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package Thread;
require Exporter;
require DynaLoader;
use vars qw($VERSION @ISA @EXPORT);
$VERSION = "1.0";
@ISA = qw(Exporter DynaLoader);
@EXPORT_OK = qw(yield cond_signal cond_broadcast cond_wait async);
=head1 NAME
Thread - multithreading
=head1 SYNOPSIS
use Thread;
my $t = new Thread \&start_sub, @start_args;
$t->join;
my $tid = Thread->self->tid;
my $tlist = Thread->list;
lock($scalar);
use Thread 'async';
use Thread 'eval';
=head1 DESCRIPTION
The C<Thread> module provides multithreading support for perl.
=head1 FUNCTIONS
=over 8
=item new \&start_sub
=item new \&start_sub, LIST
C<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 C<new> call.
C<new Thread> returns a thread object representing the newly created
thread.
=item lock VARIABLE
C<lock> places a lock on a variable until the lock goes out of scope. If
the variable is locked by another thread, the C<lock> call will block until
it's available. C<lock> is recursive, so multiple calls to C<lock> are
safe--the variable will remain locked until the outermost lock on the
variable goes out of scope.
Locks on variables only affect C<lock> calls--they do I<not> affect normal
access to a variable. (Locks on subs are different, and covered in a bit)
If you really, I<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 C<lock
@a>, any other thread doing a C<lock($a[12])> won't block.
You may also C<lock> a sub, using C<lock &sub>. Any calls to that sub from
another thread will block until the lock is released. This behaviour is not
equvalent to C<use attrs qw(locked)> in the sub. C<use attrs qw(locked)>
serializes access to a subroutine, but allows different threads
non-simultaneous access. C<lock &sub>, on the other hand, will not allow
I<any> other thread access for the duration of the lock.
Finally, C<lock> will traverse up references exactly I<one> level.
C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not.
=item async BLOCK;
C<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 C<new Thread>, C<async> returns a
thread object.
=item Thread->self
The C<Thread-E<gt>self> function returns a thread object that represents
the thread making the C<Thread-E<gt>self> call.
=item Thread->list
C<Thread-E<gt>list> returns a list of thread objects for all running and
finished but un-C<join>ed threads.
=item cond_wait VARIABLE
The C<cond_wait> function takes a B<locked> variable as a parameter,
unlocks the variable, and blocks until another thread does a C<cond_signal>
or C<cond_broadcast> for that same locked variable. The variable that
C<cond_wait> blocked on is relocked after the C<cond_wait> is satisfied.
If there are multiple threads C<cond_wait>ing on the same variable, all but
one will reblock waiting to reaquire the lock on the variable. (So if
you're only using C<cond_wait> for synchronization, give up the lock as
soon as possible)
=item cond_signal VARIABLE
The C<cond_signal> function takes a locked variable as a parameter and
unblocks one thread that's C<cond_wait>ing on that variable. If more than
one thread is blocked in a C<cond_wait> on that variable, only one (and
which one is indeterminate) will be unblocked.
If there are no threads blocked in a C<cond_wait> on the variable, the
signal is discarded.
=item cond_broadcast VARIABLE
The C<cond_broadcast> function works similarly to C<cond_wait>.
C<cond_broadcast>, though, will unblock B<all> the threads that are blocked
in a C<cond_wait> on the locked variable, rather than only one.
=back
=head1 METHODS
=over 8
=item join
C<join> waits for a thread to end and returns any values the thread exited
with. C<join> will block until the thread has ended, though it won't block
if the thread has already terminated.
If the thread being C<join>ed C<die>d, the error it died with will be
returned at this time. If you don't want the thread performing the C<join>
to die as well, you should either wrap the C<join> in an C<eval> or use the
C<eval> thread method instead of C<join>.
=item eval
The C<eval> method wraps an C<eval> around a C<join>, and so waits for a
thread to exit, passing along any values the thread might have returned.
Errors, of course, get placed into C<$@>.
=item tid
The C<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.
=head1 LIMITATIONS
The sequence number used to assign tids is a simple integer, and no
checking is done to make sure the tid isn't currently in use. If a program
creates more than 2^32 - 1 threads in a single run, threads may be assigned
duplicate tids. This limitation may be lifted in a future version of Perl.
=head1 SEE ALSO
L<attrs>, L<Thread::Queue>, L<Thread::Semaphore>, L<Thread::Specific>.
=cut
#
# Methods
#
#
# Exported functions
#
sub async (&) {
return new Thread $_[0];
}
sub eval {
return eval { shift->join; };
}
bootstrap Thread;
1;
|
