Question

ALL

I was working on a little code which is for search a thread by thread id in the processes of computer.

All my code looks like below , Please help to review it. 🙂

    using System.Diagnostics;

    public class NKDiagnostics
    {
        private Process[] m_arrSysProcesses;

        private void Init()
        {
            m_arrSysProcesses = Process.GetProcesses(".");
        }
        public static ProcessThread[] GetProcessThreads(int nProcID)
        {
            try
            {
                Process proc = Process.GetProcessById(nProcID);
                ProcessThread[] threads = new ProcessThread[proc.Threads.Count];
                proc.Threads.CopyTo(threads, 0);
                return threads;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                return null;
            }
        }
    }

and In another class, I assign a thread to execute my function named DoNothing

    ThreadPool.QueueUserWorkItem((t) => Utility.DoNothing((TimeSpan)t), 
TimeSpan.FromMinutes(1));

and the function DoNothing code is

public class Utility
    {
        public static void DoNothing(TimeSpan timeout, TextBox txtThreadId)
        {
            TimeoutHelper helper = new TimeoutHelper(timeout);
            while (true)
            {
                Thread.Sleep(1000 * 5);
                if (helper.RemainingTime() <= TimeSpan.Zero)
                {
                    MessageBox.Show("This thread's work is finished.");
                    break;
                }
                else
                {

                    if (Thread.CurrentThread.IsThreadPoolThread)
                    {
                        MessageBox.show( Thread.CurrentThread.ManagedThreadId.ToString());
                    }

                }
            }
        }
}

My problem is the Thread.CurrentThread.ManagedThreadId shows 10, I searched it in all the process. But did’t found it .

ProcessThread[] m_Threads = NKDiagnostics.GetProcessThreads(processId);
for (int i = 0; i < m_Threads.Length; i++)
            {

                if (m_Threads[i].Id.Equals(10))
                {
                    MessageBox.Show("Found it.");
                }
}

Am I missing something? why I can’t find this thread ? please help me .thanks.

Updated

The original idea of mine to do some experiment with this code is trying to find a way to get the status of the managed thread. obviously in the way I posted here doesn’t make it. so my question is how can I know the status of managed thread with specified thread id? thanks.

Answer 1

Thread.ManagedThreadId and ProcessThread.Id are not comparable. The first is assigned by the .NET runtime, while the second is the value of the native thread handle the OS assigns to each thread.

It is also not possible to map one to the other:

An operating-system ThreadId has no fixed relationship to a managed
thread, because an unmanaged host can control the relationship between
managed and unmanaged threads. Specifically, a sophisticated host can
use the Fiber API to schedule many managed threads against the same
operating system thread, or to move a managed thread among different
operating system threads.

Therefore your code cannot be made to work as is.

As an aside, there is a possible race condition here:

ProcessThread[] threads = new ProcessThread[proc.Threads.Count];
proc.Threads.CopyTo(threads, 0);

It is possible that proc.Threads is modified after the array has been initialized but before CopyTo executes. To avoid this race condition evaluate proc.Threads only once, for example:

var threads = proc.Threads.ToArray();