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NAME
Thread - Lightweight threads for Posix 1003.1c and Win32.
Module
Module Thread
Documentation
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 handle for 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
This function was supposed to terminate prematurely the thread whose handle is given. It is not
currently implemented due to problems with cleanup handlers on many POSIX 1003.1c implementations. It
always raises the Invalid_argument exception.
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 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.
Waiting for file descriptors or processes
The functions below are leftovers from an earlier, VM-based threading system. The Unix module provides
equivalent functionality, in a more general and more standard-conformant manner. It is recommended to
use Unix functions directly.
val wait_read : Unix.file_descr -> unit
This function does nothing in the current implementation of the threading library and can be removed from
all user programs.
val wait_write : Unix.file_descr -> unit
This function does nothing in the current implementation of the threading library and can be removed from
all user programs.
val wait_timed_read : Unix.file_descr -> float -> bool
See Thread.wait_timed_write .
val wait_timed_write : Unix.file_descr -> float -> bool
Suspend the execution of the calling thread until at least one character or EOF is available for reading
( wait_timed_read ) or one character can be written without blocking ( wait_timed_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. The same
functionality can be achieved with Unix.select .
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
Same function as Unix.select . Suspend the execution of the calling thread until input/output becomes
possible on the given Unix file descriptors. The arguments and results have the same meaning as for
Unix.select .
val wait_pid : int -> int * Unix.process_status
Same function as Unix.waitpid . 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 .
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 .