Interrupt Handlers as Locks: A Deadlock-Free SMP Design

Interrupt Handlers Design Document The Problem Multicore kernel development is plagued by synchronization challenges: Spinlocks waste CPU cycles and cause cache line bouncing Mutexes require complex ownership tracking and can lead to priority inversion Lock ordering must be carefully designed to avoid deadlocks Atomic operations need memory barriers and are error-prone Each new subsystem reinvents its own locking strategy What if we could build synchronization directly into the hardware's existing interrupt mechanism? This is a follow up to my Physical Memory Manager design. The Key Insight When a CPU receives an interrupt, it has no choice. It must transfer control to the registered handler. There's no skipping, no deferring, no excuses. This mandatory behavior is enforced by the CPU itself. This makes interrupts the perfect foundation for synchronization. A Simple Interrupt Architecture Most kernels hardcode handlers directly in the IDT. I add one level of indirection: 1. The IDT Ent