If I were to write a program and I wanted to be guaranteed that the program never sees an instance where, after it is running, it gets kicked off of the cpu until program termination, would I need an RTOS or is there a way to have such an experience guranteed on a regular linux os.
Example: Lets say we a running a headless Linux machine and running a program as user or root (eg reading SPI data from a sensor, listening for http requests) and there is reason to believe there is almost almost no other interaction with the machine aside from the single standalone script running.
If I wanted to ensure that my process running never gets taken off my cpu even for a moment such that I never miss valuable sensor information or incoming http requests, does this warrant a real-time operating system to keep this guarantee?
I know that Real Time OS are needed for guarantees on hard limits and hard deadlines of events. I also know that on a regular operating system it is up to the OS to decide priority and scheduling.
if this is in the wrong stack let me know.
Do you need to act on sensor readings in a constant time frame? How complicated this action should be? If all you need is to never miss a reading and you're ok with buffering them - just add a microcontroller or an FPGA in between your non-realtime device and a sensor.
Also, you can ensure some soft real time constraints even with an unpatched Linux. You can pin a process to a CPU and avoid using any syscalls in it - spin and poll instead, at 100% CPU utilisation, and then it's likely kernel will never touch it. Make sure the process binary and all the dynamic libraries (if any) are on a RAM disk (to avoid paging) and disable swap.