How to efficiently supervise Ruby Threads?

Question

Is the following inefficient? I want to allocate nearly all resources to threads but I'm wondering if in this case this loop will consume a lot of CPU time.

Thanks!

threads = create_threads #method that returns an Array of Threads
loop do
  alive = false
  threads.each do |thread|
    if thread.alive?
      alive = true
    end
  end
  break unless alive
end

Answer 1

threads.each do |thread|
  thread.join
end

Answer 2

threads.each &:join

my_thread.join returns as soon as my_thread exits.