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list.h: Add list_splice_tail() and list_splice_tail_init()

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If you are using linked lists for queues list_splice() will not do what
you would expect even if you use the elements passed reversed. We need
to handle these differently. We add list_splice_tail() and
list_splice_tail_init().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Luis R. Rodriguez
2008-08-06 15:21:26 -07:00
committed by John W. Linville
parent e6fce5b916
commit 7d283aee50
3 changed files with 40 additions and 11 deletions
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47
include/linux/list.h
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@ -215,21 +215,21 @@ static inline int list_is_singular(const struct list_head *head)
}
static inline void __list_splice(const struct list_head *list,
struct list_head *head)
struct list_head *prev,
struct list_head *next)
{
struct list_head *first = list->next;
struct list_head *last = list->prev;
struct list_head *at = head->next;
first->prev = head;
head->next = first;
first->prev = prev;
prev->next = first;
last->next = at;
at->prev = last;
last->next = next;
next->prev = last;
}
/**
* list_splice - join two lists
* list_splice - join two lists, this is designed for stacks
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
@ -237,7 +237,19 @@ static inline void list_splice(const struct list_head *list,
struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, head);
__list_splice(list, head, head->next);
}
/**
* list_splice_tail - join two lists, each list being a queue
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
static inline void list_splice_tail(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, head->prev, head);
}
/**
@ -251,7 +263,24 @@ static inline void list_splice_init(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list)) {
__list_splice(list, head);
__list_splice(list, head, head->next);
INIT_LIST_HEAD(list);
}
}
/**
* list_splice_tail_init - join two lists, each list being a queue, and
* reinitialise the emptied list.
* @list: the new list to add.
* @head: the place to add it in the first list.
*
* The list at @list is reinitialised
*/
static inline void list_splice_tail_init(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list)) {
__list_splice(list, head->prev, head);
INIT_LIST_HEAD(list);
}
}