linux底层驱动机制之自旋锁

//自旋锁
1，定义
spinlock_t lock;
int flag = 1;

2，初始化锁
 spin_lock_init(&lock);

3,加锁解锁
static int hello_open (struct inode *inode, struct file *file)
{
 //枷锁
 spin_lock(&lock);

 if(flag == 1)
 {
  flag--;
  //解锁
  spin_unlock(&lock);
  return 0;
 }
 else
 {
  //解锁
  spin_unlock(&lock);
  return -EBUSY;
 }
}
static int hello_release (struct inode *inode, struct file *file)
{

 //枷锁
 spin_lock(&lock);

 flag++;

 //解锁
 spin_unlock(&lock);
}