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_last - tests whether @list is the last entry in list @head
211 * @list: the entry to test
212 * @head: the head of the list
214 static inline int list_is_last(const struct list_head *list,
215 const struct list_head *head)
217 return list->next == head;
221 * list_empty - tests whether a list is empty
222 * @head: the list to test.
224 static inline int list_empty(const struct list_head *head)
226 return READ_ONCE(head->next) == head;
230 * list_empty_careful - tests whether a list is empty and not being modified
231 * @head: the list to test
234 * tests whether a list is empty _and_ checks that no other CPU might be
235 * in the process of modifying either member (next or prev)
237 * NOTE: using list_empty_careful() without synchronization
238 * can only be safe if the only activity that can happen
239 * to the list entry is list_del_init(). Eg. it cannot be used
240 * if another CPU could re-list_add() it.
242 static inline int list_empty_careful(const struct list_head *head)
244 struct list_head *next = head->next;
245 return (next == head) && (next == head->prev);
249 * list_rotate_left - rotate the list to the left
250 * @head: the head of the list
252 static inline void list_rotate_left(struct list_head *head)
254 struct list_head *first;
256 if (!list_empty(head)) {
258 list_move_tail(first, head);
263 * list_is_singular - tests whether a list has just one entry.
264 * @head: the list to test.
266 static inline int list_is_singular(const struct list_head *head)
268 return !list_empty(head) && (head->next == head->prev);
271 static inline void __list_cut_position(struct list_head *list,
272 struct list_head *head, struct list_head *entry)
274 struct list_head *new_first = entry->next;
275 list->next = head->next;
276 list->next->prev = list;
279 head->next = new_first;
280 new_first->prev = head;
284 * list_cut_position - cut a list into two
285 * @list: a new list to add all removed entries
286 * @head: a list with entries
287 * @entry: an entry within head, could be the head itself
288 * and if so we won't cut the list
290 * This helper moves the initial part of @head, up to and
291 * including @entry, from @head to @list. You should
292 * pass on @entry an element you know is on @head. @list
293 * should be an empty list or a list you do not care about
297 static inline void list_cut_position(struct list_head *list,
298 struct list_head *head, struct list_head *entry)
300 if (list_empty(head))
302 if (list_is_singular(head) &&
303 (head->next != entry && head != entry))
306 INIT_LIST_HEAD(list);
308 __list_cut_position(list, head, entry);
312 * list_cut_before - cut a list into two, before given entry
313 * @list: a new list to add all removed entries
314 * @head: a list with entries
315 * @entry: an entry within head, could be the head itself
317 * This helper moves the initial part of @head, up to but
318 * excluding @entry, from @head to @list. You should pass
319 * in @entry an element you know is on @head. @list should
320 * be an empty list or a list you do not care about losing
322 * If @entry == @head, all entries on @head are moved to
325 static inline void list_cut_before(struct list_head *list,
326 struct list_head *head,
327 struct list_head *entry)
329 if (head->next == entry) {
330 INIT_LIST_HEAD(list);
333 list->next = head->next;
334 list->next->prev = list;
335 list->prev = entry->prev;
336 list->prev->next = list;
341 static inline void __list_splice(const struct list_head *list,
342 struct list_head *prev,
343 struct list_head *next)
345 struct list_head *first = list->next;
346 struct list_head *last = list->prev;
356 * list_splice - join two lists, this is designed for stacks
357 * @list: the new list to add.
358 * @head: the place to add it in the first list.
360 static inline void list_splice(const struct list_head *list,
361 struct list_head *head)
363 if (!list_empty(list))
364 __list_splice(list, head, head->next);
368 * list_splice_tail - join two lists, each list being a queue
369 * @list: the new list to add.
370 * @head: the place to add it in the first list.
372 static inline void list_splice_tail(struct list_head *list,
373 struct list_head *head)
375 if (!list_empty(list))
376 __list_splice(list, head->prev, head);
380 * list_splice_init - join two lists and reinitialise the emptied list.
381 * @list: the new list to add.
382 * @head: the place to add it in the first list.
384 * The list at @list is reinitialised
386 static inline void list_splice_init(struct list_head *list,
387 struct list_head *head)
389 if (!list_empty(list)) {
390 __list_splice(list, head, head->next);
391 INIT_LIST_HEAD(list);
396 * list_splice_tail_init - join two lists and reinitialise the emptied list
397 * @list: the new list to add.
398 * @head: the place to add it in the first list.
400 * Each of the lists is a queue.
401 * The list at @list is reinitialised
403 static inline void list_splice_tail_init(struct list_head *list,
404 struct list_head *head)
406 if (!list_empty(list)) {
407 __list_splice(list, head->prev, head);
408 INIT_LIST_HEAD(list);
413 * list_entry - get the struct for this entry
414 * @ptr: the &struct list_head pointer.
415 * @type: the type of the struct this is embedded in.
416 * @member: the name of the list_head within the struct.
418 #define list_entry(ptr, type, member) \
419 container_of(ptr, type, member)
422 * list_first_entry - get the first element from a list
423 * @ptr: the list head to take the element from.
424 * @type: the type of the struct this is embedded in.
425 * @member: the name of the list_head within the struct.
427 * Note, that list is expected to be not empty.
429 #define list_first_entry(ptr, type, member) \
430 list_entry((ptr)->next, type, member)
433 * list_last_entry - get the last 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_last_entry(ptr, type, member) \
441 list_entry((ptr)->prev, type, member)
444 * list_first_entry_or_null - get the first 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 if the list is empty, it returns NULL.
451 #define list_first_entry_or_null(ptr, type, member) ({ \
452 struct list_head *head__ = (ptr); \
453 struct list_head *pos__ = READ_ONCE(head__->next); \
454 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
458 * list_next_entry - get the next element in list
459 * @pos: the type * to cursor
460 * @member: the name of the list_head within the struct.
462 #define list_next_entry(pos, member) \
463 list_entry((pos)->member.next, typeof(*(pos)), member)
466 * list_prev_entry - get the prev element in list
467 * @pos: the type * to cursor
468 * @member: the name of the list_head within the struct.
470 #define list_prev_entry(pos, member) \
471 list_entry((pos)->member.prev, typeof(*(pos)), member)
474 * list_for_each - iterate over a list
475 * @pos: the &struct list_head to use as a loop cursor.
476 * @head: the head for your list.
478 #define list_for_each(pos, head) \
479 for (pos = (head)->next; pos != (head); pos = pos->next)
482 * list_for_each_prev - iterate over a list backwards
483 * @pos: the &struct list_head to use as a loop cursor.
484 * @head: the head for your list.
486 #define list_for_each_prev(pos, head) \
487 for (pos = (head)->prev; pos != (head); pos = pos->prev)
490 * list_for_each_safe - iterate over a list safe against removal of list entry
491 * @pos: the &struct list_head to use as a loop cursor.
492 * @n: another &struct list_head to use as temporary storage
493 * @head: the head for your list.
495 #define list_for_each_safe(pos, n, head) \
496 for (pos = (head)->next, n = pos->next; pos != (head); \
497 pos = n, n = pos->next)
500 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
501 * @pos: the &struct list_head to use as a loop cursor.
502 * @n: another &struct list_head to use as temporary storage
503 * @head: the head for your list.
505 #define list_for_each_prev_safe(pos, n, head) \
506 for (pos = (head)->prev, n = pos->prev; \
508 pos = n, n = pos->prev)
511 * list_for_each_entry - iterate over list of given type
512 * @pos: the type * to use as a loop cursor.
513 * @head: the head for your list.
514 * @member: the name of the list_head within the struct.
516 #define list_for_each_entry(pos, head, member) \
517 for (pos = list_first_entry(head, typeof(*pos), member); \
518 &pos->member != (head); \
519 pos = list_next_entry(pos, member))
522 * list_for_each_entry_reverse - iterate backwards 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_reverse(pos, head, member) \
528 for (pos = list_last_entry(head, typeof(*pos), member); \
529 &pos->member != (head); \
530 pos = list_prev_entry(pos, member))
533 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
534 * @pos: the type * to use as a start point
535 * @head: the head of the list
536 * @member: the name of the list_head within the struct.
538 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
540 #define list_prepare_entry(pos, head, member) \
541 ((pos) ? : list_entry(head, typeof(*pos), member))
544 * list_for_each_entry_continue - continue iteration over list of given type
545 * @pos: the type * to use as a loop cursor.
546 * @head: the head for your list.
547 * @member: the name of the list_head within the struct.
549 * Continue to iterate over list of given type, continuing after
550 * the current position.
552 #define list_for_each_entry_continue(pos, head, member) \
553 for (pos = list_next_entry(pos, member); \
554 &pos->member != (head); \
555 pos = list_next_entry(pos, member))
558 * list_for_each_entry_continue_reverse - iterate backwards from the given point
559 * @pos: the type * to use as a loop cursor.
560 * @head: the head for your list.
561 * @member: the name of the list_head within the struct.
563 * Start to iterate over list of given type backwards, continuing after
564 * the current position.
566 #define list_for_each_entry_continue_reverse(pos, head, member) \
567 for (pos = list_prev_entry(pos, member); \
568 &pos->member != (head); \
569 pos = list_prev_entry(pos, member))
572 * list_for_each_entry_from - iterate over list of given type from the current point
573 * @pos: the type * to use as a loop cursor.
574 * @head: the head for your list.
575 * @member: the name of the list_head within the struct.
577 * Iterate over list of given type, continuing from current position.
579 #define list_for_each_entry_from(pos, head, member) \
580 for (; &pos->member != (head); \
581 pos = list_next_entry(pos, member))
584 * list_for_each_entry_from_reverse - iterate backwards over list of given type
585 * from the current point
586 * @pos: the type * to use as a loop cursor.
587 * @head: the head for your list.
588 * @member: the name of the list_head within the struct.
590 * Iterate backwards over list of given type, continuing from current position.
592 #define list_for_each_entry_from_reverse(pos, head, member) \
593 for (; &pos->member != (head); \
594 pos = list_prev_entry(pos, member))
597 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
598 * @pos: the type * to use as a loop cursor.
599 * @n: another type * to use as temporary storage
600 * @head: the head for your list.
601 * @member: the name of the list_head within the struct.
603 #define list_for_each_entry_safe(pos, n, head, member) \
604 for (pos = list_first_entry(head, typeof(*pos), member), \
605 n = list_next_entry(pos, member); \
606 &pos->member != (head); \
607 pos = n, n = list_next_entry(n, member))
610 * list_for_each_entry_safe_continue - continue list iteration safe against removal
611 * @pos: the type * to use as a loop cursor.
612 * @n: another type * to use as temporary storage
613 * @head: the head for your list.
614 * @member: the name of the list_head within the struct.
616 * Iterate over list of given type, continuing after current point,
617 * safe against removal of list entry.
619 #define list_for_each_entry_safe_continue(pos, n, head, member) \
620 for (pos = list_next_entry(pos, member), \
621 n = list_next_entry(pos, member); \
622 &pos->member != (head); \
623 pos = n, n = list_next_entry(n, member))
626 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
627 * @pos: the type * to use as a loop cursor.
628 * @n: another type * to use as temporary storage
629 * @head: the head for your list.
630 * @member: the name of the list_head within the struct.
632 * Iterate over list of given type from current point, safe against
633 * removal of list entry.
635 #define list_for_each_entry_safe_from(pos, n, head, member) \
636 for (n = list_next_entry(pos, member); \
637 &pos->member != (head); \
638 pos = n, n = list_next_entry(n, member))
641 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
642 * @pos: the type * to use as a loop cursor.
643 * @n: another type * to use as temporary storage
644 * @head: the head for your list.
645 * @member: the name of the list_head within the struct.
647 * Iterate backwards over list of given type, safe against removal
650 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
651 for (pos = list_last_entry(head, typeof(*pos), member), \
652 n = list_prev_entry(pos, member); \
653 &pos->member != (head); \
654 pos = n, n = list_prev_entry(n, member))
657 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
658 * @pos: the loop cursor used in the list_for_each_entry_safe loop
659 * @n: temporary storage used in list_for_each_entry_safe
660 * @member: the name of the list_head within the struct.
662 * list_safe_reset_next is not safe to use in general if the list may be
663 * modified concurrently (eg. the lock is dropped in the loop body). An
664 * exception to this is if the cursor element (pos) is pinned in the list,
665 * and list_safe_reset_next is called after re-taking the lock and before
666 * completing the current iteration of the loop body.
668 #define list_safe_reset_next(pos, n, member) \
669 n = list_next_entry(pos, member)
672 * Double linked lists with a single pointer list head.
673 * Mostly useful for hash tables where the two pointer list head is
675 * You lose the ability to access the tail in O(1).
678 #define HLIST_HEAD_INIT { .first = NULL }
679 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
680 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
681 static inline void INIT_HLIST_NODE(struct hlist_node *h)
687 static inline int hlist_unhashed(const struct hlist_node *h)
692 static inline int hlist_empty(const struct hlist_head *h)
694 return !READ_ONCE(h->first);
697 static inline void __hlist_del(struct hlist_node *n)
699 struct hlist_node *next = n->next;
700 struct hlist_node **pprev = n->pprev;
702 WRITE_ONCE(*pprev, next);
707 static inline void hlist_del(struct hlist_node *n)
710 n->next = LIST_POISON1;
711 n->pprev = LIST_POISON2;
714 static inline void hlist_del_init(struct hlist_node *n)
716 if (!hlist_unhashed(n)) {
722 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
724 struct hlist_node *first = h->first;
727 first->pprev = &n->next;
728 WRITE_ONCE(h->first, n);
729 n->pprev = &h->first;
732 /* next must be != NULL */
733 static inline void hlist_add_before(struct hlist_node *n,
734 struct hlist_node *next)
736 n->pprev = next->pprev;
738 next->pprev = &n->next;
739 WRITE_ONCE(*(n->pprev), n);
742 static inline void hlist_add_behind(struct hlist_node *n,
743 struct hlist_node *prev)
745 n->next = prev->next;
746 WRITE_ONCE(prev->next, n);
747 n->pprev = &prev->next;
750 n->next->pprev = &n->next;
753 /* after that we'll appear to be on some hlist and hlist_del will work */
754 static inline void hlist_add_fake(struct hlist_node *n)
759 static inline bool hlist_fake(struct hlist_node *h)
761 return h->pprev == &h->next;
765 * Check whether the node is the only node of the head without
769 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
771 return !n->next && n->pprev == &h->first;
775 * Move a list from one list head to another. Fixup the pprev
776 * reference of the first entry if it exists.
778 static inline void hlist_move_list(struct hlist_head *old,
779 struct hlist_head *new)
781 new->first = old->first;
783 new->first->pprev = &new->first;
787 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
789 #define hlist_for_each(pos, head) \
790 for (pos = (head)->first; pos ; pos = pos->next)
792 #define hlist_for_each_safe(pos, n, head) \
793 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
796 #define hlist_entry_safe(ptr, type, member) \
797 ({ typeof(ptr) ____ptr = (ptr); \
798 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
802 * hlist_for_each_entry - iterate over list of given type
803 * @pos: the type * to use as a loop cursor.
804 * @head: the head for your list.
805 * @member: the name of the hlist_node within the struct.
807 #define hlist_for_each_entry(pos, head, member) \
808 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
810 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
813 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
814 * @pos: the type * to use as a loop cursor.
815 * @member: the name of the hlist_node within the struct.
817 #define hlist_for_each_entry_continue(pos, member) \
818 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
820 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
823 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
824 * @pos: the type * to use as a loop cursor.
825 * @member: the name of the hlist_node within the struct.
827 #define hlist_for_each_entry_from(pos, member) \
829 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
832 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
833 * @pos: the type * to use as a loop cursor.
834 * @n: another &struct hlist_node to use as temporary storage
835 * @head: the head for your list.
836 * @member: the name of the hlist_node within the struct.
838 #define hlist_for_each_entry_safe(pos, n, head, member) \
839 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
840 pos && ({ n = pos->member.next; 1; }); \
841 pos = hlist_entry_safe(n, typeof(*pos), member))