usbduxsub_tmp->urbOut = NULL;
        }
        if (usbduxsub_tmp->urbPwm) {
-               if (usbduxsub_tmp->pwm_cmd_running) {
-                       usbduxsub_tmp->pwm_cmd_running = 0;
-                       usbduxsub_unlink_PwmURBs(usbduxsub_tmp);
-               }
+               /* force unlink urb */
+               usbdux_pwm_stop(usbduxsub_tmp, 1);
                kfree(usbduxsub_tmp->urbPwm->transfer_buffer);
                usbduxsub_tmp->urbPwm->transfer_buffer = NULL;
-               usb_kill_urb(usbduxsub_tmp->urbPwm);
                usb_free_urb(usbduxsub_tmp->urbPwm);
                usbduxsub_tmp->urbPwm = NULL;
        }
        usbduxsub_tmp->dac_commands = NULL;
        kfree(usbduxsub_tmp->dux_commands);
        usbduxsub_tmp->dux_commands = NULL;
-       usbduxsub_tmp->pwm_cmd_running = 0;
 }
 
 static int usbduxsigma_attach_common(struct comedi_device *dev,