Why was Thread.exclusive deprecated?
Why was Thread.exclusive deprecated? It is useful for when you're uncertain about whether the caller is multithreaded or not, and therefore cannot initialize a mutex because the mutex must be initialized in a thread-safe context where it's not possible for multiple caller threads to initialize the mutex concurrently.
One use case is here: this is an idempotent native function invoked via FFI. The contract is that it can be called repeatedly, but only by one thread at a time (concurrent calls from multiple threads can potentially corrupt its internal state):
Thread.exclusive is useful because it provides an implicit mutex you can ensure is initialized correctly before any other threads start.