SE-0306 (Second Review): Actors

Evolution Proposal Reviews
38

It might be worth nothing that Actors and Tasks together can create deadlocks. Reposting example from an earlier thread:

actor Deadlock {
	var task: Task.Handle<Int>?
	func getValue() async -> Int {
		if task == nil {
			task = detachedTask {
				return await computeValue()
			}
		}
		return await task!.get()
	}
	private func computeValue() async -> Int {
		return await getValue() + 1
	}
}

Here we end up with a task depending on its own result, so any call to the actor's getValue will await indefinitely. A deadlock of the infinite suspension kind.

Claims that actors can't deadlocks have to be taken with a grain of salt. It's true if you consider actors in isolation, but as part of a bigger system they can still end up deadlocked.

My conclusion is that we don't need non-reentrant actors because we already have them. :smirk:

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