Linux kernel 5.x wait_event_interruptible_timeout()

先看看内核源码的注释，这往往是在研究内核函数必读的一段文字，这将会给我们理解内核代码执行逻辑带来很大的帮助，一定要花时间好好理解；

函数在内核代码被定义为一个宏：

#define __wait_event_interruptible_timeout(wq_head, condition, timeout)         
        ___wait_event(wq_head, ___wait_cond_timeout(condition),                 
                      TASK_INTERRUPTIBLE, 0, timeout,                           
                      __ret = schedule_timeout(__ret))

/**

• wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
• @wq_head: the waitqueue to wait on
• @condition: a C expression for the event to wait for
• @timeout: timeout, in jiffies
• The process is put to sleep (TASK_INTERRUPTIBLE) until the
• @condition evaluates to true or a signal is received.
• The @condition is checked each time the waitqueue @wq_head is woken up.
• wake_up() has to be called after changing any variable that could
• change the result of the wait condition.
• Returns:
• 0 if the @condition evaluated to %false after the @timeout elapsed,
• 1 if the @condition evaluated to %true after the @timeout elapsed,
• the remaining jiffies (at least 1) if the @condition evaluated
• to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
• interrupted by a signal.
  */

参数一：等待队列头，struct wait_queue_head_t
参数二：等待条件
参数三：延时时间（10*HZ表示10s）

等待进程被唤醒条件：一直睡眠直到条件成立或者是定时时间到

代码注释详细解释了不同情况下函数的返回值:

基本的使用方法：

1.声明等待队列头
 wait_queue_head_t wait_queue
2.初始化等待队列头
 init_waitqueue_head(&wait_queue)
3.条件不成立让wait queue进入等待队列
 wait_event_interruptible_timeout(wait_queue,condition,timeout)
4.条件满足或者是延时时间到
 wake_up_interruptible(&wait_queue)

最后

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