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);
32 * Insert a new entry between two known consecutive entries.
34 * This is only for internal list manipulation where we know
35 * the prev/next entries already!
37 #ifndef CONFIG_DEBUG_LIST
38 static inline void __list_add(struct list_head *new,
39 struct list_head *prev,
40 struct list_head *next)
45 WRITE_ONCE(prev->next, new);
48 extern void __list_add(struct list_head *new,
49 struct list_head *prev,
50 struct list_head *next);
54 * list_add - add a new entry
55 * @new: new entry to be added
56 * @head: list head to add it after
58 * Insert a new entry after the specified head.
59 * This is good for implementing stacks.
61 static inline void list_add(struct list_head *new, struct list_head *head)
63 __list_add(new, head, head->next);
68 * list_add_tail - add a new entry
69 * @new: new entry to be added
70 * @head: list head to add it before
72 * Insert a new entry before the specified head.
73 * This is useful for implementing queues.
75 static inline void list_add_tail(struct list_head *new, struct list_head *head)
77 __list_add(new, head->prev, head);
81 * Delete a list entry by making the prev/next entries
82 * point to each other.
84 * This is only for internal list manipulation where we know
85 * the prev/next entries already!
87 static inline void __list_del(struct list_head * prev, struct list_head * next)
90 WRITE_ONCE(prev->next, next);
94 * list_del - deletes entry from list.
95 * @entry: the element to delete from the list.
96 * Note: list_empty() on entry does not return true after this, the entry is
97 * in an undefined state.
99 #ifndef CONFIG_DEBUG_LIST
100 static inline void __list_del_entry(struct list_head *entry)
102 __list_del(entry->prev, entry->next);
105 static inline void list_del(struct list_head *entry)
107 __list_del(entry->prev, entry->next);
108 entry->next = LIST_POISON1;
109 entry->prev = LIST_POISON2;
112 extern void __list_del_entry(struct list_head *entry);
113 extern void list_del(struct list_head *entry);
117 * list_replace - replace old entry by new one
118 * @old : the element to be replaced
119 * @new : the new element to insert
121 * If @old was empty, it will be overwritten.
123 static inline void list_replace(struct list_head *old,
124 struct list_head *new)
126 new->next = old->next;
127 new->next->prev = new;
128 new->prev = old->prev;
129 new->prev->next = new;
132 static inline void list_replace_init(struct list_head *old,
133 struct list_head *new)
135 list_replace(old, new);
140 * list_del_init - deletes entry from list and reinitialize it.
141 * @entry: the element to delete from the list.
143 static inline void list_del_init(struct list_head *entry)
145 __list_del_entry(entry);
146 INIT_LIST_HEAD(entry);
150 * list_move - delete from one list and add as another's head
151 * @list: the entry to move
152 * @head: the head that will precede our entry
154 static inline void list_move(struct list_head *list, struct list_head *head)
156 __list_del_entry(list);
157 list_add(list, head);
161 * list_move_tail - delete from one list and add as another's tail
162 * @list: the entry to move
163 * @head: the head that will follow our entry
165 static inline void list_move_tail(struct list_head *list,
166 struct list_head *head)
168 __list_del_entry(list);
169 list_add_tail(list, head);
173 * list_is_last - tests whether @list is the last entry in list @head
174 * @list: the entry to test
175 * @head: the head of the list
177 static inline int list_is_last(const struct list_head *list,
178 const struct list_head *head)
180 return list->next == head;
184 * list_empty - tests whether a list is empty
185 * @head: the list to test.
187 static inline int list_empty(const struct list_head *head)
189 return READ_ONCE(head->next) == head;
193 * list_empty_careful - tests whether a list is empty and not being modified
194 * @head: the list to test
197 * tests whether a list is empty _and_ checks that no other CPU might be
198 * in the process of modifying either member (next or prev)
200 * NOTE: using list_empty_careful() without synchronization
201 * can only be safe if the only activity that can happen
202 * to the list entry is list_del_init(). Eg. it cannot be used
203 * if another CPU could re-list_add() it.
205 static inline int list_empty_careful(const struct list_head *head)
207 struct list_head *next = head->next;
208 return (next == head) && (next == head->prev);
212 * list_rotate_left - rotate the list to the left
213 * @head: the head of the list
215 static inline void list_rotate_left(struct list_head *head)
217 struct list_head *first;
219 if (!list_empty(head)) {
221 list_move_tail(first, head);
226 * list_is_singular - tests whether a list has just one entry.
227 * @head: the list to test.
229 static inline int list_is_singular(const struct list_head *head)
231 return !list_empty(head) && (head->next == head->prev);
234 static inline void __list_cut_position(struct list_head *list,
235 struct list_head *head, struct list_head *entry)
237 struct list_head *new_first = entry->next;
238 list->next = head->next;
239 list->next->prev = list;
242 head->next = new_first;
243 new_first->prev = head;
247 * list_cut_position - cut a list into two
248 * @list: a new list to add all removed entries
249 * @head: a list with entries
250 * @entry: an entry within head, could be the head itself
251 * and if so we won't cut the list
253 * This helper moves the initial part of @head, up to and
254 * including @entry, from @head to @list. You should
255 * pass on @entry an element you know is on @head. @list
256 * should be an empty list or a list you do not care about
260 static inline void list_cut_position(struct list_head *list,
261 struct list_head *head, struct list_head *entry)
263 if (list_empty(head))
265 if (list_is_singular(head) &&
266 (head->next != entry && head != entry))
269 INIT_LIST_HEAD(list);
271 __list_cut_position(list, head, entry);
275 * list_cut_before - cut a list into two, before given entry
276 * @list: a new list to add all removed entries
277 * @head: a list with entries
278 * @entry: an entry within head, could be the head itself
280 * This helper moves the initial part of @head, up to but
281 * excluding @entry, from @head to @list. You should pass
282 * in @entry an element you know is on @head. @list should
283 * be an empty list or a list you do not care about losing
285 * If @entry == @head, all entries on @head are moved to
288 static inline void list_cut_before(struct list_head *list,
289 struct list_head *head,
290 struct list_head *entry)
292 if (head->next == entry) {
293 INIT_LIST_HEAD(list);
296 list->next = head->next;
297 list->next->prev = list;
298 list->prev = entry->prev;
299 list->prev->next = list;
304 static inline void __list_splice(const struct list_head *list,
305 struct list_head *prev,
306 struct list_head *next)
308 struct list_head *first = list->next;
309 struct list_head *last = list->prev;
319 * list_splice - join two lists, this is designed for stacks
320 * @list: the new list to add.
321 * @head: the place to add it in the first list.
323 static inline void list_splice(const struct list_head *list,
324 struct list_head *head)
326 if (!list_empty(list))
327 __list_splice(list, head, head->next);
331 * list_splice_tail - join two lists, each list being a queue
332 * @list: the new list to add.
333 * @head: the place to add it in the first list.
335 static inline void list_splice_tail(struct list_head *list,
336 struct list_head *head)
338 if (!list_empty(list))
339 __list_splice(list, head->prev, head);
343 * list_splice_init - join two lists and reinitialise the emptied list.
344 * @list: the new list to add.
345 * @head: the place to add it in the first list.
347 * The list at @list is reinitialised
349 static inline void list_splice_init(struct list_head *list,
350 struct list_head *head)
352 if (!list_empty(list)) {
353 __list_splice(list, head, head->next);
354 INIT_LIST_HEAD(list);
359 * list_splice_tail_init - join two lists and reinitialise the emptied list
360 * @list: the new list to add.
361 * @head: the place to add it in the first list.
363 * Each of the lists is a queue.
364 * The list at @list is reinitialised
366 static inline void list_splice_tail_init(struct list_head *list,
367 struct list_head *head)
369 if (!list_empty(list)) {
370 __list_splice(list, head->prev, head);
371 INIT_LIST_HEAD(list);
376 * list_entry - get the struct for this entry
377 * @ptr: the &struct list_head pointer.
378 * @type: the type of the struct this is embedded in.
379 * @member: the name of the list_head within the struct.
381 #define list_entry(ptr, type, member) \
382 container_of(ptr, type, member)
385 * list_first_entry - get the first element from a list
386 * @ptr: the list head to take the element from.
387 * @type: the type of the struct this is embedded in.
388 * @member: the name of the list_head within the struct.
390 * Note, that list is expected to be not empty.
392 #define list_first_entry(ptr, type, member) \
393 list_entry((ptr)->next, type, member)
396 * list_last_entry - get the last element from a list
397 * @ptr: the list head to take the element from.
398 * @type: the type of the struct this is embedded in.
399 * @member: the name of the list_head within the struct.
401 * Note, that list is expected to be not empty.
403 #define list_last_entry(ptr, type, member) \
404 list_entry((ptr)->prev, type, member)
407 * list_first_entry_or_null - get the first element from a list
408 * @ptr: the list head to take the element from.
409 * @type: the type of the struct this is embedded in.
410 * @member: the name of the list_head within the struct.
412 * Note that if the list is empty, it returns NULL.
414 #define list_first_entry_or_null(ptr, type, member) ({ \
415 struct list_head *head__ = (ptr); \
416 struct list_head *pos__ = READ_ONCE(head__->next); \
417 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
421 * list_next_entry - get the next element in list
422 * @pos: the type * to cursor
423 * @member: the name of the list_head within the struct.
425 #define list_next_entry(pos, member) \
426 list_entry((pos)->member.next, typeof(*(pos)), member)
429 * list_prev_entry - get the prev element in list
430 * @pos: the type * to cursor
431 * @member: the name of the list_head within the struct.
433 #define list_prev_entry(pos, member) \
434 list_entry((pos)->member.prev, typeof(*(pos)), member)
437 * list_for_each - iterate over a list
438 * @pos: the &struct list_head to use as a loop cursor.
439 * @head: the head for your list.
441 #define list_for_each(pos, head) \
442 for (pos = (head)->next; pos != (head); pos = pos->next)
445 * list_for_each_prev - iterate over a list backwards
446 * @pos: the &struct list_head to use as a loop cursor.
447 * @head: the head for your list.
449 #define list_for_each_prev(pos, head) \
450 for (pos = (head)->prev; pos != (head); pos = pos->prev)
453 * list_for_each_safe - iterate over a list safe against removal of list entry
454 * @pos: the &struct list_head to use as a loop cursor.
455 * @n: another &struct list_head to use as temporary storage
456 * @head: the head for your list.
458 #define list_for_each_safe(pos, n, head) \
459 for (pos = (head)->next, n = pos->next; pos != (head); \
460 pos = n, n = pos->next)
463 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
464 * @pos: the &struct list_head to use as a loop cursor.
465 * @n: another &struct list_head to use as temporary storage
466 * @head: the head for your list.
468 #define list_for_each_prev_safe(pos, n, head) \
469 for (pos = (head)->prev, n = pos->prev; \
471 pos = n, n = pos->prev)
474 * list_for_each_entry - iterate over list of given type
475 * @pos: the type * to use as a loop cursor.
476 * @head: the head for your list.
477 * @member: the name of the list_head within the struct.
479 #define list_for_each_entry(pos, head, member) \
480 for (pos = list_first_entry(head, typeof(*pos), member); \
481 &pos->member != (head); \
482 pos = list_next_entry(pos, member))
485 * list_for_each_entry_reverse - iterate backwards over list of given type.
486 * @pos: the type * to use as a loop cursor.
487 * @head: the head for your list.
488 * @member: the name of the list_head within the struct.
490 #define list_for_each_entry_reverse(pos, head, member) \
491 for (pos = list_last_entry(head, typeof(*pos), member); \
492 &pos->member != (head); \
493 pos = list_prev_entry(pos, member))
496 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
497 * @pos: the type * to use as a start point
498 * @head: the head of the list
499 * @member: the name of the list_head within the struct.
501 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
503 #define list_prepare_entry(pos, head, member) \
504 ((pos) ? : list_entry(head, typeof(*pos), member))
507 * list_for_each_entry_continue - continue iteration over list of given type
508 * @pos: the type * to use as a loop cursor.
509 * @head: the head for your list.
510 * @member: the name of the list_head within the struct.
512 * Continue to iterate over list of given type, continuing after
513 * the current position.
515 #define list_for_each_entry_continue(pos, head, member) \
516 for (pos = list_next_entry(pos, member); \
517 &pos->member != (head); \
518 pos = list_next_entry(pos, member))
521 * list_for_each_entry_continue_reverse - iterate backwards from the given point
522 * @pos: the type * to use as a loop cursor.
523 * @head: the head for your list.
524 * @member: the name of the list_head within the struct.
526 * Start to iterate over list of given type backwards, continuing after
527 * the current position.
529 #define list_for_each_entry_continue_reverse(pos, head, member) \
530 for (pos = list_prev_entry(pos, member); \
531 &pos->member != (head); \
532 pos = list_prev_entry(pos, member))
535 * list_for_each_entry_from - iterate over list of given type from the current point
536 * @pos: the type * to use as a loop cursor.
537 * @head: the head for your list.
538 * @member: the name of the list_head within the struct.
540 * Iterate over list of given type, continuing from current position.
542 #define list_for_each_entry_from(pos, head, member) \
543 for (; &pos->member != (head); \
544 pos = list_next_entry(pos, member))
547 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
548 * @pos: the type * to use as a loop cursor.
549 * @n: another type * to use as temporary storage
550 * @head: the head for your list.
551 * @member: the name of the list_head within the struct.
553 #define list_for_each_entry_safe(pos, n, head, member) \
554 for (pos = list_first_entry(head, typeof(*pos), member), \
555 n = list_next_entry(pos, member); \
556 &pos->member != (head); \
557 pos = n, n = list_next_entry(n, member))
560 * list_for_each_entry_safe_continue - continue list iteration safe against removal
561 * @pos: the type * to use as a loop cursor.
562 * @n: another type * to use as temporary storage
563 * @head: the head for your list.
564 * @member: the name of the list_head within the struct.
566 * Iterate over list of given type, continuing after current point,
567 * safe against removal of list entry.
569 #define list_for_each_entry_safe_continue(pos, n, head, member) \
570 for (pos = list_next_entry(pos, member), \
571 n = list_next_entry(pos, member); \
572 &pos->member != (head); \
573 pos = n, n = list_next_entry(n, member))
576 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
577 * @pos: the type * to use as a loop cursor.
578 * @n: another type * to use as temporary storage
579 * @head: the head for your list.
580 * @member: the name of the list_head within the struct.
582 * Iterate over list of given type from current point, safe against
583 * removal of list entry.
585 #define list_for_each_entry_safe_from(pos, n, head, member) \
586 for (n = list_next_entry(pos, member); \
587 &pos->member != (head); \
588 pos = n, n = list_next_entry(n, member))
591 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
592 * @pos: the type * to use as a loop cursor.
593 * @n: another type * to use as temporary storage
594 * @head: the head for your list.
595 * @member: the name of the list_head within the struct.
597 * Iterate backwards over list of given type, safe against removal
600 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
601 for (pos = list_last_entry(head, typeof(*pos), member), \
602 n = list_prev_entry(pos, member); \
603 &pos->member != (head); \
604 pos = n, n = list_prev_entry(n, member))
607 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
608 * @pos: the loop cursor used in the list_for_each_entry_safe loop
609 * @n: temporary storage used in list_for_each_entry_safe
610 * @member: the name of the list_head within the struct.
612 * list_safe_reset_next is not safe to use in general if the list may be
613 * modified concurrently (eg. the lock is dropped in the loop body). An
614 * exception to this is if the cursor element (pos) is pinned in the list,
615 * and list_safe_reset_next is called after re-taking the lock and before
616 * completing the current iteration of the loop body.
618 #define list_safe_reset_next(pos, n, member) \
619 n = list_next_entry(pos, member)
622 * Double linked lists with a single pointer list head.
623 * Mostly useful for hash tables where the two pointer list head is
625 * You lose the ability to access the tail in O(1).
628 #define HLIST_HEAD_INIT { .first = NULL }
629 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
630 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
631 static inline void INIT_HLIST_NODE(struct hlist_node *h)
637 static inline int hlist_unhashed(const struct hlist_node *h)
642 static inline int hlist_empty(const struct hlist_head *h)
644 return !READ_ONCE(h->first);
647 static inline void __hlist_del(struct hlist_node *n)
649 struct hlist_node *next = n->next;
650 struct hlist_node **pprev = n->pprev;
652 WRITE_ONCE(*pprev, next);
657 static inline void hlist_del(struct hlist_node *n)
660 n->next = LIST_POISON1;
661 n->pprev = LIST_POISON2;
664 static inline void hlist_del_init(struct hlist_node *n)
666 if (!hlist_unhashed(n)) {
672 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
674 struct hlist_node *first = h->first;
677 first->pprev = &n->next;
678 WRITE_ONCE(h->first, n);
679 n->pprev = &h->first;
682 /* next must be != NULL */
683 static inline void hlist_add_before(struct hlist_node *n,
684 struct hlist_node *next)
686 n->pprev = next->pprev;
688 next->pprev = &n->next;
689 WRITE_ONCE(*(n->pprev), n);
692 static inline void hlist_add_behind(struct hlist_node *n,
693 struct hlist_node *prev)
695 n->next = prev->next;
696 WRITE_ONCE(prev->next, n);
697 n->pprev = &prev->next;
700 n->next->pprev = &n->next;
703 /* after that we'll appear to be on some hlist and hlist_del will work */
704 static inline void hlist_add_fake(struct hlist_node *n)
709 static inline bool hlist_fake(struct hlist_node *h)
711 return h->pprev == &h->next;
715 * Check whether the node is the only node of the head without
719 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
721 return !n->next && n->pprev == &h->first;
725 * Move a list from one list head to another. Fixup the pprev
726 * reference of the first entry if it exists.
728 static inline void hlist_move_list(struct hlist_head *old,
729 struct hlist_head *new)
731 new->first = old->first;
733 new->first->pprev = &new->first;
737 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
739 #define hlist_for_each(pos, head) \
740 for (pos = (head)->first; pos ; pos = pos->next)
742 #define hlist_for_each_safe(pos, n, head) \
743 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
746 #define hlist_entry_safe(ptr, type, member) \
747 ({ typeof(ptr) ____ptr = (ptr); \
748 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
752 * hlist_for_each_entry - iterate over list of given type
753 * @pos: the type * to use as a loop cursor.
754 * @head: the head for your list.
755 * @member: the name of the hlist_node within the struct.
757 #define hlist_for_each_entry(pos, head, member) \
758 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
760 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
763 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
764 * @pos: the type * to use as a loop cursor.
765 * @member: the name of the hlist_node within the struct.
767 #define hlist_for_each_entry_continue(pos, member) \
768 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
770 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
773 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
774 * @pos: the type * to use as a loop cursor.
775 * @member: the name of the hlist_node within the struct.
777 #define hlist_for_each_entry_from(pos, member) \
779 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
782 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
783 * @pos: the type * to use as a loop cursor.
784 * @n: another &struct hlist_node to use as temporary storage
785 * @head: the head for your list.
786 * @member: the name of the hlist_node within the struct.
788 #define hlist_for_each_entry_safe(pos, n, head, member) \
789 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
790 pos && ({ n = pos->member.next; 1; }); \
791 pos = hlist_entry_safe(n, typeof(*pos), member))