Week 6

 Week 6 (7/30-8/5)

In this week’s readings, PA5, lectures, and quizzes, I learned how condition variables and semaphores are used to manage synchronization in multi-threaded programs. As an example of this, I learned that a condition variable lets threads wait efficiently for some condition to become true, like waiting for a buffer to be non-empty before reading. The Anderson/Dahlin method showed how to design shared objects safely by first building basic object-oriented code and then adding one lock, condition variables, and wait/signal logic in a step-by-step way. This helped me understand how to write safer and more precise threading code, such as in a simple producer-consumer buffer.

I also learned how semaphores can be used for the same types of problems, like enforcing mutual exclusion or synchronizing multiple threads at a barrier. Unlike condition variables, semaphores are more powerful but also more complex—they combine locking and signaling in one tool. For example, to solve the rendezvous problem (where threads must wait for each other), I saw how to use two semaphores to make sure both threads complete the first step before moving on. In the synchronization barrier problem, I learned that we can count how many threads have arrived and use a turnstile pattern (wait then signal) to let all threads through. These examples made abstract ideas more concrete for me.

This week's concepts helped me understand the overall idea of concurrency, especially how to coordinate and manage access to shared resources safely and correctly, which is a key challenge in modern operating systems.