I'm glad to see continued discussion. I managed to create what I believe to be the simplest test case for this behavior:

use strict;
use warnings;
use threads;
use Thread::Semaphore;

my $gag = new Thread::Semaphore(0);
async   {
            $gag->down;
            while (<>) {
                print;
            }
        }->detach;
#close STDIN; # Comment this line for race-condition behavior
$gag->up;
my $value = async   {   return 1;   }->join;

[download]

The proper behavior for this code should be to immediately return control to the OS. In its race-condition configuration under Win32, it will usually wait for one input and parrot it back and sometimes two inputs.

Based on your earlier post, I assume your 5.10 can function w/o the use of semaphores. I'll play with it a bit more to see if the addition of instrumentation to an independent log file affects the buffering behavior, but it seems like waiting for input on a shared file handle is blocking thread creation, i.e. what you said.

In reply to Re^7: threads on Windows by kennethk
in thread threads on Windows by kennethk

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