rtirq install

yes, you're totally correct, congratulations ;)

rtirq was, and still is for that matter, posed for the real-time kernel PREEMPT_RT branch of the Linux kernel (check https://rt.wiki.kernel.org/index.php/Main_Page; linux-rt-user at vger.kernel.org maillist; kernel.org/pub/linux/kernel/projects/rt/; etc.)

most of that work, as it boiled down to ground way more than a decade old, got sneaked in the main vanilla so called "Linus" kernel ever since somewhere v2.6.x, I don't recall precisely; but the most important part was/is certainly the "threadirqs" kernel boot parameter that makes it (rtirq that is) accessible to the masses--and that's what you already know ;)

enjoy