Smart Grid initiatives aim to overlay the existing power grid infrastructure with a communication and computation infrastructure to enable integration of renewable resources and increased efficiency and reliability of the electric power grid. This requires substantial changes to the existing centralized control architecture as well as the development of drastically more powerful communication and computation infrastructure. In this paper, we describe the elements required for implementation of a "Prosumer" based distributed control architecture for smart grid. We illustrate the operation of this distributed control architecture through the case study of a Demand Response application. We propose a Hard Real Time enabled, Web Services based computing infrastructure that can support the development as well as the operation of this distributed control architecture. Main components of this computing infrastructure are a Generic Real Time API (Generic RT-API) for platform independence, a Rule based Configurable API Translator, a Hard Real Time Web Services (HRT-WS) Engine and the ability to receive XML based configuration/control instructions remotely. We describe the status of our prototype implementation for this computing infrastructure using LXRT/RTAI based Hard Real Time Linux environment.