AsyncLock

AsyncLock.cs

using System;
using System.Threading;
using System.Threading.Tasks;

/// <summary>
/// A simple FIFO async lock. It does not support recursion/reentrancy.
/// </summary>
public sealed class AsyncLock
{
	private Task task = Task.CompletedTask;

	public async ValueTask LockAsync(Func<Task> whenLocked)
	{
		ArgumentNullException.ThrowIfNull(whenLocked);
		var next = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
		var prev = Interlocked.Exchange(ref task, next.Task);
		await prev.ConfigureAwait(false);
		try { await whenLocked().ConfigureAwait(false); }
		finally { next.SetResult(); }
	}
}