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 structure D):

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

The type of mutexes.

val create : unit -> t

Return a new mutex.

val lock : t -> 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 calling Mutex.lock.
val try_lock : t -> 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 -> 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.