How to understand & implement read-write locks and bounded buffers

3-Second Blueprint (English)

1. Read-write locks guard a reader counter with a mutex so the first reader acquires the write lock while later readers share access.
2. Bounded buffers synchronize producer and consumer threads using a shared mutex paired with not-full and not-empty conditions.
3. Calling pthread_cond_wait atomically releases the held mutex to sleep, then re-acquires it upon signal before rechecking state.