timeout for threads in perl

Question

I am writing a perl script to exit a thread after 5sec as shown below. but I am not able to print the message from if condition.

Output of the script is Alarm clock

How to print proper error messages from the parent process when timeout for threads.

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

my $th   = threads->create( \&sub1 );
my $thid = $th->tid();

eval
{
    $SIG{'KILL'} = sub
    {
        if ( $th->is_running() )
        {
            print "timed out, exiting the thread $thid\n";
            $th->exit();
        }
    };
    alarm(5);
    $th->join();
};

sub sub1
{
    my $i = 0;
    while ( $i == 0 )
    {
    }

}

Chankey Pathak Chankey Pathak · Accepted Answer · 2014-06-23T06:15:15

Documentation says

If you want to use alarm to time out a system call you need to use an eval/die pair.

Alternatively you can use Sys::SigAction and do something like below

use Sys::SigAction qw( timeout_call );
if ( timeout_call( 5 ,sub { $retval = DoSomething( @args ); } )
{
   print "DoSomething() timed out\n" ;
}

Edit: See the answer of mob to the question: Perl threads with alarm

Also see the discussion on thread safe alarms.

timeout for threads in perl

1 Answers