Correctness Issues
Fulfill conditions for coherence and consistency
- write propagation and atomicity
Deadlock: all system activity ceases
- Cycle of resource dependences
Livelock: no processor makes forward progress although transactions are performed at hardware level
- e.g. simultaneous writes in invalidation-based protocol
- each requests ownership, invalidating other, but loses it before winning arbitration for the bus
Starvation: one or more processors make no forward progress while others do.
- e.g. interleaved memory system with NACK on bank busy
- Often not completely eliminated (not likely, not catastrophic)