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_del_init - deletes entry from list and reinitialize it.
155 * @entry: the element to delete from the list.
157 static inline void list_del_init(struct list_head *entry)
159 __list_del_entry(entry);
160 INIT_LIST_HEAD(entry);
164 * list_move - delete from one list and add as another's head
165 * @list: the entry to move
166 * @head: the head that will precede our entry
168 static inline void list_move(struct list_head *list, struct list_head *head)
170 __list_del_entry(list);
171 list_add(list, head);
175 * list_move_tail - delete from one list and add as another's tail
176 * @list: the entry to move
177 * @head: the head that will follow our entry
179 static inline void list_move_tail(struct list_head *list,
180 struct list_head *head)
182 __list_del_entry(list);
183 list_add_tail(list, head);
187 * list_bulk_move_tail - move a subsection of a list to its tail
188 * @head: the head that will follow our entry
189 * @first: first entry to move
190 * @last: last entry to move, can be the same as first
192 * Move all entries between @first and including @last before @head.
193 * All three entries must belong to the same linked list.
195 static inline void list_bulk_move_tail(struct list_head *head,
196 struct list_head *first,
197 struct list_head *last)
199 first->prev->next = last->next;
200 last->next->prev = first->prev;
202 head->prev->next = first;
203 first->prev = head->prev;
210 * list_is_first -- tests whether @ list is the first entry in list @head
211 * @list: the entry to test
212 * @head: the head of the list
214 static inline int list_is_first(const struct list_head *list,
215 const struct list_head *head)
217 return list->prev == head;
221 * list_is_last - tests whether @list is the last entry in list @head
222 * @list: the entry to test
223 * @head: the head of the list
225 static inline int list_is_last(const struct list_head *list,
226 const struct list_head *head)
228 return list->next == head;
232 * list_empty - tests whether a list is empty
233 * @head: the list to test.
235 static inline int list_empty(const struct list_head *head)
237 return READ_ONCE(head->next) == head;
241 * list_empty_careful - tests whether a list is empty and not being modified
242 * @head: the list to test
245 * tests whether a list is empty _and_ checks that no other CPU might be
246 * in the process of modifying either member (next or prev)
248 * NOTE: using list_empty_careful() without synchronization
249 * can only be safe if the only activity that can happen
250 * to the list entry is list_del_init(). Eg. it cannot be used
251 * if another CPU could re-list_add() it.
253 static inline int list_empty_careful(const struct list_head *head)
255 struct list_head *next = head->next;
256 return (next == head) && (next == head->prev);
260 * list_rotate_left - rotate the list to the left
261 * @head: the head of the list
263 static inline void list_rotate_left(struct list_head *head)
265 struct list_head *first;
267 if (!list_empty(head)) {
269 list_move_tail(first, head);
274 * list_is_singular - tests whether a list has just one entry.
275 * @head: the list to test.
277 static inline int list_is_singular(const struct list_head *head)
279 return !list_empty(head) && (head->next == head->prev);
282 static inline void __list_cut_position(struct list_head *list,
283 struct list_head *head, struct list_head *entry)
285 struct list_head *new_first = entry->next;
286 list->next = head->next;
287 list->next->prev = list;
290 head->next = new_first;
291 new_first->prev = head;
295 * list_cut_position - cut a list into two
296 * @list: a new list to add all removed entries
297 * @head: a list with entries
298 * @entry: an entry within head, could be the head itself
299 * and if so we won't cut the list
301 * This helper moves the initial part of @head, up to and
302 * including @entry, from @head to @list. You should
303 * pass on @entry an element you know is on @head. @list
304 * should be an empty list or a list you do not care about
308 static inline void list_cut_position(struct list_head *list,
309 struct list_head *head, struct list_head *entry)
311 if (list_empty(head))
313 if (list_is_singular(head) &&
314 (head->next != entry && head != entry))
317 INIT_LIST_HEAD(list);
319 __list_cut_position(list, head, entry);
323 * list_cut_before - cut a list into two, before given entry
324 * @list: a new list to add all removed entries
325 * @head: a list with entries
326 * @entry: an entry within head, could be the head itself
328 * This helper moves the initial part of @head, up to but
329 * excluding @entry, from @head to @list. You should pass
330 * in @entry an element you know is on @head. @list should
331 * be an empty list or a list you do not care about losing
333 * If @entry == @head, all entries on @head are moved to
336 static inline void list_cut_before(struct list_head *list,
337 struct list_head *head,
338 struct list_head *entry)
340 if (head->next == entry) {
341 INIT_LIST_HEAD(list);
344 list->next = head->next;
345 list->next->prev = list;
346 list->prev = entry->prev;
347 list->prev->next = list;
352 static inline void __list_splice(const struct list_head *list,
353 struct list_head *prev,
354 struct list_head *next)
356 struct list_head *first = list->next;
357 struct list_head *last = list->prev;
367 * list_splice - join two lists, this is designed for stacks
368 * @list: the new list to add.
369 * @head: the place to add it in the first list.
371 static inline void list_splice(const struct list_head *list,
372 struct list_head *head)
374 if (!list_empty(list))
375 __list_splice(list, head, head->next);
379 * list_splice_tail - join two lists, each list being a queue
380 * @list: the new list to add.
381 * @head: the place to add it in the first list.
383 static inline void list_splice_tail(struct list_head *list,
384 struct list_head *head)
386 if (!list_empty(list))
387 __list_splice(list, head->prev, head);
391 * list_splice_init - join two lists and reinitialise the emptied list.
392 * @list: the new list to add.
393 * @head: the place to add it in the first list.
395 * The list at @list is reinitialised
397 static inline void list_splice_init(struct list_head *list,
398 struct list_head *head)
400 if (!list_empty(list)) {
401 __list_splice(list, head, head->next);
402 INIT_LIST_HEAD(list);
407 * list_splice_tail_init - join two lists and reinitialise the emptied list
408 * @list: the new list to add.
409 * @head: the place to add it in the first list.
411 * Each of the lists is a queue.
412 * The list at @list is reinitialised
414 static inline void list_splice_tail_init(struct list_head *list,
415 struct list_head *head)
417 if (!list_empty(list)) {
418 __list_splice(list, head->prev, head);
419 INIT_LIST_HEAD(list);
424 * list_entry - get the struct for this entry
425 * @ptr: the &struct list_head pointer.
426 * @type: the type of the struct this is embedded in.
427 * @member: the name of the list_head within the struct.
429 #define list_entry(ptr, type, member) \
430 container_of(ptr, type, member)
433 * list_first_entry - get the first element from a list
434 * @ptr: the list head to take the element from.
435 * @type: the type of the struct this is embedded in.
436 * @member: the name of the list_head within the struct.
438 * Note, that list is expected to be not empty.
440 #define list_first_entry(ptr, type, member) \
441 list_entry((ptr)->next, type, member)
444 * list_last_entry - get the last element from a list
445 * @ptr: the list head to take the element from.
446 * @type: the type of the struct this is embedded in.
447 * @member: the name of the list_head within the struct.
449 * Note, that list is expected to be not empty.
451 #define list_last_entry(ptr, type, member) \
452 list_entry((ptr)->prev, type, member)
455 * list_first_entry_or_null - get the first element from a list
456 * @ptr: the list head to take the element from.
457 * @type: the type of the struct this is embedded in.
458 * @member: the name of the list_head within the struct.
460 * Note that if the list is empty, it returns NULL.
462 #define list_first_entry_or_null(ptr, type, member) ({ \
463 struct list_head *head__ = (ptr); \
464 struct list_head *pos__ = READ_ONCE(head__->next); \
465 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
469 * list_next_entry - get the next element in list
470 * @pos: the type * to cursor
471 * @member: the name of the list_head within the struct.
473 #define list_next_entry(pos, member) \
474 list_entry((pos)->member.next, typeof(*(pos)), member)
477 * list_prev_entry - get the prev element in list
478 * @pos: the type * to cursor
479 * @member: the name of the list_head within the struct.
481 #define list_prev_entry(pos, member) \
482 list_entry((pos)->member.prev, typeof(*(pos)), member)
485 * list_for_each - iterate over a list
486 * @pos: the &struct list_head to use as a loop cursor.
487 * @head: the head for your list.
489 #define list_for_each(pos, head) \
490 for (pos = (head)->next; pos != (head); pos = pos->next)
493 * list_for_each_prev - iterate over a list backwards
494 * @pos: the &struct list_head to use as a loop cursor.
495 * @head: the head for your list.
497 #define list_for_each_prev(pos, head) \
498 for (pos = (head)->prev; pos != (head); pos = pos->prev)
501 * list_for_each_safe - iterate over a list safe against removal of list entry
502 * @pos: the &struct list_head to use as a loop cursor.
503 * @n: another &struct list_head to use as temporary storage
504 * @head: the head for your list.
506 #define list_for_each_safe(pos, n, head) \
507 for (pos = (head)->next, n = pos->next; pos != (head); \
508 pos = n, n = pos->next)
511 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
512 * @pos: the &struct list_head to use as a loop cursor.
513 * @n: another &struct list_head to use as temporary storage
514 * @head: the head for your list.
516 #define list_for_each_prev_safe(pos, n, head) \
517 for (pos = (head)->prev, n = pos->prev; \
519 pos = n, n = pos->prev)
522 * list_for_each_entry - iterate over list of given type
523 * @pos: the type * to use as a loop cursor.
524 * @head: the head for your list.
525 * @member: the name of the list_head within the struct.
527 #define list_for_each_entry(pos, head, member) \
528 for (pos = list_first_entry(head, typeof(*pos), member); \
529 &pos->member != (head); \
530 pos = list_next_entry(pos, member))
533 * list_for_each_entry_reverse - iterate backwards over list of given type.
534 * @pos: the type * to use as a loop cursor.
535 * @head: the head for your list.
536 * @member: the name of the list_head within the struct.
538 #define list_for_each_entry_reverse(pos, head, member) \
539 for (pos = list_last_entry(head, typeof(*pos), member); \
540 &pos->member != (head); \
541 pos = list_prev_entry(pos, member))
544 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
545 * @pos: the type * to use as a start point
546 * @head: the head of the list
547 * @member: the name of the list_head within the struct.
549 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
551 #define list_prepare_entry(pos, head, member) \
552 ((pos) ? : list_entry(head, typeof(*pos), member))
555 * list_for_each_entry_continue - continue iteration over list of given type
556 * @pos: the type * to use as a loop cursor.
557 * @head: the head for your list.
558 * @member: the name of the list_head within the struct.
560 * Continue to iterate over list of given type, continuing after
561 * the current position.
563 #define list_for_each_entry_continue(pos, head, member) \
564 for (pos = list_next_entry(pos, member); \
565 &pos->member != (head); \
566 pos = list_next_entry(pos, member))
569 * list_for_each_entry_continue_reverse - iterate backwards from the given point
570 * @pos: the type * to use as a loop cursor.
571 * @head: the head for your list.
572 * @member: the name of the list_head within the struct.
574 * Start to iterate over list of given type backwards, continuing after
575 * the current position.
577 #define list_for_each_entry_continue_reverse(pos, head, member) \
578 for (pos = list_prev_entry(pos, member); \
579 &pos->member != (head); \
580 pos = list_prev_entry(pos, member))
583 * list_for_each_entry_from - iterate over list of given type from the current point
584 * @pos: the type * to use as a loop cursor.
585 * @head: the head for your list.
586 * @member: the name of the list_head within the struct.
588 * Iterate over list of given type, continuing from current position.
590 #define list_for_each_entry_from(pos, head, member) \
591 for (; &pos->member != (head); \
592 pos = list_next_entry(pos, member))
595 * list_for_each_entry_from_reverse - iterate backwards over list of given type
596 * from the current point
597 * @pos: the type * to use as a loop cursor.
598 * @head: the head for your list.
599 * @member: the name of the list_head within the struct.
601 * Iterate backwards over list of given type, continuing from current position.
603 #define list_for_each_entry_from_reverse(pos, head, member) \
604 for (; &pos->member != (head); \
605 pos = list_prev_entry(pos, member))
608 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
609 * @pos: the type * to use as a loop cursor.
610 * @n: another type * to use as temporary storage
611 * @head: the head for your list.
612 * @member: the name of the list_head within the struct.
614 #define list_for_each_entry_safe(pos, n, head, member) \
615 for (pos = list_first_entry(head, typeof(*pos), member), \
616 n = list_next_entry(pos, member); \
617 &pos->member != (head); \
618 pos = n, n = list_next_entry(n, member))
621 * list_for_each_entry_safe_continue - continue list iteration safe against removal
622 * @pos: the type * to use as a loop cursor.
623 * @n: another type * to use as temporary storage
624 * @head: the head for your list.
625 * @member: the name of the list_head within the struct.
627 * Iterate over list of given type, continuing after current point,
628 * safe against removal of list entry.
630 #define list_for_each_entry_safe_continue(pos, n, head, member) \
631 for (pos = list_next_entry(pos, member), \
632 n = list_next_entry(pos, member); \
633 &pos->member != (head); \
634 pos = n, n = list_next_entry(n, member))
637 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
638 * @pos: the type * to use as a loop cursor.
639 * @n: another type * to use as temporary storage
640 * @head: the head for your list.
641 * @member: the name of the list_head within the struct.
643 * Iterate over list of given type from current point, safe against
644 * removal of list entry.
646 #define list_for_each_entry_safe_from(pos, n, head, member) \
647 for (n = list_next_entry(pos, member); \
648 &pos->member != (head); \
649 pos = n, n = list_next_entry(n, member))
652 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
653 * @pos: the type * to use as a loop cursor.
654 * @n: another type * to use as temporary storage
655 * @head: the head for your list.
656 * @member: the name of the list_head within the struct.
658 * Iterate backwards over list of given type, safe against removal
661 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
662 for (pos = list_last_entry(head, typeof(*pos), member), \
663 n = list_prev_entry(pos, member); \
664 &pos->member != (head); \
665 pos = n, n = list_prev_entry(n, member))
668 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
669 * @pos: the loop cursor used in the list_for_each_entry_safe loop
670 * @n: temporary storage used in list_for_each_entry_safe
671 * @member: the name of the list_head within the struct.
673 * list_safe_reset_next is not safe to use in general if the list may be
674 * modified concurrently (eg. the lock is dropped in the loop body). An
675 * exception to this is if the cursor element (pos) is pinned in the list,
676 * and list_safe_reset_next is called after re-taking the lock and before
677 * completing the current iteration of the loop body.
679 #define list_safe_reset_next(pos, n, member) \
680 n = list_next_entry(pos, member)
683 * Double linked lists with a single pointer list head.
684 * Mostly useful for hash tables where the two pointer list head is
686 * You lose the ability to access the tail in O(1).
689 #define HLIST_HEAD_INIT { .first = NULL }
690 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
691 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
692 static inline void INIT_HLIST_NODE(struct hlist_node *h)
698 static inline int hlist_unhashed(const struct hlist_node *h)
703 static inline int hlist_empty(const struct hlist_head *h)
705 return !READ_ONCE(h->first);
708 static inline void __hlist_del(struct hlist_node *n)
710 struct hlist_node *next = n->next;
711 struct hlist_node **pprev = n->pprev;
713 WRITE_ONCE(*pprev, next);
718 static inline void hlist_del(struct hlist_node *n)
721 n->next = LIST_POISON1;
722 n->pprev = LIST_POISON2;
725 static inline void hlist_del_init(struct hlist_node *n)
727 if (!hlist_unhashed(n)) {
733 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
735 struct hlist_node *first = h->first;
738 first->pprev = &n->next;
739 WRITE_ONCE(h->first, n);
740 n->pprev = &h->first;
743 /* next must be != NULL */
744 static inline void hlist_add_before(struct hlist_node *n,
745 struct hlist_node *next)
747 n->pprev = next->pprev;
749 next->pprev = &n->next;
750 WRITE_ONCE(*(n->pprev), n);
753 static inline void hlist_add_behind(struct hlist_node *n,
754 struct hlist_node *prev)
756 n->next = prev->next;
757 WRITE_ONCE(prev->next, n);
758 n->pprev = &prev->next;
761 n->next->pprev = &n->next;
764 /* after that we'll appear to be on some hlist and hlist_del will work */
765 static inline void hlist_add_fake(struct hlist_node *n)
770 static inline bool hlist_fake(struct hlist_node *h)
772 return h->pprev == &h->next;
776 * Check whether the node is the only node of the head without
780 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
782 return !n->next && n->pprev == &h->first;
786 * Move a list from one list head to another. Fixup the pprev
787 * reference of the first entry if it exists.
789 static inline void hlist_move_list(struct hlist_head *old,
790 struct hlist_head *new)
792 new->first = old->first;
794 new->first->pprev = &new->first;
798 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
800 #define hlist_for_each(pos, head) \
801 for (pos = (head)->first; pos ; pos = pos->next)
803 #define hlist_for_each_safe(pos, n, head) \
804 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
807 #define hlist_entry_safe(ptr, type, member) \
808 ({ typeof(ptr) ____ptr = (ptr); \
809 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
813 * hlist_for_each_entry - iterate over list of given type
814 * @pos: the type * to use as a loop cursor.
815 * @head: the head for your list.
816 * @member: the name of the hlist_node within the struct.
818 #define hlist_for_each_entry(pos, head, member) \
819 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
821 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
824 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
825 * @pos: the type * to use as a loop cursor.
826 * @member: the name of the hlist_node within the struct.
828 #define hlist_for_each_entry_continue(pos, member) \
829 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
831 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
834 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
835 * @pos: the type * to use as a loop cursor.
836 * @member: the name of the hlist_node within the struct.
838 #define hlist_for_each_entry_from(pos, member) \
840 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
843 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
844 * @pos: the type * to use as a loop cursor.
845 * @n: another &struct hlist_node to use as temporary storage
846 * @head: the head for your list.
847 * @member: the name of the hlist_node within the struct.
849 #define hlist_for_each_entry_safe(pos, n, head, member) \
850 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
851 pos && ({ n = pos->member.next; 1; }); \
852 pos = hlist_entry_safe(n, typeof(*pos), member))