Linux 内核链表使用举例
链表数据结构的定义很简洁：
struct list_head {
struct list_head *next, *prev;
};
list_head结构包含两个指向list_head结构的指针prev和next，该内核链表具备双链表功能，通常它都组织成双循环链表，这里的list_head没有数据域。在Linux内核链表中，不是在链表结构中包含数据，而是在数据结构中包含链表节点。下面是一个简单的内核模块的例子，包含了对链表进行插入、删除、遍历的一些函数：
list.c：
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/list.h>
typedef struct list_test_struct {
int num;
struct list_head list;
}test;
struct list_head head_list;
rwlock_t list_lock = RW_LOCK_UNLOCKED; //定义读写锁，操作前加锁，操作后解锁
void creat_list(void)
{
test *s = NULL;
int i = 0;
for (i = 0; i < 10; i++)
{
s = (test *)kmalloc(sizeof(test), GFP_ATOMIC);
if (!s) return ;
s->num = i;
write_lock(&list_lock);
list_add_tail(&(s->list), &head_list); //添加节点
write_unlock(&list_lock);
}
}
void del_data(void)
{
test *s;
struct list_head *p;
write_lock(&list_lock);
list_for_each(p, &head_list) //遍历链表
{
s = list_entry(p, test, list);
if (s->num == 4)
{
list_del(p); //删除节点
write_unlock(&list_lock);
return ;
}
}
write_unlock(&list_lock);
}
void print_list(void)
{
test *s;
struct list_head *p;
read_lock(&list_lock);
list_for_each(p, &head_list)
{
s = list_entry(p, test, list);
printk(KERN_INFO"%d\n", s->num);
}
read_unlock(&list_lock);
}
int list_test_init(void)
{
INIT_LIST_HEAD(&head_list);
creat_list();
print_list();
del_data();
print_list();
return 0;
}
void list_test_exit(void)
{
return;
}
MODULE_LICENSE("GPL");
module_init(list_test_init);
module_exit(list_test_exit);
Makefile：
obj-m += list.o KERN_DIR = /usr/src/linux-headers-2.6.32-33-generic all: make -C $(KERN_DIR) M=`pwd` modules clean: make -C $(KERN_DIR) M=`pwd` modules clean rm -rf modules.order
make后生成module，获取超级用户权限后
insmod list.ko
然后输入命令：cat var/log/messages
printk打印信息：
Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274551] 0 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274553] 1 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274555] 2 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274555] 3 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274556] 4 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274557] 5 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274558] 6 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274559] 7 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274559] 8 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274560] 9 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274561] 0 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274562] 1 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274563] 2 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274564] 3 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274564] 5 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274565] 6 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274566] 7 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274567] 8 Jun 20 16:26:01 wuwen-laptop kernel: [ 5490.274568] 9第二次输出发现节点4被删除，在这里实现：
list_for_each(p, &head_list) //遍历链表
{
s = list_entry(p, test, list);
if (s->num == 4)
{
list_del(p); //删除节点
write_unlock(&list_lock);
return ;
}
}