Industry 4.0 (I4.0) closed-loop control applications require ultra low-latency and ultra high reliability. Generalized Frequency Division Multiplexing (GFDM) promises to meet these requirements in conjunction with low Out-Of-Band (OOB) emissions. We present latency measurements of an open-source, modular, portable GFDM software implementation using the GNU Radio framework. The used implementation and its components are investigated regarding their theoretical function. We investigate the usability of the GFDM implementation for Software-Defined Radio (SDR). This is facilitated by benchmarking the various functions with respect to different parameter sets. Thus, we focus on latency measurements which provide reliable figures for SDR system design. Furthermore, we show that low latency broadband SDR systems for I4.0 applications are feasible.