Re^4: What is the correct way to finish multithreaded program?

I'm pushing undef into the queue with

foreach ( 1 .. $config->{number_of_threads} ) {

    $q->enqueue(undef);
}
[download]

and I think this will cause thread to return:

    while ( my $org = $q->dequeue() ) {

        parse_org( $org, $mech );
        $pq->enqueue($org);
    }

    say "Finishing worker [$thread_id]";

    return;
[download]

Also I have Finishing worker [SOME_ID] in the output...

Comment on Re^4: What is the correct way to finish multithreaded program? Select or Download Code

Replies are listed 'Best First'.
Re^5: What is the correct way to finish multithreaded program? by BrowserUk (Patriarch) on May 05, 2014 at 15:49 UTC
I'm pushing undef into the queue with ... and I think this will cause thread to return: It will. Eventually. But there is no guarantee -- indeed it is most unlikely -- that all of the threads will: a) get a timeslice; b) receive the undef from the queue; c) act upon it and exit; before your main thread tries to join them. The whole point of join is that it waits for the threads to finish, thus ensuring that your main thread doesn't exit before your child threads are finished. It rarely makes any sense to turn it into a non-blocking operation by calling is_joinable before calling join. The are a few specialist uses for that, but in the case of your code it only guarantees that any thread that is slow to finish will not get joined before you terminate the main thread; hence the error message. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply]
Re^5: What is the correct way to finish multithreaded program? by Anonymous Monk on May 05, 2014 at 13:08 UTC
Here you go ... just because queue is empty, doesn't mean threads are joinable Read more... (5 kB) This reliably exits with 6 running and unjoined on my old machine, YMMV	[reply] [d/l]
Re^6: What is the correct way to finish multithreaded program? by Gangabass (Vicar) on May 06, 2014 at 03:04 UTC
Thank you for nice explanation! Now I got it.	[reply]
Re^5: What is the correct way to finish multithreaded program? by Anonymous Monk on May 05, 2014 at 12:24 UTC
If you can make the code run .. and reproduce the problem, you can see the only real way to wait is to join everything not merely the immediately joinable :)	[reply]


Perl Monk, Perl Meditation
	PerlMonks