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 mval create : unit -> tReturn a new mutex.
val lock : t -> unitLock 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.
Sys_error if the mutex is already locked by the thread calling Mutex.lock.
Sys_error was not raised for recursive locking (platform-dependent behaviour)
val try_lock : t -> boolSame 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 -> unitUnlock 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.
Sys_error if the mutex is unlocked or was locked by another thread.
Sys_error was not raised when unlocking an unlocked mutex or when unlocking a mutex from a different thread.
val protect : t -> (unit -> 'a) -> 'aprotect mutex f runs f() in a critical section where mutex is locked (using 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.