22160476800

Committed 18 Feb 2026 10:32PM UTC coverage: 30.019% (+0.03%) from 29.986%

Build # 22160476800

Build Type

Pull #503

coveralls.net

Committed by

DemoBytom

Commit Message

Fixed `DisposedException` when calling `mainLoopLifetime.Cancel`

The `mainLoopLifetime.Cancel()` in `StaThreadService` was called after `TaskCompletionSource.SetResult()`. That task ending was leading to `MainLoopLifetime` being already disposed before the `Cancel()` was called, causing `DisposedException` if the completion and disposal happened fast enough.
Moving the call to `mainLoopLifetime.Cancel()` before `tcs.SetResult`/`tcs.SetException` ensures this will not happen.

Fixes #501

Pull Request Pull Request #503: Fixed `DisposedException` when calling `mainLoopLifetime.Cancel`

Run Details

640 of 2132 relevant lines covered (30.02%)

0.33 hits per line

Source File
Press 'n' to go to next uncovered line, 'b' for previous

92.59

/src/Demo.Engine.Core/Features/StaThread/StaThreadService.cs

// Copyright © Michał Dembski and contributors.
// Distributed under MIT license. See LICENSE file in the root for more information.

using System.Runtime.InteropServices;
using System.Threading.Channels;
using Demo.Engine.Core.Interfaces;
using Demo.Engine.Core.Interfaces.Platform;
using Demo.Engine.Core.Interfaces.Rendering;
using Microsoft.Extensions.Hosting;

namespace Demo.Engine.Core.Features.StaThread;

internal sealed class StaThreadService
    : IStaThreadService,
      IDisposable
{
    private readonly IHostApplicationLifetime _hostApplicationLifetime;
    private readonly ChannelReader<StaThreadRequests> _channelReader;
    private readonly IMainLoopLifetime _mainLoopLifetime;
    private bool _disposedValue;

    public Task ExecutingTask { get; }
    public bool IsRunning { get; private set; }

    public StaThreadService(
        IHostApplicationLifetime hostApplicationLifetime,
        IRenderingEngine renderingEngine,
        IOSMessageHandler osMessageHandler,
        ChannelReader<StaThreadRequests> channelReader,
        IMainLoopLifetime mainLoopLifetime)
    {
        _hostApplicationLifetime = hostApplicationLifetime;
        _channelReader = channelReader;
        _mainLoopLifetime = mainLoopLifetime;
        IsRunning = true;
        ExecutingTask = RunSTAThread(
            renderingEngine,
            osMessageHandler);
    }

    private Task RunSTAThread(
        IRenderingEngine renderingEngine,
        IOSMessageHandler osMessageHandler)
    {
        var tcs = new TaskCompletionSource();
        var thread = new Thread(()
            =>
        {
            try
            {
                using var cts = CancellationTokenSource.CreateLinkedTokenSource(
                    _hostApplicationLifetime.ApplicationStopping,
                    _mainLoopLifetime.Token);

                SingleThreadedSynchronizationContextChannel.Await(async ()
                    => await STAThread(
                        renderingEngine: renderingEngine,
                        osMessageHandler: osMessageHandler,
                        cancellationToken: cts.Token));

                FinishRunning(tcs);
            }
            catch (OperationCanceledException)
            {
                FinishRunning(tcs);
            }
            catch (Exception ex)
            {
                FinishRunning(tcs, ex);
            }
        });
        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
        {
            //Can only by set on the Windows machine. Doesn't work on Linux/MacOS
            thread.SetApartmentState(ApartmentState.STA);
            thread.Name = "Main STA thread";
        }
        else
        {
            thread.Name = "Main thread";
        }

        thread.Start();

        return tcs.Task;

        void FinishRunning(
            TaskCompletionSource tcs,
            Exception? exception = null)
        {
            /* This should be called BEFORE tcs.SetResult/tcs.SetException!
             * Otherwise _mainLoopLifetime.Cancel() gets called after the returned tcs.Task completes,
             * leading to dispoes exception on mainLoopLifetime, that's already disposed upstream! */
            IsRunning = false;
            _mainLoopLifetime.Cancel();

            if (exception is null)
            {
                tcs.SetResult();
            }
            else
            {
                tcs.SetException(exception);
            }
        }
    }

    private async Task STAThread(
        IRenderingEngine renderingEngine,
        IOSMessageHandler osMessageHandler,
        CancellationToken cancellationToken)
    {
        var doEventsOk = true;

        await foreach (var staAction in _channelReader
            .ReadAllAsync(cancellationToken)
            .WithCancellation(cancellationToken))
        {
            switch (staAction)
            {
                case StaThreadRequests.DoEventsOkRequest doEventsOkRequest:
                    doEventsOk &= doEventsOkRequest.Invoke(renderingEngine, osMessageHandler);
                    break;

                default:
                    _ = staAction.Invoke(renderingEngine, osMessageHandler);
                    break;
            }

            if (!doEventsOk || !IsRunning || cancellationToken.IsCancellationRequested)
            {
                break;
            }
        }
    }

    private void Dispose(bool disposing)
    {
        if (!_disposedValue)
        {
            if (disposing)
            {
            }

            _disposedValue = true;
        }
    }

    public void Dispose()
    {
        // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
        Dispose(disposing: true);
        GC.SuppressFinalize(this);
    }

    private sealed class SingleThreadedSynchronizationContextChannel
        : SynchronizationContext
    {
        private readonly Channel<(SendOrPostCallback d, object? state)> _channel =
            Channel.CreateUnbounded<(SendOrPostCallback d, object? state)>(
                new UnboundedChannelOptions { SingleReader = true, SingleWriter = false });

        public override void Post(SendOrPostCallback d, object? state)
            => _channel.Writer.TryWrite((d, state));

        public override void Send(SendOrPostCallback d, object? state)
            => throw new InvalidOperationException("Synchronous operations are not supported!");

        public static void Await(Func<Task> taskInvoker)
        {
            var originalContext = Current;
            try
            {
                var context = new SingleThreadedSynchronizationContextChannel();
                SetSynchronizationContext(context);

                Task task;
                try
                {
                    task = taskInvoker.Invoke();
                }
                catch (Exception ex)
                {
                    // If the invoker throws synchronously, complete the channel so the pump can exit.
                    context._channel.Writer.Complete(ex);
                    throw;
                }

                _ = task.ContinueWith(t
                    => context._channel.Writer.Complete(t.Exception),
                    TaskScheduler.Default);

                // Pump loop: block synchronously until items are available or the writer completes.
                while (context._channel.Reader.WaitToReadAsync().Preserve().GetAwaiter().GetResult())
                {
                    while (context._channel.Reader.TryRead(out var work))
                    {
                        work.d.Invoke(work.state);
                    }
                }

                task.GetAwaiter().GetResult();
            }
            finally
            {
                SetSynchronizationContext(originalContext);
            }
        }
    }
}

1	// Copyright © Michał Dembski and contributors.
2	// Distributed under MIT license. See LICENSE file in the root for more information.
3
4	using System.Runtime.InteropServices;
5	using System.Threading.Channels;
6	using Demo.Engine.Core.Interfaces;
7	using Demo.Engine.Core.Interfaces.Platform;
8	using Demo.Engine.Core.Interfaces.Rendering;
9	using Microsoft.Extensions.Hosting;
10
11	namespace Demo.Engine.Core.Features.StaThread;
12
13	internal sealed class StaThreadService
14	: IStaThreadService,
15	IDisposable
16	{
17	private readonly IHostApplicationLifetime _hostApplicationLifetime;
18	private readonly ChannelReader<StaThreadRequests> _channelReader;
19	private readonly IMainLoopLifetime _mainLoopLifetime;
20	private bool _disposedValue;
21
22	public Task ExecutingTask { get; }	1✔
23	public bool IsRunning { get; private set; }	1✔
24
25	public StaThreadService(	1✔
26	IHostApplicationLifetime hostApplicationLifetime,	1✔
27	IRenderingEngine renderingEngine,	1✔
28	IOSMessageHandler osMessageHandler,	1✔
29	ChannelReader<StaThreadRequests> channelReader,	1✔
30	IMainLoopLifetime mainLoopLifetime)	1✔
31	{
32	_hostApplicationLifetime = hostApplicationLifetime;	1✔
33	_channelReader = channelReader;	1✔
34	_mainLoopLifetime = mainLoopLifetime;	1✔
35	IsRunning = true;	1✔
36	ExecutingTask = RunSTAThread(	1✔
37	renderingEngine,	1✔
38	osMessageHandler);	1✔
39	}	1✔
40
41	private Task RunSTAThread(
42	IRenderingEngine renderingEngine,
43	IOSMessageHandler osMessageHandler)
44	{
45	var tcs = new TaskCompletionSource();	1✔
46	var thread = new Thread(()	1✔
47	=>	1✔
48	{	1✔
49	try	1✔
50	{	1✔
51	using var cts = CancellationTokenSource.CreateLinkedTokenSource(	1✔
52	_hostApplicationLifetime.ApplicationStopping,	1✔
53	_mainLoopLifetime.Token);	1✔
54		1✔
55	SingleThreadedSynchronizationContextChannel.Await(async ()	1✔
56	=> await STAThread(	1✔
57	renderingEngine: renderingEngine,	1✔
58	osMessageHandler: osMessageHandler,	1✔
59	cancellationToken: cts.Token));	1✔
60		1✔
61	FinishRunning(tcs);
62	}
63	catch (OperationCanceledException)	1✔
64	{	1✔
65	FinishRunning(tcs);	1✔
66	}	1✔
67	catch (Exception ex)
68	{	1✔
69	FinishRunning(tcs, ex);
70	}
71	});	1✔
72	if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
73	{
74	//Can only by set on the Windows machine. Doesn't work on Linux/MacOS
75	thread.SetApartmentState(ApartmentState.STA);	1✔
76	thread.Name = "Main STA thread";	1✔
77	}
78	else
79	{
80	thread.Name = "Main thread";
81	}
82
83	thread.Start();	1✔
84
85	return tcs.Task;	1✔
86
87	void FinishRunning(
88	TaskCompletionSource tcs,
89	Exception? exception = null)
90	{
91	/* This should be called BEFORE tcs.SetResult/tcs.SetException!
92	* Otherwise _mainLoopLifetime.Cancel() gets called after the returned tcs.Task completes,
93	* leading to dispoes exception on mainLoopLifetime, that's already disposed upstream! */
94	IsRunning = false;	1✔
95	_mainLoopLifetime.Cancel();	1✔
96
97	if (exception is null)
98	{
99	tcs.SetResult();	1✔
100	}
101	else
102	{
103	tcs.SetException(exception);
104	}
105	}
106	}
107
108	private async Task STAThread(
109	IRenderingEngine renderingEngine,
110	IOSMessageHandler osMessageHandler,
111	CancellationToken cancellationToken)
112	{
113	var doEventsOk = true;	1✔
114
115	await foreach (var staAction in _channelReader
116	.ReadAllAsync(cancellationToken)	1✔
117	.WithCancellation(cancellationToken))	1✔
118	{
119	switch (staAction)
120	{
121	case StaThreadRequests.DoEventsOkRequest doEventsOkRequest:
122	doEventsOk &= doEventsOkRequest.Invoke(renderingEngine, osMessageHandler);
123	break;
124
125	default:
126	_ = staAction.Invoke(renderingEngine, osMessageHandler);	1✔
127	break;
128	}
129
130	if (!doEventsOk \|\| !IsRunning \|\| cancellationToken.IsCancellationRequested)
131	{
132	break;
133	}
134	}
135	}
136
137	private void Dispose(bool disposing)
138	{
139	if (!_disposedValue)	1✔
140	{
141	if (disposing)	1✔
142	{
143	}
144
145	_disposedValue = true;	1✔
146	}
147	}	1✔
148
149	public void Dispose()
150	{
151	// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
152	Dispose(disposing: true);	1✔
153	GC.SuppressFinalize(this);	1✔
154	}	1✔
155
156	private sealed class SingleThreadedSynchronizationContextChannel
157	: SynchronizationContext
158	{
159	private readonly Channel<(SendOrPostCallback d, object? state)> _channel =	2✔
160	Channel.CreateUnbounded<(SendOrPostCallback d, object? state)>(	2✔
161	new UnboundedChannelOptions { SingleReader = true, SingleWriter = false });	2✔
162
163	public override void Post(SendOrPostCallback d, object? state)
164	=> _channel.Writer.TryWrite((d, state));	2✔
165
166	public override void Send(SendOrPostCallback d, object? state)
167	=> throw new InvalidOperationException("Synchronous operations are not supported!");	×
168
169	public static void Await(Func<Task> taskInvoker)
170	{
171	var originalContext = Current;	2✔
172	try
173	{
174	var context = new SingleThreadedSynchronizationContextChannel();	2✔
175	SetSynchronizationContext(context);	2✔
176
177	Task task;
178	try
179	{
180	task = taskInvoker.Invoke();	2✔
181	}	2✔
182	catch (Exception ex)	×
183	{
184	// If the invoker throws synchronously, complete the channel so the pump can exit.
185	context._channel.Writer.Complete(ex);	×
186	throw;	×
187	}
188
189	_ = task.ContinueWith(t	2✔
190	=> context._channel.Writer.Complete(t.Exception),	2✔
191	TaskScheduler.Default);	2✔
192
193	// Pump loop: block synchronously until items are available or the writer completes.
194	while (context._channel.Reader.WaitToReadAsync().Preserve().GetAwaiter().GetResult())	2✔
195	{
196	while (context._channel.Reader.TryRead(out var work))	2✔
197	{
198	work.d.Invoke(work.state);	2✔
199	}	2✔
200	}
201
202	task.GetAwaiter().GetResult();	2✔
203	}	×
204	finally
205	{
206	SetSynchronizationContext(originalContext);	2✔
207	}	2✔
208	}	×
209	}
210	}

DemoBytom / DemoEngine / 22160476800

Source File Press 'n' to go to next uncovered line, 'b' for previous

Source File
Press 'n' to go to next uncovered line, 'b' for previous