q = Queue.new
l = Mutex.new

Thread.new {
  sleep 0.5
  q << 1
  q << 2
  q << 3
  sleep 0.5
  q.close
}

until q.closed? && q.empty?
  p [q.closed?, q.empty?]
  p q.pop
  p [q.closed?, q.empty?]
end