producer-consumer

A producer generates data and puts it into a buffer, while a consumer takes data from the buffer. The buffer has limited size — producer must wait if full, consumer must wait if empty.

A classic synchronization problem solved using three semaphores: empty (counts free slots), full (counts filled slots), and mutex (protects buffer access).

1. Producer waits on empty semaphore (decrements)
2. Producer waits on mutex (enters critical section)
3. Producer adds item to buffer
4. Producer signals mutex (exits critical section)
5. Producer signals full (increments)
6. Consumer does the reverse

• Uses 3 semaphores: empty (N), full (0), mutex (1)
• Producer waits on empty, signals full
• Consumer waits on full, signals empty
• Mutex protects buffer data structure

• Built from: Semaphore, Counting Semaphore
• Builds into: Reader-Writer Problem
• Related: Wait Operation, Signal Operation
• Contrasts with: Reader-Writer (producer-consumer vs readers-writers)

• Wrong semaphore order can cause deadlock (always mutex last in, first out)
• Buffer must be protected by mutex during access
• Can be extended to multiple producers/consumers