gistfile1.rb

t1_setup = false
t2_setup = false
$bad = true

m = Thread.new do
  begin
    t = Thread.new do
      begin
        t2_setup = true
        sleep
      ensure
        $bad = false
      end
    end
    t1_setup = true
    sleep
  ensure
    t.kill
  end
end

Thread.pass until t1_setup and t2_setup

m.kill

puts $bad