如何取消并发的繁重任务？

Question

我有一个 Task 通过繁重的进程在其体内运行。另外，我们无法访问这个方法的主体（繁重的进程），我们必须等到完成这个过程。

现在我的问题是，如何在不中断任务的情况下取消，这样我就不会检查其中的任何值？

我的代码是这样的：

private CancellationTokenSource CTS = new CancellationTokenSource();


public void CallMyMethod(CancellationTokenSource cts)
{
    //
    // Several methods they call each other. And pass tokens to each other.
    MyProcess(cts);
}


private void MyProcess(CancellationTokenSource cts)
{
    CancellationToken token = cts.Token;

    Task.Run(() =>
    {
        token.ThrowIfCancellationRequested(); // Work just when ThrowIfCancellationRequested called. and check that again

        if (token.IsCancellationRequested) // Must be checked every time, and after the investigation not work.
            return;

        // My long time process
        HeavyProcess();  // We have no access to the body of this method

    }, token);
}


private void CancelProcess()
{
    try
    {
        //
        // I want to cancel Now, Just Now not after HeavyProcess completion or checking token again!
        //
        CTS.Cancel();
        CTS.Token.ThrowIfCancellationRequested();
    }
    catch 
    { }
}

运行后我可以取消繁重的进程吗？

Answer 1

如果您无法控制长时间运行的方法，那么协作取消将不起作用。您可以做的是将繁重的工作卸载到不同的进程，并在后台线程中监视进程：

private void MyProcess(CancellationTokenSource cts)
{
    cts.Token.ThrowIfCancellationRequested(); 

    // Move the heavy work to a different process
    var process = Process.Start(new ProcessStartInfo { /*  */ });

    // Register to the cancellation, where if the process is still
    // running, kill it.
    cts.Token.Register(() => 
    {
        if (!process.HasExited)
        {
            process.Kill();
        }
    });
}

现在，当您取消时，您会调用我们终止进程的回调：

private void CancelProcess()
{
    CTS.Cancel();
}