Semaphore.Counting.3o - Man Page

Module   Semaphore.Counting

Module Counting
: sig end

type t

The type of counting semaphores.

val make : int -> t

make n returns a new counting semaphore, with initial value n . The initial value n must be nonnegative.

Raises Invalid_argument if n < 0

val release : t -> unit

release s increments the value of semaphore s . If other threads are waiting on s , one of them is restarted. If the current value of s is equal to max_int , the value of the semaphore is unchanged and a Sys_error exception is raised to signal overflow.

Raises Sys_error if the value of the semaphore would overflow max_int

val acquire : t -> unit

acquire s blocks the calling thread until the value of semaphore s is not zero, then atomically decrements the value of s and returns.

val try_acquire : t -> bool

try_acquire s immediately returns false if the value of semaphore s is zero.  Otherwise, the value of s is atomically decremented and try_acquire s returns true .

val get_value : t -> int

get_value s returns the current value of semaphore s . The current value can be modified at any time by concurrent Semaphore.Counting.release and Semaphore.Counting.acquire operations.  Hence, the get_value operation is racy, and its result should only be used for debugging or informational messages.