• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_LIST_H
3 #define _LINUX_LIST_H
4 
5 #include <linux/types.h>
6 #include <linux/stddef.h>
7 #include <linux/poison.h>
8 #include <linux/const.h>
9 #include <linux/kernel.h>
10 
11 /*
12  * Simple doubly linked list implementation.
13  *
14  * Some of the internal functions ("__xxx") are useful when
15  * manipulating whole lists rather than single entries, as
16  * sometimes we already know the next/prev entries and we can
17  * generate better code by using them directly rather than
18  * using the generic single-entry routines.
19  */
20 
21 #define LIST_HEAD_INIT(name) { &(name), &(name) }
22 
23 #define LIST_HEAD(name) \
24 	struct list_head name = LIST_HEAD_INIT(name)
25 
INIT_LIST_HEAD(struct list_head * list)26 static inline void INIT_LIST_HEAD(struct list_head *list)
27 {
28 	WRITE_ONCE(list->next, list);
29 	list->prev = list;
30 }
31 
32 #ifdef CONFIG_DEBUG_LIST
33 extern bool __list_add_valid(struct list_head *new,
34 			      struct list_head *prev,
35 			      struct list_head *next);
36 extern bool __list_del_entry_valid(struct list_head *entry);
37 #else
__list_add_valid(struct list_head * new,struct list_head * prev,struct list_head * next)38 static inline bool __list_add_valid(struct list_head *new,
39 				struct list_head *prev,
40 				struct list_head *next)
41 {
42 	return true;
43 }
__list_del_entry_valid(struct list_head * entry)44 static inline bool __list_del_entry_valid(struct list_head *entry)
45 {
46 	return true;
47 }
48 #endif
49 
50 /*
51  * Insert a new entry between two known consecutive entries.
52  *
53  * This is only for internal list manipulation where we know
54  * the prev/next entries already!
55  */
__list_add(struct list_head * new,struct list_head * prev,struct list_head * next)56 static inline void __list_add(struct list_head *new,
57 			      struct list_head *prev,
58 			      struct list_head *next)
59 {
60 	if (!__list_add_valid(new, prev, next))
61 		return;
62 
63 	next->prev = new;
64 	new->next = next;
65 	new->prev = prev;
66 	WRITE_ONCE(prev->next, new);
67 }
68 
69 /**
70  * list_add - add a new entry
71  * @new: new entry to be added
72  * @head: list head to add it after
73  *
74  * Insert a new entry after the specified head.
75  * This is good for implementing stacks.
76  */
list_add(struct list_head * new,struct list_head * head)77 static inline void list_add(struct list_head *new, struct list_head *head)
78 {
79 	__list_add(new, head, head->next);
80 }
81 
82 
83 /**
84  * list_add_tail - add a new entry
85  * @new: new entry to be added
86  * @head: list head to add it before
87  *
88  * Insert a new entry before the specified head.
89  * This is useful for implementing queues.
90  */
list_add_tail(struct list_head * new,struct list_head * head)91 static inline void list_add_tail(struct list_head *new, struct list_head *head)
92 {
93 	__list_add(new, head->prev, head);
94 }
95 
96 /*
97  * Delete a list entry by making the prev/next entries
98  * point to each other.
99  *
100  * This is only for internal list manipulation where we know
101  * the prev/next entries already!
102  */
__list_del(struct list_head * prev,struct list_head * next)103 static inline void __list_del(struct list_head * prev, struct list_head * next)
104 {
105 	next->prev = prev;
106 	WRITE_ONCE(prev->next, next);
107 }
108 
109 /*
110  * Delete a list entry and clear the 'prev' pointer.
111  *
112  * This is a special-purpose list clearing method used in the networking code
113  * for lists allocated as per-cpu, where we don't want to incur the extra
114  * WRITE_ONCE() overhead of a regular list_del_init(). The code that uses this
115  * needs to check the node 'prev' pointer instead of calling list_empty().
116  */
__list_del_clearprev(struct list_head * entry)117 static inline void __list_del_clearprev(struct list_head *entry)
118 {
119 	__list_del(entry->prev, entry->next);
120 	entry->prev = NULL;
121 }
122 
123 /**
124  * list_del - deletes entry from list.
125  * @entry: the element to delete from the list.
126  * Note: list_empty() on entry does not return true after this, the entry is
127  * in an undefined state.
128  */
__list_del_entry(struct list_head * entry)129 static inline void __list_del_entry(struct list_head *entry)
130 {
131 	if (!__list_del_entry_valid(entry))
132 		return;
133 
134 	__list_del(entry->prev, entry->next);
135 }
136 
list_del(struct list_head * entry)137 static inline void list_del(struct list_head *entry)
138 {
139 	__list_del_entry(entry);
140 	entry->next = LIST_POISON1;
141 	entry->prev = LIST_POISON2;
142 }
143 
144 /**
145  * list_replace - replace old entry by new one
146  * @old : the element to be replaced
147  * @new : the new element to insert
148  *
149  * If @old was empty, it will be overwritten.
150  */
list_replace(struct list_head * old,struct list_head * new)151 static inline void list_replace(struct list_head *old,
152 				struct list_head *new)
153 {
154 	new->next = old->next;
155 	new->next->prev = new;
156 	new->prev = old->prev;
157 	new->prev->next = new;
158 }
159 
list_replace_init(struct list_head * old,struct list_head * new)160 static inline void list_replace_init(struct list_head *old,
161 					struct list_head *new)
162 {
163 	list_replace(old, new);
164 	INIT_LIST_HEAD(old);
165 }
166 
167 /**
168  * list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position
169  * @entry1: the location to place entry2
170  * @entry2: the location to place entry1
171  */
list_swap(struct list_head * entry1,struct list_head * entry2)172 static inline void list_swap(struct list_head *entry1,
173 			     struct list_head *entry2)
174 {
175 	struct list_head *pos = entry2->prev;
176 
177 	list_del(entry2);
178 	list_replace(entry1, entry2);
179 	if (pos == entry1)
180 		pos = entry2;
181 	list_add(entry1, pos);
182 }
183 
184 /**
185  * list_del_init - deletes entry from list and reinitialize it.
186  * @entry: the element to delete from the list.
187  */
list_del_init(struct list_head * entry)188 static inline void list_del_init(struct list_head *entry)
189 {
190 	__list_del_entry(entry);
191 	INIT_LIST_HEAD(entry);
192 }
193 
194 /**
195  * list_move - delete from one list and add as another's head
196  * @list: the entry to move
197  * @head: the head that will precede our entry
198  */
list_move(struct list_head * list,struct list_head * head)199 static inline void list_move(struct list_head *list, struct list_head *head)
200 {
201 	__list_del_entry(list);
202 	list_add(list, head);
203 }
204 
205 /**
206  * list_move_tail - delete from one list and add as another's tail
207  * @list: the entry to move
208  * @head: the head that will follow our entry
209  */
list_move_tail(struct list_head * list,struct list_head * head)210 static inline void list_move_tail(struct list_head *list,
211 				  struct list_head *head)
212 {
213 	__list_del_entry(list);
214 	list_add_tail(list, head);
215 }
216 
217 /**
218  * list_bulk_move_tail - move a subsection of a list to its tail
219  * @head: the head that will follow our entry
220  * @first: first entry to move
221  * @last: last entry to move, can be the same as first
222  *
223  * Move all entries between @first and including @last before @head.
224  * All three entries must belong to the same linked list.
225  */
list_bulk_move_tail(struct list_head * head,struct list_head * first,struct list_head * last)226 static inline void list_bulk_move_tail(struct list_head *head,
227 				       struct list_head *first,
228 				       struct list_head *last)
229 {
230 	first->prev->next = last->next;
231 	last->next->prev = first->prev;
232 
233 	head->prev->next = first;
234 	first->prev = head->prev;
235 
236 	last->next = head;
237 	head->prev = last;
238 }
239 
240 /**
241  * list_is_first -- tests whether @list is the first entry in list @head
242  * @list: the entry to test
243  * @head: the head of the list
244  */
list_is_first(const struct list_head * list,const struct list_head * head)245 static inline int list_is_first(const struct list_head *list,
246 					const struct list_head *head)
247 {
248 	return list->prev == head;
249 }
250 
251 /**
252  * list_is_last - tests whether @list is the last entry in list @head
253  * @list: the entry to test
254  * @head: the head of the list
255  */
list_is_last(const struct list_head * list,const struct list_head * head)256 static inline int list_is_last(const struct list_head *list,
257 				const struct list_head *head)
258 {
259 	return list->next == head;
260 }
261 
262 /**
263  * list_empty - tests whether a list is empty
264  * @head: the list to test.
265  */
list_empty(const struct list_head * head)266 static inline int list_empty(const struct list_head *head)
267 {
268 	return READ_ONCE(head->next) == head;
269 }
270 
271 /**
272  * list_empty_careful - tests whether a list is empty and not being modified
273  * @head: the list to test
274  *
275  * Description:
276  * tests whether a list is empty _and_ checks that no other CPU might be
277  * in the process of modifying either member (next or prev)
278  *
279  * NOTE: using list_empty_careful() without synchronization
280  * can only be safe if the only activity that can happen
281  * to the list entry is list_del_init(). Eg. it cannot be used
282  * if another CPU could re-list_add() it.
283  */
list_empty_careful(const struct list_head * head)284 static inline int list_empty_careful(const struct list_head *head)
285 {
286 	struct list_head *next = head->next;
287 	return (next == head) && (next == head->prev);
288 }
289 
290 /**
291  * list_rotate_left - rotate the list to the left
292  * @head: the head of the list
293  */
list_rotate_left(struct list_head * head)294 static inline void list_rotate_left(struct list_head *head)
295 {
296 	struct list_head *first;
297 
298 	if (!list_empty(head)) {
299 		first = head->next;
300 		list_move_tail(first, head);
301 	}
302 }
303 
304 /**
305  * list_rotate_to_front() - Rotate list to specific item.
306  * @list: The desired new front of the list.
307  * @head: The head of the list.
308  *
309  * Rotates list so that @list becomes the new front of the list.
310  */
list_rotate_to_front(struct list_head * list,struct list_head * head)311 static inline void list_rotate_to_front(struct list_head *list,
312 					struct list_head *head)
313 {
314 	/*
315 	 * Deletes the list head from the list denoted by @head and
316 	 * places it as the tail of @list, this effectively rotates the
317 	 * list so that @list is at the front.
318 	 */
319 	list_move_tail(head, list);
320 }
321 
322 /**
323  * list_is_singular - tests whether a list has just one entry.
324  * @head: the list to test.
325  */
list_is_singular(const struct list_head * head)326 static inline int list_is_singular(const struct list_head *head)
327 {
328 	return !list_empty(head) && (head->next == head->prev);
329 }
330 
__list_cut_position(struct list_head * list,struct list_head * head,struct list_head * entry)331 static inline void __list_cut_position(struct list_head *list,
332 		struct list_head *head, struct list_head *entry)
333 {
334 	struct list_head *new_first = entry->next;
335 	list->next = head->next;
336 	list->next->prev = list;
337 	list->prev = entry;
338 	entry->next = list;
339 	head->next = new_first;
340 	new_first->prev = head;
341 }
342 
343 /**
344  * list_cut_position - cut a list into two
345  * @list: a new list to add all removed entries
346  * @head: a list with entries
347  * @entry: an entry within head, could be the head itself
348  *	and if so we won't cut the list
349  *
350  * This helper moves the initial part of @head, up to and
351  * including @entry, from @head to @list. You should
352  * pass on @entry an element you know is on @head. @list
353  * should be an empty list or a list you do not care about
354  * losing its data.
355  *
356  */
list_cut_position(struct list_head * list,struct list_head * head,struct list_head * entry)357 static inline void list_cut_position(struct list_head *list,
358 		struct list_head *head, struct list_head *entry)
359 {
360 	if (list_empty(head))
361 		return;
362 	if (list_is_singular(head) &&
363 		(head->next != entry && head != entry))
364 		return;
365 	if (entry == head)
366 		INIT_LIST_HEAD(list);
367 	else
368 		__list_cut_position(list, head, entry);
369 }
370 
371 /**
372  * list_cut_before - cut a list into two, before given entry
373  * @list: a new list to add all removed entries
374  * @head: a list with entries
375  * @entry: an entry within head, could be the head itself
376  *
377  * This helper moves the initial part of @head, up to but
378  * excluding @entry, from @head to @list.  You should pass
379  * in @entry an element you know is on @head.  @list should
380  * be an empty list or a list you do not care about losing
381  * its data.
382  * If @entry == @head, all entries on @head are moved to
383  * @list.
384  */
list_cut_before(struct list_head * list,struct list_head * head,struct list_head * entry)385 static inline void list_cut_before(struct list_head *list,
386 				   struct list_head *head,
387 				   struct list_head *entry)
388 {
389 	if (head->next == entry) {
390 		INIT_LIST_HEAD(list);
391 		return;
392 	}
393 	list->next = head->next;
394 	list->next->prev = list;
395 	list->prev = entry->prev;
396 	list->prev->next = list;
397 	head->next = entry;
398 	entry->prev = head;
399 }
400 
__list_splice(const struct list_head * list,struct list_head * prev,struct list_head * next)401 static inline void __list_splice(const struct list_head *list,
402 				 struct list_head *prev,
403 				 struct list_head *next)
404 {
405 	struct list_head *first = list->next;
406 	struct list_head *last = list->prev;
407 
408 	first->prev = prev;
409 	prev->next = first;
410 
411 	last->next = next;
412 	next->prev = last;
413 }
414 
415 /**
416  * list_splice - join two lists, this is designed for stacks
417  * @list: the new list to add.
418  * @head: the place to add it in the first list.
419  */
list_splice(const struct list_head * list,struct list_head * head)420 static inline void list_splice(const struct list_head *list,
421 				struct list_head *head)
422 {
423 	if (!list_empty(list))
424 		__list_splice(list, head, head->next);
425 }
426 
427 /**
428  * list_splice_tail - join two lists, each list being a queue
429  * @list: the new list to add.
430  * @head: the place to add it in the first list.
431  */
list_splice_tail(struct list_head * list,struct list_head * head)432 static inline void list_splice_tail(struct list_head *list,
433 				struct list_head *head)
434 {
435 	if (!list_empty(list))
436 		__list_splice(list, head->prev, head);
437 }
438 
439 /**
440  * list_splice_init - join two lists and reinitialise the emptied list.
441  * @list: the new list to add.
442  * @head: the place to add it in the first list.
443  *
444  * The list at @list is reinitialised
445  */
list_splice_init(struct list_head * list,struct list_head * head)446 static inline void list_splice_init(struct list_head *list,
447 				    struct list_head *head)
448 {
449 	if (!list_empty(list)) {
450 		__list_splice(list, head, head->next);
451 		INIT_LIST_HEAD(list);
452 	}
453 }
454 
455 /**
456  * list_splice_tail_init - join two lists and reinitialise the emptied list
457  * @list: the new list to add.
458  * @head: the place to add it in the first list.
459  *
460  * Each of the lists is a queue.
461  * The list at @list is reinitialised
462  */
list_splice_tail_init(struct list_head * list,struct list_head * head)463 static inline void list_splice_tail_init(struct list_head *list,
464 					 struct list_head *head)
465 {
466 	if (!list_empty(list)) {
467 		__list_splice(list, head->prev, head);
468 		INIT_LIST_HEAD(list);
469 	}
470 }
471 
472 /**
473  * list_entry - get the struct for this entry
474  * @ptr:	the &struct list_head pointer.
475  * @type:	the type of the struct this is embedded in.
476  * @member:	the name of the list_head within the struct.
477  */
478 #define list_entry(ptr, type, member) \
479 	container_of(ptr, type, member)
480 
481 /**
482  * list_first_entry - get the first element from a list
483  * @ptr:	the list head to take the element from.
484  * @type:	the type of the struct this is embedded in.
485  * @member:	the name of the list_head within the struct.
486  *
487  * Note, that list is expected to be not empty.
488  */
489 #define list_first_entry(ptr, type, member) \
490 	list_entry((ptr)->next, type, member)
491 
492 /**
493  * list_last_entry - get the last element from a list
494  * @ptr:	the list head to take the element from.
495  * @type:	the type of the struct this is embedded in.
496  * @member:	the name of the list_head within the struct.
497  *
498  * Note, that list is expected to be not empty.
499  */
500 #define list_last_entry(ptr, type, member) \
501 	list_entry((ptr)->prev, type, member)
502 
503 /**
504  * list_first_entry_or_null - get the first element from a list
505  * @ptr:	the list head to take the element from.
506  * @type:	the type of the struct this is embedded in.
507  * @member:	the name of the list_head within the struct.
508  *
509  * Note that if the list is empty, it returns NULL.
510  */
511 #define list_first_entry_or_null(ptr, type, member) ({ \
512 	struct list_head *head__ = (ptr); \
513 	struct list_head *pos__ = READ_ONCE(head__->next); \
514 	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
515 })
516 
517 /**
518  * list_next_entry - get the next element in list
519  * @pos:	the type * to cursor
520  * @member:	the name of the list_head within the struct.
521  */
522 #define list_next_entry(pos, member) \
523 	list_entry((pos)->member.next, typeof(*(pos)), member)
524 
525 /**
526  * list_prev_entry - get the prev element in list
527  * @pos:	the type * to cursor
528  * @member:	the name of the list_head within the struct.
529  */
530 #define list_prev_entry(pos, member) \
531 	list_entry((pos)->member.prev, typeof(*(pos)), member)
532 
533 /**
534  * list_for_each	-	iterate over a list
535  * @pos:	the &struct list_head to use as a loop cursor.
536  * @head:	the head for your list.
537  */
538 #define list_for_each(pos, head) \
539 	for (pos = (head)->next; pos != (head); pos = pos->next)
540 
541 /**
542  * list_for_each_prev	-	iterate over a list backwards
543  * @pos:	the &struct list_head to use as a loop cursor.
544  * @head:	the head for your list.
545  */
546 #define list_for_each_prev(pos, head) \
547 	for (pos = (head)->prev; pos != (head); pos = pos->prev)
548 
549 /**
550  * list_for_each_safe - iterate over a list safe against removal of list entry
551  * @pos:	the &struct list_head to use as a loop cursor.
552  * @n:		another &struct list_head to use as temporary storage
553  * @head:	the head for your list.
554  */
555 #define list_for_each_safe(pos, n, head) \
556 	for (pos = (head)->next, n = pos->next; pos != (head); \
557 		pos = n, n = pos->next)
558 
559 /**
560  * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
561  * @pos:	the &struct list_head to use as a loop cursor.
562  * @n:		another &struct list_head to use as temporary storage
563  * @head:	the head for your list.
564  */
565 #define list_for_each_prev_safe(pos, n, head) \
566 	for (pos = (head)->prev, n = pos->prev; \
567 	     pos != (head); \
568 	     pos = n, n = pos->prev)
569 
570 /**
571  * list_for_each_entry	-	iterate over list of given type
572  * @pos:	the type * to use as a loop cursor.
573  * @head:	the head for your list.
574  * @member:	the name of the list_head within the struct.
575  */
576 #define list_for_each_entry(pos, head, member)				\
577 	for (pos = list_first_entry(head, typeof(*pos), member);	\
578 	     &pos->member != (head);					\
579 	     pos = list_next_entry(pos, member))
580 
581 /**
582  * list_for_each_entry_reverse - iterate backwards over list of given type.
583  * @pos:	the type * to use as a loop cursor.
584  * @head:	the head for your list.
585  * @member:	the name of the list_head within the struct.
586  */
587 #define list_for_each_entry_reverse(pos, head, member)			\
588 	for (pos = list_last_entry(head, typeof(*pos), member);		\
589 	     &pos->member != (head); 					\
590 	     pos = list_prev_entry(pos, member))
591 
592 /**
593  * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
594  * @pos:	the type * to use as a start point
595  * @head:	the head of the list
596  * @member:	the name of the list_head within the struct.
597  *
598  * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
599  */
600 #define list_prepare_entry(pos, head, member) \
601 	((pos) ? : list_entry(head, typeof(*pos), member))
602 
603 /**
604  * list_for_each_entry_continue - continue iteration over list of given type
605  * @pos:	the type * to use as a loop cursor.
606  * @head:	the head for your list.
607  * @member:	the name of the list_head within the struct.
608  *
609  * Continue to iterate over list of given type, continuing after
610  * the current position.
611  */
612 #define list_for_each_entry_continue(pos, head, member) 		\
613 	for (pos = list_next_entry(pos, member);			\
614 	     &pos->member != (head);					\
615 	     pos = list_next_entry(pos, member))
616 
617 /**
618  * list_for_each_entry_continue_reverse - iterate backwards from the given point
619  * @pos:	the type * to use as a loop cursor.
620  * @head:	the head for your list.
621  * @member:	the name of the list_head within the struct.
622  *
623  * Start to iterate over list of given type backwards, continuing after
624  * the current position.
625  */
626 #define list_for_each_entry_continue_reverse(pos, head, member)		\
627 	for (pos = list_prev_entry(pos, member);			\
628 	     &pos->member != (head);					\
629 	     pos = list_prev_entry(pos, member))
630 
631 /**
632  * list_for_each_entry_from - iterate over list of given type from the current point
633  * @pos:	the type * to use as a loop cursor.
634  * @head:	the head for your list.
635  * @member:	the name of the list_head within the struct.
636  *
637  * Iterate over list of given type, continuing from current position.
638  */
639 #define list_for_each_entry_from(pos, head, member) 			\
640 	for (; &pos->member != (head);					\
641 	     pos = list_next_entry(pos, member))
642 
643 /**
644  * list_for_each_entry_from_reverse - iterate backwards over list of given type
645  *                                    from the current point
646  * @pos:	the type * to use as a loop cursor.
647  * @head:	the head for your list.
648  * @member:	the name of the list_head within the struct.
649  *
650  * Iterate backwards over list of given type, continuing from current position.
651  */
652 #define list_for_each_entry_from_reverse(pos, head, member)		\
653 	for (; &pos->member != (head);					\
654 	     pos = list_prev_entry(pos, member))
655 
656 /**
657  * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
658  * @pos:	the type * to use as a loop cursor.
659  * @n:		another type * to use as temporary storage
660  * @head:	the head for your list.
661  * @member:	the name of the list_head within the struct.
662  */
663 #define list_for_each_entry_safe(pos, n, head, member)			\
664 	for (pos = list_first_entry(head, typeof(*pos), member),	\
665 		n = list_next_entry(pos, member);			\
666 	     &pos->member != (head); 					\
667 	     pos = n, n = list_next_entry(n, member))
668 
669 /**
670  * list_for_each_entry_safe_continue - continue list iteration safe against removal
671  * @pos:	the type * to use as a loop cursor.
672  * @n:		another type * to use as temporary storage
673  * @head:	the head for your list.
674  * @member:	the name of the list_head within the struct.
675  *
676  * Iterate over list of given type, continuing after current point,
677  * safe against removal of list entry.
678  */
679 #define list_for_each_entry_safe_continue(pos, n, head, member) 		\
680 	for (pos = list_next_entry(pos, member), 				\
681 		n = list_next_entry(pos, member);				\
682 	     &pos->member != (head);						\
683 	     pos = n, n = list_next_entry(n, member))
684 
685 /**
686  * list_for_each_entry_safe_from - iterate over list from current point safe against removal
687  * @pos:	the type * to use as a loop cursor.
688  * @n:		another type * to use as temporary storage
689  * @head:	the head for your list.
690  * @member:	the name of the list_head within the struct.
691  *
692  * Iterate over list of given type from current point, safe against
693  * removal of list entry.
694  */
695 #define list_for_each_entry_safe_from(pos, n, head, member) 			\
696 	for (n = list_next_entry(pos, member);					\
697 	     &pos->member != (head);						\
698 	     pos = n, n = list_next_entry(n, member))
699 
700 /**
701  * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
702  * @pos:	the type * to use as a loop cursor.
703  * @n:		another type * to use as temporary storage
704  * @head:	the head for your list.
705  * @member:	the name of the list_head within the struct.
706  *
707  * Iterate backwards over list of given type, safe against removal
708  * of list entry.
709  */
710 #define list_for_each_entry_safe_reverse(pos, n, head, member)		\
711 	for (pos = list_last_entry(head, typeof(*pos), member),		\
712 		n = list_prev_entry(pos, member);			\
713 	     &pos->member != (head); 					\
714 	     pos = n, n = list_prev_entry(n, member))
715 
716 /**
717  * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
718  * @pos:	the loop cursor used in the list_for_each_entry_safe loop
719  * @n:		temporary storage used in list_for_each_entry_safe
720  * @member:	the name of the list_head within the struct.
721  *
722  * list_safe_reset_next is not safe to use in general if the list may be
723  * modified concurrently (eg. the lock is dropped in the loop body). An
724  * exception to this is if the cursor element (pos) is pinned in the list,
725  * and list_safe_reset_next is called after re-taking the lock and before
726  * completing the current iteration of the loop body.
727  */
728 #define list_safe_reset_next(pos, n, member)				\
729 	n = list_next_entry(pos, member)
730 
731 /*
732  * Double linked lists with a single pointer list head.
733  * Mostly useful for hash tables where the two pointer list head is
734  * too wasteful.
735  * You lose the ability to access the tail in O(1).
736  */
737 
738 #define HLIST_HEAD_INIT { .first = NULL }
739 #define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
740 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
INIT_HLIST_NODE(struct hlist_node * h)741 static inline void INIT_HLIST_NODE(struct hlist_node *h)
742 {
743 	h->next = NULL;
744 	h->pprev = NULL;
745 }
746 
hlist_unhashed(const struct hlist_node * h)747 static inline int hlist_unhashed(const struct hlist_node *h)
748 {
749 	return !h->pprev;
750 }
751 
hlist_empty(const struct hlist_head * h)752 static inline int hlist_empty(const struct hlist_head *h)
753 {
754 	return !READ_ONCE(h->first);
755 }
756 
__hlist_del(struct hlist_node * n)757 static inline void __hlist_del(struct hlist_node *n)
758 {
759 	struct hlist_node *next = n->next;
760 	struct hlist_node **pprev = n->pprev;
761 
762 	WRITE_ONCE(*pprev, next);
763 	if (next)
764 		next->pprev = pprev;
765 }
766 
hlist_del(struct hlist_node * n)767 static inline void hlist_del(struct hlist_node *n)
768 {
769 	__hlist_del(n);
770 	n->next = LIST_POISON1;
771 	n->pprev = LIST_POISON2;
772 }
773 
hlist_del_init(struct hlist_node * n)774 static inline void hlist_del_init(struct hlist_node *n)
775 {
776 	if (!hlist_unhashed(n)) {
777 		__hlist_del(n);
778 		INIT_HLIST_NODE(n);
779 	}
780 }
781 
hlist_add_head(struct hlist_node * n,struct hlist_head * h)782 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
783 {
784 	struct hlist_node *first = h->first;
785 	n->next = first;
786 	if (first)
787 		first->pprev = &n->next;
788 	WRITE_ONCE(h->first, n);
789 	n->pprev = &h->first;
790 }
791 
792 /* next must be != NULL */
hlist_add_before(struct hlist_node * n,struct hlist_node * next)793 static inline void hlist_add_before(struct hlist_node *n,
794 					struct hlist_node *next)
795 {
796 	n->pprev = next->pprev;
797 	n->next = next;
798 	next->pprev = &n->next;
799 	WRITE_ONCE(*(n->pprev), n);
800 }
801 
hlist_add_behind(struct hlist_node * n,struct hlist_node * prev)802 static inline void hlist_add_behind(struct hlist_node *n,
803 				    struct hlist_node *prev)
804 {
805 	n->next = prev->next;
806 	prev->next = n;
807 	n->pprev = &prev->next;
808 
809 	if (n->next)
810 		n->next->pprev  = &n->next;
811 }
812 
813 /* after that we'll appear to be on some hlist and hlist_del will work */
hlist_add_fake(struct hlist_node * n)814 static inline void hlist_add_fake(struct hlist_node *n)
815 {
816 	n->pprev = &n->next;
817 }
818 
hlist_fake(struct hlist_node * h)819 static inline bool hlist_fake(struct hlist_node *h)
820 {
821 	return h->pprev == &h->next;
822 }
823 
824 /*
825  * Check whether the node is the only node of the head without
826  * accessing head:
827  */
828 static inline bool
hlist_is_singular_node(struct hlist_node * n,struct hlist_head * h)829 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
830 {
831 	return !n->next && n->pprev == &h->first;
832 }
833 
834 /*
835  * Move a list from one list head to another. Fixup the pprev
836  * reference of the first entry if it exists.
837  */
hlist_move_list(struct hlist_head * old,struct hlist_head * new)838 static inline void hlist_move_list(struct hlist_head *old,
839 				   struct hlist_head *new)
840 {
841 	new->first = old->first;
842 	if (new->first)
843 		new->first->pprev = &new->first;
844 	old->first = NULL;
845 }
846 
847 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
848 
849 #define hlist_for_each(pos, head) \
850 	for (pos = (head)->first; pos ; pos = pos->next)
851 
852 #define hlist_for_each_safe(pos, n, head) \
853 	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
854 	     pos = n)
855 
856 #define hlist_entry_safe(ptr, type, member) \
857 	({ typeof(ptr) ____ptr = (ptr); \
858 	   ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
859 	})
860 
861 /**
862  * hlist_for_each_entry	- iterate over list of given type
863  * @pos:	the type * to use as a loop cursor.
864  * @head:	the head for your list.
865  * @member:	the name of the hlist_node within the struct.
866  */
867 #define hlist_for_each_entry(pos, head, member)				\
868 	for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
869 	     pos;							\
870 	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
871 
872 /**
873  * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
874  * @pos:	the type * to use as a loop cursor.
875  * @member:	the name of the hlist_node within the struct.
876  */
877 #define hlist_for_each_entry_continue(pos, member)			\
878 	for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
879 	     pos;							\
880 	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
881 
882 /**
883  * hlist_for_each_entry_from - iterate over a hlist continuing from current point
884  * @pos:	the type * to use as a loop cursor.
885  * @member:	the name of the hlist_node within the struct.
886  */
887 #define hlist_for_each_entry_from(pos, member)				\
888 	for (; pos;							\
889 	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
890 
891 /**
892  * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
893  * @pos:	the type * to use as a loop cursor.
894  * @n:		another &struct hlist_node to use as temporary storage
895  * @head:	the head for your list.
896  * @member:	the name of the hlist_node within the struct.
897  */
898 #define hlist_for_each_entry_safe(pos, n, head, member) 		\
899 	for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
900 	     pos && ({ n = pos->member.next; 1; });			\
901 	     pos = hlist_entry_safe(n, typeof(*pos), member))
902 
903 #endif
904