1. 函数原型
内核中的链表结构如下,只有前后两个指针,没有数据项,可以很方便的构成双向链表
struct list_head {
struct list_head *next, *prev;
};
1.1. static inline void INIT_LIST_HEAD(struct list_head *list)
运行的时候初始化链表,两个指针都指向结点自己的地址
static inline void INIT_LIST_HEAD(struct list_head *list)
{
WRITE_ONCE(list->next, list);
list->prev = list;
}
1.2. static inline void list_add(struct list_head new, struct list_head head);
从指定结点后面插入一个结点,new为要插入的新节点的地址,head为要插入的结点,新结点从head结点后面插入
/**
* list_add - add a new entry
* @new: new entry to be added
* @head: list head to add it after
*
* Insert a new entry after the specified head.
* This is good for implementing stacks.
*/
static inline void list_add(struct list_head *new, struct list_head *head)
{
__list_add(new, head, head->next);
}
其中,__list_add()函数定义如下,在知道前后结点的情况下,插入结点
/*
* Insert a new entry between two known consecutive entries.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
static inline void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next)
{
if (!__list_add_valid(new, prev, next))
return;
next->prev = new;
new->next = next;
new->prev = prev;
WRITE_ONCE(prev->next, new);
}
1.3. static inline void list_add_tail(struct list_head new, struct list_head head)
从链表尾部插入结点
/**
* list_add_tail - add a new entry
* @new: new entry to be added
* @head: list head to add it before
*
* Insert a new entry before the specified head.
* This is useful for implementing queues.
*/
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
__list_add(new, head->prev, head);
}
1.4. static inline void list_del(struct list_head *entry)
两个宏定义,删除下来的prev、next指针指向这两个特殊值,这样设置是为了保证不在链表中的结点项不可访问--对LIST_POISON1和LIST_POISON2的访问都将引起页故障。
/*
* These are non-NULL pointers that will result in page faults
* under normal circumstances, used to verify that nobody uses
* non-initialized list entries.
*/
#define LIST_POISON1 ((void *) 0x100 + POISON_POINTER_DELTA)
#define LIST_POISON2 ((void *) 0x122 + POISON_POINTER_DELTA)
static inline void list_del(struct list_head *entry)
{
__list_del_entry(entry);
entry->next = LIST_POISON1;
entry->prev = LIST_POISON2;
}
其中__list_del_entry()函数定义如下:
/*
* Delete a list entry by making the prev/next entries
* point to each other.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
next->prev = prev;
WRITE_ONCE(prev->next, next);
}
/*
* Delete a list entry and clear the 'prev' pointer.
*
* This is a special-purpose list clearing method used in the networking code
* for lists allocated as per-cpu, where we don't want to incur the extra
* WRITE_ONCE() overhead of a regular list_del_init(). The code that uses this
* needs to check the node 'prev' pointer instead of calling list_empty().
*/
static inline void __list_del_clearprev(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
entry->prev = NULL;
}
/**
* list_del - deletes entry from list.
* @entry: the element to delete from the list.
* Note: list_empty() on entry does not return true after this, the entry is
* in an undefined state.
*/
static inline void __list_del_entry(struct list_head *entry)
{
if (!__list_del_entry_valid(entry))
return;
__list_del(entry->prev, entry->next);
}
1.5. static inline void list_replace(struct list_head old,struct list_head new)
替换链表中的结点,
/**
* list_replace - replace old entry by new one
* @old : the element to be replaced
* @new : the new element to insert
*
* If @old was empty, it will be overwritten.
*/
static inline void list_replace(struct list_head *old,
struct list_head *new)
{
new->next = old->next;
new->next->prev = new;
new->prev = old->prev;
new->prev->next = new;
}
1.6. static inline void list_replace_init(struct list_head old,struct list_head new)
替换,将被替换的结点初始化为一个新链表
static inline void list_replace_init(struct list_head *old,
struct list_head *new)
{
list_replace(old, new);
INIT_LIST_HEAD(old);
}
1.7. static inline void list_swap(struct list_head entry1,struct list_head entry2)
交换两个结点
/**
* list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position
* @entry1: the location to place entry2
* @entry2: the location to place entry1
*/
static inline void list_swap(struct list_head *entry1,
struct list_head *entry2)
{
struct list_head *pos = entry2->prev;
list_del(entry2);
list_replace(entry1, entry2);
if (pos == entry1)
pos = entry2;
list_add(entry1, pos);
}
1.8. static inline void list_del_init(struct list_head *entry)
删除一项并初始化
/**
* list_del_init - deletes entry from list and reinitialize it.
* @entry: the element to delete from the list.
*/
static inline void list_del_init(struct list_head *entry)
{
__list_del_entry(entry);
INIT_LIST_HEAD(entry);
}
1.9. static inline void list_move(struct list_head list, struct list_head head)
搬移操作,将原本属于链表的一个结点移动到另一个链表的操作
/**
* list_move - delete from one list and add as another's head
* @list: the entry to move
* @head: the head that will precede our entry
*/
static inline void list_move(struct list_head *list, struct list_head *head)
{
__list_del_entry(list);
list_add(list, head);
}
1.10. static inline void list_move_tail(struct list_head list,struct list_head head)
/**
* list_move_tail - delete from one list and add as another's tail
* @list: the entry to move
* @head: the head that will follow our entry
*/
static inline void list_move_tail(struct list_head *list,
struct list_head *head)
{
__list_del_entry(list);
list_add_tail(list, head);
}
1.11. static inline void list_bulk_move_tail(struct list_head head, struct list_head first, struct list_head *last)
/**
* list_bulk_move_tail - move a subsection of a list to its tail
* @head: the head that will follow our entry
* @first: first entry to move
* @last: last entry to move, can be the same as first
*
* Move all entries between @first and including @last before @head.
* All three entries must belong to the same linked list.
*/
static inline void list_bulk_move_tail(struct list_head *head,
struct list_head *first,
struct list_head *last)
{
first->prev->next = last->next;
last->next->prev = first->prev;
head->prev->next = first;
first->prev = head->prev;
last->next = head;
head->prev = last;
}
1.12. static inline int list_is_first(const struct list_head list,const struct list_head head)
判断结点是否为首结点
/**
* list_is_first -- tests whether @list is the first entry in list @head
* @list: the entry to test
* @head: the head of the list
*/
static inline int list_is_first(const struct list_head *list,
const struct list_head *head)
{
return list->prev == head;
}
1.13. static inline int list_is_last(const struct list_head list, const struct list_head head)
判断结点是否为尾结点
/**
* list_is_last - tests whether @list is the last entry in list @head
* @list: the entry to test
* @head: the head of the list
*/
static inline int list_is_last(const struct list_head *list,
const struct list_head *head)
{
return list->next == head;
}
1.14. static inline int list_empty(const struct list_head *head)
判断是否是一个空链表
/**
* list_empty - tests whether a list is empty
* @head: the list to test.
*/
static inline int list_empty(const struct list_head *head)
{
return READ_ONCE(head->next) == head;
}
1.15. static inline int list_empty_careful(const struct list_head *head)
/**
* list_empty_careful - tests whether a list is empty and not being modified
* @head: the list to test
*
* Description:
* tests whether a list is empty _and_ checks that no other CPU might be
* in the process of modifying either member (next or prev)
*
* NOTE: using list_empty_careful() without synchronization
* can only be safe if the only activity that can happen
* to the list entry is list_del_init(). Eg. it cannot be used
* if another CPU could re-list_add() it.
*/
static inline int list_empty_careful(const struct list_head *head)
{
struct list_head *next = head->next;
return (next == head) && (next == head->prev);
}
1.16. static inline void list_rotate_left(struct list_head *head)
翻转链表
/**
* list_rotate_left - rotate the list to the left
* @head: the head of the list
*/
static inline void list_rotate_left(struct list_head *head)
{
struct list_head *first;
if (!list_empty(head)) {
first = head->next;
list_move_tail(first, head);
}
}
1.17. static inline void list_rotate_to_front(struct list_head list,struct list_head head)
/**
* list_rotate_to_front() - Rotate list to specific item.
* @list: The desired new front of the list.
* @head: The head of the list.
*
* Rotates list so that @list becomes the new front of the list.
*/
static inline void list_rotate_to_front(struct list_head *list,
struct list_head *head)
{
/*
* Deletes the list head from the list denoted by @head and
* places it as the tail of @list, this effectively rotates the
* list so that @list is at the front.
*/
list_move_tail(head, list);
}
1.18. static inline int list_is_singular(const struct list_head *head)
判断一个链表是否只有一项
/**
* list_is_singular - tests whether a list has just one entry.
* @head: the list to test.
*/
static inline int list_is_singular(const struct list_head *head)
{
return !list_empty(head) && (head->next == head->prev);
}
1.19. static inline void list_cut_position(struct list_head list,struct list_head head, struct list_head *entry)
将一个链表拆分为两个
/**
* list_cut_position - cut a list into two
* @list: a new list to add all removed entries
* @head: a list with entries
* @entry: an entry within head, could be the head itself
* and if so we won't cut the list
*
* This helper moves the initial part of @head, up to and
* including @entry, from @head to @list. You should
* pass on @entry an element you know is on @head. @list
* should be an empty list or a list you do not care about
* losing its data.
*
*/
static inline void list_cut_position(struct list_head *list,
struct list_head *head, struct list_head *entry)
{
if (list_empty(head))
return;
if (list_is_singular(head) &&
(head->next != entry && head != entry))
return;
if (entry == head)
INIT_LIST_HEAD(list);
else
__list_cut_position(list, head, entry);
}
1.20. static inline void list_cut_before(struct list_head list,struct list_head head,struct list_head *entry)
/**
* list_cut_before - cut a list into two, before given entry
* @list: a new list to add all removed entries
* @head: a list with entries
* @entry: an entry within head, could be the head itself
*
* This helper moves the initial part of @head, up to but
* excluding @entry, from @head to @list. You should pass
* in @entry an element you know is on @head. @list should
* be an empty list or a list you do not care about losing
* its data.
* If @entry == @head, all entries on @head are moved to
* @list.
*/
static inline void list_cut_before(struct list_head *list,
struct list_head *head,
struct list_head *entry)
{
if (head->next == entry) {
INIT_LIST_HEAD(list);
return;
}
list->next = head->next;
list->next->prev = list;
list->prev = entry->prev;
list->prev->next = list;
head->next = entry;
entry->prev = head;
}
1.21. static inline void list_splice(const struct list_head list,struct list_head head)
连接两个链表
/**
* 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.
*/
static inline void list_splice(const struct list_head *list,
struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, head, head->next);
}
1.22. static inline void list_splice_tail(struct list_head list,struct list_head head)
/**
* 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);
}
1.23. static inline void list_splice_init(struct list_head list, struct list_head head)
/**
* list_splice_init - join two lists 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_init(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list)) {
__list_splice(list, head, head->next);
INIT_LIST_HEAD(list);
}
}
1.24. static inline void list_splice_tail_init(struct list_head list, struct list_head head)
/**
* list_splice_tail_init - join two lists and reinitialise the emptied list
* @list: the new list to add.
* @head: the place to add it in the first list.
*
* Each of the lists is a queue.
* 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);
}
}
2. 使用的宏定义
2.1. LIST_HEAD_INIT
#define LIST_HEAD_INIT(name) { &(name), &(name) }
2.2. LIST_HEAD
#define LIST_HEAD(name) \
struct list_head name = LIST_HEAD_INIT(name)
2.3. list_entry
#define list_entry(ptr, type, member) \
container_of(ptr, type, member)
2.4. list_first_entry
#define list_first_entry(ptr, type, member) \
list_entry((ptr)->next, type, member)
2.5. list_last_entry
#define list_last_entry(ptr, type, member) \
list_entry((ptr)->prev, type, member)
2.6. list_first_entry_or_null
#define list_first_entry_or_null(ptr, type, member) ({ \
struct list_head *head__ = (ptr); \
struct list_head *pos__ = READ_ONCE(head__->next); \
pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
})
2.7. list_next_entry
#define list_next_entry(pos, member) \
list_entry((pos)->member.next, typeof(*(pos)), member)
2.8. list_prev_entry
#define list_prev_entry(pos, member) \
list_entry((pos)->member.prev, typeof(*(pos)), member)
2.9. list_for_each
#define list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); pos = pos->next)
2.10. list_for_each_prev
#define list_for_each_prev(pos, head) \
for (pos = (head)->prev; pos != (head); pos = pos->prev)
2.11. list_for_each_safe
#define list_for_each_safe(pos, n, head) \
for (pos = (head)->next, n = pos->next; pos != (head); \
pos = n, n = pos->next)
2.12. list_for_each_prev_safe
#define list_for_each_prev_safe(pos, n, head) \
for (pos = (head)->prev, n = pos->prev; \
pos != (head); \
pos = n, n = pos->prev)
2.13. list_for_each_entry
#define list_for_each_entry(pos, head, member) \
for (pos = list_first_entry(head, typeof(*pos), member); \
&pos->member != (head); \
pos = list_next_entry(pos, member))
2.14. list_for_each_entry_reverse
#define list_for_each_entry_reverse(pos, head, member) \
for (pos = list_last_entry(head, typeof(*pos), member); \
&pos->member != (head); \
pos = list_prev_entry(pos, member))
2.15. list_prepare_entry
#define list_prepare_entry(pos, head, member) \
((pos) ? : list_entry(head, typeof(*pos), member))
2.16. list_for_each_entry_continue
#define list_for_each_entry_continue(pos, head, member) \
for (pos = list_next_entry(pos, member); \
&pos->member != (head); \
pos = list_next_entry(pos, member))
2.17. list_for_each_entry_from_reverse
#define list_for_each_entry_from_reverse(pos, head, member) \
for (; &pos->member != (head); \
pos = list_prev_entry(pos, member))
2.18. list_for_each_entry_safe
#define list_for_each_entry_safe(pos, n, head, member) \
for (pos = list_first_entry(head, typeof(*pos), member), \
n = list_next_entry(pos, member); \
&pos->member != (head); \
pos = n, n = list_next_entry(n, member))
2.19. list_for_each_entry_safe_continue
#define list_for_each_entry_safe_continue(pos, n, head, member) \
for (pos = list_next_entry(pos, member), \
n = list_next_entry(pos, member); \
&pos->member != (head); \
pos = n, n = list_next_entry(n, member))
2.20. list_for_each_entry_safe_from
#define list_for_each_entry_safe_from(pos, n, head, member) \
for (n = list_next_entry(pos, member); \
&pos->member != (head); \
pos = n, n = list_next_entry(n, member))
2.21. list_for_each_entry_safe_reverse
#define list_for_each_entry_safe_reverse(pos, n, head, member) \
for (pos = list_last_entry(head, typeof(*pos), member), \
n = list_prev_entry(pos, member); \
&pos->member != (head); \
pos = n, n = list_prev_entry(n, member))
2.22. list_safe_reset_next
#define list_safe_reset_next(pos, n, member) \
n = list_next_entry(pos, member)
评论