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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.

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 folloing 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
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