package threads;
-use 5.007_003;
+use 5.008;
use strict;
use warnings;
use Config;
This Perl hasn't been configured and built properly for the threads
module to work. (The 'useithreads' configuration option hasn't been used.)
-Having threads support requires all of Perl and all of the modules in
+Having threads support requires all of Perl and all of the XS modules in
the Perl installation to be rebuilt, it is not just a question of adding
the threads module. (In other words, threaded and non-threaded Perls
are binary incompatible.)
our @ISA = qw(Exporter DynaLoader);
-our %EXPORT_TAGS = ( all => [qw()]);
+our %EXPORT_TAGS = ( all => [qw(yield)]);
our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
return threads->new($cref,@_);
}
+sub object {
+ return undef unless @_ > 1;
+ foreach (threads->list) {
+ return $_ if $_->tid == $_[1];
+ }
+ return undef;
+}
+
$threads::threads = 1;
bootstrap threads $VERSION;
=head1 SYNOPSIS
-use threads;
-
-sub start_thread {
- print "Thread started\n";
-}
-
-my $thread = threads->create("start_thread","argument");
+ use threads;
-$thread->create(sub { print "I am a thread"},"argument");
-
-$thread->join();
+ sub start_thread {
+ print "Thread started\n";
+ }
-$thread->detach();
+ my $thread = threads->create("start_thread","argument");
+ my $thread2 = $thread->create(sub { print "I am a thread"},"argument");
+ my $thread3 = async { foreach (@files) { ... } };
-$thread = threads->self();
+ $thread->join();
+ $thread->detach();
-threads->tid();
-threads->self->tid();
+ $thread = threads->self();
+ $thread = threads->object( $tid );
-$thread->tid();
+ $thread->tid();
+ threads->tid();
+ threads->self->tid();
-threads->yield();
+ threads->yield();
-threads->list();
+ threads->list();
=head1 DESCRIPTION
Perl 5.6 introduced something called interpreter threads. Interpreter
threads are different from "5005threads" (the thread model of Perl
5.005) by creating a new perl interpreter per thread and not sharing
-any data or state between threads.
+any data or state between threads by default.
Prior to perl 5.8 this has only been available to people embedding
perl and for emulating fork() on windows.
variables are per default thread local. To use shared variables one
must use threads::shared.
-It is also important to note that you preferably enable threads by
-doing C<use threads> as early as possible and that it is not possible
-to enable threading inside an eval ""; In particular, if you are
-intending to share variables with threads::shared, you must
-C<use threads> before you C<use threads::shared> and threads will emit
-a warning if you do it the other way around.
+It is also important to note that you must enable threads by doing
+C<use threads> as early as possible in the script itself and that it
+is not possible to enable threading inside an C<eval "">, C<do>,
+C<require>, or C<use>. In particular, if you are intending to share
+variables with threads::shared, you must C<use threads> before you
+C<use threads::shared> and C<threads> will emit a warning if you do
+it the other way around.
=over
This will create a new thread with the entry point function and give
it LIST as parameters. It will return the corresponding threads
-object.
+object. The new() method is an alias for create().
=item $thread->join
-This will wait for the corresponding thread to join. When it finishes
-join will return the return values of the entry point function. If a
-thread has been detached, an error will be thrown..
+This will wait for the corresponding thread to join. When the thread
+finishes, join() will return the return values of the entry point
+function. If the thread has been detached, an error will be thrown.
+
+The context (scalar or list) of the thread creation is also the
+context for join(). This means that if you intend to return an array
+from a thread, you must use C<my ($thread) = threads->new(...)>, and
+that if you intend to return a scalar, you must use C<my $thread = ...>.
+
+If the program exits without all other threads having been either
+joined or detached, then a warning will be issued. (A program exits
+either because one of its threads explicitly calls exit(), or in the
+case of the main thread, reaches the end of the main program file.)
+
=item $thread->detach
-Will throw away the return value from the thread and make it
-non-joinable.
+Will make the thread unjoinable, and cause any eventual return value
+to be discarded.
=item threads->self
-This will return the object for the current thread.
+This will return the thread object for the current thread.
=item $thread->tid
-This will return the id of the thread. threads->tid() is a quick way
-to get current thread id if you don't have your thread handy.
+This will return the id of the thread. Thread IDs are integers, with
+the main thread in a program being 0. Currently Perl assigns a unique
+tid to every thread ever created in your program, assigning the first
+thread to be created a tid of 1, and increasing the tid by 1 for each
+new thread that's created.
+
+NB the class method C<< threads->tid() >> is a quick way to get the
+current thread id if you don't have your thread object handy.
+
+=item threads->object( tid )
+
+This will return the thread object for the thread associated with the
+specified tid. Returns undef if there is no thread associated with the tid
+or no tid is specified or the specified tid is undef.
=item threads->yield();
-This will tell the OS to let this thread yield CPU time to other threads.
-However this is highly depending on the underlying thread implementation.
+This is a suggestion to the OS to let this thread yield CPU time to other
+threads. What actually happens is highly dependent upon the underlying
+thread implementation.
+
+You may do C<use threads qw(yield)> then use just a bare C<yield> in your
+code.
=item threads->list();
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<threads->new>, C<async>
+semi-colon after the closing brace. Like C<< threads->new >>, C<async>
returns a thread object.
=back
A thread (not necessarily the main thread) exited while there were
still other threads running. Usually it's a good idea to first collect
the return values of the created threads by joining them, and only then
-exit from then main thread.
+exit from the main thread.
=back
-=head1 BUGS / TODO
+=head1 TODO
-The current implmentation of threads has been an attempt to get
+The current implementation of threads has been an attempt to get
a correct threading system working that could be built on,
and optimized, in newer versions of perl.
-Current the overhead of creating a thread is rather large,
+Currently the overhead of creating a thread is rather large,
also the cost of returning values can be large. These are areas
were there most likely will be work done to optimize what data
that needs to be cloned.
+=head1 BUGS
+
=over
=item Parent-Child threads.
On some platforms it might not be possible to destroy "parent"
threads while there are still existing child "threads".
-This will be possibly be fixed in later versions of perl.
-
+This will possibly be fixed in later versions of perl.
+
=item tid is I32
-The tid is a 32 bit integer, it can potentially overflow.
+The thread id is a 32 bit integer, it can potentially overflow.
This might be fixed in a later version of perl.
=item Returning objects
When you return an object the entire stash that the object is blessed
-as well. This will lead to a large memory usage.
-The ideal situation would be to detect the original stash if it existed.
+as well. This will lead to a large memory usage. The ideal situation
+would be to detect the original stash if it existed.
+
+=item Creating threads inside BEGIN blocks
+
+Creating threads inside BEGIN blocks (or during the compilation phase
+in general) does not work. (In Windows, trying to use fork() inside
+BEGIN blocks is an equally losing proposition, since it has been
+implemented in very much the same way as threads.)
=item PERL_OLD_SIGNALS are not threadsafe, will not be.
+If your Perl has been built with PERL_OLD_SIGNALS (one has
+to explicitly add that symbol to ccflags, see C<perl -V>),
+signal handling is not threadsafe.
+
=back
=head1 AUTHOR and COPYRIGHT
please join perl-ithreads@perl.org for more information
-
-
-
=head1 SEE ALSO
-L<perl>, L<threads::shared>, L<perlcall>, L<perlembed>, L<perlguts>
+L<threads::shared>, L<perlthrtut>,
+L<http://www.perl.com/pub/a/2002/06/11/threads.html>,
+L<perlcall>, L<perlembed>, L<perlguts>
=cut
projects / p5sagit/p5-mst-13.2.git / blobdiff