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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_rotate_to_front() - Rotate list to specific item.
275 * @list: The desired new front of the list.
276 * @head: The head of the list.
278 * Rotates list so that @list becomes the new front of the list.
280 static inline void list_rotate_to_front(struct list_head
*list
,
281 struct list_head
*head
)
284 * Deletes the list head from the list denoted by @head and
285 * places it as the tail of @list, this effectively rotates the
286 * list so that @list is at the front.
288 list_move_tail(head
, list
);
292 * list_is_singular - tests whether a list has just one entry.
293 * @head: the list to test.
295 static inline int list_is_singular(const struct list_head
*head
)
297 return !list_empty(head
) && (head
->next
== head
->prev
);
300 static inline void __list_cut_position(struct list_head
*list
,
301 struct list_head
*head
, struct list_head
*entry
)
303 struct list_head
*new_first
= entry
->next
;
304 list
->next
= head
->next
;
305 list
->next
->prev
= list
;
308 head
->next
= new_first
;
309 new_first
->prev
= head
;
313 * list_cut_position - cut a list into two
314 * @list: a new list to add all removed entries
315 * @head: a list with entries
316 * @entry: an entry within head, could be the head itself
317 * and if so we won't cut the list
319 * This helper moves the initial part of @head, up to and
320 * including @entry, from @head to @list. You should
321 * pass on @entry an element you know is on @head. @list
322 * should be an empty list or a list you do not care about
326 static inline void list_cut_position(struct list_head
*list
,
327 struct list_head
*head
, struct list_head
*entry
)
329 if (list_empty(head
))
331 if (list_is_singular(head
) &&
332 (head
->next
!= entry
&& head
!= entry
))
335 INIT_LIST_HEAD(list
);
337 __list_cut_position(list
, head
, entry
);
341 * list_cut_before - cut a list into two, before given entry
342 * @list: a new list to add all removed entries
343 * @head: a list with entries
344 * @entry: an entry within head, could be the head itself
346 * This helper moves the initial part of @head, up to but
347 * excluding @entry, from @head to @list. You should pass
348 * in @entry an element you know is on @head. @list should
349 * be an empty list or a list you do not care about losing
351 * If @entry == @head, all entries on @head are moved to
354 static inline void list_cut_before(struct list_head
*list
,
355 struct list_head
*head
,
356 struct list_head
*entry
)
358 if (head
->next
== entry
) {
359 INIT_LIST_HEAD(list
);
362 list
->next
= head
->next
;
363 list
->next
->prev
= list
;
364 list
->prev
= entry
->prev
;
365 list
->prev
->next
= list
;
370 static inline void __list_splice(const struct list_head
*list
,
371 struct list_head
*prev
,
372 struct list_head
*next
)
374 struct list_head
*first
= list
->next
;
375 struct list_head
*last
= list
->prev
;
385 * list_splice - join two lists, this is designed for stacks
386 * @list: the new list to add.
387 * @head: the place to add it in the first list.
389 static inline void list_splice(const struct list_head
*list
,
390 struct list_head
*head
)
392 if (!list_empty(list
))
393 __list_splice(list
, head
, head
->next
);
397 * list_splice_tail - join two lists, each list being a queue
398 * @list: the new list to add.
399 * @head: the place to add it in the first list.
401 static inline void list_splice_tail(struct list_head
*list
,
402 struct list_head
*head
)
404 if (!list_empty(list
))
405 __list_splice(list
, head
->prev
, head
);
409 * list_splice_init - join two lists and reinitialise the emptied list.
410 * @list: the new list to add.
411 * @head: the place to add it in the first list.
413 * The list at @list is reinitialised
415 static inline void list_splice_init(struct list_head
*list
,
416 struct list_head
*head
)
418 if (!list_empty(list
)) {
419 __list_splice(list
, head
, head
->next
);
420 INIT_LIST_HEAD(list
);
425 * list_splice_tail_init - join two lists and reinitialise the emptied list
426 * @list: the new list to add.
427 * @head: the place to add it in the first list.
429 * Each of the lists is a queue.
430 * The list at @list is reinitialised
432 static inline void list_splice_tail_init(struct list_head
*list
,
433 struct list_head
*head
)
435 if (!list_empty(list
)) {
436 __list_splice(list
, head
->prev
, head
);
437 INIT_LIST_HEAD(list
);
442 * list_entry - get the struct for this entry
443 * @ptr: the &struct list_head pointer.
444 * @type: the type of the struct this is embedded in.
445 * @member: the name of the list_head within the struct.
447 #define list_entry(ptr, type, member) \
448 container_of(ptr, type, member)
451 * list_first_entry - get the first element from a list
452 * @ptr: the list head to take the element from.
453 * @type: the type of the struct this is embedded in.
454 * @member: the name of the list_head within the struct.
456 * Note, that list is expected to be not empty.
458 #define list_first_entry(ptr, type, member) \
459 list_entry((ptr)->next, type, member)
462 * list_last_entry - get the last element from a list
463 * @ptr: the list head to take the element from.
464 * @type: the type of the struct this is embedded in.
465 * @member: the name of the list_head within the struct.
467 * Note, that list is expected to be not empty.
469 #define list_last_entry(ptr, type, member) \
470 list_entry((ptr)->prev, type, member)
473 * list_first_entry_or_null - get the first element from a list
474 * @ptr: the list head to take the element from.
475 * @type: the type of the struct this is embedded in.
476 * @member: the name of the list_head within the struct.
478 * Note that if the list is empty, it returns NULL.
480 #define list_first_entry_or_null(ptr, type, member) ({ \
481 struct list_head *head__ = (ptr); \
482 struct list_head *pos__ = READ_ONCE(head__->next); \
483 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
487 * list_next_entry - get the next element in list
488 * @pos: the type * to cursor
489 * @member: the name of the list_head within the struct.
491 #define list_next_entry(pos, member) \
492 list_entry((pos)->member.next, typeof(*(pos)), member)
495 * list_prev_entry - get the prev element in list
496 * @pos: the type * to cursor
497 * @member: the name of the list_head within the struct.
499 #define list_prev_entry(pos, member) \
500 list_entry((pos)->member.prev, typeof(*(pos)), member)
503 * list_for_each - iterate over a list
504 * @pos: the &struct list_head to use as a loop cursor.
505 * @head: the head for your list.
507 #define list_for_each(pos, head) \
508 for (pos = (head)->next; pos != (head); pos = pos->next)
511 * list_for_each_prev - iterate over a list backwards
512 * @pos: the &struct list_head to use as a loop cursor.
513 * @head: the head for your list.
515 #define list_for_each_prev(pos, head) \
516 for (pos = (head)->prev; pos != (head); pos = pos->prev)
519 * list_for_each_safe - iterate over a list safe against removal of list entry
520 * @pos: the &struct list_head to use as a loop cursor.
521 * @n: another &struct list_head to use as temporary storage
522 * @head: the head for your list.
524 #define list_for_each_safe(pos, n, head) \
525 for (pos = (head)->next, n = pos->next; pos != (head); \
526 pos = n, n = pos->next)
529 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
530 * @pos: the &struct list_head to use as a loop cursor.
531 * @n: another &struct list_head to use as temporary storage
532 * @head: the head for your list.
534 #define list_for_each_prev_safe(pos, n, head) \
535 for (pos = (head)->prev, n = pos->prev; \
537 pos = n, n = pos->prev)
540 * list_for_each_entry - iterate over list of given type
541 * @pos: the type * to use as a loop cursor.
542 * @head: the head for your list.
543 * @member: the name of the list_head within the struct.
545 #define list_for_each_entry(pos, head, member) \
546 for (pos = list_first_entry(head, typeof(*pos), member); \
547 &pos->member != (head); \
548 pos = list_next_entry(pos, member))
551 * list_for_each_entry_reverse - iterate backwards over list of given type.
552 * @pos: the type * to use as a loop cursor.
553 * @head: the head for your list.
554 * @member: the name of the list_head within the struct.
556 #define list_for_each_entry_reverse(pos, head, member) \
557 for (pos = list_last_entry(head, typeof(*pos), member); \
558 &pos->member != (head); \
559 pos = list_prev_entry(pos, member))
562 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
563 * @pos: the type * to use as a start point
564 * @head: the head of the list
565 * @member: the name of the list_head within the struct.
567 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
569 #define list_prepare_entry(pos, head, member) \
570 ((pos) ? : list_entry(head, typeof(*pos), member))
573 * list_for_each_entry_continue - continue iteration over list of given type
574 * @pos: the type * to use as a loop cursor.
575 * @head: the head for your list.
576 * @member: the name of the list_head within the struct.
578 * Continue to iterate over list of given type, continuing after
579 * the current position.
581 #define list_for_each_entry_continue(pos, head, member) \
582 for (pos = list_next_entry(pos, member); \
583 &pos->member != (head); \
584 pos = list_next_entry(pos, member))
587 * list_for_each_entry_continue_reverse - iterate backwards from the given point
588 * @pos: the type * to use as a loop cursor.
589 * @head: the head for your list.
590 * @member: the name of the list_head within the struct.
592 * Start to iterate over list of given type backwards, continuing after
593 * the current position.
595 #define list_for_each_entry_continue_reverse(pos, head, member) \
596 for (pos = list_prev_entry(pos, member); \
597 &pos->member != (head); \
598 pos = list_prev_entry(pos, member))
601 * list_for_each_entry_from - iterate over list of given type from the current point
602 * @pos: the type * to use as a loop cursor.
603 * @head: the head for your list.
604 * @member: the name of the list_head within the struct.
606 * Iterate over list of given type, continuing from current position.
608 #define list_for_each_entry_from(pos, head, member) \
609 for (; &pos->member != (head); \
610 pos = list_next_entry(pos, member))
613 * list_for_each_entry_from_reverse - iterate backwards over list of given type
614 * from the current point
615 * @pos: the type * to use as a loop cursor.
616 * @head: the head for your list.
617 * @member: the name of the list_head within the struct.
619 * Iterate backwards over list of given type, continuing from current position.
621 #define list_for_each_entry_from_reverse(pos, head, member) \
622 for (; &pos->member != (head); \
623 pos = list_prev_entry(pos, member))
626 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
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 #define list_for_each_entry_safe(pos, n, head, member) \
633 for (pos = list_first_entry(head, typeof(*pos), member), \
634 n = list_next_entry(pos, member); \
635 &pos->member != (head); \
636 pos = n, n = list_next_entry(n, member))
639 * list_for_each_entry_safe_continue - continue list iteration safe against removal
640 * @pos: the type * to use as a loop cursor.
641 * @n: another type * to use as temporary storage
642 * @head: the head for your list.
643 * @member: the name of the list_head within the struct.
645 * Iterate over list of given type, continuing after current point,
646 * safe against removal of list entry.
648 #define list_for_each_entry_safe_continue(pos, n, head, member) \
649 for (pos = list_next_entry(pos, member), \
650 n = list_next_entry(pos, member); \
651 &pos->member != (head); \
652 pos = n, n = list_next_entry(n, member))
655 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
656 * @pos: the type * to use as a loop cursor.
657 * @n: another type * to use as temporary storage
658 * @head: the head for your list.
659 * @member: the name of the list_head within the struct.
661 * Iterate over list of given type from current point, safe against
662 * removal of list entry.
664 #define list_for_each_entry_safe_from(pos, n, head, member) \
665 for (n = list_next_entry(pos, member); \
666 &pos->member != (head); \
667 pos = n, n = list_next_entry(n, member))
670 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
671 * @pos: the type * to use as a loop cursor.
672 * @n: another type * to use as temporary storage
673 * @head: the head for your list.
674 * @member: the name of the list_head within the struct.
676 * Iterate backwards over list of given type, safe against removal
679 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
680 for (pos = list_last_entry(head, typeof(*pos), member), \
681 n = list_prev_entry(pos, member); \
682 &pos->member != (head); \
683 pos = n, n = list_prev_entry(n, member))
686 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
687 * @pos: the loop cursor used in the list_for_each_entry_safe loop
688 * @n: temporary storage used in list_for_each_entry_safe
689 * @member: the name of the list_head within the struct.
691 * list_safe_reset_next is not safe to use in general if the list may be
692 * modified concurrently (eg. the lock is dropped in the loop body). An
693 * exception to this is if the cursor element (pos) is pinned in the list,
694 * and list_safe_reset_next is called after re-taking the lock and before
695 * completing the current iteration of the loop body.
697 #define list_safe_reset_next(pos, n, member) \
698 n = list_next_entry(pos, member)
701 * Double linked lists with a single pointer list head.
702 * Mostly useful for hash tables where the two pointer list head is
704 * You lose the ability to access the tail in O(1).
707 #define HLIST_HEAD_INIT { .first = NULL }
708 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
709 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
710 static inline void INIT_HLIST_NODE(struct hlist_node
*h
)
716 static inline int hlist_unhashed(const struct hlist_node
*h
)
721 static inline int hlist_empty(const struct hlist_head
*h
)
723 return !READ_ONCE(h
->first
);
726 static inline void __hlist_del(struct hlist_node
*n
)
728 struct hlist_node
*next
= n
->next
;
729 struct hlist_node
**pprev
= n
->pprev
;
731 WRITE_ONCE(*pprev
, next
);
736 static inline void hlist_del(struct hlist_node
*n
)
739 n
->next
= LIST_POISON1
;
740 n
->pprev
= LIST_POISON2
;
743 static inline void hlist_del_init(struct hlist_node
*n
)
745 if (!hlist_unhashed(n
)) {
751 static inline void hlist_add_head(struct hlist_node
*n
, struct hlist_head
*h
)
753 struct hlist_node
*first
= h
->first
;
756 first
->pprev
= &n
->next
;
757 WRITE_ONCE(h
->first
, n
);
758 n
->pprev
= &h
->first
;
761 /* next must be != NULL */
762 static inline void hlist_add_before(struct hlist_node
*n
,
763 struct hlist_node
*next
)
765 n
->pprev
= next
->pprev
;
767 next
->pprev
= &n
->next
;
768 WRITE_ONCE(*(n
->pprev
), n
);
771 static inline void hlist_add_behind(struct hlist_node
*n
,
772 struct hlist_node
*prev
)
774 n
->next
= prev
->next
;
775 WRITE_ONCE(prev
->next
, n
);
776 n
->pprev
= &prev
->next
;
779 n
->next
->pprev
= &n
->next
;
782 /* after that we'll appear to be on some hlist and hlist_del will work */
783 static inline void hlist_add_fake(struct hlist_node
*n
)
788 static inline bool hlist_fake(struct hlist_node
*h
)
790 return h
->pprev
== &h
->next
;
794 * Check whether the node is the only node of the head without
798 hlist_is_singular_node(struct hlist_node
*n
, struct hlist_head
*h
)
800 return !n
->next
&& n
->pprev
== &h
->first
;
804 * Move a list from one list head to another. Fixup the pprev
805 * reference of the first entry if it exists.
807 static inline void hlist_move_list(struct hlist_head
*old
,
808 struct hlist_head
*new)
810 new->first
= old
->first
;
812 new->first
->pprev
= &new->first
;
816 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
818 #define hlist_for_each(pos, head) \
819 for (pos = (head)->first; pos ; pos = pos->next)
821 #define hlist_for_each_safe(pos, n, head) \
822 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
825 #define hlist_entry_safe(ptr, type, member) \
826 ({ typeof(ptr) ____ptr = (ptr); \
827 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
831 * hlist_for_each_entry - iterate over list of given type
832 * @pos: the type * to use as a loop cursor.
833 * @head: the head for your list.
834 * @member: the name of the hlist_node within the struct.
836 #define hlist_for_each_entry(pos, head, member) \
837 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
839 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
842 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
843 * @pos: the type * to use as a loop cursor.
844 * @member: the name of the hlist_node within the struct.
846 #define hlist_for_each_entry_continue(pos, member) \
847 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
849 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
852 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
853 * @pos: the type * to use as a loop cursor.
854 * @member: the name of the hlist_node within the struct.
856 #define hlist_for_each_entry_from(pos, member) \
858 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
861 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
862 * @pos: the type * to use as a loop cursor.
863 * @n: another &struct hlist_node to use as temporary storage
864 * @head: the head for your list.
865 * @member: the name of the hlist_node within the struct.
867 #define hlist_for_each_entry_safe(pos, n, head, member) \
868 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
869 pos && ({ n = pos->member.next; 1; }); \
870 pos = hlist_entry_safe(n, typeof(*pos), member))