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Module Lwt_monitor

module Lwt_monitor: sig .. end

Monitors

Monitors implement a combined lock for synchronization with conditional variables for notification.

type t

The monitor type, used to synchronize the activity of threads around a common shared resource or critical section of code.

type 'a condition

Condition variable type. The type parameter denotes the type of value propagated from notifier to waiter.

val create_condition : unit -> 'a condition

create_condition () creates a new condition variable.

val create : unit -> t

create () creates a new monitor.

val lock : t -> unit Lwt.t

lock mon locks a monitor to gain exclusive access to a shared resource. If the monitor is currently locked by another thread, the thread calling lock will block until the monitor is unlocked. Note that a monitor must not be "re-entered", i.e. lock called more than once without an intervening unlock call.

val unlock : t -> unit

unlock mon unlocks a monitor. This releases exclusive access to a shared resource and allows other threads to enter the monitor.

val with_lock : t -> (unit -> 'a Lwt.t) -> 'a Lwt.t

with_lock mon f is used to lock a monitor within a block scope. The function f () is called with the monitor locked, and its result is returned from the call to with_lock. If an exception is raised from f, the monitor is also unlocked before the scope of with_lock is exited.

val wait : t -> 'a condition -> 'a Lwt.t

wait mon condvar will cause the current thread to block, awaiting notification for a condition variable, condvar. The calling thread be within the monitor (must have previously called lock or be within the scope of with_lock). The monitor is temporarily unlocked until the condition is notified. Upon notification, the monitor is re-locked before wait returns and the thread's activity is resumed. When the awaited condition is notified, the value parameter passed to notify is returned.

val notify : t -> 'a condition -> 'a -> unit

notify mon condvar value notifies that a condition is ready. A single waiting thread will be awoken and will receive the notification value which will be returned from wait. The calling thread be within the monitor (must have previously called lock or be within the scope of with_lock). Note that condition notification is not "sticky", i.e. if there is no waiter when notify is called, the notification will be missed and the value discarded.

val notify_all : t -> 'a condition -> 'a -> unit

notify_all mon condvar value notifies all waiting threads. Each will be awoken in turn and will receive the same notification value. The calling thread be within the monitor (must have previously called lock or be within the scope of with_lock).