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);
274 static inline void __list_splice(const struct list_head *list,
275 struct list_head *prev,
276 struct list_head *next)
278 struct list_head *first = list->next;
279 struct list_head *last = list->prev;
289 * list_splice - join two lists, this is designed for stacks
290 * @list: the new list to add.
291 * @head: the place to add it in the first list.
293 static inline void list_splice(const struct list_head *list,
294 struct list_head *head)
296 if (!list_empty(list))
297 __list_splice(list, head, head->next);
301 * list_splice_tail - join two lists, each list being a queue
302 * @list: the new list to add.
303 * @head: the place to add it in the first list.
305 static inline void list_splice_tail(struct list_head *list,
306 struct list_head *head)
308 if (!list_empty(list))
309 __list_splice(list, head->prev, head);
313 * list_splice_init - join two lists and reinitialise the emptied list.
314 * @list: the new list to add.
315 * @head: the place to add it in the first list.
317 * The list at @list is reinitialised
319 static inline void list_splice_init(struct list_head *list,
320 struct list_head *head)
322 if (!list_empty(list)) {
323 __list_splice(list, head, head->next);
324 INIT_LIST_HEAD(list);
329 * list_splice_tail_init - join two lists and reinitialise the emptied list
330 * @list: the new list to add.
331 * @head: the place to add it in the first list.
333 * Each of the lists is a queue.
334 * The list at @list is reinitialised
336 static inline void list_splice_tail_init(struct list_head *list,
337 struct list_head *head)
339 if (!list_empty(list)) {
340 __list_splice(list, head->prev, head);
341 INIT_LIST_HEAD(list);
346 * list_entry - get the struct for this entry
347 * @ptr: the &struct list_head pointer.
348 * @type: the type of the struct this is embedded in.
349 * @member: the name of the list_head within the struct.
351 #define list_entry(ptr, type, member) \
352 container_of(ptr, type, member)
355 * list_first_entry - get the first element from a list
356 * @ptr: the list head to take the element from.
357 * @type: the type of the struct this is embedded in.
358 * @member: the name of the list_head within the struct.
360 * Note, that list is expected to be not empty.
362 #define list_first_entry(ptr, type, member) \
363 list_entry((ptr)->next, type, member)
366 * list_last_entry - get the last element from a list
367 * @ptr: the list head to take the element from.
368 * @type: the type of the struct this is embedded in.
369 * @member: the name of the list_head within the struct.
371 * Note, that list is expected to be not empty.
373 #define list_last_entry(ptr, type, member) \
374 list_entry((ptr)->prev, type, member)
377 * list_first_entry_or_null - get the first element from a list
378 * @ptr: the list head to take the element from.
379 * @type: the type of the struct this is embedded in.
380 * @member: the name of the list_head within the struct.
382 * Note that if the list is empty, it returns NULL.
384 #define list_first_entry_or_null(ptr, type, member) ({ \
385 struct list_head *head__ = (ptr); \
386 struct list_head *pos__ = READ_ONCE(head__->next); \
387 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
391 * list_next_entry - get the next element in list
392 * @pos: the type * to cursor
393 * @member: the name of the list_head within the struct.
395 #define list_next_entry(pos, member) \
396 list_entry((pos)->member.next, typeof(*(pos)), member)
399 * list_prev_entry - get the prev element in list
400 * @pos: the type * to cursor
401 * @member: the name of the list_head within the struct.
403 #define list_prev_entry(pos, member) \
404 list_entry((pos)->member.prev, typeof(*(pos)), member)
407 * list_for_each - iterate over a list
408 * @pos: the &struct list_head to use as a loop cursor.
409 * @head: the head for your list.
411 #define list_for_each(pos, head) \
412 for (pos = (head)->next; pos != (head); pos = pos->next)
415 * list_for_each_prev - iterate over a list backwards
416 * @pos: the &struct list_head to use as a loop cursor.
417 * @head: the head for your list.
419 #define list_for_each_prev(pos, head) \
420 for (pos = (head)->prev; pos != (head); pos = pos->prev)
423 * list_for_each_safe - iterate over a list safe against removal of list entry
424 * @pos: the &struct list_head to use as a loop cursor.
425 * @n: another &struct list_head to use as temporary storage
426 * @head: the head for your list.
428 #define list_for_each_safe(pos, n, head) \
429 for (pos = (head)->next, n = pos->next; pos != (head); \
430 pos = n, n = pos->next)
433 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
434 * @pos: the &struct list_head to use as a loop cursor.
435 * @n: another &struct list_head to use as temporary storage
436 * @head: the head for your list.
438 #define list_for_each_prev_safe(pos, n, head) \
439 for (pos = (head)->prev, n = pos->prev; \
441 pos = n, n = pos->prev)
444 * list_for_each_entry - iterate over list of given type
445 * @pos: the type * to use as a loop cursor.
446 * @head: the head for your list.
447 * @member: the name of the list_head within the struct.
449 #define list_for_each_entry(pos, head, member) \
450 for (pos = list_first_entry(head, typeof(*pos), member); \
451 &pos->member != (head); \
452 pos = list_next_entry(pos, member))
455 * list_for_each_entry_reverse - iterate backwards over list of given type.
456 * @pos: the type * to use as a loop cursor.
457 * @head: the head for your list.
458 * @member: the name of the list_head within the struct.
460 #define list_for_each_entry_reverse(pos, head, member) \
461 for (pos = list_last_entry(head, typeof(*pos), member); \
462 &pos->member != (head); \
463 pos = list_prev_entry(pos, member))
466 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
467 * @pos: the type * to use as a start point
468 * @head: the head of the list
469 * @member: the name of the list_head within the struct.
471 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
473 #define list_prepare_entry(pos, head, member) \
474 ((pos) ? : list_entry(head, typeof(*pos), member))
477 * list_for_each_entry_continue - continue iteration over list of given type
478 * @pos: the type * to use as a loop cursor.
479 * @head: the head for your list.
480 * @member: the name of the list_head within the struct.
482 * Continue to iterate over list of given type, continuing after
483 * the current position.
485 #define list_for_each_entry_continue(pos, head, member) \
486 for (pos = list_next_entry(pos, member); \
487 &pos->member != (head); \
488 pos = list_next_entry(pos, member))
491 * list_for_each_entry_continue_reverse - iterate backwards from the given point
492 * @pos: the type * to use as a loop cursor.
493 * @head: the head for your list.
494 * @member: the name of the list_head within the struct.
496 * Start to iterate over list of given type backwards, continuing after
497 * the current position.
499 #define list_for_each_entry_continue_reverse(pos, head, member) \
500 for (pos = list_prev_entry(pos, member); \
501 &pos->member != (head); \
502 pos = list_prev_entry(pos, member))
505 * list_for_each_entry_from - iterate over list of given type from the current point
506 * @pos: the type * to use as a loop cursor.
507 * @head: the head for your list.
508 * @member: the name of the list_head within the struct.
510 * Iterate over list of given type, continuing from current position.
512 #define list_for_each_entry_from(pos, head, member) \
513 for (; &pos->member != (head); \
514 pos = list_next_entry(pos, member))
517 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
518 * @pos: the type * to use as a loop cursor.
519 * @n: another type * to use as temporary storage
520 * @head: the head for your list.
521 * @member: the name of the list_head within the struct.
523 #define list_for_each_entry_safe(pos, n, head, member) \
524 for (pos = list_first_entry(head, typeof(*pos), member), \
525 n = list_next_entry(pos, member); \
526 &pos->member != (head); \
527 pos = n, n = list_next_entry(n, member))
530 * list_for_each_entry_safe_continue - continue list iteration safe against removal
531 * @pos: the type * to use as a loop cursor.
532 * @n: another type * to use as temporary storage
533 * @head: the head for your list.
534 * @member: the name of the list_head within the struct.
536 * Iterate over list of given type, continuing after current point,
537 * safe against removal of list entry.
539 #define list_for_each_entry_safe_continue(pos, n, head, member) \
540 for (pos = list_next_entry(pos, member), \
541 n = list_next_entry(pos, member); \
542 &pos->member != (head); \
543 pos = n, n = list_next_entry(n, member))
546 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
547 * @pos: the type * to use as a loop cursor.
548 * @n: another type * to use as temporary storage
549 * @head: the head for your list.
550 * @member: the name of the list_head within the struct.
552 * Iterate over list of given type from current point, safe against
553 * removal of list entry.
555 #define list_for_each_entry_safe_from(pos, n, head, member) \
556 for (n = list_next_entry(pos, member); \
557 &pos->member != (head); \
558 pos = n, n = list_next_entry(n, member))
561 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
562 * @pos: the type * to use as a loop cursor.
563 * @n: another type * to use as temporary storage
564 * @head: the head for your list.
565 * @member: the name of the list_head within the struct.
567 * Iterate backwards over list of given type, safe against removal
570 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
571 for (pos = list_last_entry(head, typeof(*pos), member), \
572 n = list_prev_entry(pos, member); \
573 &pos->member != (head); \
574 pos = n, n = list_prev_entry(n, member))
577 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
578 * @pos: the loop cursor used in the list_for_each_entry_safe loop
579 * @n: temporary storage used in list_for_each_entry_safe
580 * @member: the name of the list_head within the struct.
582 * list_safe_reset_next is not safe to use in general if the list may be
583 * modified concurrently (eg. the lock is dropped in the loop body). An
584 * exception to this is if the cursor element (pos) is pinned in the list,
585 * and list_safe_reset_next is called after re-taking the lock and before
586 * completing the current iteration of the loop body.
588 #define list_safe_reset_next(pos, n, member) \
589 n = list_next_entry(pos, member)
592 * Double linked lists with a single pointer list head.
593 * Mostly useful for hash tables where the two pointer list head is
595 * You lose the ability to access the tail in O(1).
598 #define HLIST_HEAD_INIT { .first = NULL }
599 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
600 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
601 static inline void INIT_HLIST_NODE(struct hlist_node *h)
607 static inline int hlist_unhashed(const struct hlist_node *h)
612 static inline int hlist_empty(const struct hlist_head *h)
614 return !READ_ONCE(h->first);
617 static inline void __hlist_del(struct hlist_node *n)
619 struct hlist_node *next = n->next;
620 struct hlist_node **pprev = n->pprev;
622 WRITE_ONCE(*pprev, next);
627 static inline void hlist_del(struct hlist_node *n)
630 n->next = LIST_POISON1;
631 n->pprev = LIST_POISON2;
634 static inline void hlist_del_init(struct hlist_node *n)
636 if (!hlist_unhashed(n)) {
642 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
644 struct hlist_node *first = h->first;
647 first->pprev = &n->next;
648 WRITE_ONCE(h->first, n);
649 n->pprev = &h->first;
652 /* next must be != NULL */
653 static inline void hlist_add_before(struct hlist_node *n,
654 struct hlist_node *next)
656 n->pprev = next->pprev;
658 next->pprev = &n->next;
659 WRITE_ONCE(*(n->pprev), n);
662 static inline void hlist_add_behind(struct hlist_node *n,
663 struct hlist_node *prev)
665 n->next = prev->next;
666 WRITE_ONCE(prev->next, n);
667 n->pprev = &prev->next;
670 n->next->pprev = &n->next;
673 /* after that we'll appear to be on some hlist and hlist_del will work */
674 static inline void hlist_add_fake(struct hlist_node *n)
679 static inline bool hlist_fake(struct hlist_node *h)
681 return h->pprev == &h->next;
685 * Check whether the node is the only node of the head without
689 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
691 return !n->next && n->pprev == &h->first;
695 * Move a list from one list head to another. Fixup the pprev
696 * reference of the first entry if it exists.
698 static inline void hlist_move_list(struct hlist_head *old,
699 struct hlist_head *new)
701 new->first = old->first;
703 new->first->pprev = &new->first;
707 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
709 #define hlist_for_each(pos, head) \
710 for (pos = (head)->first; pos ; pos = pos->next)
712 #define hlist_for_each_safe(pos, n, head) \
713 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
716 #define hlist_entry_safe(ptr, type, member) \
717 ({ typeof(ptr) ____ptr = (ptr); \
718 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
722 * hlist_for_each_entry - iterate over list of given type
723 * @pos: the type * to use as a loop cursor.
724 * @head: the head for your list.
725 * @member: the name of the hlist_node within the struct.
727 #define hlist_for_each_entry(pos, head, member) \
728 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
730 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
733 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
734 * @pos: the type * to use as a loop cursor.
735 * @member: the name of the hlist_node within the struct.
737 #define hlist_for_each_entry_continue(pos, member) \
738 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
740 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
743 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
744 * @pos: the type * to use as a loop cursor.
745 * @member: the name of the hlist_node within the struct.
747 #define hlist_for_each_entry_from(pos, member) \
749 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
752 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
753 * @pos: the type * to use as a loop cursor.
754 * @n: another &struct hlist_node to use as temporary storage
755 * @head: the head for your list.
756 * @member: the name of the hlist_node within the struct.
758 #define hlist_for_each_entry_safe(pos, n, head, member) \
759 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
760 pos && ({ n = pos->member.next; 1; }); \
761 pos = hlist_entry_safe(n, typeof(*pos), member))