Linux-based hard real-time OS?

Question

linux

Hello.
My challenge was to find a Linux-based, fully supported Linux, or hard real-time Linux itself.
Hard real time is a required attribute.
Googling showed that there are not so many options:
1) LynxOS (Linux support is not completely clear, proprietary, expensive)
2) RTLinux (it scares that Linux is running as a separate preempted process (because, in fact, real-time mode is lost) )
3) ART Linux (for me, this is the most interesting option so far: a separate kernel, which in the form of a deb package can be installed perfectly on the same ubuntu / debian; as I understand it, writing drivers will not look like such a magical process as in RTLinux)
4) ???
At the moment, the architecture is x86, but the use case on the SPARC architecture is quite possible.
I would be very grateful if you tell me about the strengths and weaknesses of certain solutions, what and why you use.
QNX does not need to be offered.

Answer 1

QNX does not need to be offered.
imho, and completely in vain .

Answer 2

if the Customer forbids QNX, offer him the ZOSRV KDA.xxxxx-xx, these systems are binary compatible. Neither QNX nor KPDA work on the SPARC architecture, but if SPARC means Elbrus, that is, the “compiler”, in particular, QNX4 was run through it and launched on Elbrus, everything seemed to work.

Answer 3

Is it just that vanilla Linux with the rt-preempt patch doesn't work? Isn't it the same eggs as ART-Linux?

Answer 4

Linux is very good for your purposes.
We wrote above that this is soft realtime, but apparently they didn’t quite understand the issue.
The fact is that the standard Linux kernel in the latest editions supports the launch of processes with real-time priority, but execution for a certain period is guaranteed there with a certain probability.
RT Patch from a friend named Ingo Molnar allows you to make the kernel work in hard real time. In this case, the overall performance drops slightly.
You can read more here:
https://rt.wiki.kernel.org/index.php/RT_PREMPT_HO... I quote
:
The standard Linux kernel only meets soft real-time requirements: it provides basic POSIX operations for userspace time handling but has no guarantees for hard timing deadlines. With Ingo Molnar's Realtime Preemption patch (referenced to as RT-Preempt in this document) and Thomas Gleixner's generic clock event layer with high resolution support, the kernel gains hard realtime capabilities.
It is possible to assemble such a kernel for different architectures.
You can contact with me any time.
Good luck to you =)

Answer 5

In addition, about the strengths and weaknesses.
Pros: The ability to use different architectures, many drivers will work (just rebuild them), if you wish, you can finish the open source code, no royalties or other payments.
Cons: Various pitfalls may not be documented.
Needs to be tested extensively due to the first reason.