4 #include <linux/types.h>
5 #include <linux/stddef.h>
6 #include <linux/poison.h>
7 #include <linux/const.h>
8 #include <linux/kernel.h>
11 * Simple doubly linked list implementation.
13 * Some of the internal functions ("__xxx") are useful when
14 * manipulating whole lists rather than single entries, as
15 * sometimes we already know the next/prev entries and we can
16 * generate better code by using them directly rather than
17 * using the generic single-entry routines.
20 #define LIST_HEAD_INIT(name) { &(name), &(name) }
22 #define LIST_HEAD(name) \
23 struct list_head name = LIST_HEAD_INIT(name)
25 static inline void INIT_LIST_HEAD(struct list_head *list)
27 WRITE_ONCE(list->next, list);
31 #ifdef CONFIG_DEBUG_LIST
32 extern bool __list_add_valid(struct list_head *new,
33 struct list_head *prev,
34 struct list_head *next);
35 extern bool __list_del_entry_valid(struct list_head *entry);
37 static inline bool __list_add_valid(struct list_head *new,
38 struct list_head *prev,
39 struct list_head *next)
43 static inline bool __list_del_entry_valid(struct list_head *entry)
50 * Insert a new entry between two known consecutive entries.
52 * This is only for internal list manipulation where we know
53 * the prev/next entries already!
55 static inline void __list_add(struct list_head *new,
56 struct list_head *prev,
57 struct list_head *next)
59 if (!__list_add_valid(new, prev, next))
65 WRITE_ONCE(prev->next, new);
69 * list_add - add a new entry
70 * @new: new entry to be added
71 * @head: list head to add it after
73 * Insert a new entry after the specified head.
74 * This is good for implementing stacks.
76 static inline void list_add(struct list_head *new, struct list_head *head)
78 __list_add(new, head, head->next);
83 * list_add_tail - add a new entry
84 * @new: new entry to be added
85 * @head: list head to add it before
87 * Insert a new entry before the specified head.
88 * This is useful for implementing queues.
90 static inline void list_add_tail(struct list_head *new, struct list_head *head)
92 __list_add(new, head->prev, head);
96 * Delete a list entry by making the prev/next entries
97 * point to each other.
99 * This is only for internal list manipulation where we know
100 * the prev/next entries already!
102 static inline void __list_del(struct list_head * prev, struct list_head * next)
105 WRITE_ONCE(prev->next, next);
109 * list_del - deletes entry from list.
110 * @entry: the element to delete from the list.
111 * Note: list_empty() on entry does not return true after this, the entry is
112 * in an undefined state.
114 static inline void __list_del_entry(struct list_head *entry)
116 if (!__list_del_entry_valid(entry))
119 __list_del(entry->prev, entry->next);
122 static inline void list_del(struct list_head *entry)
124 __list_del_entry(entry);
125 entry->next = LIST_POISON1;
126 entry->prev = LIST_POISON2;
130 * list_replace - replace old entry by new one
131 * @old : the element to be replaced
132 * @new : the new element to insert
134 * If @old was empty, it will be overwritten.
136 static inline void list_replace(struct list_head *old,
137 struct list_head *new)
139 new->next = old->next;
140 new->next->prev = new;
141 new->prev = old->prev;
142 new->prev->next = new;
145 static inline void list_replace_init(struct list_head *old,
146 struct list_head *new)
148 list_replace(old, new);
153 * list_del_init - deletes entry from list and reinitialize it.
154 * @entry: the element to delete from the list.
156 static inline void list_del_init(struct list_head *entry)
158 __list_del_entry(entry);
159 INIT_LIST_HEAD(entry);
163 * list_move - delete from one list and add as another's head
164 * @list: the entry to move
165 * @head: the head that will precede our entry
167 static inline void list_move(struct list_head *list, struct list_head *head)
169 __list_del_entry(list);
170 list_add(list, head);
174 * list_move_tail - delete from one list and add as another's tail
175 * @list: the entry to move
176 * @head: the head that will follow our entry
178 static inline void list_move_tail(struct list_head *list,
179 struct list_head *head)
181 __list_del_entry(list);
182 list_add_tail(list, head);
186 * list_is_last - tests whether @list is the last entry in list @head
187 * @list: the entry to test
188 * @head: the head of the list
190 static inline int list_is_last(const struct list_head *list,
191 const struct list_head *head)
193 return list->next == head;
197 * list_empty - tests whether a list is empty
198 * @head: the list to test.
200 static inline int list_empty(const struct list_head *head)
202 return READ_ONCE(head->next) == head;
206 * list_empty_careful - tests whether a list is empty and not being modified
207 * @head: the list to test
210 * tests whether a list is empty _and_ checks that no other CPU might be
211 * in the process of modifying either member (next or prev)
213 * NOTE: using list_empty_careful() without synchronization
214 * can only be safe if the only activity that can happen
215 * to the list entry is list_del_init(). Eg. it cannot be used
216 * if another CPU could re-list_add() it.
218 static inline int list_empty_careful(const struct list_head *head)
220 struct list_head *next = head->next;
221 return (next == head) && (next == head->prev);
225 * list_rotate_left - rotate the list to the left
226 * @head: the head of the list
228 static inline void list_rotate_left(struct list_head *head)
230 struct list_head *first;
232 if (!list_empty(head)) {
234 list_move_tail(first, head);
239 * list_is_singular - tests whether a list has just one entry.
240 * @head: the list to test.
242 static inline int list_is_singular(const struct list_head *head)
244 return !list_empty(head) && (head->next == head->prev);
247 static inline void __list_cut_position(struct list_head *list,
248 struct list_head *head, struct list_head *entry)
250 struct list_head *new_first = entry->next;
251 list->next = head->next;
252 list->next->prev = list;
255 head->next = new_first;
256 new_first->prev = head;
260 * list_cut_position - cut a list into two
261 * @list: a new list to add all removed entries
262 * @head: a list with entries
263 * @entry: an entry within head, could be the head itself
264 * and if so we won't cut the list
266 * This helper moves the initial part of @head, up to and
267 * including @entry, from @head to @list. You should
268 * pass on @entry an element you know is on @head. @list
269 * should be an empty list or a list you do not care about
273 static inline void list_cut_position(struct list_head *list,
274 struct list_head *head, struct list_head *entry)
276 if (list_empty(head))
278 if (list_is_singular(head) &&
279 (head->next != entry && head != entry))
282 INIT_LIST_HEAD(list);
284 __list_cut_position(list, head, entry);
287 static inline void __list_splice(const struct list_head *list,
288 struct list_head *prev,
289 struct list_head *next)
291 struct list_head *first = list->next;
292 struct list_head *last = list->prev;
302 * list_splice - join two lists, this is designed for stacks
303 * @list: the new list to add.
304 * @head: the place to add it in the first list.
306 static inline void list_splice(const struct list_head *list,
307 struct list_head *head)
309 if (!list_empty(list))
310 __list_splice(list, head, head->next);
314 * list_splice_tail - join two lists, each list being a queue
315 * @list: the new list to add.
316 * @head: the place to add it in the first list.
318 static inline void list_splice_tail(struct list_head *list,
319 struct list_head *head)
321 if (!list_empty(list))
322 __list_splice(list, head->prev, head);
326 * list_splice_init - join two lists and reinitialise the emptied list.
327 * @list: the new list to add.
328 * @head: the place to add it in the first list.
330 * The list at @list is reinitialised
332 static inline void list_splice_init(struct list_head *list,
333 struct list_head *head)
335 if (!list_empty(list)) {
336 __list_splice(list, head, head->next);
337 INIT_LIST_HEAD(list);
342 * list_splice_tail_init - join two lists and reinitialise the emptied list
343 * @list: the new list to add.
344 * @head: the place to add it in the first list.
346 * Each of the lists is a queue.
347 * The list at @list is reinitialised
349 static inline void list_splice_tail_init(struct list_head *list,
350 struct list_head *head)
352 if (!list_empty(list)) {
353 __list_splice(list, head->prev, head);
354 INIT_LIST_HEAD(list);
359 * list_entry - get the struct for this entry
360 * @ptr: the &struct list_head pointer.
361 * @type: the type of the struct this is embedded in.
362 * @member: the name of the list_head within the struct.
364 #define list_entry(ptr, type, member) \
365 container_of(ptr, type, member)
368 * list_first_entry - get the first element from a list
369 * @ptr: the list head to take the element from.
370 * @type: the type of the struct this is embedded in.
371 * @member: the name of the list_head within the struct.
373 * Note, that list is expected to be not empty.
375 #define list_first_entry(ptr, type, member) \
376 list_entry((ptr)->next, type, member)
379 * list_last_entry - get the last element from a list
380 * @ptr: the list head to take the element from.
381 * @type: the type of the struct this is embedded in.
382 * @member: the name of the list_head within the struct.
384 * Note, that list is expected to be not empty.
386 #define list_last_entry(ptr, type, member) \
387 list_entry((ptr)->prev, type, member)
390 * list_first_entry_or_null - get the first element from a list
391 * @ptr: the list head to take the element from.
392 * @type: the type of the struct this is embedded in.
393 * @member: the name of the list_head within the struct.
395 * Note that if the list is empty, it returns NULL.
397 #define list_first_entry_or_null(ptr, type, member) ({ \
398 struct list_head *head__ = (ptr); \
399 struct list_head *pos__ = READ_ONCE(head__->next); \
400 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
404 * list_next_entry - get the next element in list
405 * @pos: the type * to cursor
406 * @member: the name of the list_head within the struct.
408 #define list_next_entry(pos, member) \
409 list_entry((pos)->member.next, typeof(*(pos)), member)
412 * list_prev_entry - get the prev element in list
413 * @pos: the type * to cursor
414 * @member: the name of the list_head within the struct.
416 #define list_prev_entry(pos, member) \
417 list_entry((pos)->member.prev, typeof(*(pos)), member)
420 * list_for_each - iterate over a list
421 * @pos: the &struct list_head to use as a loop cursor.
422 * @head: the head for your list.
424 #define list_for_each(pos, head) \
425 for (pos = (head)->next; pos != (head); pos = pos->next)
428 * list_for_each_prev - iterate over a list backwards
429 * @pos: the &struct list_head to use as a loop cursor.
430 * @head: the head for your list.
432 #define list_for_each_prev(pos, head) \
433 for (pos = (head)->prev; pos != (head); pos = pos->prev)
436 * list_for_each_safe - iterate over a list safe against removal of list entry
437 * @pos: the &struct list_head to use as a loop cursor.
438 * @n: another &struct list_head to use as temporary storage
439 * @head: the head for your list.
441 #define list_for_each_safe(pos, n, head) \
442 for (pos = (head)->next, n = pos->next; pos != (head); \
443 pos = n, n = pos->next)
446 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
447 * @pos: the &struct list_head to use as a loop cursor.
448 * @n: another &struct list_head to use as temporary storage
449 * @head: the head for your list.
451 #define list_for_each_prev_safe(pos, n, head) \
452 for (pos = (head)->prev, n = pos->prev; \
454 pos = n, n = pos->prev)
457 * list_for_each_entry - iterate over list of given type
458 * @pos: the type * to use as a loop cursor.
459 * @head: the head for your list.
460 * @member: the name of the list_head within the struct.
462 #define list_for_each_entry(pos, head, member) \
463 for (pos = list_first_entry(head, typeof(*pos), member); \
464 &pos->member != (head); \
465 pos = list_next_entry(pos, member))
468 * list_for_each_entry_reverse - iterate backwards over list of given type.
469 * @pos: the type * to use as a loop cursor.
470 * @head: the head for your list.
471 * @member: the name of the list_head within the struct.
473 #define list_for_each_entry_reverse(pos, head, member) \
474 for (pos = list_last_entry(head, typeof(*pos), member); \
475 &pos->member != (head); \
476 pos = list_prev_entry(pos, member))
479 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
480 * @pos: the type * to use as a start point
481 * @head: the head of the list
482 * @member: the name of the list_head within the struct.
484 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
486 #define list_prepare_entry(pos, head, member) \
487 ((pos) ? : list_entry(head, typeof(*pos), member))
490 * list_for_each_entry_continue - continue iteration over list of given type
491 * @pos: the type * to use as a loop cursor.
492 * @head: the head for your list.
493 * @member: the name of the list_head within the struct.
495 * Continue to iterate over list of given type, continuing after
496 * the current position.
498 #define list_for_each_entry_continue(pos, head, member) \
499 for (pos = list_next_entry(pos, member); \
500 &pos->member != (head); \
501 pos = list_next_entry(pos, member))
504 * list_for_each_entry_continue_reverse - iterate backwards from the given point
505 * @pos: the type * to use as a loop cursor.
506 * @head: the head for your list.
507 * @member: the name of the list_head within the struct.
509 * Start to iterate over list of given type backwards, continuing after
510 * the current position.
512 #define list_for_each_entry_continue_reverse(pos, head, member) \
513 for (pos = list_prev_entry(pos, member); \
514 &pos->member != (head); \
515 pos = list_prev_entry(pos, member))
518 * list_for_each_entry_from - iterate over list of given type from the current point
519 * @pos: the type * to use as a loop cursor.
520 * @head: the head for your list.
521 * @member: the name of the list_head within the struct.
523 * Iterate over list of given type, continuing from current position.
525 #define list_for_each_entry_from(pos, head, member) \
526 for (; &pos->member != (head); \
527 pos = list_next_entry(pos, member))
530 * list_for_each_entry_from_reverse - iterate backwards over list of given type
531 * from the current point
532 * @pos: the type * to use as a loop cursor.
533 * @head: the head for your list.
534 * @member: the name of the list_head within the struct.
536 * Iterate backwards over list of given type, continuing from current position.
538 #define list_for_each_entry_from_reverse(pos, head, member) \
539 for (; &pos->member != (head); \
540 pos = list_prev_entry(pos, member))
543 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
544 * @pos: the type * to use as a loop cursor.
545 * @n: another type * to use as temporary storage
546 * @head: the head for your list.
547 * @member: the name of the list_head within the struct.
549 #define list_for_each_entry_safe(pos, n, head, member) \
550 for (pos = list_first_entry(head, typeof(*pos), member), \
551 n = list_next_entry(pos, member); \
552 &pos->member != (head); \
553 pos = n, n = list_next_entry(n, member))
556 * list_for_each_entry_safe_continue - continue list iteration safe against removal
557 * @pos: the type * to use as a loop cursor.
558 * @n: another type * to use as temporary storage
559 * @head: the head for your list.
560 * @member: the name of the list_head within the struct.
562 * Iterate over list of given type, continuing after current point,
563 * safe against removal of list entry.
565 #define list_for_each_entry_safe_continue(pos, n, head, member) \
566 for (pos = list_next_entry(pos, member), \
567 n = list_next_entry(pos, member); \
568 &pos->member != (head); \
569 pos = n, n = list_next_entry(n, member))
572 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
573 * @pos: the type * to use as a loop cursor.
574 * @n: another type * to use as temporary storage
575 * @head: the head for your list.
576 * @member: the name of the list_head within the struct.
578 * Iterate over list of given type from current point, safe against
579 * removal of list entry.
581 #define list_for_each_entry_safe_from(pos, n, head, member) \
582 for (n = list_next_entry(pos, member); \
583 &pos->member != (head); \
584 pos = n, n = list_next_entry(n, member))
587 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
588 * @pos: the type * to use as a loop cursor.
589 * @n: another type * to use as temporary storage
590 * @head: the head for your list.
591 * @member: the name of the list_head within the struct.
593 * Iterate backwards over list of given type, safe against removal
596 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
597 for (pos = list_last_entry(head, typeof(*pos), member), \
598 n = list_prev_entry(pos, member); \
599 &pos->member != (head); \
600 pos = n, n = list_prev_entry(n, member))
603 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
604 * @pos: the loop cursor used in the list_for_each_entry_safe loop
605 * @n: temporary storage used in list_for_each_entry_safe
606 * @member: the name of the list_head within the struct.
608 * list_safe_reset_next is not safe to use in general if the list may be
609 * modified concurrently (eg. the lock is dropped in the loop body). An
610 * exception to this is if the cursor element (pos) is pinned in the list,
611 * and list_safe_reset_next is called after re-taking the lock and before
612 * completing the current iteration of the loop body.
614 #define list_safe_reset_next(pos, n, member) \
615 n = list_next_entry(pos, member)
618 * Double linked lists with a single pointer list head.
619 * Mostly useful for hash tables where the two pointer list head is
621 * You lose the ability to access the tail in O(1).
624 #define HLIST_HEAD_INIT { .first = NULL }
625 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
626 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
627 static inline void INIT_HLIST_NODE(struct hlist_node *h)
633 static inline int hlist_unhashed(const struct hlist_node *h)
638 static inline int hlist_empty(const struct hlist_head *h)
640 return !READ_ONCE(h->first);
643 static inline void __hlist_del(struct hlist_node *n)
645 struct hlist_node *next = n->next;
646 struct hlist_node **pprev = n->pprev;
648 WRITE_ONCE(*pprev, next);
653 static inline void hlist_del(struct hlist_node *n)
656 n->next = LIST_POISON1;
657 n->pprev = LIST_POISON2;
660 static inline void hlist_del_init(struct hlist_node *n)
662 if (!hlist_unhashed(n)) {
668 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
670 struct hlist_node *first = h->first;
673 first->pprev = &n->next;
674 WRITE_ONCE(h->first, n);
675 n->pprev = &h->first;
678 /* next must be != NULL */
679 static inline void hlist_add_before(struct hlist_node *n,
680 struct hlist_node *next)
682 n->pprev = next->pprev;
684 next->pprev = &n->next;
685 WRITE_ONCE(*(n->pprev), n);
688 static inline void hlist_add_behind(struct hlist_node *n,
689 struct hlist_node *prev)
691 n->next = prev->next;
692 WRITE_ONCE(prev->next, n);
693 n->pprev = &prev->next;
696 n->next->pprev = &n->next;
699 /* after that we'll appear to be on some hlist and hlist_del will work */
700 static inline void hlist_add_fake(struct hlist_node *n)
705 static inline bool hlist_fake(struct hlist_node *h)
707 return h->pprev == &h->next;
711 * Check whether the node is the only node of the head without
715 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
717 return !n->next && n->pprev == &h->first;
721 * Move a list from one list head to another. Fixup the pprev
722 * reference of the first entry if it exists.
724 static inline void hlist_move_list(struct hlist_head *old,
725 struct hlist_head *new)
727 new->first = old->first;
729 new->first->pprev = &new->first;
733 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
735 #define hlist_for_each(pos, head) \
736 for (pos = (head)->first; pos ; pos = pos->next)
738 #define hlist_for_each_safe(pos, n, head) \
739 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
742 #define hlist_entry_safe(ptr, type, member) \
743 ({ typeof(ptr) ____ptr = (ptr); \
744 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
748 * hlist_for_each_entry - iterate over list of given type
749 * @pos: the type * to use as a loop cursor.
750 * @head: the head for your list.
751 * @member: the name of the hlist_node within the struct.
753 #define hlist_for_each_entry(pos, head, member) \
754 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
756 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
759 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
760 * @pos: the type * to use as a loop cursor.
761 * @member: the name of the hlist_node within the struct.
763 #define hlist_for_each_entry_continue(pos, member) \
764 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
766 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
769 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
770 * @pos: the type * to use as a loop cursor.
771 * @member: the name of the hlist_node within the struct.
773 #define hlist_for_each_entry_from(pos, member) \
775 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
778 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
779 * @pos: the type * to use as a loop cursor.
780 * @n: another &struct hlist_node to use as temporary storage
781 * @head: the head for your list.
782 * @member: the name of the hlist_node within the struct.
784 #define hlist_for_each_entry_safe(pos, n, head, member) \
785 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
786 pos && ({ n = pos->member.next; 1; }); \
787 pos = hlist_entry_safe(n, typeof(*pos), member))