DARK2 FAQ page 2008

This page contains technical questions and their answers. New questions are added at the bottom of the page..

• 1. Why can I not access the papers directory on the course home page?
• 2. What is the difference between Dark2-IT and Dark2-MN2
• 3. Why is it OK that none of the Dekker threads may win under SC?
• 4. What is the store order for x86?

1. Why can I not access the papers directory on the course home page?

For copyright reasons, that page can only be accessed from the local network at the IT department.

2. What is the difference between Dark2-IT and Dark2-MN2

You'll need to write an extra report about microprocessors or perform an extra lab on your own for MN2 (and thus get more points).

3. Why is it OK that none of the Dekker threads may win under SC?

SC means that there is ONE global interleaving of accesses from both threads that everybody agrees on.
One such interlerleaving could be

1: A := 1
2: B := 1
1: if (B == 0) ...
2: if (A == 0) ...

In that case, none of the threads will declare success

4. What is the store order for x86?

x86 guarantees causal correctness, i.e., if an obesevation of an event A causes event B to happen, A will be globally ordered before B (see the "What value will get printed slide". x86 will guarantee that "1" will always get printed. However, there is no global order between stores made by different processors, i.e., there is not a global store order like the one in TSO.