Linux内核list_head学习（二）

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前一篇文章讨论了list_head 结构的基本结构和实现原理，本文主要介绍一下实例代码。

自己如果想在应用程序中使用list_head 的相应操作（当然应该没人使用了，C++ STL提供了list 用起来貌似更方便），在应用程序中需要包含自己的 "list.h" 头文件：

/*注：这个list.h 是为了配合示例程序而建的，内容来自：linux/include/linux/list.h 和相关文件*/#ifndef _LINUX_LIST_H#define _LINUX_LIST_H struct list_head {         struct list_head *next, *prev;};#define LIST_HEAD_INIT(name) { &(name), &(name) }#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)#define container_of(ptr, type, member) ({                      \        const typeof( ((type *)0)->member ) *__mptr = (ptr);    \        (type *)( (char *)__mptr - offsetof(type,member) );})static inline void INIT_LIST_HEAD(struct list_head *list){        list->next = list;        list->prev = list;}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;}static inline void list_add(struct list_head *new, struct list_head *head){        __list_add(new, head, head->next);}  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 = NULL;        entry->prev = NULL;}#define prefetch(x) __builtin_prefetch(x)//注：这里prefetch 是gcc的一个优化，也可以不要#define list_for_each(pos, head) \         for (pos = (head)->next; prefetch(pos->next), pos != (head); \                 pos = pos->next)#define list_entry(ptr, type, member) \         container_of(ptr, type, member)#endif

写了一个简单的应用程序：

#include "list.h" #include <stdio.h> #include <string.h>#define MAX_NAME_LEN 32#define MAX_ID_LEN 10typedef struct stud{    struct list_head list;    char name[MAX_NAME_LEN];    char stu_number[MAX_ID_LEN];}num_n_stu;int main(void){    struct list_head head;    num_n_stu stu_1;    num_n_stu stu_2;    num_n_stu *entry;    struct list_head *p;    INIT_LIST_HEAD(&head);    strcpy(stu_1.name,"lisi");    strcpy(stu_1.stu_number,"10000000");    strcpy(stu_2.name,"zhangsan");    strcpy(stu_2.stu_number,"10000001");    list_add(&stu_1.list,&head);    list_add(&stu_2.list,&head);    list_del(&stu_2.list);    list_for_each(p,&head)    {        entry=list_entry(p,struct stud,list);        printf("name: %s\n",entry->name);        printf("stu_number: %s\n",entry->stu_number);    }    list_del(&stu_1.list);    return 0;}

在Linux内核中可以使用这个以类似驱动模块的形式加载到内核：（这里就不用使用自定义的list.h了）

#include <linux/list.h>#include <linux/init.h>#include <linux/module.h>MODULE_LICENSE("GPL");#define MAX_NAME_LEN 32#define MAX_ID_LEN 10typedef struct stud{    struct list_head list;    char name[MAX_NAME_LEN];    char stu_number[MAX_ID_LEN];}num_n_stu;static int my_main(void){    struct list_head head;    num_n_stu stu_1;    num_n_stu stu_2;    num_n_stu *entry;    struct list_head *p;    INIT_LIST_HEAD(&head);    strcpy(stu_1.name,"lisi");    strcpy(stu_1.stu_number,"10000000");    strcpy(stu_2.name,"zhangsan");    strcpy(stu_2.stu_number,"10000001");    list_add(&stu_1.list,&head);    list_add(&stu_2.list,&head);    list_del(&stu_2.list);    list_for_each(p,&head)    {        entry=list_entry(p,struct stud,list);        printk("name: %s\n",entry->name);        printk("stu_number: %s\n",entry->stu_number);    }        list_del(&stu_1.list);        return 0;}static void my_exit(void){    printk("my_exit ! \n");}module_init(my_main);module_exit(my_exit);

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