The PREEMPT_RT patches are the first option for every developer when a real-time solution is required. For some developers, the PREEMPT_RT patches transform Linux into a real-time solution suitable for their needs. This solution could not replace a real-time operation system, but is, in fact, suitable for a large number of systems.
The biggest advantage that PREEMPT_RT has over other real-time solutions for Linux is that it actually transforms Linux into a real-time operating system. All the other alternatives usually create a microkernel that is executed as a hypervisor and Linux is only executed as a task of it, so the communication of real-time tasks with the non-real-time ones is done through this microkernel. For the PREEMPT_RT patch, this problem is no more.
The standard version of the Linux kernel is only able to offer soft real-time requirements, such as basic POSIX user space operations where no deadline is guaranteed. Adding patches, such as Ingo Molnar's PREEMPT_RT patch...
