]>
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1 /* SPDX-License-Identifier: GPL-2.0 */
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>
12 * Simple doubly linked list implementation.
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.
21 #define LIST_HEAD_INIT(name) { &(name), &(name) }
23 #define LIST_HEAD(name) \
24 struct list_head name = LIST_HEAD_INIT(name)
26 static inline void INIT_LIST_HEAD(struct list_head
*list
)
28 WRITE_ONCE(list
->next
, list
);
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
);
38 static inline bool __list_add_valid(struct list_head
*new,
39 struct list_head
*prev
,
40 struct list_head
*next
)
44 static inline bool __list_del_entry_valid(struct list_head
*entry
)
51 * Insert a new entry between two known consecutive entries.
53 * This is only for internal list manipulation where we know
54 * the prev/next entries already!
56 static inline void __list_add(struct list_head
*new,
57 struct list_head
*prev
,
58 struct list_head
*next
)
60 if (!__list_add_valid(new, prev
, next
))
66 WRITE_ONCE(prev
->next
, new);
70 * list_add - add a new entry
71 * @new: new entry to be added
72 * @head: list head to add it after
74 * Insert a new entry after the specified head.
75 * This is good for implementing stacks.
77 static inline void list_add(struct list_head
*new, struct list_head
*head
)
79 __list_add(new, head
, head
->next
);
84 * list_add_tail - add a new entry
85 * @new: new entry to be added
86 * @head: list head to add it before
88 * Insert a new entry before the specified head.
89 * This is useful for implementing queues.
91 static inline void list_add_tail(struct list_head
*new, struct list_head
*head
)
93 __list_add(new, head
->prev
, head
);
97 * Delete a list entry by making the prev/next entries
98 * point to each other.
100 * This is only for internal list manipulation where we know
101 * the prev/next entries already!
103 static inline void __list_del(struct list_head
* prev
, struct list_head
* next
)
106 WRITE_ONCE(prev
->next
, next
);
110 * Delete a list entry and clear the 'prev' pointer.
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().
117 static inline void __list_del_clearprev(struct list_head
*entry
)
119 __list_del(entry
->prev
, entry
->next
);
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.
129 static inline void __list_del_entry(struct list_head
*entry
)
131 if (!__list_del_entry_valid(entry
))
134 __list_del(entry
->prev
, entry
->next
);
137 static inline void list_del(struct list_head
*entry
)
139 __list_del_entry(entry
);
140 entry
->next
= LIST_POISON1
;
141 entry
->prev
= LIST_POISON2
;
145 * list_replace - replace old entry by new one
146 * @old : the element to be replaced
147 * @new : the new element to insert
149 * If @old was empty, it will be overwritten.
151 static inline void list_replace(struct list_head
*old
,
152 struct list_head
*new)
154 new->next
= old
->next
;
155 new->next
->prev
= new;
156 new->prev
= old
->prev
;
157 new->prev
->next
= new;
160 static inline void list_replace_init(struct list_head
*old
,
161 struct list_head
*new)
163 list_replace(old
, new);
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
172 static inline void list_swap(struct list_head
*entry1
,
173 struct list_head
*entry2
)
175 struct list_head
*pos
= entry2
->prev
;
178 list_replace(entry1
, entry2
);
181 list_add(entry1
, pos
);
185 * list_del_init - deletes entry from list and reinitialize it.
186 * @entry: the element to delete from the list.
188 static inline void list_del_init(struct list_head
*entry
)
190 __list_del_entry(entry
);
191 INIT_LIST_HEAD(entry
);
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
199 static inline void list_move(struct list_head
*list
, struct list_head
*head
)
201 __list_del_entry(list
);
202 list_add(list
, head
);
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
210 static inline void list_move_tail(struct list_head
*list
,
211 struct list_head
*head
)
213 __list_del_entry(list
);
214 list_add_tail(list
, head
);
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
223 * Move all entries between @first and including @last before @head.
224 * All three entries must belong to the same linked list.
226 static inline void list_bulk_move_tail(struct list_head
*head
,
227 struct list_head
*first
,
228 struct list_head
*last
)
230 first
->prev
->next
= last
->next
;
231 last
->next
->prev
= first
->prev
;
233 head
->prev
->next
= first
;
234 first
->prev
= head
->prev
;
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
245 static inline int list_is_first(const struct list_head
*list
,
246 const struct list_head
*head
)
248 return list
->prev
== head
;
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
256 static inline int list_is_last(const struct list_head
*list
,
257 const struct list_head
*head
)
259 return list
->next
== head
;
263 * list_empty - tests whether a list is empty
264 * @head: the list to test.
266 static inline int list_empty(const struct list_head
*head
)
268 return READ_ONCE(head
->next
) == head
;
272 * list_empty_careful - tests whether a list is empty and not being modified
273 * @head: the list to test
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)
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.
284 static inline int list_empty_careful(const struct list_head
*head
)
286 struct list_head
*next
= head
->next
;
287 return (next
== head
) && (next
== head
->prev
);
291 * list_rotate_left - rotate the list to the left
292 * @head: the head of the list
294 static inline void list_rotate_left(struct list_head
*head
)
296 struct list_head
*first
;
298 if (!list_empty(head
)) {
300 list_move_tail(first
, head
);
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.
309 * Rotates list so that @list becomes the new front of the list.
311 static inline void list_rotate_to_front(struct list_head
*list
,
312 struct list_head
*head
)
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.
319 list_move_tail(head
, list
);
323 * list_is_singular - tests whether a list has just one entry.
324 * @head: the list to test.
326 static inline int list_is_singular(const struct list_head
*head
)
328 return !list_empty(head
) && (head
->next
== head
->prev
);
331 static inline void __list_cut_position(struct list_head
*list
,
332 struct list_head
*head
, struct list_head
*entry
)
334 struct list_head
*new_first
= entry
->next
;
335 list
->next
= head
->next
;
336 list
->next
->prev
= list
;
339 head
->next
= new_first
;
340 new_first
->prev
= head
;
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
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
357 static inline void list_cut_position(struct list_head
*list
,
358 struct list_head
*head
, struct list_head
*entry
)
360 if (list_empty(head
))
362 if (list_is_singular(head
) &&
363 (head
->next
!= entry
&& head
!= entry
))
366 INIT_LIST_HEAD(list
);
368 __list_cut_position(list
, head
, entry
);
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
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
382 * If @entry == @head, all entries on @head are moved to
385 static inline void list_cut_before(struct list_head
*list
,
386 struct list_head
*head
,
387 struct list_head
*entry
)
389 if (head
->next
== entry
) {
390 INIT_LIST_HEAD(list
);
393 list
->next
= head
->next
;
394 list
->next
->prev
= list
;
395 list
->prev
= entry
->prev
;
396 list
->prev
->next
= list
;
401 static inline void __list_splice(const struct list_head
*list
,
402 struct list_head
*prev
,
403 struct list_head
*next
)
405 struct list_head
*first
= list
->next
;
406 struct list_head
*last
= list
->prev
;
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.
420 static inline void list_splice(const struct list_head
*list
,
421 struct list_head
*head
)
423 if (!list_empty(list
))
424 __list_splice(list
, head
, head
->next
);
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.
432 static inline void list_splice_tail(struct list_head
*list
,
433 struct list_head
*head
)
435 if (!list_empty(list
))
436 __list_splice(list
, head
->prev
, head
);
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.
444 * The list at @list is reinitialised
446 static inline void list_splice_init(struct list_head
*list
,
447 struct list_head
*head
)
449 if (!list_empty(list
)) {
450 __list_splice(list
, head
, head
->next
);
451 INIT_LIST_HEAD(list
);
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.
460 * Each of the lists is a queue.
461 * The list at @list is reinitialised
463 static inline void list_splice_tail_init(struct list_head
*list
,
464 struct list_head
*head
)
466 if (!list_empty(list
)) {
467 __list_splice(list
, head
->prev
, head
);
468 INIT_LIST_HEAD(list
);
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.
478 #define list_entry(ptr, type, member) \
479 container_of(ptr, type, member)
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.
487 * Note, that list is expected to be not empty.
489 #define list_first_entry(ptr, type, member) \
490 list_entry((ptr)->next, type, member)
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.
498 * Note, that list is expected to be not empty.
500 #define list_last_entry(ptr, type, member) \
501 list_entry((ptr)->prev, type, member)
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.
509 * Note that if the list is empty, it returns NULL.
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; \
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.
522 #define list_next_entry(pos, member) \
523 list_entry((pos)->member.next, typeof(*(pos)), member)
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.
530 #define list_prev_entry(pos, member) \
531 list_entry((pos)->member.prev, typeof(*(pos)), member)
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.
538 #define list_for_each(pos, head) \
539 for (pos = (head)->next; pos != (head); pos = pos->next)
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.
546 #define list_for_each_prev(pos, head) \
547 for (pos = (head)->prev; pos != (head); pos = pos->prev)
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.
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)
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.
565 #define list_for_each_prev_safe(pos, n, head) \
566 for (pos = (head)->prev, n = pos->prev; \
568 pos = n, n = pos->prev)
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.
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))
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.
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))
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.
598 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
600 #define list_prepare_entry(pos, head, member) \
601 ((pos) ? : list_entry(head, typeof(*pos), member))
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.
609 * Continue to iterate over list of given type, continuing after
610 * the current position.
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))
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.
623 * Start to iterate over list of given type backwards, continuing after
624 * the current position.
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))
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.
637 * Iterate over list of given type, continuing from current position.
639 #define list_for_each_entry_from(pos, head, member) \
640 for (; &pos->member != (head); \
641 pos = list_next_entry(pos, member))
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.
650 * Iterate backwards over list of given type, continuing from current position.
652 #define list_for_each_entry_from_reverse(pos, head, member) \
653 for (; &pos->member != (head); \
654 pos = list_prev_entry(pos, member))
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.
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))
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.
676 * Iterate over list of given type, continuing after current point,
677 * safe against removal of list entry.
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))
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.
692 * Iterate over list of given type from current point, safe against
693 * removal of list entry.
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))
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.
707 * Iterate backwards over list of given type, safe against removal
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))
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.
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.
728 #define list_safe_reset_next(pos, n, member) \
729 n = list_next_entry(pos, member)
732 * Double linked lists with a single pointer list head.
733 * Mostly useful for hash tables where the two pointer list head is
735 * You lose the ability to access the tail in O(1).
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)
741 static inline void INIT_HLIST_NODE(struct hlist_node
*h
)
747 static inline int hlist_unhashed(const struct hlist_node
*h
)
752 static inline int hlist_empty(const struct hlist_head
*h
)
754 return !READ_ONCE(h
->first
);
757 static inline void __hlist_del(struct hlist_node
*n
)
759 struct hlist_node
*next
= n
->next
;
760 struct hlist_node
**pprev
= n
->pprev
;
762 WRITE_ONCE(*pprev
, next
);
767 static inline void hlist_del(struct hlist_node
*n
)
770 n
->next
= LIST_POISON1
;
771 n
->pprev
= LIST_POISON2
;
774 static inline void hlist_del_init(struct hlist_node
*n
)
776 if (!hlist_unhashed(n
)) {
782 static inline void hlist_add_head(struct hlist_node
*n
, struct hlist_head
*h
)
784 struct hlist_node
*first
= h
->first
;
787 first
->pprev
= &n
->next
;
788 WRITE_ONCE(h
->first
, n
);
789 n
->pprev
= &h
->first
;
792 /* next must be != NULL */
793 static inline void hlist_add_before(struct hlist_node
*n
,
794 struct hlist_node
*next
)
796 n
->pprev
= next
->pprev
;
798 next
->pprev
= &n
->next
;
799 WRITE_ONCE(*(n
->pprev
), n
);
802 static inline void hlist_add_behind(struct hlist_node
*n
,
803 struct hlist_node
*prev
)
805 n
->next
= prev
->next
;
807 n
->pprev
= &prev
->next
;
810 n
->next
->pprev
= &n
->next
;
813 /* after that we'll appear to be on some hlist and hlist_del will work */
814 static inline void hlist_add_fake(struct hlist_node
*n
)
819 static inline bool hlist_fake(struct hlist_node
*h
)
821 return h
->pprev
== &h
->next
;
825 * Check whether the node is the only node of the head without
829 hlist_is_singular_node(struct hlist_node
*n
, struct hlist_head
*h
)
831 return !n
->next
&& n
->pprev
== &h
->first
;
835 * Move a list from one list head to another. Fixup the pprev
836 * reference of the first entry if it exists.
838 static inline void hlist_move_list(struct hlist_head
*old
,
839 struct hlist_head
*new)
841 new->first
= old
->first
;
843 new->first
->pprev
= &new->first
;
847 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
849 #define hlist_for_each(pos, head) \
850 for (pos = (head)->first; pos ; pos = pos->next)
852 #define hlist_for_each_safe(pos, n, head) \
853 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
856 #define hlist_entry_safe(ptr, type, member) \
857 ({ typeof(ptr) ____ptr = (ptr); \
858 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
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.
867 #define hlist_for_each_entry(pos, head, member) \
868 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
870 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
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.
877 #define hlist_for_each_entry_continue(pos, member) \
878 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
880 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
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.
887 #define hlist_for_each_entry_from(pos, member) \
889 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
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.
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))