I was hoping that they'd use a dedicated hard real-time OS, like VxWorks, FreeRTOS, uC/OS-III, or QNX rather than a desktop/server OS with some RT extensions bolted on.
A priori it seems it would have been the way to go but looking at the figure showing the Flex-6000 architecture I think the real realtime stuff is done in hardware (FPGA and TI Video processor) with the Arm processor supervising the whole thing. The version of Linux running on the Arm nay have some realtime extensions but not the critical parts.
This is just a guess.
Jean-Claude PJ2BVU