秒表是线程安全的吗？

Question

there is a part of my code:

private void Wait(String expectedResponse)
{
    waitTimeout = 30;
    Stopwatch sw = new Stopwatch();
    sw.Start();
    while (!inputBuffer.Contains(expectedResponse))
    {
        if (sw.Elapsed.Seconds < waitTimeout)
        {
            Thread.Sleep(1);
        }
        else
        {
            sw.Stop();
            throw new Exception("Timeout");
        }
    }
    sw.Stop();
    Console.WriteLine("SUCCESS");
}

The Wait method runs in the main thread and sometimes in the thread that creates the main thread.

And sometimes the method of program infinitely loops, although the time (30 seconds) has passed, and the exception is not generated.

So, what's a problem? StopWatch class is not thread-safety? and if so, how to rewrite the code?

Any ideas?

Thank you!

Answer 1

From MSDN :

Thread Safety

Any public static members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Also I don't see any thread-sensitive call/method in your codes. You're instantiating a thread-local Stopwatch and using it. Btw, Thread.Sleep(1) will try to block for 1ms (but this is OS specific, windows will block for ~15ms) and still there is no problem about threads.

Now I think there is a problem with your inputBuffer , why because it's not thread-local. If more than one thread tries to use it at the same time, that will cause inconsistency. You may try Stream.Synchronized or implement your own thread-safe stream class.

I also suggest you to use step-by-step debugging or use at least some breakpoints to understand what is going on.