ready = false
t = Thread.new do
  f = Fiber.new do
    begin
      Fiber.yield
    ensure
      STDERR.puts "suspended fiber ensure"
    end
  end
  f.resume

  f2 = Fiber.new do
    begin
      ready = true
      sleep
    ensure
      STDERR.puts "current fiber ensure"
    end
  end
  f2.resume
end

Thread.pass until ready && t.stop?

# let the program end, it's the same as #exit or an exception for this behavior