Thread - phpMan

NAME
    Thread - Manipulate threads in Perl (for old code only)

DEPRECATED
    The "Thread" module served as the frontend to the old-style thread
    model, called *5005threads*, that was introduced in release 5.005. That
    model was deprecated, and has been removed in version 5.10.

    For old code and interim backwards compatibility, the "Thread" module
    has been reworked to function as a frontend for the new interpreter
    threads (*ithreads*) model. However, some previous functionality is not
    available. Further, the data sharing models between the two thread
    models are completely different, and anything to do with data sharing
    has to be thought differently. With *ithreads*, you must explicitly
    "share()" variables between the threads.

    You are strongly encouraged to migrate any existing threaded code to the
    new model (i.e., use the "threads" and "threads::shared" modules) as
    soon as possible.

HISTORY
    In Perl 5.005, the thread model was that all data is implicitly shared,
    and shared access to data has to be explicitly synchronized. This model
    is called *5005threads*.

    In Perl 5.6, a new model was introduced in which all is was thread local
    and shared access to data has to be explicitly declared. This model is
    called *ithreads*, for "interpreter threads".

    In Perl 5.6, the *ithreads* model was not available as a public API;
    only as an internal API that was available for extension writers, and to
    implement fork() emulation on Win32 platforms.

    In Perl 5.8, the *ithreads* model became available through the "threads"
    module, and the *5005threads* model was deprecated.

    In Perl 5.10, the *5005threads* model was removed from the Perl
    interpreter.

SYNOPSIS
        use Thread qw(:DEFAULT async yield);

        my $t = Thread->new(\&start_sub, @start_args);

        $result = $t->join;
        $t->detach;

        if ($t->done) {
            $t->join;
        }

        if($t->equal($another_thread)) {
            # ...
        }

        yield();

        my $tid = Thread->self->tid;

        lock($scalar);
        lock(@array);
        lock(%hash);

        my @list = Thread->list;

DESCRIPTION
    The "Thread" module provides multithreading support for Perl.

FUNCTIONS
    $thread = Thread->new(\&start_sub)
    $thread = Thread->new(\&start_sub, LIST)
            "new" starts a new thread of execution in the referenced
            subroutine. The optional list is passed as parameters to the
            subroutine. Execution continues in both the subroutine and the
            code after the "new" call.

            "Thread->new" returns a thread object representing the newly
            created thread.

    lock VARIABLE
            "lock" places a lock on a variable until the lock goes out of
            scope.

            If the variable is locked by another thread, the "lock" call
            will block until it's available. "lock" is recursive, so
            multiple calls to "lock" are safe--the variable will remain
            locked until the outermost lock on the variable goes out of
            scope.

            Locks on variables only affect "lock" calls--they do *not*
            affect normal access to a variable. (Locks on subs are
            different, and covered in a bit.) If you really, *really* want
            locks to block access, then go ahead and tie them to something
            and manage this yourself. This is done on purpose. While
            managing access to variables is a good thing, Perl doesn't force
            you out of its living room...

            If a container object, such as a hash or array, is locked, all
            the elements of that container are not locked. For example, if a
            thread does a "lock @a", any other thread doing a "lock($a[12])"
            won't block.

            Finally, "lock" will traverse up references exactly *one* level.
            "lock(\$a)" is equivalent to "lock($a)", while "lock(\\$a)" is
            not.

    async BLOCK;
            "async" creates a thread to execute the block immediately
            following it. This block is treated as an anonymous sub, and so
            must have a semi-colon after the closing brace. Like
            "Thread->new", "async" returns a thread object.

    Thread->self
            The "Thread->self" function returns a thread object that
            represents the thread making the "Thread->self" call.

    Thread->list
            Returns a list of all non-joined, non-detached Thread objects.

    cond_wait VARIABLE
            The "cond_wait" function takes a locked variable as a parameter,
            unlocks the variable, and blocks until another thread does a
            "cond_signal" or "cond_broadcast" for that same locked variable.
            The variable that "cond_wait" blocked on is relocked after the
            "cond_wait" is satisfied. If there are multiple threads
            "cond_wait"ing on the same variable, all but one will reblock
            waiting to re-acquire the lock on the variable. (So if you're
            only using "cond_wait" for synchronization, give up the lock as
            soon as possible.)

    cond_signal VARIABLE
            The "cond_signal" function takes a locked variable as a
            parameter and unblocks one thread that's "cond_wait"ing on that
            variable. If more than one thread is blocked in a "cond_wait" on
            that variable, only one (and which one is indeterminate) will be
            unblocked.

            If there are no threads blocked in a "cond_wait" on the
            variable, the signal is discarded.

    cond_broadcast VARIABLE
            The "cond_broadcast" function works similarly to "cond_signal".
            "cond_broadcast", though, will unblock all the threads that are
            blocked in a "cond_wait" on the locked variable, rather than
            only one.

    yield   The "yield" function allows another thread to take control of
            the CPU. The exact results are implementation-dependent.

METHODS
    join    "join" waits for a thread to end and returns any values the
            thread exited with. "join" will block until the thread has
            ended, though it won't block if the thread has already
            terminated.

            If the thread being "join"ed "die"d, the error it died with will
            be returned at this time. If you don't want the thread
            performing the "join" to die as well, you should either wrap the
            "join" in an "eval" or use the "eval" thread method instead of
            "join".

    detach  "detach" tells a thread that it is never going to be joined i.e.
            that all traces of its existence can be removed once it stops
            running. Errors in detached threads will not be visible anywhere
            - if you want to catch them, you should use $SIG{__DIE__} or
            something like that.

    equal   "equal" tests whether two thread objects represent the same
            thread and returns true if they do.

    tid     The "tid" method returns the tid of a thread. The tid is a
            monotonically increasing integer assigned when a thread is
            created. The main thread of a program will have a tid of zero,
            while subsequent threads will have tids assigned starting with
            one.

    done    The "done" method returns true if the thread you're checking has
            finished, and false otherwise.

DEFUNCT
    The following were implemented with *5005threads*, but are no longer
    available with *ithreads*.

    lock(\&sub)
            With 5005threads, you could also "lock" a sub such that any
            calls to that sub from another thread would block until the lock
            was released.

            Also, subroutines could be declared with the ":locked" attribute
            which would serialize access to the subroutine, but allowed
            different threads non-simultaneous access.

    eval    The "eval" method wrapped an "eval" around a "join", and so
            waited for a thread to exit, passing along any values the thread
            might have returned and placing any errors into $@.

    flags   The "flags" method returned the flags for the thread - an
            integer value corresponding to the internal flags for the
            thread.

SEE ALSO
    threads, threads::shared, Thread::Queue, Thread::Semaphore