=head1 DESCRIPTION
This tutorial describes the use of Perl interpreter threads (sometimes
-referred to as I<ithreads>) that was first introduced in Perl 5.6.0. In this
+referred to as I<ithreads>). In this
model, each thread runs in its own Perl interpreter, and any data sharing
between threads must be explicit. The user-level interface for I<ithreads>
uses the L<threads> class.
B<NOTE>: There was another older Perl threading flavor called the 5.005 model
-that used the L<Threads> class. This old model was known to have problems, is
+that used the L<threads> class. This old model was known to have problems, is
deprecated, and was removed for release 5.10. You are
strongly encouraged to migrate any existing 5.005 threads code to the new
model as soon as possible.
like:
use Config;
- $Config{useithreads} or die('Recompile Perl with threads to run this program.');
+ $Config{useithreads} or
+ die('Recompile Perl with threads to run this program.');
A possibly-threaded program using a possibly-threaded module might
have code like this:
sub sub1 {
my @InboundParameters = @_;
print("In the thread\n");
- print('Got parameters >', join('<>', @InboundParameters), "<\n");
+ print('Got parameters >', join('<>',@InboundParameters), "<\n");
}
The last example illustrates another feature of threads. You can spawn
... create some threads ...
- $hash{a} = 1; # All threads see exists($hash{a}) and $hash{a} == 1
+ $hash{a} = 1; # All threads see exists($hash{a})
+ # and $hash{a} == 1
$hash{a} = $var; # okay - copy-by-value: same effect as previous
$hash{a} = $svar; # okay - copy-by-value: same effect as previous
$hash{a} = \$svar; # okay - a reference to a shared variable
while ($TryCount--) {
$semaphore->down();
$LocalCopy = $GlobalVariable;
- print("$TryCount tries left for sub $SubNumber (\$GlobalVariable is $GlobalVariable)\n");
+ print("$TryCount tries left for sub $SubNumber "
+ ."(\$GlobalVariable is $GlobalVariable)\n");
sleep(2);
$LocalCopy++;
$GlobalVariable = $LocalCopy;
Confused yet? It's time for an example program to show some of the
things we've covered. This program finds prime numbers using threads.
- 1 #!/usr/bin/perl
- 2 # prime-pthread, courtesy of Tom Christiansen
- 3
- 4 use strict;
- 5 use warnings;
- 6
- 7 use threads;
- 8 use Thread::Queue;
- 9
- 10 sub check_num {
- 11 my ($upstream, $cur_prime) = @_;
- 12 my $kid;
- 13 my $downstream = Thread::Queue->new();
- 14 while (my $num = $upstream->dequeue()) {
- 15 next unless ($num % $cur_prime);
- 16 if ($kid) {
- 17 $downstream->enqueue($num);
- 18 } else {
- 19 print("Found prime: $num\n");
- 20 $kid = threads->create(\&check_num, $downstream, $num);
- 21 if (! $kid) {
- 22 warn("Sorry. Ran out of threads.\n");
- 23 last;
- 24 }
- 25 }
- 26 }
- 27 if ($kid) {
- 28 $downstream->enqueue(undef);
- 29 $kid->join();
- 30 }
- 31 }
- 32
- 33 my $stream = Thread::Queue->new(3..1000, undef);
- 34 check_num($stream, 2);
+ 1 #!/usr/bin/perl
+ 2 # prime-pthread, courtesy of Tom Christiansen
+ 3
+ 4 use strict;
+ 5 use warnings;
+ 6
+ 7 use threads;
+ 8 use Thread::Queue;
+ 9
+ 10 sub check_num {
+ 11 my ($upstream, $cur_prime) = @_;
+ 12 my $kid;
+ 13 my $downstream = Thread::Queue->new();
+ 14 while (my $num = $upstream->dequeue()) {
+ 15 next unless ($num % $cur_prime);
+ 16 if ($kid) {
+ 17 $downstream->enqueue($num);
+ 18 } else {
+ 19 print("Found prime: $num\n");
+ 20 $kid = threads->create(\&check_num, $downstream, $num);
+ 21 if (! $kid) {
+ 22 warn("Sorry. Ran out of threads.\n");
+ 23 last;
+ 24 }
+ 25 }
+ 26 }
+ 27 if ($kid) {
+ 28 $downstream->enqueue(undef);
+ 29 $kid->join();
+ 30 }
+ 31 }
+ 32
+ 33 my $stream = Thread::Queue->new(3..1000, undef);
+ 34 check_num($stream, 2);
This program uses the pipeline model to generate prime numbers. Each
thread in the pipeline has an input queue that feeds numbers to be
guarantee that a signal sent to a multi-threaded Perl application
will get intercepted by any particular thread. (However, a recently
added feature does provide the capability to send signals between
-threads. See L<threads/"THREAD SIGNALLING> for more details.)
+threads. See L<threads/THREAD SIGNALLING> for more details.)
=head1 Thread-Safety of System Libraries
Annotated POD for L<threads>:
L<http://annocpan.org/?mode=search&field=Module&name=threads>
-Lastest version of L<threads> on CPAN:
+Latest version of L<threads> on CPAN:
L<http://search.cpan.org/search?module=threads>
Annotated POD for L<threads::shared>:
L<http://annocpan.org/?mode=search&field=Module&name=threads%3A%3Ashared>
-Lastest version of L<threads::shared> on CPAN:
+Latest version of L<threads::shared> on CPAN:
L<http://search.cpan.org/search?module=threads%3A%3Ashared>
Perl threads mailing list:
-L<http://lists.cpan.org/showlist.cgi?name=iThreads>
+L<http://lists.perl.org/list/ithreads.html>
=head1 Bibliography
https://perl5.git.perl.org / perl5.git / blobdiff