How can I wake a sleeping thread in C #?

Question

Before people tell me this: I do not use Thread.sleep for anything but trying to find a way around it. I am trying to handle other people with future code that may not be .Sleep () for free. I understand very well how terrible it is for synchronizing things.

I accept a stream in a piece of my code. I want to be able to set a limit on this thread lifetime. My usual way to do this is as follows:

Thread outer = new Thread(() => { externalThread.Start(); externalThread.Join(); }); outer.Start(); outer.Join(lifetime); if (outer.ThreadState != ThreadState.Stopped) { outer.Abort(); } inner.Join(); 

Since then, I have discovered that I apparently cannot wake the sleeping thread before the dream ends. Worse, it still writes to the console if I give it a 10 millisecond life:

 new Thread(() => { Thread.Sleep(2000); Console.WriteLine("second"); }) 

Although I understand .Abort () is not a hard limit on thread execution. It seems like 2 seconds would have been enough warning, but I think not ...

I tried checking the status of WaitSleepJoin and .Interrupt (); it throws a thread or throws an exception (sorry, not sure. Windows tells me that it crashed if the debugger is not working, and if it is running, it works as if the interrupt was not called) and still writes to the console through 2 seconds, .Resume () does not seem to do anything for the sleeping thread.

Is there a way to wake a thread without waiting for the end of its sleep? I understand that stopping is not “immediate”, so Console.WriteLine can be called independently; this is the second second waiting for me. What if it's a 10 day wait? Since I can’t control the flows that enter, I don’t know, and this is not a way to prevent this ...

Answer 1

There is no way to wake a thread from sleep. You can only interrupt the thread by calling Abort or Interrupt (both of which throw a ThreadAbortException).

But to solve the question of why at startup:

 new Thread(() => { Thread.Sleep(2000); Console.WriteLine("second"); }) 

with a timeout of 10 ms, it still prints because your code to control the lifetime of the thread does not do what you want to do.

So you have externalThread and external. You start an external one (which starts a new thread, lets call it thread 1) and from an external start of a call on an external thread (which starts a new thread, lets call it thread 2). So, you just started two new threads.

When you call outer.About() , it only interrupts thread 1. The thread started by calling externalThread.Start() , thread 2 continues execution until completion, since nothing interrupts it.

I'm not sure what you are trying to accomplish using an extra external thread. Won't it be easier:

 externalThread.Start(); externalThread.Join(lifetime); if (externalThread.ThreadState != ThreadState.Stopped) { externalThread.Abort(); } 

Answer 2

Use WaitOne + timer to control threads of unknown origin.

or if you have control over the workflow code:

kinda hacky way, to achieve a more "responsive sleep" when you don't like the timers / other threads used to wake the thread up.

use it instead of regular Thread.Sleep

  private void WaitFor(int milis) { const int interval = 500; if (milis <= interval) { throw new ArgumentException(); } var sections = milis / interval; for (var s = 0; s < sections && (!ShouldQuit); ++s) { Thread.Sleep(interval); } } 

note the ShouldQuit flag, which is a class field accessible from both threads

of course this has worse cpu usage characteristics than event / timer based expectations