linux内核链表

内核链表---include/linux/list.h

链表数据结构定义

struct list_head

{

struct list_head *next,*prev;

}

内核链表具备双链表功能，实际上，通常它都组织成双向循环链表。

链表操作---

初始化链表头

INIT_LIST_HEAD(list_head *head)

内核代码

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

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */

插入节点---

list_add(struct list_head *new,struct list_head *head)

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

void __list_add(struct list_head *new,
                  struct list_head *prev,
                  struct list_head *next)
{
    WARN(next->prev != prev,
        "list_add corruption. next->prev should be "
        "prev (%p), but was %p. (next=%p).\n",
        prev, next->prev, next);
    WARN(prev->next != next,
        "list_add corruption. prev->next should be "
        "next (%p), but was %p. (prev=%p).\n",
        next, prev->next, prev);
    next->prev = new;
    new->next = next;
    new->prev = prev;
    prev->next = new;
}
EXPORT_SYMBOL(__list_add);

list_add_tail(struct list_head *new,struct list_head *head)

删除节点---

list_del(struct list_head *entry)

static inline void list_del(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    entry->next = LIST_POISON1;赋给安全的指针。
    entry->prev = LIST_POISON2;
}

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

提取数据-----

list_entry(ptr,type,member)---已知数据结构中节点的指针ptr，type大的结构的类型，member小结构在大结构中对应的成员名。函数返回指向大结构的指针。

#define list_entry(ptr, type, member) \
    container_of(ptr, type, member)

#define container_of(ptr, type, member) ({            \
    const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
    (type *)( (char *)__mptr - offsetof(type,member) );})

container_of(ptr, type, member)

2009-04-13 15:38:16|  分类： linux相关学习 |字号 订阅

指针ptr指向结构体type中的成员member；通过指针ptr，返回结构体type的起始地址

#define container_of(ptr, type, member) ({                  \
    const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
    (type *)( (char *)__mptr - offsetof(type,member) );})
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
1.ptr为物理地址,其类型和member类型一致,最终使用typeof( ((type *)0)->member )
  由编译器自动返回member的类型
2.type为包含member成员的结构体
3.offsetof(type,member)为member成员在type结构体中的偏移值,大小范围0~sizeof(type)字节 (因为以0地址为type类型数据结构的起始地址)
4.ptr- offsetof()就等于包含该ptr的type结构体父变量的物理起始地址,强制转换为(type*).

应用举例：

#define list_entry(ptr, type, member)                         \
    container_of(ptr, type, member)

#define list_for_each_entry(pos, head, member)                \
    for (pos = list_entry((head)->next, typeof(*pos), member);\
     prefetch(pos->member.next), &pos->member != (head);      \
     pos = list_entry(pos->member.next, typeof(*pos), member))
//-------------------------------------------------------------
list_entry((head)->next, typeof(*pos), member)返回(head)->next物理指针所处位置向前减去offsetof()个字节数据之后, 其父变量pos的物理地址,父变量的类型在编译时由typeof(*pos)自动返回(gliethttp).
所以list_for_each_entry遍历head下面挂接的类型为typeof(*pos)的childs结构体们,当然每个child结构体包含struct list_head node之类相似的双向链表list_head类型项,就这样通过循环pos将依次指向双向链表上的各个child.(member就是child类型中被定义的变量名)
//-------------------------------------------------------------
下面一段程序摘自: drivers/usb/driver.c
struct usb_dynids {
    spinlock_t lock;
    struct list_head list;
};
struct usb_dynid {
    struct list_head node;
    struct usb_device_id id;
};
static const struct usb_device_id *usb_match_dynamic_id(struct usb_interface *intf,
                            struct usb_driver *drv)
{
    struct usb_dynid *dynid;

    spin_lock(&drv->dynids.lock);
//1. drv->dynids.list为head,即:树根,父亲,正如上面的struct usb_dynids
//2. dynid为child,其中drv->dynids.list.next存放了第一个child结构体中的
//   struct list_head类型名字为node的物理地址值.
//3. 看着很复杂,其实翻译出来就简单多了(gliethttp)
//模型为for(child;child != head;child = child->next)
// for(dynid = container_of(drv->dynids.list.next, struct usb_dynid,nod);
//     dynid->node != &drv->dynids.list;
//     dynid = container_of(dynid->node.next, struct usb_dynid,nod)
//     )
    list_for_each_entry(dynid, &drv->dynids.list, node) {
        if (usb_match_one_id(intf, &dynid->id)) {
            spin_unlock(&drv->dynids.lock);
            return &dynid->id;
        }
    }
    spin_unlock(&drv->dynids.lock);
    return NULL;
}

遍历---

list_for_each(struct list_head *pos,struct list_head *head)

#define list_for_each(pos, head) \
    for (pos = (head)->next; prefetch(pos->next), pos != (head); \
            pos = pos->next)

列子--

list_for_each(pos,head)

{

card=list_entry(entry,struct cs_card,list)

if(card->dev_midi==minor)

break;

}