1#ifndef _LINUX_LIST_H
2#define _LINUX_LIST_H
3
4#include <linux/stddef.h>
5#include <linux/poison.h>
6
7#ifndef ARCH_HAS_PREFETCH
8#define ARCH_HAS_PREFETCH
9static inline void prefetch(const void *x) {;}
10#endif
11
12/*
13 * Simple doubly linked list implementation.
14 *
15 * Some of the internal functions ("__xxx") are useful when
16 * manipulating whole lists rather than single entries, as
17 * sometimes we already know the next/prev entries and we can
18 * generate better code by using them directly rather than
19 * using the generic single-entry routines.
20 */
21
22struct list_head {
23	struct list_head *next, *prev;
24};
25
26#define LIST_HEAD_INIT(name) { &(name), &(name) }
27
28#define LIST_HEAD(name) \
29	struct list_head name = LIST_HEAD_INIT(name)
30
31static inline void INIT_LIST_HEAD(struct list_head *list)
32{
33	list->next = list;
34	list->prev = list;
35}
36
37/*
38 * Insert a new entry between two known consecutive entries.
39 *
40 * This is only for internal list manipulation where we know
41 * the prev/next entries already!
42 */
43static inline void __list_add(struct list_head *new,
44			      struct list_head *prev,
45			      struct list_head *next)
46{
47	next->prev = new;
48	new->next = next;
49	new->prev = prev;
50	prev->next = new;
51}
52
53/**
54 * list_add - add a new entry
55 * @new: new entry to be added
56 * @head: list head to add it after
57 *
58 * Insert a new entry after the specified head.
59 * This is good for implementing stacks.
60 */
61static inline void list_add(struct list_head *new, struct list_head *head)
62{
63	__list_add(new, head, head->next);
64}
65
66/**
67 * list_add_tail - add a new entry
68 * @new: new entry to be added
69 * @head: list head to add it before
70 *
71 * Insert a new entry before the specified head.
72 * This is useful for implementing queues.
73 */
74static inline void list_add_tail(struct list_head *new, struct list_head *head)
75{
76	__list_add(new, head->prev, head);
77}
78
79/*
80 * Delete a list entry by making the prev/next entries
81 * point to each other.
82 *
83 * This is only for internal list manipulation where we know
84 * the prev/next entries already!
85 */
86static inline void __list_del(struct list_head *prev, struct list_head *next)
87{
88	next->prev = prev;
89	prev->next = next;
90}
91
92/**
93 * list_del - deletes entry from list.
94 * @entry: the element to delete from the list.
95 * Note: list_empty() on entry does not return true after this, the entry is
96 * in an undefined state.
97 */
98static inline void list_del(struct list_head *entry)
99{
100	__list_del(entry->prev, entry->next);
101	entry->next = LIST_POISON1;
102	entry->prev = LIST_POISON2;
103}
104
105/**
106 * list_replace - replace old entry by new one
107 * @old : the element to be replaced
108 * @new : the new element to insert
109 *
110 * If @old was empty, it will be overwritten.
111 */
112static inline void list_replace(struct list_head *old,
113				struct list_head *new)
114{
115	new->next = old->next;
116	new->next->prev = new;
117	new->prev = old->prev;
118	new->prev->next = new;
119}
120
121static inline void list_replace_init(struct list_head *old,
122					struct list_head *new)
123{
124	list_replace(old, new);
125	INIT_LIST_HEAD(old);
126}
127
128/**
129 * list_del_init - deletes entry from list and reinitialize it.
130 * @entry: the element to delete from the list.
131 */
132static inline void list_del_init(struct list_head *entry)
133{
134	__list_del(entry->prev, entry->next);
135	INIT_LIST_HEAD(entry);
136}
137
138/**
139 * list_move - delete from one list and add as another's head
140 * @list: the entry to move
141 * @head: the head that will precede our entry
142 */
143static inline void list_move(struct list_head *list, struct list_head *head)
144{
145	__list_del(list->prev, list->next);
146	list_add(list, head);
147}
148
149/**
150 * list_move_tail - delete from one list and add as another's tail
151 * @list: the entry to move
152 * @head: the head that will follow our entry
153 */
154static inline void list_move_tail(struct list_head *list,
155				  struct list_head *head)
156{
157	__list_del(list->prev, list->next);
158	list_add_tail(list, head);
159}
160
161/**
162 * list_is_last - tests whether @list is the last entry in list @head
163 * @list: the entry to test
164 * @head: the head of the list
165 */
166static inline int list_is_last(const struct list_head *list,
167				const struct list_head *head)
168{
169	return list->next == head;
170}
171
172/**
173 * list_empty - tests whether a list is empty
174 * @head: the list to test.
175 */
176static inline int list_empty(const struct list_head *head)
177{
178	return head->next == head;
179}
180
181/**
182 * list_empty_careful - tests whether a list is empty and not being modified
183 * @head: the list to test
184 *
185 * Description:
186 * tests whether a list is empty _and_ checks that no other CPU might be
187 * in the process of modifying either member (next or prev)
188 *
189 * NOTE: using list_empty_careful() without synchronization
190 * can only be safe if the only activity that can happen
191 * to the list entry is list_del_init(). Eg. it cannot be used
192 * if another CPU could re-list_add() it.
193 */
194static inline int list_empty_careful(const struct list_head *head)
195{
196	struct list_head *next = head->next;
197	return (next == head) && (next == head->prev);
198}
199
200/**
201 * list_is_singular - tests whether a list has just one entry.
202 * @head: the list to test.
203 */
204static inline int list_is_singular(const struct list_head *head)
205{
206	return !list_empty(head) && (head->next == head->prev);
207}
208
209static inline void __list_cut_position(struct list_head *list,
210		struct list_head *head, struct list_head *entry)
211{
212	struct list_head *new_first = entry->next;
213	list->next = head->next;
214	list->next->prev = list;
215	list->prev = entry;
216	entry->next = list;
217	head->next = new_first;
218	new_first->prev = head;
219}
220
221/**
222 * list_cut_position - cut a list into two
223 * @list: a new list to add all removed entries
224 * @head: a list with entries
225 * @entry: an entry within head, could be the head itself
226 *	and if so we won't cut the list
227 *
228 * This helper moves the initial part of @head, up to and
229 * including @entry, from @head to @list. You should
230 * pass on @entry an element you know is on @head. @list
231 * should be an empty list or a list you do not care about
232 * losing its data.
233 *
234 */
235static inline void list_cut_position(struct list_head *list,
236		struct list_head *head, struct list_head *entry)
237{
238	if (list_empty(head))
239		return;
240	if (list_is_singular(head) &&
241		(head->next != entry && head != entry))
242		return;
243	if (entry == head)
244		INIT_LIST_HEAD(list);
245	else
246		__list_cut_position(list, head, entry);
247}
248
249static inline void __list_splice(const struct list_head *list,
250				 struct list_head *prev,
251				 struct list_head *next)
252{
253	struct list_head *first = list->next;
254	struct list_head *last = list->prev;
255
256	first->prev = prev;
257	prev->next = first;
258
259	last->next = next;
260	next->prev = last;
261}
262
263/**
264 * list_splice - join two lists, this is designed for stacks
265 * @list: the new list to add.
266 * @head: the place to add it in the first list.
267 */
268static inline void list_splice(const struct list_head *list,
269				struct list_head *head)
270{
271	if (!list_empty(list))
272		__list_splice(list, head, head->next);
273}
274
275/**
276 * list_splice_tail - join two lists, each list being a queue
277 * @list: the new list to add.
278 * @head: the place to add it in the first list.
279 */
280static inline void list_splice_tail(struct list_head *list,
281				struct list_head *head)
282{
283	if (!list_empty(list))
284		__list_splice(list, head->prev, head);
285}
286
287/**
288 * list_splice_init - join two lists and reinitialise the emptied list.
289 * @list: the new list to add.
290 * @head: the place to add it in the first list.
291 *
292 * The list at @list is reinitialised
293 */
294static inline void list_splice_init(struct list_head *list,
295				    struct list_head *head)
296{
297	if (!list_empty(list)) {
298		__list_splice(list, head, head->next);
299		INIT_LIST_HEAD(list);
300	}
301}
302
303/**
304 * list_splice_tail_init - join two lists and reinitialise the emptied list
305 * @list: the new list to add.
306 * @head: the place to add it in the first list.
307 *
308 * Each of the lists is a queue.
309 * The list at @list is reinitialised
310 */
311static inline void list_splice_tail_init(struct list_head *list,
312					 struct list_head *head)
313{
314	if (!list_empty(list)) {
315		__list_splice(list, head->prev, head);
316		INIT_LIST_HEAD(list);
317	}
318}
319
320/**
321 * list_entry - get the struct for this entry
322 * @ptr:	the &struct list_head pointer.
323 * @type:	the type of the struct this is embedded in.
324 * @member:	the name of the list_struct within the struct.
325 */
326#define list_entry(ptr, type, member) \
327	container_of(ptr, type, member)
328
329/**
330 * list_first_entry - get the first element from a list
331 * @ptr:	the list head to take the element from.
332 * @type:	the type of the struct this is embedded in.
333 * @member:	the name of the list_struct within the struct.
334 *
335 * Note, that list is expected to be not empty.
336 */
337#define list_first_entry(ptr, type, member) \
338	list_entry((ptr)->next, type, member)
339
340/**
341 * list_last_entry - get the last element from a list
342 * @ptr:	the list head to take the element from.
343 * @type:	the type of the struct this is embedded in.
344 * @member:	the name of the list_struct within the struct.
345 *
346 * Note, that list is expected to be not empty.
347 */
348#define list_last_entry(ptr, type, member) \
349	list_entry((ptr)->prev, type, member)
350
351/**
352 * list_first_entry_or_null - get the first element from a list
353 * @ptr:	the list head to take the element from.
354 * @type:	the type of the struct this is embedded in.
355 * @member:	the name of the list_head within the struct.
356 *
357 * Note that if the list is empty, it returns NULL.
358 */
359#define list_first_entry_or_null(ptr, type, member) ({ \
360	struct list_head *head__ = (ptr); \
361	struct list_head *pos__ = READ_ONCE(head__->next); \
362	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
363})
364
365/**
366 * list_for_each	-	iterate over a list
367 * @pos:	the &struct list_head to use as a loop cursor.
368 * @head:	the head for your list.
369 */
370#define list_for_each(pos, head) \
371	for (pos = (head)->next; prefetch(pos->next), pos != (head); \
372		pos = pos->next)
373
374/**
375 * __list_for_each	-	iterate over a list
376 * @pos:	the &struct list_head to use as a loop cursor.
377 * @head:	the head for your list.
378 *
379 * This variant differs from list_for_each() in that it's the
380 * simplest possible list iteration code, no prefetching is done.
381 * Use this for code that knows the list to be very short (empty
382 * or 1 entry) most of the time.
383 */
384#define __list_for_each(pos, head) \
385	for (pos = (head)->next; pos != (head); pos = pos->next)
386
387/**
388 * list_for_each_prev	-	iterate over a list backwards
389 * @pos:	the &struct list_head to use as a loop cursor.
390 * @head:	the head for your list.
391 */
392#define list_for_each_prev(pos, head) \
393	for (pos = (head)->prev; prefetch(pos->prev), pos != (head); \
394		pos = pos->prev)
395
396/**
397 * list_for_each_safe - iterate over a list safe against removal of list entry
398 * @pos:	the &struct list_head to use as a loop cursor.
399 * @n:		another &struct list_head to use as temporary storage
400 * @head:	the head for your list.
401 */
402#define list_for_each_safe(pos, n, head) \
403	for (pos = (head)->next, n = pos->next; pos != (head); \
404		pos = n, n = pos->next)
405
406/**
407 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
408 * @pos:	the &struct list_head to use as a loop cursor.
409 * @n:		another &struct list_head to use as temporary storage
410 * @head:	the head for your list.
411 */
412#define list_for_each_prev_safe(pos, n, head) \
413	for (pos = (head)->prev, n = pos->prev; \
414	     prefetch(pos->prev), pos != (head); \
415	     pos = n, n = pos->prev)
416
417/**
418 * list_for_each_entry	-	iterate over list of given type
419 * @pos:	the type * to use as a loop cursor.
420 * @head:	the head for your list.
421 * @member:	the name of the list_struct within the struct.
422 */
423#define list_for_each_entry(pos, head, member)				\
424	for (pos = list_entry((head)->next, typeof(*pos), member);	\
425	     prefetch(pos->member.next), &pos->member != (head);	\
426	     pos = list_entry(pos->member.next, typeof(*pos), member))
427
428/**
429 * list_for_each_entry_reverse - iterate backwards over list of given type.
430 * @pos:	the type * to use as a loop cursor.
431 * @head:	the head for your list.
432 * @member:	the name of the list_struct within the struct.
433 */
434#define list_for_each_entry_reverse(pos, head, member)			\
435	for (pos = list_entry((head)->prev, typeof(*pos), member);	\
436	     prefetch(pos->member.prev), &pos->member != (head);	\
437	     pos = list_entry(pos->member.prev, typeof(*pos), member))
438
439/**
440 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
441 * @pos:	the type * to use as a start point
442 * @head:	the head of the list
443 * @member:	the name of the list_struct within the struct.
444 *
445 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
446 */
447#define list_prepare_entry(pos, head, member) \
448	((pos) ? : list_entry(head, typeof(*pos), member))
449
450/**
451 * list_for_each_entry_continue - continue iteration over list of given type
452 * @pos:	the type * to use as a loop cursor.
453 * @head:	the head for your list.
454 * @member:	the name of the list_struct within the struct.
455 *
456 * Continue to iterate over list of given type, continuing after
457 * the current position.
458 */
459#define list_for_each_entry_continue(pos, head, member)			\
460	for (pos = list_entry(pos->member.next, typeof(*pos), member);	\
461	     prefetch(pos->member.next), &pos->member != (head);	\
462	     pos = list_entry(pos->member.next, typeof(*pos), member))
463
464/**
465 * list_for_each_entry_continue_reverse - iterate backwards from the given point
466 * @pos:	the type * to use as a loop cursor.
467 * @head:	the head for your list.
468 * @member:	the name of the list_struct within the struct.
469 *
470 * Start to iterate over list of given type backwards, continuing after
471 * the current position.
472 */
473#define list_for_each_entry_continue_reverse(pos, head, member)		\
474	for (pos = list_entry(pos->member.prev, typeof(*pos), member);	\
475	     prefetch(pos->member.prev), &pos->member != (head);	\
476	     pos = list_entry(pos->member.prev, typeof(*pos), member))
477
478/**
479 * list_for_each_entry_from - iterate over list of given type from the current point
480 * @pos:	the type * to use as a loop cursor.
481 * @head:	the head for your list.
482 * @member:	the name of the list_struct within the struct.
483 *
484 * Iterate over list of given type, continuing from current position.
485 */
486#define list_for_each_entry_from(pos, head, member)			\
487	for (; prefetch(pos->member.next), &pos->member != (head);	\
488	     pos = list_entry(pos->member.next, typeof(*pos), member))
489
490/**
491 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
492 * @pos:	the type * to use as a loop cursor.
493 * @n:		another type * to use as temporary storage
494 * @head:	the head for your list.
495 * @member:	the name of the list_struct within the struct.
496 */
497#define list_for_each_entry_safe(pos, n, head, member)			\
498	for (pos = list_entry((head)->next, typeof(*pos), member),	\
499		n = list_entry(pos->member.next, typeof(*pos), member);	\
500	     &pos->member != (head);					\
501	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
502
503/**
504 * list_for_each_entry_safe_continue
505 * @pos:	the type * to use as a loop cursor.
506 * @n:		another type * to use as temporary storage
507 * @head:	the head for your list.
508 * @member:	the name of the list_struct within the struct.
509 *
510 * Iterate over list of given type, continuing after current point,
511 * safe against removal of list entry.
512 */
513#define list_for_each_entry_safe_continue(pos, n, head, member)			\
514	for (pos = list_entry(pos->member.next, typeof(*pos), member),		\
515		n = list_entry(pos->member.next, typeof(*pos), member);		\
516	     &pos->member != (head);						\
517	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
518
519/**
520 * list_for_each_entry_safe_from
521 * @pos:	the type * to use as a loop cursor.
522 * @n:		another type * to use as temporary storage
523 * @head:	the head for your list.
524 * @member:	the name of the list_struct within the struct.
525 *
526 * Iterate over list of given type from current point, safe against
527 * removal of list entry.
528 */
529#define list_for_each_entry_safe_from(pos, n, head, member)			\
530	for (n = list_entry(pos->member.next, typeof(*pos), member);		\
531	     &pos->member != (head);						\
532	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
533
534/**
535 * list_for_each_entry_safe_reverse
536 * @pos:	the type * to use as a loop cursor.
537 * @n:		another type * to use as temporary storage
538 * @head:	the head for your list.
539 * @member:	the name of the list_struct within the struct.
540 *
541 * Iterate backwards over list of given type, safe against removal
542 * of list entry.
543 */
544#define list_for_each_entry_safe_reverse(pos, n, head, member)		\
545	for (pos = list_entry((head)->prev, typeof(*pos), member),	\
546		n = list_entry(pos->member.prev, typeof(*pos), member);	\
547	     &pos->member != (head);					\
548	     pos = n, n = list_entry(n->member.prev, typeof(*n), member))
549
550/*
551 * Double linked lists with a single pointer list head.
552 * Mostly useful for hash tables where the two pointer list head is
553 * too wasteful.
554 * You lose the ability to access the tail in O(1).
555 */
556
557struct hlist_head {
558	struct hlist_node *first;
559};
560
561struct hlist_node {
562	struct hlist_node *next, **pprev;
563};
564
565#define HLIST_HEAD_INIT { .first = NULL }
566#define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
567#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
568static inline void INIT_HLIST_NODE(struct hlist_node *h)
569{
570	h->next = NULL;
571	h->pprev = NULL;
572}
573
574static inline int hlist_unhashed(const struct hlist_node *h)
575{
576	return !h->pprev;
577}
578
579static inline int hlist_empty(const struct hlist_head *h)
580{
581	return !h->first;
582}
583
584static inline void __hlist_del(struct hlist_node *n)
585{
586	struct hlist_node *next = n->next;
587	struct hlist_node **pprev = n->pprev;
588	*pprev = next;
589	if (next)
590		next->pprev = pprev;
591}
592
593static inline void hlist_del(struct hlist_node *n)
594{
595	__hlist_del(n);
596	n->next = LIST_POISON1;
597	n->pprev = LIST_POISON2;
598}
599
600static inline void hlist_del_init(struct hlist_node *n)
601{
602	if (!hlist_unhashed(n)) {
603		__hlist_del(n);
604		INIT_HLIST_NODE(n);
605	}
606}
607
608static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
609{
610	struct hlist_node *first = h->first;
611	n->next = first;
612	if (first)
613		first->pprev = &n->next;
614	h->first = n;
615	n->pprev = &h->first;
616}
617
618/* next must be != NULL */
619static inline void hlist_add_before(struct hlist_node *n,
620					struct hlist_node *next)
621{
622	n->pprev = next->pprev;
623	n->next = next;
624	next->pprev = &n->next;
625	*(n->pprev) = n;
626}
627
628static inline void hlist_add_after(struct hlist_node *n,
629					struct hlist_node *next)
630{
631	next->next = n->next;
632	n->next = next;
633	next->pprev = &n->next;
634
635	if(next->next)
636		next->next->pprev  = &next->next;
637}
638
639#define hlist_entry(ptr, type, member) container_of(ptr,type,member)
640
641#define hlist_for_each(pos, head) \
642	for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
643	     pos = pos->next)
644
645#define hlist_for_each_safe(pos, n, head) \
646	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
647	     pos = n)
648
649#define hlist_entry_safe(ptr, type, member) \
650	({ typeof(ptr) ____ptr = (ptr); \
651	   ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
652	})
653
654/**
655 * hlist_for_each_entry	- iterate over list of given type
656 * @pos:	the type * to use as a loop cursor.
657 * @head:	the head for your list.
658 * @member:	the name of the hlist_node within the struct.
659 */
660#define hlist_for_each_entry(pos, head, member)				\
661	for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
662	     pos;							\
663	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
664
665/**
666 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
667 * @pos:	the type * to use as a loop cursor.
668 * @member:	the name of the hlist_node within the struct.
669 */
670#define hlist_for_each_entry_continue(pos, member)			\
671	for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
672	     pos;							\
673	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
674
675/**
676 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
677 * @pos:	the type * to use as a loop cursor.
678 * @member:	the name of the hlist_node within the struct.
679 */
680#define hlist_for_each_entry_from(pos, member)				\
681	for (; pos;							\
682	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
683
684/**
685 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
686 * @pos:	the type * to use as a loop cursor.
687 * @n:		a &struct hlist_node to use as temporary storage
688 * @head:	the head for your list.
689 * @member:	the name of the hlist_node within the struct.
690 */
691#define hlist_for_each_entry_safe(pos, n, head, member) 		\
692	for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
693	     pos && ({ n = pos->member.next; 1; });			\
694	     pos = hlist_entry_safe(n, typeof(*pos), member))
695
696#endif
697