ensure_reactor_running

# File actioncable/lib/action_cable/subscription_adapter/evented_redis.rb, line 70
        def ensure_reactor_running
          return if EventMachine.reactor_running?
          @@mutex.synchronize do
            Thread.new { EventMachine.run } unless EventMachine.reactor_running?
            Thread.pass until EventMachine.reactor_running?
          end
        end