SIGCHLD sometimes not delivered. Race condition?

02_success.t

use strict;
use warnings FATAL => 'all';
use POE;
use POE::Quickie;
use Test::More tests => 5;

POE::Session->create(
    package_states => [
        (__PACKAGE__) => [qw(
            _start
            stdout
            stderr
        )],
    ],
);

POE::Kernel->run;

sub _start {
    my $heap = $_[HEAP];

    my $quickie = POE::Quickie->new(trace => 1);
    $quickie->run(
        Program     => sub { print "foo\n" },
        StdoutEvent => 'stdout',
        Context     => 'baz',
    );
}

sub stdout {
    my ($heap, $output, $pid, $context) = @_[HEAP, ARG0..ARG2];
    is($output, 'foo', 'Got stdout');
    is($context, 'baz', 'Got context');
    my $procs = POE::Quickie->processes();
    is($procs->{$pid}, 'baz', '$quickie->processes() works');

    POE::Quickie->run(
        Program     => sub { warn "bar\n" },
        StderrEvent => 'stderr',
        Context     => 'quux',
    );
}

sub stderr {
    my ($heap, $error, $context) = @_[HEAP, ARG0, ARG2];
    is($error, 'bar', 'Got stderr');
    is($context, 'quux', 'Got context');
}

gistfile1.txt

$ for i in {1..1000}; do prove -vl 02_success.t; done
t/02_success.t .. 
1..5
=== 15671 === 2 -> _start (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Kernel.pm at 1413)
=== 15671 === 2 -> _create_wheel (from /mnt/stuff/src/my-cpan/poe-quickie/lib/POE/Quickie.pm at 93)
=== 15671 === 2 -> POE::Wheel::Run(1) -> select stderr (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15671 === 2 -> POE::Wheel::Run(1) -> select stdout (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15671 === 2 -> _child_stdout (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Wheel/Run.pm at 691)
ok 1 - Got stdout
ok 2 - Got context
ok 3 - $quickie->processes() works
=== 15671 === 2 -> _create_wheel (from /mnt/stuff/src/my-cpan/poe-quickie/lib/POE/Quickie.pm at 93)
=== 15671 === 2 -> POE::Wheel::Run(2) -> select stderr (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15671 === 2 -> _child_stderr (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Wheel/Run.pm at 791)
ok 4 - Got stderr
ok 5 - Got context
=== 15671 === 2 -> POE::Wheel::Run(1) -> select stdout (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15671 === 2 -> POE::Wheel::Run(2) -> select stdout (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15671 === 2 -> _child_signal (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/Signals.pm at 602)
=== 15671 === 2 -> POE::Wheel::Run(2) -> select stderr (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15671 === 2 -> _child_signal (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/Signals.pm at 602)
=== 15671 === 2 -> _stop (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/Sessions.pm at 571)
ok
All tests successful.
Files=1, Tests=5,  0 wallclock secs ( 0.03 usr  0.01 sys +  0.08 cusr  0.01 csys =  0.13 CPU)
Result: PASS
t/02_success.t .. 
1..5
=== 15675 === 2 -> _start (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Kernel.pm at 1413)
=== 15675 === 2 -> _create_wheel (from /mnt/stuff/src/my-cpan/poe-quickie/lib/POE/Quickie.pm at 93)
=== 15675 === 2 -> POE::Wheel::Run(1) -> select stderr (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15675 === 2 -> POE::Wheel::Run(1) -> select stdout (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15675 === 2 -> _child_stdout (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Wheel/Run.pm at 691)
ok 1 - Got stdout
ok 2 - Got context
ok 3 - $quickie->processes() works
=== 15675 === 2 -> _create_wheel (from /mnt/stuff/src/my-cpan/poe-quickie/lib/POE/Quickie.pm at 93)
=== 15675 === 2 -> POE::Wheel::Run(2) -> select stderr (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15675 === 2 -> _child_stderr (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Wheel/Run.pm at 791)
ok 4 - Got stderr
ok 5 - Got context
=== 15675 === 2 -> POE::Wheel::Run(1) -> select stdout (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15675 === 2 -> POE::Wheel::Run(2) -> select stdout (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)
=== 15675 === 2 -> _child_signal (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/Signals.pm at 602)
=== 15675 === 2 -> POE::Wheel::Run(2) -> select stderr (from /home/hinrik/perl5/perlbrew/perls/perl-5.13.11/lib/site_perl/5.13.11/POE/Resource/FileHandles.pm at 240)