Linux最简单的休眠方式是wait_event(queue,condition)及其变种，在实现休眠的同时，它也检查进程等待的条件。四种wait_event形式如下：
wait_event(queue,condition);/*不可中断休眠，不推荐*/
wait_event_interruptible(queue,condition);/*推荐，返回非零值意味着休眠被中断，且驱动应返回-ERESTARTSYS*/
wait_event_timeout(queue,condition,timeout);
wait_event_interruptible_timeout(queue,conditon,timeout);/*有限的时间的休眠，若超时，则不管条件为何值返回0*/
唤醒休眠进程的函数：wake_up
void wake_up(wait_queue_head_t *queue);
void wake_up_interruptible(wait_queue_head *queue);
惯例：用wake_up唤醒wait_event，用wake_up_interruptible唤醒wait_event_interruptible
休眠与唤醒 实例分析：
本例实现效果为：任何从该设备上读取的进程均被置于休眠。只要某个进程向给设备写入，所有休眠的进程就会被唤醒。
static DECLARE_WAIT_QUEUE_HEAD(wq);
static int flag =0;
ssize_t sleepy_read(struct file *filp,char __user *buf,size_t count,loff_t *pos)
{
pirntk(KERN_DEBUG "process %i (%s) going to sleep\n",current->pid,current->comm);
wait_event_interruptible(wq,flag!=0);
flag=0;
printk(KERN_DEBUG "awoken %i (%s) \n",current->pid,current->comm);
return 0;
}
ssize_t sleepy_write(struct file *filp,const char __user *buf,size_t count,loff_t *pos)
{
printk(KERN_DEBUG "process %i (%s) awakening the readers ...\n",current->pid,current->comm);
flag=1;
wake_up_interruptible(&wq);
return count; /*成功并避免重试*/
}