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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 | (* $Id: netplex_mutex.mli 1708 2012-02-16 00:12:17Z gerd $ *)
(** Netplex-wide mutexes *)
open Netplex_types
(** 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.
{b Thread safety:} Full. The functions can be called from any thread.
*)
val plugin : 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 {b 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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