Problem
I. Explain why interrupts are not appropriate for implementing synchronization primitives in multiprocessor systems.
II. A multithreaded web server wishes to keep track of the number of requests it services (known as hits). Consider the two following strategies to prevent a race condition on the variable hits. The first strategy is to use a basic mutex lock when updating hits:
int hits;
mutex lock hit lock;
hit lock.acquire();
hits++;
hit lock.release();
A second strategy is to use an atomic integer:
atomic t hits;
atomic inc(&hits);
Explain which of these two strategies is more efficient (make sure you explain WHY it is more efficient).
III. Describe two kernel data structures in which race conditions are possible. Explain how a race condition can occur.