There is a "real-time patch" for the Linux kernel which enables the processor to unfairly schedule certain processes that ask for higher priority. Although the term "patch" may make it seem like this is just a partial solution, it really refers to the fact that the programming code used to enable this kind of unfair scheduling is not included in standard kernels; the standard kernel code must have this code "patched" into it.

The default behaviour of a real-time kernel is still to use the "fair queueing" system by default. This is good, because most processes don't need to have consistently low latencies. Only specific processes are designed to request high-priority scheduling. Each process is given (or asks for) a priority number, and the real-time kernel will always give processing time to the process with the highest priority number, even if that process uses up all of the available processing time. This puts regular applications at a disadvantage: when a high-priority process is running, the rest of the system may be unable to function properly. In extreme (and very rare!) cases, a real-time process can encounter an error, use up all the processing time, and disallow any other process from running - effectively locking you out of your computer. Security measures have been taken to help ensure this doesn't happen, but as with anything, there is no guarantee. If you use a real-time kernel, you are exposing yourself to a slightly higher risk of system crashes.

A real-time kernel should not be used on a computer that acts as a server, for these reasons.