1 /* SPDX-License-Identifier: GPL-2.0 */
5 #include <linux/container_of.h>
6 #include <linux/types.h>
7 #include <linux/stddef.h>
8 #include <linux/poison.h>
9 #include <linux/const.h>
11 #include <asm/barrier.h>
14 * Circular doubly linked list implementation.
16 * Some of the internal functions ("__xxx") are useful when
17 * manipulating whole lists rather than single entries, as
18 * sometimes we already know the next/prev entries and we can
19 * generate better code by using them directly rather than
20 * using the generic single-entry routines.
23 #define LIST_HEAD_INIT(name) { &(name), &(name) }
25 #define LIST_HEAD(name) \
26 struct list_head name = LIST_HEAD_INIT(name)
29 * INIT_LIST_HEAD - Initialize a list_head structure
30 * @list: list_head structure to be initialized.
32 * Initializes the list_head to point to itself. If it is a list header,
33 * the result is an empty list.
35 static inline void INIT_LIST_HEAD(struct list_head *list)
37 WRITE_ONCE(list->next, list);
38 WRITE_ONCE(list->prev, list);
41 #ifdef CONFIG_DEBUG_LIST
42 extern bool __list_add_valid(struct list_head *new,
43 struct list_head *prev,
44 struct list_head *next);
45 extern bool __list_del_entry_valid(struct list_head *entry);
47 static inline bool __list_add_valid(struct list_head *new,
48 struct list_head *prev,
49 struct list_head *next)
53 static inline bool __list_del_entry_valid(struct list_head *entry)
60 * Insert a new entry between two known consecutive entries.
62 * This is only for internal list manipulation where we know
63 * the prev/next entries already!
65 static inline void __list_add(struct list_head *new,
66 struct list_head *prev,
67 struct list_head *next)
69 if (!__list_add_valid(new, prev, next))
75 WRITE_ONCE(prev->next, new);
79 * list_add - add a new entry
80 * @new: new entry to be added
81 * @head: list head to add it after
83 * Insert a new entry after the specified head.
84 * This is good for implementing stacks.
86 static inline void list_add(struct list_head *new, struct list_head *head)
88 __list_add(new, head, head->next);
93 * list_add_tail - add a new entry
94 * @new: new entry to be added
95 * @head: list head to add it before
97 * Insert a new entry before the specified head.
98 * This is useful for implementing queues.
100 static inline void list_add_tail(struct list_head *new, struct list_head *head)
102 __list_add(new, head->prev, head);
106 * Delete a list entry by making the prev/next entries
107 * point to each other.
109 * This is only for internal list manipulation where we know
110 * the prev/next entries already!
112 static inline void __list_del(struct list_head * prev, struct list_head * next)
115 WRITE_ONCE(prev->next, next);
119 * Delete a list entry and clear the 'prev' pointer.
121 * This is a special-purpose list clearing method used in the networking code
122 * for lists allocated as per-cpu, where we don't want to incur the extra
123 * WRITE_ONCE() overhead of a regular list_del_init(). The code that uses this
124 * needs to check the node 'prev' pointer instead of calling list_empty().
126 static inline void __list_del_clearprev(struct list_head *entry)
128 __list_del(entry->prev, entry->next);
132 static inline void __list_del_entry(struct list_head *entry)
134 if (!__list_del_entry_valid(entry))
137 __list_del(entry->prev, entry->next);
141 * list_del - deletes entry from list.
142 * @entry: the element to delete from the list.
143 * Note: list_empty() on entry does not return true after this, the entry is
144 * in an undefined state.
146 static inline void list_del(struct list_head *entry)
148 __list_del_entry(entry);
149 entry->next = LIST_POISON1;
150 entry->prev = LIST_POISON2;
154 * list_replace - replace old entry by new one
155 * @old : the element to be replaced
156 * @new : the new element to insert
158 * If @old was empty, it will be overwritten.
160 static inline void list_replace(struct list_head *old,
161 struct list_head *new)
163 new->next = old->next;
164 new->next->prev = new;
165 new->prev = old->prev;
166 new->prev->next = new;
170 * list_replace_init - replace old entry by new one and initialize the old one
171 * @old : the element to be replaced
172 * @new : the new element to insert
174 * If @old was empty, it will be overwritten.
176 static inline void list_replace_init(struct list_head *old,
177 struct list_head *new)
179 list_replace(old, new);
184 * list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position
185 * @entry1: the location to place entry2
186 * @entry2: the location to place entry1
188 static inline void list_swap(struct list_head *entry1,
189 struct list_head *entry2)
191 struct list_head *pos = entry2->prev;
194 list_replace(entry1, entry2);
197 list_add(entry1, pos);
201 * list_del_init - deletes entry from list and reinitialize it.
202 * @entry: the element to delete from the list.
204 static inline void list_del_init(struct list_head *entry)
206 __list_del_entry(entry);
207 INIT_LIST_HEAD(entry);
211 * list_move - delete from one list and add as another's head
212 * @list: the entry to move
213 * @head: the head that will precede our entry
215 static inline void list_move(struct list_head *list, struct list_head *head)
217 __list_del_entry(list);
218 list_add(list, head);
222 * list_move_tail - delete from one list and add as another's tail
223 * @list: the entry to move
224 * @head: the head that will follow our entry
226 static inline void list_move_tail(struct list_head *list,
227 struct list_head *head)
229 __list_del_entry(list);
230 list_add_tail(list, head);
234 * list_bulk_move_tail - move a subsection of a list to its tail
235 * @head: the head that will follow our entry
236 * @first: first entry to move
237 * @last: last entry to move, can be the same as first
239 * Move all entries between @first and including @last before @head.
240 * All three entries must belong to the same linked list.
242 static inline void list_bulk_move_tail(struct list_head *head,
243 struct list_head *first,
244 struct list_head *last)
246 first->prev->next = last->next;
247 last->next->prev = first->prev;
249 head->prev->next = first;
250 first->prev = head->prev;
257 * list_is_first -- tests whether @list is the first entry in list @head
258 * @list: the entry to test
259 * @head: the head of the list
261 static inline int list_is_first(const struct list_head *list, const struct list_head *head)
263 return list->prev == head;
267 * list_is_last - tests whether @list is the last entry in list @head
268 * @list: the entry to test
269 * @head: the head of the list
271 static inline int list_is_last(const struct list_head *list, const struct list_head *head)
273 return list->next == head;
277 * list_is_head - tests whether @list is the list @head
278 * @list: the entry to test
279 * @head: the head of the list
281 static inline int list_is_head(const struct list_head *list, const struct list_head *head)
287 * list_empty - tests whether a list is empty
288 * @head: the list to test.
290 static inline int list_empty(const struct list_head *head)
292 return READ_ONCE(head->next) == head;
296 * list_del_init_careful - deletes entry from list and reinitialize it.
297 * @entry: the element to delete from the list.
299 * This is the same as list_del_init(), except designed to be used
300 * together with list_empty_careful() in a way to guarantee ordering
301 * of other memory operations.
303 * Any memory operations done before a list_del_init_careful() are
304 * guaranteed to be visible after a list_empty_careful() test.
306 static inline void list_del_init_careful(struct list_head *entry)
308 __list_del_entry(entry);
309 WRITE_ONCE(entry->prev, entry);
310 smp_store_release(&entry->next, entry);
314 * list_empty_careful - tests whether a list is empty and not being modified
315 * @head: the list to test
318 * tests whether a list is empty _and_ checks that no other CPU might be
319 * in the process of modifying either member (next or prev)
321 * NOTE: using list_empty_careful() without synchronization
322 * can only be safe if the only activity that can happen
323 * to the list entry is list_del_init(). Eg. it cannot be used
324 * if another CPU could re-list_add() it.
326 static inline int list_empty_careful(const struct list_head *head)
328 struct list_head *next = smp_load_acquire(&head->next);
329 return list_is_head(next, head) && (next == READ_ONCE(head->prev));
333 * list_rotate_left - rotate the list to the left
334 * @head: the head of the list
336 static inline void list_rotate_left(struct list_head *head)
338 struct list_head *first;
340 if (!list_empty(head)) {
342 list_move_tail(first, head);
347 * list_rotate_to_front() - Rotate list to specific item.
348 * @list: The desired new front of the list.
349 * @head: The head of the list.
351 * Rotates list so that @list becomes the new front of the list.
353 static inline void list_rotate_to_front(struct list_head *list,
354 struct list_head *head)
357 * Deletes the list head from the list denoted by @head and
358 * places it as the tail of @list, this effectively rotates the
359 * list so that @list is at the front.
361 list_move_tail(head, list);
365 * list_is_singular - tests whether a list has just one entry.
366 * @head: the list to test.
368 static inline int list_is_singular(const struct list_head *head)
370 return !list_empty(head) && (head->next == head->prev);
373 static inline void __list_cut_position(struct list_head *list,
374 struct list_head *head, struct list_head *entry)
376 struct list_head *new_first = entry->next;
377 list->next = head->next;
378 list->next->prev = list;
381 head->next = new_first;
382 new_first->prev = head;
386 * list_cut_position - cut a list into two
387 * @list: a new list to add all removed entries
388 * @head: a list with entries
389 * @entry: an entry within head, could be the head itself
390 * and if so we won't cut the list
392 * This helper moves the initial part of @head, up to and
393 * including @entry, from @head to @list. You should
394 * pass on @entry an element you know is on @head. @list
395 * should be an empty list or a list you do not care about
399 static inline void list_cut_position(struct list_head *list,
400 struct list_head *head, struct list_head *entry)
402 if (list_empty(head))
404 if (list_is_singular(head) && !list_is_head(entry, head) && (entry != head->next))
406 if (list_is_head(entry, head))
407 INIT_LIST_HEAD(list);
409 __list_cut_position(list, head, entry);
413 * list_cut_before - cut a list into two, before given entry
414 * @list: a new list to add all removed entries
415 * @head: a list with entries
416 * @entry: an entry within head, could be the head itself
418 * This helper moves the initial part of @head, up to but
419 * excluding @entry, from @head to @list. You should pass
420 * in @entry an element you know is on @head. @list should
421 * be an empty list or a list you do not care about losing
423 * If @entry == @head, all entries on @head are moved to
426 static inline void list_cut_before(struct list_head *list,
427 struct list_head *head,
428 struct list_head *entry)
430 if (head->next == entry) {
431 INIT_LIST_HEAD(list);
434 list->next = head->next;
435 list->next->prev = list;
436 list->prev = entry->prev;
437 list->prev->next = list;
442 static inline void __list_splice(const struct list_head *list,
443 struct list_head *prev,
444 struct list_head *next)
446 struct list_head *first = list->next;
447 struct list_head *last = list->prev;
457 * list_splice - join two lists, this is designed for stacks
458 * @list: the new list to add.
459 * @head: the place to add it in the first list.
461 static inline void list_splice(const struct list_head *list,
462 struct list_head *head)
464 if (!list_empty(list))
465 __list_splice(list, head, head->next);
469 * list_splice_tail - join two lists, each list being a queue
470 * @list: the new list to add.
471 * @head: the place to add it in the first list.
473 static inline void list_splice_tail(struct list_head *list,
474 struct list_head *head)
476 if (!list_empty(list))
477 __list_splice(list, head->prev, head);
481 * list_splice_init - join two lists and reinitialise the emptied list.
482 * @list: the new list to add.
483 * @head: the place to add it in the first list.
485 * The list at @list is reinitialised
487 static inline void list_splice_init(struct list_head *list,
488 struct list_head *head)
490 if (!list_empty(list)) {
491 __list_splice(list, head, head->next);
492 INIT_LIST_HEAD(list);
497 * list_splice_tail_init - join two lists and reinitialise the emptied list
498 * @list: the new list to add.
499 * @head: the place to add it in the first list.
501 * Each of the lists is a queue.
502 * The list at @list is reinitialised
504 static inline void list_splice_tail_init(struct list_head *list,
505 struct list_head *head)
507 if (!list_empty(list)) {
508 __list_splice(list, head->prev, head);
509 INIT_LIST_HEAD(list);
514 * list_entry - get the struct for this entry
515 * @ptr: the &struct list_head pointer.
516 * @type: the type of the struct this is embedded in.
517 * @member: the name of the list_head within the struct.
519 #define list_entry(ptr, type, member) \
520 container_of(ptr, type, member)
523 * list_first_entry - get the first element from a list
524 * @ptr: the list head to take the element from.
525 * @type: the type of the struct this is embedded in.
526 * @member: the name of the list_head within the struct.
528 * Note, that list is expected to be not empty.
530 #define list_first_entry(ptr, type, member) \
531 list_entry((ptr)->next, type, member)
534 * list_last_entry - get the last element from a list
535 * @ptr: the list head to take the element from.
536 * @type: the type of the struct this is embedded in.
537 * @member: the name of the list_head within the struct.
539 * Note, that list is expected to be not empty.
541 #define list_last_entry(ptr, type, member) \
542 list_entry((ptr)->prev, type, member)
545 * list_first_entry_or_null - get the first element from a list
546 * @ptr: the list head to take the element from.
547 * @type: the type of the struct this is embedded in.
548 * @member: the name of the list_head within the struct.
550 * Note that if the list is empty, it returns NULL.
552 #define list_first_entry_or_null(ptr, type, member) ({ \
553 struct list_head *head__ = (ptr); \
554 struct list_head *pos__ = READ_ONCE(head__->next); \
555 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
559 * list_next_entry - get the next element in list
560 * @pos: the type * to cursor
561 * @member: the name of the list_head within the struct.
563 #define list_next_entry(pos, member) \
564 list_entry((pos)->member.next, typeof(*(pos)), member)
567 * list_next_entry_circular - get the next element in list
568 * @pos: the type * to cursor.
569 * @head: the list head to take the element from.
570 * @member: the name of the list_head within the struct.
572 * Wraparound if pos is the last element (return the first element).
573 * Note, that list is expected to be not empty.
575 #define list_next_entry_circular(pos, head, member) \
576 (list_is_last(&(pos)->member, head) ? \
577 list_first_entry(head, typeof(*(pos)), member) : list_next_entry(pos, member))
580 * list_prev_entry - get the prev element in list
581 * @pos: the type * to cursor
582 * @member: the name of the list_head within the struct.
584 #define list_prev_entry(pos, member) \
585 list_entry((pos)->member.prev, typeof(*(pos)), member)
588 * list_prev_entry_circular - get the prev element in list
589 * @pos: the type * to cursor.
590 * @head: the list head to take the element from.
591 * @member: the name of the list_head within the struct.
593 * Wraparound if pos is the first element (return the last element).
594 * Note, that list is expected to be not empty.
596 #define list_prev_entry_circular(pos, head, member) \
597 (list_is_first(&(pos)->member, head) ? \
598 list_last_entry(head, typeof(*(pos)), member) : list_prev_entry(pos, member))
601 * list_for_each - iterate over a list
602 * @pos: the &struct list_head to use as a loop cursor.
603 * @head: the head for your list.
605 #define list_for_each(pos, head) \
606 for (pos = (head)->next; !list_is_head(pos, (head)); pos = pos->next)
609 * list_for_each_rcu - Iterate over a list in an RCU-safe fashion
610 * @pos: the &struct list_head to use as a loop cursor.
611 * @head: the head for your list.
613 #define list_for_each_rcu(pos, head) \
614 for (pos = rcu_dereference((head)->next); \
615 !list_is_head(pos, (head)); \
616 pos = rcu_dereference(pos->next))
619 * list_for_each_continue - continue iteration over a list
620 * @pos: the &struct list_head to use as a loop cursor.
621 * @head: the head for your list.
623 * Continue to iterate over a list, continuing after the current position.
625 #define list_for_each_continue(pos, head) \
626 for (pos = pos->next; !list_is_head(pos, (head)); pos = pos->next)
629 * list_for_each_prev - iterate over a list backwards
630 * @pos: the &struct list_head to use as a loop cursor.
631 * @head: the head for your list.
633 #define list_for_each_prev(pos, head) \
634 for (pos = (head)->prev; !list_is_head(pos, (head)); pos = pos->prev)
637 * list_for_each_safe - iterate over a list safe against removal of list entry
638 * @pos: the &struct list_head to use as a loop cursor.
639 * @n: another &struct list_head to use as temporary storage
640 * @head: the head for your list.
642 #define list_for_each_safe(pos, n, head) \
643 for (pos = (head)->next, n = pos->next; \
644 !list_is_head(pos, (head)); \
645 pos = n, n = pos->next)
648 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
649 * @pos: the &struct list_head to use as a loop cursor.
650 * @n: another &struct list_head to use as temporary storage
651 * @head: the head for your list.
653 #define list_for_each_prev_safe(pos, n, head) \
654 for (pos = (head)->prev, n = pos->prev; \
655 !list_is_head(pos, (head)); \
656 pos = n, n = pos->prev)
659 * list_count_nodes - count nodes in the list
660 * @head: the head for your list.
662 static inline size_t list_count_nodes(struct list_head *head)
664 struct list_head *pos;
667 list_for_each(pos, head)
674 * list_entry_is_head - test if the entry points to the head of the list
675 * @pos: the type * to cursor
676 * @head: the head for your list.
677 * @member: the name of the list_head within the struct.
679 #define list_entry_is_head(pos, head, member) \
680 (&pos->member == (head))
683 * list_for_each_entry - iterate over list of given type
684 * @pos: the type * to use as a loop cursor.
685 * @head: the head for your list.
686 * @member: the name of the list_head within the struct.
688 #define list_for_each_entry(pos, head, member) \
689 for (pos = list_first_entry(head, typeof(*pos), member); \
690 !list_entry_is_head(pos, head, member); \
691 pos = list_next_entry(pos, member))
694 * list_for_each_entry_reverse - iterate backwards over list of given type.
695 * @pos: the type * to use as a loop cursor.
696 * @head: the head for your list.
697 * @member: the name of the list_head within the struct.
699 #define list_for_each_entry_reverse(pos, head, member) \
700 for (pos = list_last_entry(head, typeof(*pos), member); \
701 !list_entry_is_head(pos, head, member); \
702 pos = list_prev_entry(pos, member))
705 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
706 * @pos: the type * to use as a start point
707 * @head: the head of the list
708 * @member: the name of the list_head within the struct.
710 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
712 #define list_prepare_entry(pos, head, member) \
713 ((pos) ? : list_entry(head, typeof(*pos), member))
716 * list_for_each_entry_continue - continue iteration over list of given type
717 * @pos: the type * to use as a loop cursor.
718 * @head: the head for your list.
719 * @member: the name of the list_head within the struct.
721 * Continue to iterate over list of given type, continuing after
722 * the current position.
724 #define list_for_each_entry_continue(pos, head, member) \
725 for (pos = list_next_entry(pos, member); \
726 !list_entry_is_head(pos, head, member); \
727 pos = list_next_entry(pos, member))
730 * list_for_each_entry_continue_reverse - iterate backwards from the given point
731 * @pos: the type * to use as a loop cursor.
732 * @head: the head for your list.
733 * @member: the name of the list_head within the struct.
735 * Start to iterate over list of given type backwards, continuing after
736 * the current position.
738 #define list_for_each_entry_continue_reverse(pos, head, member) \
739 for (pos = list_prev_entry(pos, member); \
740 !list_entry_is_head(pos, head, member); \
741 pos = list_prev_entry(pos, member))
744 * list_for_each_entry_from - iterate over list of given type from the current point
745 * @pos: the type * to use as a loop cursor.
746 * @head: the head for your list.
747 * @member: the name of the list_head within the struct.
749 * Iterate over list of given type, continuing from current position.
751 #define list_for_each_entry_from(pos, head, member) \
752 for (; !list_entry_is_head(pos, head, member); \
753 pos = list_next_entry(pos, member))
756 * list_for_each_entry_from_reverse - iterate backwards over list of given type
757 * from the current point
758 * @pos: the type * to use as a loop cursor.
759 * @head: the head for your list.
760 * @member: the name of the list_head within the struct.
762 * Iterate backwards over list of given type, continuing from current position.
764 #define list_for_each_entry_from_reverse(pos, head, member) \
765 for (; !list_entry_is_head(pos, head, member); \
766 pos = list_prev_entry(pos, member))
769 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
770 * @pos: the type * to use as a loop cursor.
771 * @n: another type * to use as temporary storage
772 * @head: the head for your list.
773 * @member: the name of the list_head within the struct.
775 #define list_for_each_entry_safe(pos, n, head, member) \
776 for (pos = list_first_entry(head, typeof(*pos), member), \
777 n = list_next_entry(pos, member); \
778 !list_entry_is_head(pos, head, member); \
779 pos = n, n = list_next_entry(n, member))
782 * list_for_each_entry_safe_continue - continue list iteration safe against removal
783 * @pos: the type * to use as a loop cursor.
784 * @n: another type * to use as temporary storage
785 * @head: the head for your list.
786 * @member: the name of the list_head within the struct.
788 * Iterate over list of given type, continuing after current point,
789 * safe against removal of list entry.
791 #define list_for_each_entry_safe_continue(pos, n, head, member) \
792 for (pos = list_next_entry(pos, member), \
793 n = list_next_entry(pos, member); \
794 !list_entry_is_head(pos, head, member); \
795 pos = n, n = list_next_entry(n, member))
798 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
799 * @pos: the type * to use as a loop cursor.
800 * @n: another type * to use as temporary storage
801 * @head: the head for your list.
802 * @member: the name of the list_head within the struct.
804 * Iterate over list of given type from current point, safe against
805 * removal of list entry.
807 #define list_for_each_entry_safe_from(pos, n, head, member) \
808 for (n = list_next_entry(pos, member); \
809 !list_entry_is_head(pos, head, member); \
810 pos = n, n = list_next_entry(n, member))
813 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
814 * @pos: the type * to use as a loop cursor.
815 * @n: another type * to use as temporary storage
816 * @head: the head for your list.
817 * @member: the name of the list_head within the struct.
819 * Iterate backwards over list of given type, safe against removal
822 #define list_for_each_entry_safe_reverse(pos, n, head, member) \
823 for (pos = list_last_entry(head, typeof(*pos), member), \
824 n = list_prev_entry(pos, member); \
825 !list_entry_is_head(pos, head, member); \
826 pos = n, n = list_prev_entry(n, member))
829 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
830 * @pos: the loop cursor used in the list_for_each_entry_safe loop
831 * @n: temporary storage used in list_for_each_entry_safe
832 * @member: the name of the list_head within the struct.
834 * list_safe_reset_next is not safe to use in general if the list may be
835 * modified concurrently (eg. the lock is dropped in the loop body). An
836 * exception to this is if the cursor element (pos) is pinned in the list,
837 * and list_safe_reset_next is called after re-taking the lock and before
838 * completing the current iteration of the loop body.
840 #define list_safe_reset_next(pos, n, member) \
841 n = list_next_entry(pos, member)
844 * Double linked lists with a single pointer list head.
845 * Mostly useful for hash tables where the two pointer list head is
847 * You lose the ability to access the tail in O(1).
850 #define HLIST_HEAD_INIT { .first = NULL }
851 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
852 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
853 static inline void INIT_HLIST_NODE(struct hlist_node *h)
860 * hlist_unhashed - Has node been removed from list and reinitialized?
861 * @h: Node to be checked
863 * Not that not all removal functions will leave a node in unhashed
864 * state. For example, hlist_nulls_del_init_rcu() does leave the
865 * node in unhashed state, but hlist_nulls_del() does not.
867 static inline int hlist_unhashed(const struct hlist_node *h)
873 * hlist_unhashed_lockless - Version of hlist_unhashed for lockless use
874 * @h: Node to be checked
876 * This variant of hlist_unhashed() must be used in lockless contexts
877 * to avoid potential load-tearing. The READ_ONCE() is paired with the
878 * various WRITE_ONCE() in hlist helpers that are defined below.
880 static inline int hlist_unhashed_lockless(const struct hlist_node *h)
882 return !READ_ONCE(h->pprev);
886 * hlist_empty - Is the specified hlist_head structure an empty hlist?
887 * @h: Structure to check.
889 static inline int hlist_empty(const struct hlist_head *h)
891 return !READ_ONCE(h->first);
894 static inline void __hlist_del(struct hlist_node *n)
896 struct hlist_node *next = n->next;
897 struct hlist_node **pprev = n->pprev;
899 WRITE_ONCE(*pprev, next);
901 WRITE_ONCE(next->pprev, pprev);
905 * hlist_del - Delete the specified hlist_node from its list
906 * @n: Node to delete.
908 * Note that this function leaves the node in hashed state. Use
909 * hlist_del_init() or similar instead to unhash @n.
911 static inline void hlist_del(struct hlist_node *n)
914 n->next = LIST_POISON1;
915 n->pprev = LIST_POISON2;
919 * hlist_del_init - Delete the specified hlist_node from its list and initialize
920 * @n: Node to delete.
922 * Note that this function leaves the node in unhashed state.
924 static inline void hlist_del_init(struct hlist_node *n)
926 if (!hlist_unhashed(n)) {
933 * hlist_add_head - add a new entry at the beginning of the hlist
934 * @n: new entry to be added
935 * @h: hlist head to add it after
937 * Insert a new entry after the specified head.
938 * This is good for implementing stacks.
940 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
942 struct hlist_node *first = h->first;
943 WRITE_ONCE(n->next, first);
945 WRITE_ONCE(first->pprev, &n->next);
946 WRITE_ONCE(h->first, n);
947 WRITE_ONCE(n->pprev, &h->first);
951 * hlist_add_before - add a new entry before the one specified
952 * @n: new entry to be added
953 * @next: hlist node to add it before, which must be non-NULL
955 static inline void hlist_add_before(struct hlist_node *n,
956 struct hlist_node *next)
958 WRITE_ONCE(n->pprev, next->pprev);
959 WRITE_ONCE(n->next, next);
960 WRITE_ONCE(next->pprev, &n->next);
961 WRITE_ONCE(*(n->pprev), n);
965 * hlist_add_behind - add a new entry after the one specified
966 * @n: new entry to be added
967 * @prev: hlist node to add it after, which must be non-NULL
969 static inline void hlist_add_behind(struct hlist_node *n,
970 struct hlist_node *prev)
972 WRITE_ONCE(n->next, prev->next);
973 WRITE_ONCE(prev->next, n);
974 WRITE_ONCE(n->pprev, &prev->next);
977 WRITE_ONCE(n->next->pprev, &n->next);
981 * hlist_add_fake - create a fake hlist consisting of a single headless node
982 * @n: Node to make a fake list out of
984 * This makes @n appear to be its own predecessor on a headless hlist.
985 * The point of this is to allow things like hlist_del() to work correctly
986 * in cases where there is no list.
988 static inline void hlist_add_fake(struct hlist_node *n)
994 * hlist_fake: Is this node a fake hlist?
995 * @h: Node to check for being a self-referential fake hlist.
997 static inline bool hlist_fake(struct hlist_node *h)
999 return h->pprev == &h->next;
1003 * hlist_is_singular_node - is node the only element of the specified hlist?
1004 * @n: Node to check for singularity.
1005 * @h: Header for potentially singular list.
1007 * Check whether the node is the only node of the head without
1008 * accessing head, thus avoiding unnecessary cache misses.
1011 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
1013 return !n->next && n->pprev == &h->first;
1017 * hlist_move_list - Move an hlist
1018 * @old: hlist_head for old list.
1019 * @new: hlist_head for new list.
1021 * Move a list from one list head to another. Fixup the pprev
1022 * reference of the first entry if it exists.
1024 static inline void hlist_move_list(struct hlist_head *old,
1025 struct hlist_head *new)
1027 new->first = old->first;
1029 new->first->pprev = &new->first;
1033 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
1035 #define hlist_for_each(pos, head) \
1036 for (pos = (head)->first; pos ; pos = pos->next)
1038 #define hlist_for_each_safe(pos, n, head) \
1039 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
1042 #define hlist_entry_safe(ptr, type, member) \
1043 ({ typeof(ptr) ____ptr = (ptr); \
1044 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
1048 * hlist_for_each_entry - iterate over list of given type
1049 * @pos: the type * to use as a loop cursor.
1050 * @head: the head for your list.
1051 * @member: the name of the hlist_node within the struct.
1053 #define hlist_for_each_entry(pos, head, member) \
1054 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
1056 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
1059 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
1060 * @pos: the type * to use as a loop cursor.
1061 * @member: the name of the hlist_node within the struct.
1063 #define hlist_for_each_entry_continue(pos, member) \
1064 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
1066 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
1069 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
1070 * @pos: the type * to use as a loop cursor.
1071 * @member: the name of the hlist_node within the struct.
1073 #define hlist_for_each_entry_from(pos, member) \
1075 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
1078 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
1079 * @pos: the type * to use as a loop cursor.
1080 * @n: a &struct hlist_node to use as temporary storage
1081 * @head: the head for your list.
1082 * @member: the name of the hlist_node within the struct.
1084 #define hlist_for_each_entry_safe(pos, n, head, member) \
1085 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
1086 pos && ({ n = pos->member.next; 1; }); \
1087 pos = hlist_entry_safe(n, typeof(*pos), member))