OCaml library : Mutex (original) (raw)

Module Mutex

module Mutex: sig .. end

Locks for mutual exclusion.

Mutexes (mutual-exclusion locks) are used to implement critical sections and protect shared mutable data structures against concurrent accesses. The typical use is (if m is the mutex associated with the data structureD):

     Mutex.lock m;
     (* Critical section that operates over D *);
     Mutex.unlock m
   

type ``t

val create : unit -> [t](Mutex.html#TYPEt)

val lock : [t](Mutex.html#TYPEt) -> unit

Lock the given mutex. Only one thread can have the mutex locked at any time. A thread that attempts to lock a mutex already locked by another thread will suspend until the other thread unlocks the mutex.

• Before 4.12 Sys_error was not raised for recursive locking (platform-dependent behaviour)
• Raises Sys_error if the mutex is already locked by the thread callingMutex.lock.

val try_lock : [t](Mutex.html#TYPEt) -> bool

Same as Mutex.lock, but does not suspend the calling thread if the mutex is already locked: just return false immediately in that case. If the mutex is unlocked, lock it and return true.

val unlock : [t](Mutex.html#TYPEt) -> unit

Unlock the given mutex. Other threads suspended trying to lock the mutex will restart. The mutex must have been previously locked by the thread that calls Mutex.unlock.

• Before 4.12 Sys_error was not raised when unlocking an unlocked mutex or when unlocking a mutex from a different thread.
• Raises Sys_error if the mutex is unlocked or was locked by another thread.

val protect : [t](Mutex.html#TYPEt) -> (unit -> 'a) -> 'a

protect mutex f runs f() in a critical section where mutex is locked (using Mutex.lock); it then takes care of releasing mutex, whether f() returned a value or raised an exception.

The unlocking operation is guaranteed to always takes place, even in the event an asynchronous exception (e.g. Sys.Break) is raised in some signal handler.

• Since 5.1