如果没有IO线程来处理异步结果，会发生什么情况？(What happens if there are no IO threads to handle async result?)

 我想知道当没有IO线程处理异步调用的结果时会发生什么。 
 
 假设你做了一个异步web请求（在服务器应用程序中，所有异步代码都由线程池处理）。 操作系统会发出信号，告诉您何时有结果，何时需要IO线程来读取套接字中的字节。 如果没有IO线程可用，因为这些线程都在使用中（全部含义由线程池设置的最大值）会发生什么情况？ 有信号可以等待，直到有线程可用的队列吗？ 还是信号只是闻所未闻？ 如果后者发生，等待等待的代码会发生什么？ 

I'm wondering what happens when there are no IO threads to handle the result of an async call. 
 
Say you make an async web request (in a server application so all async code is handeled by the thread pool). The OS will signal when there is a result for you and when it does you'll need an IO thread to read the bytes from the socket. If there are no IO threads available because that are all in use (all meaning up to the max set by the thread pool) what happens? Is there a queue where the signal can wait until there is a thread available? Or does the signal just go unheard? If the latter happens, what happens to the code waiting on the await?

原文：https://stackoverflow.com/questions/39053762