>That's particularly interesting because at one time years ago, I saw suggestions that Linux could run as a task on an RTOS. I've worked with systems that ran

>That's particularly interesting because at one time years ago, I saw suggestions that Linux could run as a task on an RTOS. I've worked with systems that ran Linux as a task of uITRON as well as threadX, both on somewhat obscure ARM hardware. Linux managed the MMU but had a large carveout for the RTOS code. They had some strange interrupt management so that Linux could 'disable interrupts' but while Linux IRQs were disabled, an RTOS IRQ could still fire and context switch back to an RTOS task. I haven't seen anything like this on RPi though, but it's totally doable.