Module Thread

module Thread: sig .. end

Lightweight threads for Posix 1003.1c and Win32.

type t

The type of thread handles.

Thread creation and termination

val create : ('a -> 'b) -> 'a -> t

Thread.create funct arg creates a new thread of control, in which the function application funct arg is executed concurrently with the other threads of the program. The application of Thread.create returns the handle of the newly created thread. The new thread terminates when the application funct arg returns, either normally or by raising an uncaught exception. In the latter case, the exception is printed on standard error, but not propagated back to the parent thread. Similarly, the result of the application funct arg is discarded and not directly accessible to the parent thread.

val self : unit -> t

Return the thread currently executing.

val id : t -> int

Return the identifier of the given thread. A thread identifier is an integer that identifies uniquely the thread. It can be used to build data structures indexed by threads.

val exit : unit -> unit

Terminate prematurely the currently executing thread.

val kill : t -> unit

Terminate prematurely the thread whose handle is given.

Suspending threads

val delay : float -> unit

delay d suspends the execution of the calling thread for d seconds. The other program threads continue to run during this time.

val join : t -> unit

join th suspends the execution of the calling thread until the thread th has terminated.

val wait_read : Unix.file_descr -> unit

See Thread.wait_write.

val wait_write : Unix.file_descr -> unit

This function does nothing in this implementation.

val wait_timed_read : Unix.file_descr -> float -> bool

See Thread.wait_timed_read.

val wait_timed_write : Unix.file_descr -> float -> bool

Suspend the execution of the calling thread until at least one character is available for reading (wait_read) or one character can be written without blocking (wait_write) on the given Unix file descriptor. Wait for at most the amount of time given as second argument (in seconds). Return true if the file descriptor is ready for input/output and false if the timeout expired.

These functions return immediately true in the Win32 implementation.

val select : Unix.file_descr list ->
       Unix.file_descr list ->
       Unix.file_descr list ->
       float -> Unix.file_descr list * Unix.file_descr list * Unix.file_descr list

Suspend the execution of the calling thead until input/output becomes possible on the given Unix file descriptors. The arguments and results have the same meaning as for Unix.select. This function is not implemented yet under Win32.

val wait_pid : int -> int * Unix.process_status

wait_pid p suspends the execution of the calling thread until the process specified by the process identifier p terminates. Returns the pid of the child caught and its termination status, as per Unix.wait. This function is not implemented under MacOS.

val yield : unit -> unit

Re-schedule the calling thread without suspending it. This function can be used to give scheduling hints, telling the scheduler that now is a good time to switch to other threads.

Management of signals

Signal handling follows the POSIX thread model: signals generated by a thread are delivered to that thread; signals generated externally are delivered to one of the threads that does not block it. Each thread possesses a set of blocked signals, which can be modified using Thread.sigmask. This set is inherited at thread creation time. Per-thread signal masks are supported only by the system thread library under Unix, but not under Win32, nor by the VM thread library.

val sigmask : Unix.sigprocmask_command -> int list -> int list

sigmask cmd sigs changes the set of blocked signals for the calling thread. If cmd is SIG_SETMASK, blocked signals are set to those in the list sigs. If cmd is SIG_BLOCK, the signals in sigs are added to the set of blocked signals. If cmd is SIG_UNBLOCK, the signals in sigs are removed from the set of blocked signals. sigmask returns the set of previously blocked signals for the thread.

val wait_signal : int list -> int

wait_signal sigs suspends the execution of the calling thread until the process receives one of the signals specified in the list sigs. It then returns the number of the signal received. Signal handlers attached to the signals in sigs will not be invoked. The signals sigs are expected to be blocked before calling wait_signal.