1、数据结构

struct list_head
{
    struct list_head *next, *prev;
};

这里用一个list_head类型的结构体，它包含两个指向本身的指针prev和next，从而具备了双向链表的功能。与一般双向链表不同的是，该结构没有数据域。而它一般也是作为我们实际运用的双向链表中一个数据成员。例如：

struct my_struct
{
    struct list_head list;
    unsigned  long  num;
    char name[20];
};

2、创建list_head结构
链表在使用前是要初始化的，而大多数情况下，链表都是动态创建的，所以一般就是在运行时初始化。
通常使用两种方法：

1.显式初始化
struct list_head example_list;
INIT_LIST_HEAD(&example_list);
2.隐式初始化
LIST_HEAD(example_list);

3、API接口
（1）初始化

#define LIST_HEAD_INIT(name) { &(name), &(name) }
#define LIST_HEAD(name) \
    struct list_head name = LIST_HEAD_INIT(name)

static inline void INIT_LIST_HEAD(struct list_head *list)
{
    list->next = list;
    list->prev = list;
}

（2）节点插入

static inline void __list_add(struct list_head *new,
              struct list_head *prev,
              struct list_head *next)
{
    next->prev = new;
    new->next = next;
    new->prev = prev;
    prev->next = new;
}

头插
static __inline__ void list_add(struct list_head *new, struct list_head *head)
{
    __list_add(new, head, head->next);
}
尾插
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
    __list_add(new, head->prev, head);
}

（3）节点删除

static __inline__ void __list_del(struct list_head * prev,
              struct list_head * next)
{
    next->prev = prev;
    prev->next = next;
}

static inline void list_del(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    entry->next = LIST_POISON1;
    entry->prev = LIST_POISON2;
}

static inline void list_del_init(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    INIT_LIST_HEAD(entry);
}

（4）节点替换

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;
}

static inline void list_replace_init(struct list_head *old,
                    struct list_head *new)
{
    list_replace(old, new);
    INIT_LIST_HEAD(old);
}

（5）节点转移（从一个链上删除之后添加到新链中）

static inline void list_move(struct list_head *list, struct list_head *head)
{
    __list_del(list->prev, list->next);
    list_add(list, head);
}

static inline void list_move_tail(struct list_head *list,
                  struct list_head *head)
{
    __list_del(list->prev, list->next);
    list_add_tail(list, head);
}

（6）判断节点是否是尾节点

static inline int list_is_last(const struct list_head *list,
                const struct list_head *head)
{
    return list->next == head;
}

（7）判断链表是否为空

static inline int list_empty(const struct list_head *head)
{
    return head->next == head;
}

static inline int list_empty_careful(const struct list_head *head)
{
    struct list_head *next = head->next;
    return (next == head) && (next == head->prev);
}
描述：
tests whether a list is empty _and_ checks that no other CPU might be
 in the process of modifying either member (next or prev)

（8）旋转链表的第一个节点到最后

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);
    }
}

（9）判断链表是否只有一个节点

static inline int list_is_singular(const struct list_head *head)
{
    return !list_empty(head) && (head->next == head->prev);
}

（10）分割链表

static inline void __list_cut_position(struct list_head *list,
        struct list_head *head, struct list_head *entry)
{
    struct list_head *new_first = entry->next;
    list->next = head->next;
    list->next->prev = list;
    list->prev = entry;
    entry->next = list;
    head->next = new_first;
    new_first->prev = head;
}

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);
}

注：
list：将剪切的结点要加进来的链表
head：被剪切的链表
entry：所指位于由head所指领头的链表内，它可以指向head，但是这样的话，head就不能被剪切了，在代码中调用了INIT_LIST_HEAD(list)。是将head（不包括head）到entry之间的所有结点剪切下来加到list所指向的链表中。这个操作之后就有了两个链表head和list。

（11）链表合并

static inline void __list_splice(const struct list_head *list,
                 struct list_head *prev,
                 struct list_head *next)
{
    struct list_head *first = list->next;
    struct list_head *last = list->prev;

    first->prev = prev;
    prev->next = first;

    last->next = next;
    next->prev = last;
}
栈设计
static inline void list_splice(const struct list_head *list,
                struct list_head *head)
{
    if (!list_empty(list))
        __list_splice(list, head, head->next);
}
队列设计
static inline void list_splice_tail(struct list_head *list,
                struct list_head *head)
{
    if (!list_empty(list))
        __list_splice(list, head->prev, head);
}
合并两个链表后初始化空链表
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);
    }
}

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);
    }
}

（12）container_of宏获取type类型结构体的起始指针

#define container_of(ptr, type, member) \
    ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

参数
 * @ptr:    the &struct list_head pointer.
 * @type:    the type of the struct this is embedded in.
 * @member:    the name of the list_struct within the struct.

（13）获取第一个节点元素

#define list_first_entry(ptr, type, member) \
    list_entry((ptr)->next, type, member)

#define list_first_entry_or_null(ptr, type, member) \
    (!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)

（14）获取指定pos的下一个节点元素

#define list_next_entry(pos, member) \
    list_entry((pos)->member.next, typeof(*(pos)), member)

（14）获取指定pos的上一个节点元素

#define list_prev_entry(pos, member) \
    list_entry((pos)->member.prev, typeof(*(pos)), member)

（15）遍历链表

正向遍历
#define list_for_each(pos, head) \
    for (pos = (head)->next; pos != (head); pos = pos->next)
注意：此宏必要把list_head放在数据结构第一项成员，至此，它的地址也就是结构变量的地址。
反向遍历
#define list_for_each_prev(pos, head) \
    for (pos = (head)->prev; pos != (head); pos = pos->prev)
安全遍历
#define list_for_each_safe(pos, n, head) \
    for (pos = (head)->next, n = pos->next; pos != (head); \
        pos = n, n = pos->next)
#define list_for_each_prev_safe(pos, n, head) \
    for (pos = (head)->prev, n = pos->prev; \
         pos != (head); \
         pos = n, n = pos->prev)

从head节点开始（不包括head节点！）遍历它的每一个节点！它用n先将下一个要遍历的节点保存起来，防止删除本节点后，无法找到下一个节点，而出现错误！

（16）循环遍历每一个pos中的member子项

正向遍历
#define list_for_each_entry(pos, head, member)                \
    for (pos = list_entry((head)->next, typeof(*pos), member);    \
         &pos->member != (head);     \
         pos = list_entry(pos->member.next, typeof(*pos), member))
反向遍历
#define list_for_each_entry_reverse(pos, head, member)            \
    for (pos = list_entry((head)->prev, typeof(*pos), member);    \
         &pos->member != (head);     \
         pos = list_entry(pos->member.prev, typeof(*pos), member))
判断pos这个指针是否为空，为空的话给它赋值list_entry(head, typeof(*pos), member)这条语句求出来的结构体的地址！
#define list_prepare_entry(pos, head, member) \
    ((pos) ? : list_entry(head, typeof(*pos), member))
已知指向某个结构体的指针pos，以及指向它中的member成员的head指针，从它的下一个结构体开始向后遍历这个链表。
#define list_for_each_entry_continue(pos, head, member)         \
    for (pos = list_entry(pos->member.next, typeof(*pos), member);    \
         &pos->member != (head);    \
         pos = list_entry(pos->member.next, typeof(*pos), member))
已知指向某个结构体的指针pos，以及指向它中的member成员的head指针，从它的前一个结构体开始向前遍历这个链表。
#define list_for_each_entry_continue_reverse(pos, head, member)        \
    for (pos = list_entry(pos->member.prev, typeof(*pos), member);    \
         &pos->member != (head);    \
         pos = list_entry(pos->member.prev, typeof(*pos), member))
从pos节点开始，向后遍历链表。
#define list_for_each_entry_from(pos, head, member)             \
    for (; &pos->member != (head);    \
         pos = list_entry(pos->member.next, typeof(*pos), member))
先保存下一个要遍历的节点！从head下一个节点向后遍历链表。
#define list_for_each_entry_safe(pos, n, head, member)            \
    for (pos = list_entry((head)->next, typeof(*pos), member),    \
        n = list_entry(pos->member.next, typeof(*pos), member);    \
         &pos->member != (head);                     \
         pos = n, n = list_entry(n->member.next, typeof(*n), member))
先保存下一个要遍历的节点！从pos下一个节点向后遍历链表。
#define list_for_each_entry_safe_continue(pos, n, head, member)         \
    for (pos = list_entry(pos->member.next, typeof(*pos), member),         \
        n = list_entry(pos->member.next, typeof(*pos), member);        \
         &pos->member != (head);                        \
         pos = n, n = list_entry(n->member.next, typeof(*n), member))
先保存下一个要遍历的节点！从pos节点向后遍历链表。
#define list_for_each_entry_safe_from(pos, n, head, member)             \
    for (n = list_entry(pos->member.next, typeof(*pos), member);        \
         &pos->member != (head);                        \
         pos = n, n = list_entry(n->member.next, typeof(*n), member))
先保存下一个要遍历的节点！从链表尾部向前遍历链表。
#define list_for_each_entry_safe_reverse(pos, n, head, member)        \
    for (pos = list_entry((head)->prev, typeof(*pos), member),    \
        n = list_entry(pos->member.prev, typeof(*pos), member);    \
         &pos->member != (head);                     \
         pos = n, n = list_entry(n->member.prev, typeof(*n), member))
获取n结构体指针
#define list_safe_reset_next(pos, n, member)                \
    n = list_entry(pos->member.next, typeof(*pos), member)

4、list_for_each和list_for_each_entry实例

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include "list.h"

typedef struct Node
{
    struct list_head node;
    int a;
    int b;
}NODE;

typedef struct Head
{
    struct list_head list;
    int count;
}HEAD;

HEAD ghead;

int main(int argc,char **argv)
{
    struct list_head *pos=NULL;
    struct list_head *head=NULL;
    NODE *pNode = NULL;
    NODE *pPosNode = NULL;
    int i = 0;
    INIT_LIST_HEAD(&(ghead.list));
    ghead.count=0;

    for(i=0;i<10;i++)
    {
        pNode = (NODE *)malloc(sizeof(NODE));
        if(!pNode)
        {
            return -1;
        }
        memset(pNode,0,sizeof(NODE));
        pNode->a=i+1;
        pNode->b=i+2;
        //list_add(&pNode->node,&(ghead.list));
        list_add_tail(&pNode->node,&(ghead.list));
    }

    head = &(ghead.list);
    list_for_each(pos,head)
    {
        pNode = list_entry(pos,NODE,node);
        printf("list_for_each %d-%d\n",pNode->a,pNode->b);
        pNode = NULL;
    }

    list_for_each_entry(pPosNode,&(ghead.list),node)
    {
        printf("list_for_each_entry %d-%d\n",pPosNode->a,pPosNode->b);
    }

    return 0;
}
执行结果
list_for_each 1-2
list_for_each 2-3
list_for_each 3-4
list_for_each 4-5
list_for_each 5-6
list_for_each 6-7
list_for_each 7-8
list_for_each 8-9
list_for_each 9-10
list_for_each 10-11
list_for_each_entry 1-2
list_for_each_entry 2-3
list_for_each_entry 3-4
list_for_each_entry 4-5
list_for_each_entry 5-6
list_for_each_entry 6-7
list_for_each_entry 7-8
list_for_each_entry 8-9
list_for_each_entry 9-10
list_for_each_entry 10-11

5.内核list.h源文件
list.h