use after_fork hook instead of tempfile

t/06-wait-all-children-with-timeout.t

@@ -4,7 +4,6 @@ use strict;
 use warnings;
 
 use Fcntl qw/:flock/;
-use File::Temp qw/tempfile/;
 use Test::More tests => 4;
 
 use Parallel::Prefork;
@@ -18,33 +17,24 @@ my $pm = Parallel::Prefork->new({
     }
 });
 
-my ($fh, $filename) = tempfile;
-syswrite $fh, '0', 1;
-close $fh;
+my $sig_retain_cnt = 1;
+$pm->after_fork(sub {
+    $sig_retain_cnt++;
+});
 
 my $manager_pid = $$;
 
 until ($pm->signal_received) {
     $pm->start and next;
 
-    open my $fh, '+<', $filename
-        or die "failed to open temporary file: $filename: ";
-    flock $fh, LOCK_EX;
-    sysread $fh, my $c, 10;
-    $c++;
-    seek $fh, 0, 0;
-    syswrite $fh, $c, length($c);
-    flock $fh, LOCK_UN;
-    close $fh;
-
     my $rcv = 0;
     local $SIG{TERM} = sub { $rcv++ };
 
-    if ($c == $pm->max_workers) {
+    if ($sig_retain_cnt == $pm->max_workers) {
         kill 'TERM', $manager_pid;
     }
 
-    1 while $rcv < $c;
+    1 while $rcv < $sig_retain_cnt;
 
     $pm->finish;
 }
@@ -56,5 +46,3 @@ $pm->wait_all_children();
 is $pm->num_workers, 0, 'all workers reaped.';
 
 is($reaped, $pm->max_workers, "properly called on_child_reap callback");
-
-unlink $filename;