锁的学习-----自旋锁学习的突发乱想

最近学习锁已有点走火入魔，然后做了以下这个测试(虽然不知道有什么用，但是做个记录=-=)：

测试内容：在spin_lock获取了锁，且不unlock的情况下对数据进行访问。

相关代码

1、read函数：

ssize_t spin_lock_sleep_read(struct file * filp, char __user * buf, size_t count,
   loff_t * f_pos)
{
 struct spin_lock_sleep_dev *dev = filp->private_data;
 ssize_t retval = 0;

 spin_lock(&dev->lock);

 dev->str = "wrtie in spin lock!";

 //spin_unlock(&dev->lock); 这部分会在退出module的时候做

 return retval;
}

2、write函数：

ssize_t spin_lock_sleep_write(struct file * filp, const char __user * buf,
    size_t count, loff_t * f_pos)
{
 struct spin_lock_sleep_dev *dev = filp->private_data;
 ssize_t retval = 0; 

 dev->str = "write something to test!";
 
 return retval;
}

3、退出module函数：

void spin_lock_sleep_cleanup(void)
{
 int i;
 dev_t devno = MKDEV(spin_lock_sleep_major, spin_lock_sleep_minor);

 printk(KERN_INFO "spin_lock sleep module unloaded now!\n");
 
 if (spin_lock_sleep_devices) {
  for (i = 0; i < spin_lock_sleep_nr_devs; i++) {
   printk("%s\n",spin_lock_sleep_devices[i].str);
   if(spin_is_locked(&(spin_lock_sleep_devices[i].lock)) != 0)
   {
    printk("unlock now!\n");   
    spin_unlock(&spin_lock_sleep_devices[i].lock);
   }
   cdev_del(&spin_lock_sleep_devices[i].cdev);
  }
  kfree(spin_lock_sleep_devices);
 }

 
 unregister_chrdev_region(devno, spin_lock_sleep_nr_devs);

}

1、常规操作：insmod module、创建设备节点

2、读设备节点(执行read函数)，如下图，自旋锁锁上不解锁
3、写设备节点(执行write函数)，如下图

4、注销module，查看相关数据，已被修改=-=