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 * list_del - deletes entry from list.
111 * @entry: the element to delete from the list.
112 * Note: list_empty() on entry does not return true after this, the entry is
113 * in an undefined state.
115 static inline void __list_del_entry(struct list_head *entry)
117 if (!__list_del_entry_valid(entry))
120 __list_del(entry->prev, entry->next);
123 static inline void list_del(struct list_head *entry)
125 __list_del_entry(entry);
126 entry->next = LIST_POISON1;
127 entry->prev = LIST_POISON2;
131 * list_replace - replace old entry by new one
132 * @old : the element to be replaced
133 * @new : the new element to insert
135 * If @old was empty, it will be overwritten.
137 static inline void list_replace(struct list_head *old,
138 struct list_head *new)
140 new->next = old->next;
141 new->next->prev = new;
142 new->prev = old->prev;
143 new->prev->next = new;
146 static inline void list_replace_init(struct list_head *old,
147 struct list_head *new)
149 list_replace(old, new);
154 * list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position
155 * @entry1: the location to place entry2
156 * @entry2: the location to place entry1
158 static inline void list_swap(struct list_head *entry1,
159 struct list_head *entry2)
161 struct list_head *pos = entry2->prev;
164 list_replace(entry1, entry2);
167 list_add(entry1, pos);
171 * list_del_init - deletes entry from list and reinitialize it.
172 * @entry: the element to delete from the list.
174 static inline void list_del_init(struct list_head *entry)
176 __list_del_entry(entry);
177 INIT_LIST_HEAD(entry);
181 * list_move - delete from one list and add as another's head
182 * @list: the entry to move
183 * @head: the head that will precede our entry
185 static inline void list_move(struct list_head *list, struct list_head *head)
187 __list_del_entry(list);
188 list_add(list, head);
192 * list_move_tail - delete from one list and add as another's tail
193 * @list: the entry to move
194 * @head: the head that will follow our entry
196 static inline void list_move_tail(struct list_head *list,
197 struct list_head *head)
199 __list_del_entry(list);
200 list_add_tail(list, head);
204 * list_bulk_move_tail - move a subsection of a list to its tail
205 * @head: the head that will follow our entry
206 * @first: first entry to move
207 * @last: last entry to move, can be the same as first
209 * Move all entries between @first and including @last before @head.
210 * All three entries must belong to the same linked list.
212 static inline void list_bulk_move_tail(struct list_head *head,
213 struct list_head *first,
214 struct list_head *last)
216 first->prev->next = last->next;
217 last->next->prev = first->prev;
219 head->prev->next = first;
220 first->prev = head->prev;
227 * list_is_first -- tests whether @list is the first entry in list @head
228 * @list: the entry to test
229 * @head: the head of the list
231 static inline int list_is_first(const struct list_head *list,
232 const struct list_head *head)
234 return list->prev == head;
238 * list_is_last - tests whether @list is the last entry in list @head
239 * @list: the entry to test
240 * @head: the head of the list
242 static inline int list_is_last(const struct list_head *list,
243 const struct list_head *head)
245 return list->next == head;
249 * list_empty - tests whether a list is empty
250 * @head: the list to test.
252 static inline int list_empty(const struct list_head *head)
254 return READ_ONCE(head->next) == head;
258 * list_empty_careful - tests whether a list is empty and not being modified
259 * @head: the list to test
262 * tests whether a list is empty _and_ checks that no other CPU might be
263 * in the process of modifying either member (next or prev)
265 * NOTE: using list_empty_careful() without synchronization
266 * can only be safe if the only activity that can happen
267 * to the list entry is list_del_init(). Eg. it cannot be used
268 * if another CPU could re-list_add() it.
270 static inline int list_empty_careful(const struct list_head *head)
272 struct list_head *next = head->next;
273 return (next == head) && (next == head->prev);
277 * list_rotate_left - rotate the list to the left
278 * @head: the head of the list
280 static inline void list_rotate_left(struct list_head *head)
282 struct list_head *first;
284 if (!list_empty(head)) {
286 list_move_tail(first, head);
291 * list_rotate_to_front() - Rotate list to specific item.
292 * @list: The desired new front of the list.
293 * @head: The head of the list.
295 * Rotates list so that @list becomes the new front of the list.
297 static inline void list_rotate_to_front(struct list_head *list,
298 struct list_head *head)
301 * Deletes the list head from the list denoted by @head and
302 * places it as the tail of @list, this effectively rotates the
303 * list so that @list is at the front.
305 list_move_tail(head, list);
309 * list_is_singular - tests whether a list has just one entry.
310 * @head: the list to test.
312 static inline int list_is_singular(const struct list_head *head)
314 return !list_empty(head) && (head->next == head->prev);
317 static inline void __list_cut_position(struct list_head *list,
318 struct list_head *head, struct list_head *entry)
320 struct list_head *new_first = entry->next;
321 list->next = head->next;
322 list->next->prev = list;
325 head->next = new_first;
326 new_first->prev = head;
330 * list_cut_position - cut a list into two
331 * @list: a new list to add all removed entries
332 * @head: a list with entries
333 * @entry: an entry within head, could be the head itself
334 * and if so we won't cut the list
336 * This helper moves the initial part of @head, up to and
337 * including @entry, from @head to @list. You should
338 * pass on @entry an element you know is on @head. @list
339 * should be an empty list or a list you do not care about
343 static inline void list_cut_position(struct list_head *list,
344 struct list_head *head, struct list_head *entry)
346 if (list_empty(head))
348 if (list_is_singular(head) &&
349 (head->next != entry && head != entry))
352 INIT_LIST_HEAD(list);
354 __list_cut_position(list, head, entry);
358 * list_cut_before - cut a list into two, before given entry
359 * @list: a new list to add all removed entries
360 * @head: a list with entries
361 * @entry: an entry within head, could be the head itself
363 * This helper moves the initial part of @head, up to but
364 * excluding @entry, from @head to @list. You should pass
365 * in @entry an element you know is on @head. @list should
366 * be an empty list or a list you do not care about losing
368 * If @entry == @head, all entries on @head are moved to
371 static inline void list_cut_before(struct list_head *list,
372 struct list_head *head,
373 struct list_head *entry)
375 if (head->next == entry) {
376 INIT_LIST_HEAD(list);
379 list->next = head->next;
380 list->next->prev = list;
381 list->prev = entry->prev;
382 list->prev->next = list;
387 static inline void __list_splice(const struct list_head *list,
388 struct list_head *prev,
389 struct list_head *next)
391 struct list_head *first = list->next;
392 struct list_head *last = list->prev;
402 * list_splice - join two lists, this is designed for stacks
403 * @list: the new list to add.
404 * @head: the place to add it in the first list.
406 static inline void list_splice(const struct list_head *list,
407 struct list_head *head)
409 if (!list_empty(list))
410 __list_splice(list, head, head->next);
414 * list_splice_tail - join two lists, each list being a queue
415 * @list: the new list to add.
416 * @head: the place to add it in the first list.
418 static inline void list_splice_tail(struct list_head *list,
419 struct list_head *head)
421 if (!list_empty(list))
422 __list_splice(list, head->prev, head);
426 * list_splice_init - join two lists and reinitialise the emptied list.
427 * @list: the new list to add.
428 * @head: the place to add it in the first list.
430 * The list at @list is reinitialised
432 static inline void list_splice_init(struct list_head *list,
433 struct list_head *head)
435 if (!list_empty(list)) {
436 __list_splice(list, head, head->next);
437 INIT_LIST_HEAD(list);
442 * list_splice_tail_init - join two lists and reinitialise the emptied list
443 * @list: the new list to add.
444 * @head: the place to add it in the first list.
446 * Each of the lists is a queue.
447 * The list at @list is reinitialised
449 static inline void list_splice_tail_init(struct list_head *list,
450 struct list_head *head)
452 if (!list_empty(list)) {
453 __list_splice(list, head->prev, head);
454 INIT_LIST_HEAD(list);
459 * list_entry - get the struct for this entry
460 * @ptr: the &struct list_head pointer.
461 * @type: the type of the struct this is embedded in.
462 * @member: the name of the list_head within the struct.
464 #define list_entry(ptr, type, member) \
465 container_of(ptr, type, member)
468 * list_first_entry - get the first element from a list
469 * @ptr: the list head to take the element from.
470 * @type: the type of the struct this is embedded in.
471 * @member: the name of the list_head within the struct.
473 * Note, that list is expected to be not empty.
475 #define list_first_entry(ptr, type, member) \
476 list_entry((ptr)->next, type, member)
479 * list_last_entry - get the last element from a list
480 * @ptr: the list head to take the element from.
481 * @type: the type of the struct this is embedded in.
482 * @member: the name of the list_head within the struct.
484 * Note, that list is expected to be not empty.
486 #define list_last_entry(ptr, type, member) \
487 list_entry((ptr)->prev, type, member)
490 * list_first_entry_or_null - get the first element from a list
491 * @ptr: the list head to take the element from.
492 * @type: the type of the struct this is embedded in.
493 * @member: the name of the list_head within the struct.
495 * Note that if the list is empty, it returns NULL.
497 #define list_first_entry_or_null(ptr, type, member) ({ \
498 struct list_head *head__ = (ptr); \
499 struct list_head *pos__ = READ_ONCE(head__->next); \
500 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
504 * list_next_entry - get the next element in list
505 * @pos: the type * to cursor
506 * @member: the name of the list_head within the struct.
508 #define list_next_entry(pos, member) \
509 list_entry((pos)->member.next, typeof(*(pos)), member)
512 * list_prev_entry - get the prev element in list
513 * @pos: the type * to cursor
514 * @member: the name of the list_head within the struct.
516 #define list_prev_entry(pos, member) \
517 list_entry((pos)->member.prev, typeof(*(pos)), member)
520 * list_for_each - iterate over a list
521 * @pos: the &struct list_head to use as a loop cursor.
522 * @head: the head for your list.
524 #define list_for_each(pos, head) \
525 for (pos = (head)->next; pos != (head); pos = pos->next)
528 * list_for_each_prev - iterate over a list backwards
529 * @pos: the &struct list_head to use as a loop cursor.
530 * @head: the head for your list.
532 #define list_for_each_prev(pos, head) \
533 for (pos = (head)->prev; pos != (head); pos = pos->prev)
536 * list_for_each_safe - iterate over a list safe against removal of list entry
537 * @pos: the &struct list_head to use as a loop cursor.
538 * @n: another &struct list_head to use as temporary storage
539 * @head: the head for your list.
541 #define list_for_each_safe(pos, n, head) \
542 for (pos = (head)->next, n = pos->next; pos != (head); \
543 pos = n, n = pos->next)
546 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
547 * @pos: the &struct list_head to use as a loop cursor.
548 * @n: another &struct list_head to use as temporary storage
549 * @head: the head for your list.
551 #define list_for_each_prev_safe(pos, n, head) \
552 for (pos = (head)->prev, n = pos->prev; \
554 pos = n, n = pos->prev)
557 * list_for_each_entry - iterate over list of given type
558 * @pos: the type * to use as a loop cursor.
559 * @head: the head for your list.
560 * @member: the name of the list_head within the struct.
562 #define list_for_each_entry(pos, head, member) \
563 for (pos = list_first_entry(head, typeof(*pos), member); \
564 &pos->member != (head); \
565 pos = list_next_entry(pos, member))
568 * list_for_each_entry_reverse - iterate backwards over list of given type.
569 * @pos: the type * to use as a loop cursor.
570 * @head: the head for your list.
571 * @member: the name of the list_head within the struct.
573 #define list_for_each_entry_reverse(pos, head, member) \
574 for (pos = list_last_entry(head, typeof(*pos), member); \
575 &pos->member != (head); \
576 pos = list_prev_entry(pos, member))
579 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
580 * @pos: the type * to use as a start point
581 * @head: the head of the list
582 * @member: the name of the list_head within the struct.
584 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
586 #define list_prepare_entry(pos, head, member) \
587 ((pos) ? : list_entry(head, typeof(*pos), member))
590 * list_for_each_entry_continue - continue iteration over list of given type
591 * @pos: the type * to use as a loop cursor.
592 * @head: the head for your list.
593 * @member: the name of the list_head within the struct.
595 * Continue to iterate over list of given type, continuing after
596 * the current position.
598 #define list_for_each_entry_continue(pos, head, member) \
599 for (pos = list_next_entry(pos, member); \
600 &pos->member != (head); \
601 pos = list_next_entry(pos, member))
604 * list_for_each_entry_continue_reverse - iterate backwards from the given point
605 * @pos: the type * to use as a loop cursor.
606 * @head: the head for your list.
607 * @member: the name of the list_head within the struct.
609 * Start to iterate over list of given type backwards, continuing after
610 * the current position.
612 #define list_for_each_entry_continue_reverse(pos, head, member) \
613 for (pos = list_prev_entry(pos, member); \
614 &pos->member != (head); \
615 pos = list_prev_entry(pos, member))
618 * list_for_each_entry_from - iterate over list of given type from the current point
619 * @pos: the type * to use as a loop cursor.
620 * @head: the head for your list.
621 * @member: the name of the list_head within the struct.
623 * Iterate over list of given type, continuing from current position.
625 #define list_for_each_entry_from(pos, head, member) \
626 for (; &pos->member != (head); \
627 pos = list_next_entry(pos, member))
630 * list_for_each_entry_from_reverse - iterate backwards over list of given type
631 * from the current point
632 * @pos: the type * to use as a loop cursor.
633 * @head: the head for your list.
634 * @member: the name of the list_head within the struct.
636 * Iterate backwards over list of given type, continuing from current position.
638 #define list_for_each_entry_from_reverse(pos, head, member) \
639 for (; &pos->member != (head); \
640 pos = list_prev_entry(pos, member))
643 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
644 * @pos: the type * to use as a loop cursor.
645 * @n: another type * to use as temporary storage
646 * @head: the head for your list.
647 * @member: the name of the list_head within the struct.
649 #define list_for_each_entry_safe(pos, n, head, member) \
650 for (pos = list_first_entry(head, typeof(*pos), member), \
651 n = list_next_entry(pos, member); \
652 &pos->member != (head); \
653 pos = n, n = list_next_entry(n, member))
656 * list_for_each_entry_safe_continue - continue list iteration safe against removal
657 * @pos: the type * to use as a loop cursor.
658 * @n: another type * to use as temporary storage
659 * @head: the head for your list.
660 * @member: the name of the list_head within the struct.
662 * Iterate over list of given type, continuing after current point,
663 * safe against removal of list entry.
665 #define list_for_each_entry_safe_continue(pos, n, head, member) \
666 for (pos = list_next_entry(pos, member), \
667 n = list_next_entry(pos, member); \
668 &pos->member != (head); \
669 pos = n, n = list_next_entry(n, member))
672 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
673 * @pos: the type * to use as a loop cursor.
674 * @n: another type * to use as temporary storage
675 * @head: the head for your list.
676 * @member: the name of the list_head within the struct.
678 * Iterate over list of given type from current point, safe against
679 * removal of list entry.
681 #define list_for_each_entry_safe_from(pos, n, head, member) \
682 for (n = list_next_entry(pos, member); \
683 &pos->member != (head); \
684 pos = n, n = list_next_entry(n, member))
687 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
688 * @pos: the type * to use as a loop cursor.
689 * @n: another type * to use as temporary storage
690 * @head: the head for your list.
691 * @member: the name of the list_head within the struct.
693 * Iterate backwards over list of given type, safe against removal
696 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
697 for (pos = list_last_entry(head, typeof(*pos), member), \
698 n = list_prev_entry(pos, member); \
699 &pos->member != (head); \
700 pos = n, n = list_prev_entry(n, member))
703 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
704 * @pos: the loop cursor used in the list_for_each_entry_safe loop
705 * @n: temporary storage used in list_for_each_entry_safe
706 * @member: the name of the list_head within the struct.
708 * list_safe_reset_next is not safe to use in general if the list may be
709 * modified concurrently (eg. the lock is dropped in the loop body). An
710 * exception to this is if the cursor element (pos) is pinned in the list,
711 * and list_safe_reset_next is called after re-taking the lock and before
712 * completing the current iteration of the loop body.
714 #define list_safe_reset_next(pos, n, member) \
715 n = list_next_entry(pos, member)
718 * Double linked lists with a single pointer list head.
719 * Mostly useful for hash tables where the two pointer list head is
721 * You lose the ability to access the tail in O(1).
724 #define HLIST_HEAD_INIT { .first = NULL }
725 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
726 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
727 static inline void INIT_HLIST_NODE(struct hlist_node *h)
733 static inline int hlist_unhashed(const struct hlist_node *h)
738 static inline int hlist_empty(const struct hlist_head *h)
740 return !READ_ONCE(h->first);
743 static inline void __hlist_del(struct hlist_node *n)
745 struct hlist_node *next = n->next;
746 struct hlist_node **pprev = n->pprev;
748 WRITE_ONCE(*pprev, next);
753 static inline void hlist_del(struct hlist_node *n)
756 n->next = LIST_POISON1;
757 n->pprev = LIST_POISON2;
760 static inline void hlist_del_init(struct hlist_node *n)
762 if (!hlist_unhashed(n)) {
768 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
770 struct hlist_node *first = h->first;
773 first->pprev = &n->next;
774 WRITE_ONCE(h->first, n);
775 n->pprev = &h->first;
778 /* next must be != NULL */
779 static inline void hlist_add_before(struct hlist_node *n,
780 struct hlist_node *next)
782 n->pprev = next->pprev;
784 next->pprev = &n->next;
785 WRITE_ONCE(*(n->pprev), n);
788 static inline void hlist_add_behind(struct hlist_node *n,
789 struct hlist_node *prev)
791 n->next = prev->next;
792 WRITE_ONCE(prev->next, n);
793 n->pprev = &prev->next;
796 n->next->pprev = &n->next;
799 /* after that we'll appear to be on some hlist and hlist_del will work */
800 static inline void hlist_add_fake(struct hlist_node *n)
805 static inline bool hlist_fake(struct hlist_node *h)
807 return h->pprev == &h->next;
811 * Check whether the node is the only node of the head without
815 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
817 return !n->next && n->pprev == &h->first;
821 * Move a list from one list head to another. Fixup the pprev
822 * reference of the first entry if it exists.
824 static inline void hlist_move_list(struct hlist_head *old,
825 struct hlist_head *new)
827 new->first = old->first;
829 new->first->pprev = &new->first;
833 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
835 #define hlist_for_each(pos, head) \
836 for (pos = (head)->first; pos ; pos = pos->next)
838 #define hlist_for_each_safe(pos, n, head) \
839 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
842 #define hlist_entry_safe(ptr, type, member) \
843 ({ typeof(ptr) ____ptr = (ptr); \
844 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
848 * hlist_for_each_entry - iterate over list of given type
849 * @pos: the type * to use as a loop cursor.
850 * @head: the head for your list.
851 * @member: the name of the hlist_node within the struct.
853 #define hlist_for_each_entry(pos, head, member) \
854 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
856 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
859 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
860 * @pos: the type * to use as a loop cursor.
861 * @member: the name of the hlist_node within the struct.
863 #define hlist_for_each_entry_continue(pos, member) \
864 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
866 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
869 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
870 * @pos: the type * to use as a loop cursor.
871 * @member: the name of the hlist_node within the struct.
873 #define hlist_for_each_entry_from(pos, member) \
875 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
878 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
879 * @pos: the type * to use as a loop cursor.
880 * @n: another &struct hlist_node to use as temporary storage
881 * @head: the head for your list.
882 * @member: the name of the hlist_node within the struct.
884 #define hlist_for_each_entry_safe(pos, n, head, member) \
885 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
886 pos && ({ n = pos->member.next; 1; }); \
887 pos = hlist_entry_safe(n, typeof(*pos), member))