Question

I’m making some tests using threads in Perl 5.10.1 but I’m having some problems. First of all I have Debian GNU/Linux squeeze/sid with 2.6.32-5-amd64 (64 bits).

This is my script

#!/usr/bin/perl -w
use strict;
use warnings;
use threads;  

sub threadProcess{
    my ($number, $counter) = @_; 
    print "Enter thread #" . $number . "\n";
    while($counter < 10){
        print "Thread #" . $number . ": " . $counter . "\n";
        $counter++;
    }
    print "Exit thread #" . $number . "\n";
}

sub main{ 
    my $counter = 0;

    my $thr1 = threads->create(\&threadProcess, 1, $counter);  
    my $thr2 = threads->create(\&threadProcess, 2, $counter); 

    my $res1 = $thr1->join();  
    my $res2 = $thr2->join(); 

    print "Bye...\n";
}

main(@ARGV);

And this is the output:

Enter thread #1
Thread #1: 0
Thread #1: 1
Thread #1: 2
Thread #1: 3
Thread #1: 4
Thread #1: 5
Thread #1: 6
Thread #1: 7
Thread #1: 8
Thread #1: 9
Exit thread #1
Enter thread #2
Thread #2: 0
Thread #2: 1
Thread #2: 2
Thread #2: 3
Thread #2: 4
Thread #2: 5
Thread #2: 6
Thread #2: 7
Thread #2: 8
Thread #2: 9
Exit thread #2
Bye...

What may be the problem? Thanks in advance!

Answer 1

Nothing, except that the job of threadProcess is so short that the first thread can finish before the second thread can get initialized.

Put a delay in your loop and you will see the threads working at the same time.

while($counter < 10){
    print "Thread #" . $number . ": " . $counter . "\n";
    sleep 1;      # or Time::HiRes::sleep 0.25, etc.
    $counter++;
}