使用wait_event_interruptible和wake_up_all在一起

问题描述

对于涉及使用阻塞和锁调度流程一类项目，我们应该使用两个内核函数：

  INT wait_event_interruptible（wait_queue_head_t Q，条件）;
无效wake_up_all（wait_queue_head_t * Q）;
 

wait_event_interruptible的解释是：

And the explanation of wake_up_all is:

I'm having a hard time figuring out how exactly these functions work and how to use them together. For example, when does the CONDITION get checked? Does wait_event_interruptible continuously poll, or does it only recheck the condition when wake_up_all is called? This explanation is a little unclear.

If you could give an example of how to use these functions together that would be very helpful.

解决方案

The whole point of a scheduler is to avoid polling in cases like this. What happens is precisely described in what you quoted : The condition is only rechecked on wake_up, ie for example if a given task is waiting for data to be produced :

• consumer check if data is available

• if not (ie condition false) it goes to sleepand is added to a wait queue

• retry when waked up

While on the producer side

• Once data is produced, set some flag, or add something to a listso that the condition evaluated by the consumer becomes true

• call wake_up or wake_up all on a waitqueue

Now , I suggest you try to use them, and come back with another question AND code you tried if it does not work the way you want.

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