Ocamlnet 3 Reference Manual : Netplex_mutex

# Module Netplex_mutex

    module Netplex_mutex: sig .. end

Netplex-wide mutexes

These are mutexes that work in both multi-processing and multi-threading netplex environments. They are implemented on top of `Netplex_semaphore`, and use the same name space for named objects.

For implementation issues, see `Netplex_semaphore`.

It is not required to create mutexes: A mutex is automatically created when the name is used for the first time. Mutexes are initially always in unlocked state.

Mutexes do not stack: A container cannot lock a mutex several times. (The second lock attempt would result in a deadlock.)

There is no deadlock detection.

If a container holding mutexes terminates the mutexes are automatically unlocked.

Mutex are not owned by their container. It is allowed that a different container unlocks the mutex.

Technically, a mutex named `n` is implemented by a semaphore `n`. If the mutex is locked, the semaphore has the value 0, and if it is unlocked, it has value 1.

Thread safety: Full. The functions can be called from any thread.

    val plugin : Netplex_types.plugin

To enable mutexes, call the controller's `add_plugin` method with this object as argument. This can e.g. be done in the `post_add_hook` of the processor.
The following functions can only be invoked in container contexts. Outside of such a context the exception `Netplex_cenv.Not_in_container_thread` is raised.

    type mutex

    val access : string -> mutex

Access the named mutex. If the mutex does not exist, it is created in unlocked state

    val lock : mutex -> unit

Wait until the mutex is free, and locks it

    val unlock : mutex -> unit

Unlocks the mutex. This is a no-op if the mutex is not locked