---

Semaphore emptyA = M-x;

Semaphore emptyB = N-y;

Semaphore fullA = x;

Semaphore fullB = y;

Semaphore mutexA = 1;

Semaphore mutexB = 1;

A

{

P(fullA);P(mutexA);fetch mail;V(mutexA);V(emptyA);

answer question and bring forward a new issue

P(emptyB): P(mutexB); put mail; V(mutexB); V(fullB);

}