package moonpool

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Module Moonpool.Suspend_Source

Suspensions.

This is only going to work on OCaml 5.x.

NOTE: this is not stable for now.

  • alert unstable this module is an implementation detail of moonpool for now

(Private) suspending tasks using Effects.

This module is an implementation detail of Moonpool and should not be used outside of it, except by experts to implement Runner.

Sourcetype suspension = (unit, exn * Printexc.raw_backtrace) result -> unit

A suspended computation

Sourcetype task = unit -> unit
Sourcetype suspension_handler = {
  1. handle : run:(with_handler:bool -> task -> unit) -> suspension -> unit;
}

The handler that knows what to do with the suspended computation.

The handler is given two things:

  • the suspended computation (which can be resumed with a result eventually);
  • a run function that can be used to start tasks to perform some computation.

This means that a fork-join primitive, for example, can use a single call to suspend to:

  • suspend the caller until the fork-join is done
  • use run to start all the tasks. Typically run is called multiple times, which is where the "fork" part comes from. Each call to run potentially runs in parallel with the other calls. The calls must coordinate so that, once they are all done, the suspended caller is resumed with the aggregated result of the computation.
Sourcetype Effect.t +=
  1. | Suspend : suspension_handler -> unit Effect.t
    (*

    The effect used to suspend the current thread and pass it, suspended, to the handler. The handler will ensure that the suspension is resumed later once some computation has been done.

    *)
Sourceval suspend : suspension_handler -> unit

suspend h jumps back to the nearest with_suspend and calls h.handle with the current continuation k and a task runner function.

Sourceval with_suspend : run:(with_handler:bool -> task -> unit) -> (unit -> unit) -> unit

with_suspend ~run f runs f() in an environment where suspend will work. If f() suspends with suspension handler h, this calls h ~run k where k is the suspension.

This will not do anything on OCaml 4.x.