Example of synchronous blocking causing deadlock

AsyncDeadlock.cs

async Task PauseAsync()
{
    // Normal asynchronous method call
    await Task.Delay(1000);
}

void Pause()
{
    // Synchronous method blocking on asynchronous method
    PauseAsync().Wait();
}

var maxNumWorkerThreads = Environment.ProcessorCount;
Console.WriteLine($"Limit number of worker threads to {maxNumWorkerThreads}");
ThreadPool.SetMaxThreads(maxNumWorkerThreads, maxNumWorkerThreads);

// When number of tasks equals maxNumWorkerThreads - 1, it will deadlock
var numTasks = maxNumWorkerThreads - 1;
var tasks = new List<Task>();
for (var i = 0; i < numTasks; i++)
{
    Console.WriteLine($"Starting task in worker thread #{i + 1}");
    tasks.Add(Task.Run(() => Pause()));
}

Console.WriteLine("Waiting for tasks to complete");
Task.WaitAll(tasks.ToArray());
Console.WriteLine("All tasks complete");