Linux并发控制---解决竞态的一种操作--->原子操作

            static inline void atomic_set(atomic_t *v, int i); //设置原子的值   
      　　    atomic_t = ATOMIC_INIT(0);          //定义原子变量并且初始化为0         

2. 获取原子变量的值

1. 1.                                 #define atomic_read(v)  ((v)->counter)   //返回原子变量的值  (*(volatile int *)&(v)->counter)

1. 1.                                     #define atomic_add(i, v)    (void) atomic_add_return(i, v) //把v的值加 i#define atomic_inc(v)       (void) atomic_add_return(1, v)     //vz自加#define atomic_sub(i, v)    (void) atomic_sub_return(i, v)   
      #define atomic_dec(v)       (void) atomic_sub_return(1, v)   //v自减

       

#include <linux/init.h>
#include <linux/module.h>

/*驱动注册的头文件，包含驱动的结构体和注册和卸载的函数*/
#include <linux/platform_device.h>
/*注册杂项设备头文件*/
#include <linux/miscdevice.h>
/*注册设备节点的文件结构体*/
#include <linux/fs.h>
//原子操作的函数头文件
#include <asm/atomic.h>
#include <asm/types.h>

#define DRIVER_NAME "atomic_int"
#define DEVICE_NAME "atomic_int"
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("HKY");

//定义原子变量,并初始化为0static atomic_t value_atomic = ATOMIC_INIT(0);

staticint atomic_int_open(struct inode *inode, struct file *file){
    printk(KERN_EMERG "atomic_int open in!n");    
    
    if(atomic_read(&value_atomic)){
        return -EBUSY;
    }
    
    atomic_inc(&value_atomic);
    
    printk(KERN_EMERG "atomic_int open success!n");    
    return0;
}

staticint atomic_int_release(struct inode *inode, struct file *file){
    printk(KERN_EMERG "atomic_int releasen");
    
    atomic_dec(&value_atomic);
    
    return0;
}

staticstruct file_operations atomic_int_ops = {
    .owner = THIS_MODULE,
    .open = atomic_int_open,
    .release = atomic_int_release,
};


staticstruct miscdevice atomic_int_dev = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = DEVICE_NAME,
    .fops = &atomic_int_ops,
};


staticint atomic_int_probe(struct platform_device *pdv){
    
    printk(KERN_EMERG "tinitializedn");
    misc_register(&atomic_int_dev);
    
    return0;
}

staticint atomic_int_remove(struct platform_device *pdv){
    
    printk(KERN_EMERG "tremoven");
    misc_deregister(&atomic_int_dev);
    return0;
}

struct platform_driver atomic_int_driver = {
    .probe = atomic_int_probe,
    .remove = atomic_int_remove,
    .driver = {
        .name = DRIVER_NAME,
        .owner = THIS_MODULE,
    }
};


staticint atomic_int_init(void)
{
    int DriverState;
    
    printk(KERN_EMERG "HELLO WORLD enter!n");
    DriverState = platform_driver_register(&atomic_int_driver);
    
    printk(KERN_EMERG "tDriverState is %dn",DriverState);
    return0;
}


staticvoid atomic_int_exit(void)
{
    printk(KERN_EMERG "HELLO WORLD exit!n");
    
    platform_driver_unregister(&atomic_int_driver);    
}

module_init(atomic_int_init);
module_exit(atomic_int_exit);