A method, a system and a computer program product for controlling the hardware priority of hardware threads in a data processing system. A Thread Priority Control (TPC) utility assigns a primary level and one or more secondary levels of hardware priority to a hardware thread. When a hardware thread initiates execution in the absence of a system call, the TPC utility enables execution based on the primary level. When the hardware thread initiates execution within a system call, the TPC utility dynamically adjusts execution from the primary level to the secondary level associated with the system call. The TPC utility adjusts hardware priority levels in order to: (a) raise the hardware priority of one hardware thread relative to another; (b) reduce energy consumed by the hardware thread; and (c) fulfill requirements of time critical hardware sections.