Runaway real-time processes can cause the system to halt or can slow the system response so much that the system appears to halt.
If you have a runaway process on a SPARC system, press Stop-A. You might have to do this more than one time. If this doesn't work, or on non-SPARC systems, turn the power off, wait a moment, then turn it back on.
When a high priority real-time process does not relinquish control of the CPU, there is no simple way to regain control of the system until the infinite loop is forced to terminate. Such a runaway process does not respond to control-C. Attempts to use a shell set at a higher priority than that of a runaway process do not work.