fix: try executing on the thread pool

src/Paramore.Brighter/Tasks/BrighterSynchronizationContext.cs

@@ -33,10 +33,8 @@ namespace Paramore.Brighter.Tasks
     /// Only uses one thread, so predictable performance, but may have many messages queued. Once queue length exceeds
     /// buffer size, we will stop reading new work.
     /// </remarks>
-    internal class BrighterSynchronizationContext : SynchronizationContext
+    public class BrighterSynchronizationContext : SynchronizationContext
     {
-        private readonly ExecutionContext? _executionContext;
-
         /// <summary>
         /// Gets the synchronization helper.
         /// </summary>
@@ -62,7 +60,6 @@ internal class BrighterSynchronizationContext : SynchronizationContext
         public BrighterSynchronizationContext(BrighterSynchronizationHelper synchronizationHelper)
         {
             SynchronizationHelper = synchronizationHelper;
-            _executionContext = ExecutionContext.Capture();
         }
 
         /// <summary>
@@ -132,8 +129,7 @@ public override void Post(SendOrPostCallback callback, object? state)
             Debug.IndentLevel = 0;
 
             if (callback == null) throw new ArgumentNullException(nameof(callback));
-            var ctxt = ExecutionContext.Capture();
-            bool queued = SynchronizationHelper.Enqueue(new ContextMessage(callback, state, ctxt), true);
+            bool queued = SynchronizationHelper.Enqueue(new ContextMessage(callback, state), true);
 
             if (queued) return;
 
@@ -143,26 +139,19 @@ public override void Post(SendOrPostCallback callback, object? state)
             // If the execution context can help, we might be able to redirect; if not just run immediately on this thread
 
             var contextCallback = new ContextCallback(callback);
-            if (ctxt != null && ctxt  != _executionContext)
-            {
-                Debug.WriteLine(string.Empty);
-                Debug.IndentLevel = 1;
-                Debug.WriteLine($"BrighterSynchronizationContext: Post Failed to queue {callback.Method.Name} on thread {Thread.CurrentThread.ManagedThreadId}");
-                Debug.WriteLine($"BrighterSynchronizationContext: Parent Task {ParentTaskId}");
-                Debug.IndentLevel = 0;
-                SynchronizationHelper.ExecuteOnContext(ctxt, contextCallback, state);
-            }
-            else
-            {
-                Debug.WriteLine(string.Empty);
-                Debug.IndentLevel = 1;
-                Debug.WriteLine($"BrighterSynchronizationContext: Post Failed to queue {callback.Method.Name} on thread {Thread.CurrentThread.ManagedThreadId}");
-                Debug.WriteLine($"BrighterSynchronizationContext: Parent Task {ParentTaskId}");
-                Debug.IndentLevel = 0;
-                //just execute inline
-                SynchronizationHelper.ExecuteImmediately(contextCallback, state); 
-            }
+
             Debug.WriteLine(string.Empty);
+            Debug.IndentLevel = 1;
+            Debug.WriteLine($"BrighterSynchronizationContext: Post Failed to queue {callback.Method.Name} on thread {Thread.CurrentThread.ManagedThreadId}");
+            Debug.WriteLine($"BrighterSynchronizationContext: Parent Task {ParentTaskId}");
+            Debug.IndentLevel = 0;
+
+            //just execute inline
+            // current thread already owns the context, so just execute inline to prevent deadlocks
+            //if (BrighterSynchronizationHelper.Current == SynchronizationHelper)
+                //SynchronizationHelper.ExecuteImmediately(contextCallback, state);
+            //else
+                base.Post(callback, state);
 
         }
 
@@ -186,8 +175,7 @@ public override void Send(SendOrPostCallback callback, object? state)
             }
             else
             {
-                var ctxt = ExecutionContext.Capture();
-                var task = SynchronizationHelper.MakeTask(new ContextMessage(callback, state, ctxt));
+                var task = SynchronizationHelper.MakeTask(new ContextMessage(callback, state));
                 if (!task.Wait(Timeout)) // Timeout mechanism
                     throw new TimeoutException("BrighterSynchronizationContext: Send operation timed out.");
             }

src/Paramore.Brighter/Tasks/ContextMessage.cs

@@ -16,11 +16,9 @@ public struct ContextMessage
     /// </summary>
     /// <param name="callback">The callback to execute.</param>
     /// <param name="state">The state to pass to the callback.</param>
-    /// <param name="ctxt">The execution context, mainly intended for debugging purposes</param>
-    public ContextMessage(SendOrPostCallback callback, object? state, ExecutionContext? ctxt)
+    public ContextMessage(SendOrPostCallback callback, object? state)
     {
         Callback = callback;
         State = state;
-        Context = ctxt;
     }
 }

tests/Paramore.Brighter.Core.Tests/Tasks/BrighterSynchronizationContextsTests.cs

@@ -151,26 +151,26 @@ public void Current_WithoutAsyncContext_IsNull()
     }
 
     [Fact]
-    public void Current_FromAsyncContext_IsAsyncContext()
+    public void Current_FromBrighterSynchronizationHelper_IsBrighterSynchronizationHelper()
     {
-        BrighterSynchronizationHelper observedContext = null;
-        var context = new BrighterSynchronizationHelper();
+        BrighterSynchronizationHelper observedHelper = null;
+        var helper = new BrighterSynchronizationHelper();
 
-        var task = context.Factory.StartNew(
-            () => { observedContext = BrighterSynchronizationHelper.Current; },
-            context.Factory.CancellationToken,
-            context.Factory.CreationOptions | TaskCreationOptions.DenyChildAttach,
-            context.TaskScheduler);
+        var task = helper.Factory.StartNew(
+            () => { observedHelper = BrighterSynchronizationHelper.Current; },
+            helper.Factory.CancellationToken,
+            helper.Factory.CreationOptions | TaskCreationOptions.DenyChildAttach,
+            helper.TaskScheduler);
 
-        context.Execute(task);
+        helper.Execute(task);
 
-        observedContext.Should().Be(context);
+        observedHelper.Should().Be(helper);
     }
 
     [Fact]
-    public void SynchronizationContextCurrent_FromAsyncContext_IsAsyncContextSynchronizationContext()
+    public void SynchronizationContextCurrent_FromBrighterSynchronizationHelper_IsBrighterSynchronizationHelperSynchronizationContext()
     {
-        System.Threading.SynchronizationContext observedContext = null;
+        System.Threading.SynchronizationContext? observedContext = null;
         var context = new BrighterSynchronizationHelper();
 
         var task = context.Factory.StartNew(
@@ -360,6 +360,35 @@ public async Task Task_AfterExecute_Runs_On_ThreadPool()
 
         threadPoolExceptionRan.Should().BeTrue();
     }
+
+    [Fact]
+    public async Task SynchronizationContextCurrent_FromAsyncContext_PostFromAnotherThread()
+    {
+        System.Threading.SynchronizationContext? observedContext = null;
+        var helper = new BrighterSynchronizationHelper();
+
+        var task = helper.Factory.StartNew(
+            () => { observedContext =BrighterSynchronizationContext.Current; },
+            helper.Factory.CancellationToken,
+            helper.Factory.CreationOptions | TaskCreationOptions.DenyChildAttach,
+            helper.TaskScheduler);
+
+        //this should complete the task
+        helper.Execute(task);
+
+        //but this simulates us being disposed
+        observedContext.OperationCompleted();
+
+        //we may be called on a different thread
+        int value = 1;
+        await Task.Run(() =>
+        {
+            observedContext .Post(_ => value = 2, null);
+        });
+
+        value.Should().Be(2);
+
+    }
 
     [Fact]
     public void SynchronizationContext_IsEqualToCopyOfItself()