EdgeCampus will install smart door controllers on every lab. Each controller reads a student card, asks the edge server whether the student may enter, opens the lock, and must always allow opening from the inside in an emergency (fire alarm) within 50 ms, even if the network or the card-reader software fails.
Two proposals:
- P1: a small Linux image (monolithic kernel) with the card-reader driver, a network stack and the door application.
- P2: a real-time microkernel with the card-reader driver, network stack and door logic as separate user-mode servers; the emergency-exit logic is a separate high-priority task.
Write an architecture decision record (context, options, decision, consequences) that:
- Compares P1 and P2 on reliability, timing guarantees, security (attack surface), development effort and hardware cost.
- Explains, using this chapter's concepts (kernel/user mode, isolation, interrupts and priorities, timer), what happens in each design when the card-reader driver crashes during a fire alarm.
- Decides, and lists two tests that would prove the 50 ms emergency requirement.