Question

In this program I create a fork, and then call domultithreading from it. It then creates a few threads.

sub domultithreading {
    #Not my function
    my ($num) = @_;
    my @thrs;
    my $i = 0;
    my $connectionsperthread = 50;
    while ( $i < $num ) {
        $thrs[$i] = threads->create( \&doconnections, $connectionsperthread, 1 );
        $i += $connectionsperthread;
    }
    my @threadslist = threads->list();
    while ( $#threadslist > 0 ) {
        $failed = 0;
    }
}

sub kill {
    #how can I kill the threads made in domultithreading?
    kill 9, $pid;
    print "\nkilling $pid\n";
}

I then want to be able to kill the fork and its threads, however I can’t figure it out. Any suggestions?

Thanks a lot

Answer 1

Perl provides two concurrency models: Processes and Threads. While you shouldn’t neccessarily mix these two without a good reason, threads do model processes quite closely, so we can nearly treat them as such. Specifically, we can send signals to threads.

Processes can be signalled with the kill function: kill SIGNAL => $pid, while threads can be signalled with the kill method: $thr->kill(SIGNAL). This method returns the thread object. Signals can be intercepted when setting signal handlers in the %SIG hash.

This means that every process TERM signal handler TERMs all the child threads like

 $_->kill(9)->join() for threads->list;

and every thread TERM signal handler simply exits the thread, or does cleaning up:

 threads->exit; # exit the current thread