168 * list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position
169 * @entry1: the location to place entry2
170 * @entry2: the location to place entry1
172 static inline void list_swap(struct list_head *entry1,
173 struct list_head *entry2)
175 struct list_head *pos = entry2->prev;
178 list_replace(entry1, entry2);
181 list_add(entry1, pos);
185 * list_del_init - deletes entry from list and reinitialize it.
186 * @entry: the element to delete from the list.
188 static inline void list_del_init(struct list_head *entry)
190 __list_del_entry(entry);
191 INIT_LIST_HEAD(entry);
195 * list_move - delete from one list and add as another's head
196 * @list: the entry to move
197 * @head: the head that will precede our entry
199 static inline void list_move(struct list_head *list, struct list_head *head)
201 __list_del_entry(list);
202 list_add(list, head);
206 * list_move_tail - delete from one list and add as another's tail
207 * @list: the entry to move
208 * @head: the head that will follow our entry
210 static inline void list_move_tail(struct list_head *list,
211 struct list_head *head)
213 __list_del_entry(list);
214 list_add_tail(list, head);
218 * list_bulk_move_tail - move a subsection of a list to its tail
219 * @head: the head that will follow our entry
220 * @first: first entry to move
221 * @last: last entry to move, can be the same as first
223 * Move all entries between @first and including @last before @head.
224 * All three entries must belong to the same linked list.
226 static inline void list_bulk_move_tail(struct list_head *head,
227 struct list_head *first,
228 struct list_head *last)
230 first->prev->next = last->next;
231 last->next->prev = first->prev;
233 head->prev->next = first;
234 first->prev = head->prev;
241 * list_is_first -- tests whether @list is the first entry in list @head
242 * @list: the entry to test
243 * @head: the head of the list
245 static inline int list_is_first(const struct list_head *list,
246 const struct list_head *head)
248 return list->prev == head;
252 * list_is_last - tests whether @list is the last entry in list @head
253 * @list: the entry to test
254 * @head: the head of the list
256 static inline int list_is_last(const struct list_head *list,
257 const struct list_head *head)
259 return list->next == head;
263 * list_empty - tests whether a list is empty
264 * @head: the list to test.
266 static inline int list_empty(const struct list_head *head)
268 return READ_ONCE(head->next) == head;
272 * list_empty_careful - tests whether a list is empty and not being modified
273 * @head: the list to test
276 * tests whether a list is empty _and_ checks that no other CPU might be
277 * in the process of modifying either member (next or prev)
279 * NOTE: using list_empty_careful() without synchronization
280 * can only be safe if the only activity that can happen
281 * to the list entry is list_del_init(). Eg. it cannot be used
282 * if another CPU could re-list_add() it.
284 static inline int list_empty_careful(const struct list_head *head)
286 struct list_head *next = head->next;
287 return (next == head) && (next == head->prev);
291 * list_rotate_left - rotate the list to the left
292 * @head: the head of the list
294 static inline void list_rotate_left(struct list_head *head)
296 struct list_head *first;
298 if (!list_empty(head)) {
300 list_move_tail(first, head);
305 * list_rotate_to_front() - Rotate list to specific item.
306 * @list: The desired new front of the list.
307 * @head: The head of the list.
309 * Rotates list so that @list becomes the new front of the list.
311 static inline void list_rotate_to_front(struct list_head *list,
312 struct list_head *head)
315 * Deletes the list head from the list denoted by @head and
316 * places it as the tail of @list, this effectively rotates the
317 * list so that @list is at the front.
319 list_move_tail(head, list);
323 * list_is_singular - tests whether a list has just one entry.
324 * @head: the list to test.
326 static inline int list_is_singular(const struct list_head *head)
328 return !list_empty(head) && (head->next == head->prev);
331 static inline void __list_cut_position(struct list_head *list,
332 struct list_head *head, struct list_head *entry)
334 struct list_head *new_first = entry->next;
335 list->next = head->next;
336 list->next->prev = list;
339 head->next = new_first;
340 new_first->prev = head;
344 * list_cut_position - cut a list into two
345 * @list: a new list to add all removed entries
346 * @head: a list with entries
347 * @entry: an entry within head, could be the head itself
348 * and if so we won't cut the list
350 * This helper moves the initial part of @head, up to and
351 * including @entry, from @head to @list. You should
352 * pass on @entry an element you know is on @head. @list
353 * should be an empty list or a list you do not care about
357 static inline void list_cut_position(struct list_head *list,
358 struct list_head *head, struct list_head *entry)
360 if (list_empty(head))
362 if (list_is_singular(head) &&
363 (head->next != entry && head != entry))
366 INIT_LIST_HEAD(list);
368 __list_cut_position(list, head, entry);
372 * list_cut_before - cut a list into two, before given entry
373 * @list: a new list to add all removed entries
374 * @head: a list with entries
375 * @entry: an entry within head, could be the head itself
377 * This helper moves the initial part of @head, up to but
378 * excluding @entry, from @head to @list. You should pass
379 * in @entry an element you know is on @head. @list should
380 * be an empty list or a list you do not care about losing
382 * If @entry == @head, all entries on @head are moved to
385 static inline void list_cut_before(struct list_head *list,
386 struct list_head *head,
387 struct list_head *entry)
389 if (head->next == entry) {
390 INIT_LIST_HEAD(list);
393 list->next = head->next;
394 list->next->prev = list;
395 list->prev = entry->prev;
396 list->prev->next = list;
401 static inline void __list_splice(const struct list_head *list,
402 struct list_head *prev,
403 struct list_head *next)
405 struct list_head *first = list->next;
406 struct list_head *last = list->prev;
416 * list_splice - join two lists, this is designed for stacks
417 * @list: the new list to add.
418 * @head: the place to add it in the first list.
420 static inline void list_splice(const struct list_head *list,
421 struct list_head *head)
423 if (!list_empty(list))
424 __list_splice(list, head, head->next);
428 * list_splice_tail - join two lists, each list being a queue
429 * @list: the new list to add.
430 * @head: the place to add it in the first list.
432 static inline void list_splice_tail(struct list_head *list,
433 struct list_head *head)
435 if (!list_empty(list))
436 __list_splice(list, head->prev, head);
440 * list_splice_init - join two lists and reinitialise the emptied list.
441 * @list: the new list to add.
442 * @head: the place to add it in the first list.
444 * The list at @list is reinitialised
446 static inline void list_splice_init(struct list_head *list,
447 struct list_head *head)
449 if (!list_empty(list)) {
450 __list_splice(list, head, head->next);
451 INIT_LIST_HEAD(list);
456 * list_splice_tail_init - join two lists and reinitialise the emptied list
457 * @list: the new list to add.
458 * @head: the place to add it in the first list.
460 * Each of the lists is a queue.
461 * The list at @list is reinitialised
463 static inline void list_splice_tail_init(struct list_head *list,
464 struct list_head *head)
466 if (!list_empty(list)) {
467 __list_splice(list, head->prev, head);
468 INIT_LIST_HEAD(list);
473 * list_entry - get the struct for this entry
474 * @ptr: the &struct list_head pointer.
475 * @type: the type of the struct this is embedded in.
476 * @member: the name of the list_head within the struct.
478 #define list_entry(ptr, type, member) \
479 container_of(ptr, type, member)
482 * list_first_entry - get the first element from a list
483 * @ptr: the list head to take the element from.
484 * @type: the type of the struct this is embedded in.
485 * @member: the name of the list_head within the struct.
487 * Note, that list is expected to be not empty.
489 #define list_first_entry(ptr, type, member) \
490 list_entry((ptr)->next, type, member)
493 * list_last_entry - get the last element from a list
494 * @ptr: the list head to take the element from.
495 * @type: the type of the struct this is embedded in.
496 * @member: the name of the list_head within the struct.
498 * Note, that list is expected to be not empty.
500 #define list_last_entry(ptr, type, member) \
501 list_entry((ptr)->prev, type, member)
504 * list_first_entry_or_null - get the first element from a list
505 * @ptr: the list head to take the element from.
506 * @type: the type of the struct this is embedded in.
507 * @member: the name of the list_head within the struct.
509 * Note that if the list is empty, it returns NULL.
511 #define list_first_entry_or_null(ptr, type, member) ({ \
512 struct list_head *head__ = (ptr); \
513 struct list_head *pos__ = READ_ONCE(head__->next); \
514 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
518 * list_next_entry - get the next element in list
519 * @pos: the type * to cursor
520 * @member: the name of the list_head within the struct.
522 #define list_next_entry(pos, member) \
523 list_entry((pos)->member.next, typeof(*(pos)), member)
526 * list_prev_entry - get the prev element in list
527 * @pos: the type * to cursor
528 * @member: the name of the list_head within the struct.
530 #define list_prev_entry(pos, member) \
531 list_entry((pos)->member.prev, typeof(*(pos)), member)
534 * list_for_each - iterate over a list
535 * @pos: the &struct list_head to use as a loop cursor.
536 * @head: the head for your list.
538 #define list_for_each(pos, head) \
539 for (pos = (head)->next; pos != (head); pos = pos->next)
542 * list_for_each_prev - iterate over a list backwards
543 * @pos: the &struct list_head to use as a loop cursor.
544 * @head: the head for your list.
546 #define list_for_each_prev(pos, head) \
547 for (pos = (head)->prev; pos != (head); pos = pos->prev)
550 * list_for_each_safe - iterate over a list safe against removal of list entry
551 * @pos: the &struct list_head to use as a loop cursor.
552 * @n: another &struct list_head to use as temporary storage
553 * @head: the head for your list.
555 #define list_for_each_safe(pos, n, head) \
556 for (pos = (head)->next, n = pos->next; pos != (head); \
557 pos = n, n = pos->next)
560 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
561 * @pos: the &struct list_head to use as a loop cursor.
562 * @n: another &struct list_head to use as temporary storage
563 * @head: the head for your list.
565 #define list_for_each_prev_safe(pos, n, head) \
566 for (pos = (head)->prev, n = pos->prev; \
568 pos = n, n = pos->prev)
571 * list_entry_is_head - test if the entry points to the head of the list
572 * @pos: the type * to cursor
573 * @head: the head for your list.
574 * @member: the name of the list_head within the struct.
576 #define list_entry_is_head(pos, head, member) \
577 (&pos->member == (head))
580 * list_for_each_entry - iterate over list of given type
581 * @pos: the type * to use as a loop cursor.
582 * @head: the head for your list.
583 * @member: the name of the list_head within the struct.
585 #define list_for_each_entry(pos, head, member) \
586 for (pos = list_first_entry(head, typeof(*pos), member); \
587 !list_entry_is_head(pos, head, member); \
588 pos = list_next_entry(pos, member))
591 * list_for_each_entry_reverse - iterate backwards over list of given type.
592 * @pos: the type * to use as a loop cursor.
593 * @head: the head for your list.
594 * @member: the name of the list_head within the struct.
596 #define list_for_each_entry_reverse(pos, head, member) \
597 for (pos = list_last_entry(head, typeof(*pos), member); \
598 !list_entry_is_head(pos, head, member); \
599 pos = list_prev_entry(pos, member))
602 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
603 * @pos: the type * to use as a start point
604 * @head: the head of the list
605 * @member: the name of the list_head within the struct.
607 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
609 #define list_prepare_entry(pos, head, member) \
610 ((pos) ? : list_entry(head, typeof(*pos), member))
613 * list_for_each_entry_continue - continue iteration over list of given type
614 * @pos: the type * to use as a loop cursor.
615 * @head: the head for your list.
616 * @member: the name of the list_head within the struct.
618 * Continue to iterate over list of given type, continuing after
619 * the current position.
621 #define list_for_each_entry_continue(pos, head, member) \
622 for (pos = list_next_entry(pos, member); \
623 !list_entry_is_head(pos, head, member); \
624 pos = list_next_entry(pos, member))
627 * list_for_each_entry_continue_reverse - iterate backwards from the given point
628 * @pos: the type * to use as a loop cursor.
629 * @head: the head for your list.
630 * @member: the name of the list_head within the struct.
632 * Start to iterate over list of given type backwards, continuing after
633 * the current position.
635 #define list_for_each_entry_continue_reverse(pos, head, member) \
636 for (pos = list_prev_entry(pos, member); \
637 !list_entry_is_head(pos, head, member); \
638 pos = list_prev_entry(pos, member))
641 * list_for_each_entry_from - iterate over list of given type from the current point
642 * @pos: the type * to use as a loop cursor.
643 * @head: the head for your list.
644 * @member: the name of the list_head within the struct.
646 * Iterate over list of given type, continuing from current position.
648 #define list_for_each_entry_from(pos, head, member) \
649 for (; !list_entry_is_head(pos, head, member); \
650 pos = list_next_entry(pos, member))
653 * list_for_each_entry_from_reverse - iterate backwards over list of given type
654 * from the current point
655 * @pos: the type * to use as a loop cursor.
656 * @head: the head for your list.
657 * @member: the name of the list_head within the struct.
659 * Iterate backwards over list of given type, continuing from current position.
661 #define list_for_each_entry_from_reverse(pos, head, member) \
662 for (; !list_entry_is_head(pos, head, member); \
663 pos = list_prev_entry(pos, member))
666 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
667 * @pos: the type * to use as a loop cursor.
668 * @n: another type * to use as temporary storage
669 * @head: the head for your list.
670 * @member: the name of the list_head within the struct.
672 #define list_for_each_entry_safe(pos, n, head, member) \
673 for (pos = list_first_entry(head, typeof(*pos), member), \
674 n = list_next_entry(pos, member); \
675 !list_entry_is_head(pos, head, member); \
676 pos = n, n = list_next_entry(n, member))
679 * list_for_each_entry_safe_continue - continue list iteration safe against removal
680 * @pos: the type * to use as a loop cursor.
681 * @n: another type * to use as temporary storage
682 * @head: the head for your list.
683 * @member: the name of the list_head within the struct.
685 * Iterate over list of given type, continuing after current point,
686 * safe against removal of list entry.
688 #define list_for_each_entry_safe_continue(pos, n, head, member) \
689 for (pos = list_next_entry(pos, member), \
690 n = list_next_entry(pos, member); \
691 !list_entry_is_head(pos, head, member); \
692 pos = n, n = list_next_entry(n, member))
695 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
696 * @pos: the type * to use as a loop cursor.
697 * @n: another type * to use as temporary storage
698 * @head: the head for your list.
699 * @member: the name of the list_head within the struct.
701 * Iterate over list of given type from current point, safe against
702 * removal of list entry.
704 #define list_for_each_entry_safe_from(pos, n, head, member) \
705 for (n = list_next_entry(pos, member); \
706 !list_entry_is_head(pos, head, member); \
707 pos = n, n = list_next_entry(n, member))
710 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
711 * @pos: the type * to use as a loop cursor.
712 * @n: another type * to use as temporary storage
713 * @head: the head for your list.
714 * @member: the name of the list_head within the struct.
716 * Iterate backwards over list of given type, safe against removal
719 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
720 for (pos = list_last_entry(head, typeof(*pos), member), \
721 n = list_prev_entry(pos, member); \
722 !list_entry_is_head(pos, head, member); \
723 pos = n, n = list_prev_entry(n, member))
726 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
727 * @pos: the loop cursor used in the list_for_each_entry_safe loop
728 * @n: temporary storage used in list_for_each_entry_safe
729 * @member: the name of the list_head within the struct.
731 * list_safe_reset_next is not safe to use in general if the list may be
732 * modified concurrently (eg. the lock is dropped in the loop body). An
733 * exception to this is if the cursor element (pos) is pinned in the list,
734 * and list_safe_reset_next is called after re-taking the lock and before
735 * completing the current iteration of the loop body.
737 #define list_safe_reset_next(pos, n, member) \
738 n = list_next_entry(pos, member)
741 * Double linked lists with a single pointer list head.
742 * Mostly useful for hash tables where the two pointer list head is
744 * You lose the ability to access the tail in O(1).
747 #define HLIST_HEAD_INIT { .first = NULL }
748 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
749 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
750 static inline void INIT_HLIST_NODE(struct hlist_node *h)
756 static inline int hlist_unhashed(const struct hlist_node *h)
761 static inline int hlist_empty(const struct hlist_head *h)
763 return !READ_ONCE(h->first);
766 static inline void __hlist_del(struct hlist_node *n)
768 struct hlist_node *next = n->next;
769 struct hlist_node **pprev = n->pprev;
771 WRITE_ONCE(*pprev, next);
776 static inline void hlist_del(struct hlist_node *n)
779 n->next = LIST_POISON1;
780 n->pprev = LIST_POISON2;
783 static inline void hlist_del_init(struct hlist_node *n)
785 if (!hlist_unhashed(n)) {
791 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
793 struct hlist_node *first = h->first;
796 first->pprev = &n->next;
797 WRITE_ONCE(h->first, n);
798 n->pprev = &h->first;
801 /* next must be != NULL */
802 static inline void hlist_add_before(struct hlist_node *n,
803 struct hlist_node *next)
805 n->pprev = next->pprev;
807 next->pprev = &n->next;
808 WRITE_ONCE(*(n->pprev), n);
811 static inline void hlist_add_behind(struct hlist_node *n,
812 struct hlist_node *prev)
814 n->next = prev->next;
816 n->pprev = &prev->next;
819 n->next->pprev = &n->next;
822 /* after that we'll appear to be on some hlist and hlist_del will work */
823 static inline void hlist_add_fake(struct hlist_node *n)
828 static inline bool hlist_fake(struct hlist_node *h)
830 return h->pprev == &h->next;
834 * Check whether the node is the only node of the head without
838 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
840 return !n->next && n->pprev == &h->first;
844 * Move a list from one list head to another. Fixup the pprev
845 * reference of the first entry if it exists.
847 static inline void hlist_move_list(struct hlist_head *old,
848 struct hlist_head *new)
850 new->first = old->first;
852 new->first->pprev = &new->first;
856 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
858 #define hlist_for_each(pos, head) \
859 for (pos = (head)->first; pos ; pos = pos->next)
861 #define hlist_for_each_safe(pos, n, head) \
862 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
865 #define hlist_entry_safe(ptr, type, member) \
866 ({ typeof(ptr) ____ptr = (ptr); \
867 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
871 * hlist_for_each_entry - iterate over list of given type
872 * @pos: the type * to use as a loop cursor.
873 * @head: the head for your list.
874 * @member: the name of the hlist_node within the struct.
876 #define hlist_for_each_entry(pos, head, member) \
877 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
879 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
882 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
883 * @pos: the type * to use as a loop cursor.
884 * @member: the name of the hlist_node within the struct.
886 #define hlist_for_each_entry_continue(pos, member) \
887 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
889 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
892 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
893 * @pos: the type * to use as a loop cursor.
894 * @member: the name of the hlist_node within the struct.
896 #define hlist_for_each_entry_from(pos, member) \
898 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
901 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
902 * @pos: the type * to use as a loop cursor.
903 * @n: another &struct hlist_node to use as temporary storage
904 * @head: the head for your list.
905 * @member: the name of the hlist_node within the struct.
907 #define hlist_for_each_entry_safe(pos, n, head, member) \
908 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
909 pos && ({ n = pos->member.next; 1; }); \
910 pos = hlist_entry_safe(n, typeof(*pos), member))