linux底层驱动机制之信号量

//信号量
1,定义
struct semaphore sem;

2,初始化
sema_init(&sem,1);

3,获得信号量，释放信号量
static int hello_open (struct inode *inode, struct file *file)
{ 
 if(down_trylock(&sem))
  return -EBUSY;
 return 0;
}
static int hello_release (struct inode *inode, struct file *file)
{
 up(&sem);
 printk("call hello release\n");
 return 0;
}