Bug 4269 - A new thread from threadpool cannot be named
Summary: A new thread from threadpool cannot be named
Alias: None
Product: Class Libraries
Classification: Mono
Component: mscorlib ()
Version: 2.10.x
Hardware: PC Windows
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2012-04-05 12:48 UTC by haohaolee
Modified: 2012-04-09 04:12 UTC (History)
2 users (show)

Is this bug a regression?: ---
Last known good build:

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Description haohaolee 2012-04-05 12:48:03 UTC

using System;
using System.Threading;

public class Example {
    public static void Main() {
        // Queue the task.
        ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadProc));

        Console.WriteLine("Main thread does some work, then sleeps.");

        Console.WriteLine("Main thread exits.");

    static void ThreadProc(Object stateInfo) {
        Thread.CurrentThread.Name = "My Worker"; // there will be an exception here

        Console.WriteLine("Hello from the thread pool.");

dmcs thread.cs 
mono thread.exe

Main thread does some work, then sleeps.

Unhandled Exception: System.InvalidOperationException: Thread.Name can only be set once.
  at (wrapper managed-to-native) System.Threading.Thread:SetName_internal (System.Threading.InternalThread,string)
  at System.Threading.Thread.set_Name (System.String value) [0x00000] in <filename unknown>:0
  at Example.ThreadProc (System.Object stateInfo) [0x00000] in <filename unknown>:0


Expected behavior: No exception and the thread name is set. Because this is the behavior of Microsoft .Net.
Comment 1 Zoltan Varga 2012-04-09 02:37:56 UTC
Fixed in master/2.10.
Comment 2 haohaolee 2012-04-09 03:33:09 UTC
Thanks for the quick fix.

i want to add some comments. The thread from the threadpool not only can be named, but also is null at first, according to the MS .net behaviors.

that means:

static void ThreadProc(Object stateInfo) {

    Debug.Assert( Thread.CurrentThread.Name == null );
    Thread.CurrentThread.Name = "My Worker"; 

    Console.WriteLine("Hello from the thread pool.");

Have seen your fix, I'm not sure if it makes sure that the thread's name is null at the beginning. Currently its name is "Threadpool worker"
Comment 3 Zoltan Varga 2012-04-09 04:12:17 UTC
Mono is different in this regard from .net, we give initial names to these threads. This seems useful, so I left it as it is.