9. Deliverables • Project Demonstration • Hard copy and electronic versions of • Project source code • Brain98 source code • Description of project • Normal description as per last project plus • Answering all questions and providing discussion • Graphical output from experimentation

10. Hardware Solutions to Mutual Exclusion • Many systems provide hardware support to critical section code. • Simple: Disable interrupts during critical section. • Would this provide mutual exclusion?? • Problems:

11. Hardware Solutions • Many systems provide hardware support to critical section code. • Simple: Disable interrupts during critical section. • Would this provide mutual exclusion?? • Problems: • Do not want to do this at user level. • Does not scale to multiprocessor system. • OK for OS to do so for short periods of time, not users.

12. Most machines provide special atomic hardware instructions • Atomic = non-interruptable • Either test memory word and set value • Or swap contents of two memory words