Re: seg faults when i use thread->new from a thread - am i using threads incorrectly?

[Arthur Bergman]

On onsdag, apr 2, 2003, at 03:19 Europe/Stockholm, Bradley W. Langhorst 
wrote:

I just found this newsgroup - so I hope no one is annoyed that I'm
posting
something very similar to what i posted on c.l.p.m
Not at all, :)

I'm seeing unusual problems when i try to start a new thread from a
previously created thread.
This has been known to be a bit wonky on Win32, but not under unix 
(which I assume you are using because you like forks.pm)

I've written a INET socket program to respond to incoming messages with
new
messages sent out on a different socket.
I start a new thread for every incoming request .
When I don't need to spawn new threads the program works reliably.
However, some incoming requests have to create multiple responses so 
I'm
creating new threads...

I get seg faults when that happens with some of my tests

./agent.pl
Segmentation fault
 ./agent.pl
Segmentation fault
A backtrace would be nice,,

gdb perl
run ./agent.pl
bt
I also see leaked scalars when when it my test doesn't induce a seg
fault
Probably the same thing.

here's the code that creates the inner threads:
Is there something wrong with this?
(I was surprised to find that I could not return multiple values from a
join
- thus the array_ref and splice)
Because of some unknown reason the thread runs with the context of when 
it is created, so to return an array you need to do
($thread) = threads->new(....
so the thread gets a list context

    foreach $subtask (@$ra_tasks) {
        log_msg("Trying to schedule $subtask asynchronously\n",10);
        #thread so these can occur simultaneously
        $thr = threads->new(\&schedule_task,
                            $subtask,
                            $earliest_start,
                            $bid_by,
                            $req_id);
        log_msg("adding thread $thr to list of workers\n", 12);
        push @workers, $thr;
    }
    #now gather the results from the workers

    foreach $thr (@workers) {

        eval {
            $ra_ret = $thr->join();
        };
        if ($@) {
            die("subcontracing failed: [EMAIL PROTECTED]");
        } else {
            ($start_time,$end_time, $ra_bids) = splice(@$ra_ret,0,3);
            push @subtasks, {'first_start' => $start_time,
                             'last_end' => $end_time,
                             'bids' => $ra_bids};
        }
    }
Do you know when you are getting the coredump, in new() or in join?

Also, what modules are you using?

Arthur