Runaway real-time processes can cause the system to halt. Such runaway processes can also slow the system response so much that the system appears to halt.
When a high priority real-time process does not relinquish control of the CPU, you must break the infinite loop in order to regain control of the system. Such a runaway process does not respond to Control-C. Attempts to use a shell set at a higher priority than the priority of the runaway process do not work.