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Fix ScheduledTaskExecutor deadlock when TrySetResult runs continuations inline #2953

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Merged
martincostello merged 3 commits into from
Mar 3, 2026
+22 −1
Merged

Fix ScheduledTaskExecutor deadlock when TrySetResult runs continuations inline #2953

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aa841d5
Add failing test for inline continuation deadlock
crnhrv Mar 3, 2026
e71c0b7
Make sure we run task continuations async
crnhrv Mar 3, 2026
7e93baf
Use the xunit test cancellation token
crnhrv Mar 3, 2026
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2 changes: 1 addition & 1 deletion src/Polly.Core/CircuitBreaker/Controller/ScheduledTaskExecutor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ public Task ScheduleTask(Func<Task> taskFactory)
}
#endif

var source = new TaskCompletionSource<object>();
var source = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);

_tasks.Enqueue(new Entry(taskFactory, source));
_semaphore.Release();
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21 changes: 21 additions & 0 deletions test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs
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Expand Up @@ -129,6 +129,27 @@ public void Dispose_WhenScheduledTaskExecuting()
#pragma warning restore xUnit1031
}

[Fact]
public void ScheduleTask_InlineContinuationDoesNotDeadlock()
{
var timeout = TimeSpan.FromMilliseconds(250);
using var scheduler = new ScheduledTaskExecutor();

var firstTask = scheduler.ScheduleTask(() => Task.CompletedTask);

var continuationTask = firstTask.ContinueWith(
_ =>
{
var secondTask = scheduler.ScheduleTask(() => Task.CompletedTask);
secondTask.Wait(timeout);
},
CancellationToken,
TaskContinuationOptions.ExecuteSynchronously,
TaskScheduler.Default);

continuationTask.Wait(timeout).ShouldBeTrue();
}

[Fact]
public async Task Dispose_EnsureNoBackgroundProcessing()
{
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