Computer Science 322
Operating Systems

Mount Holyoke College
Spring 2008

Lecture 13: Synchronization Problems
Date: Wednesday, March 5, 2008


Lecture Assignment

Due at the start of class, Friday, March 7.

Please turn in a hard copy (typeset or handwritten are OK). We will discuss this problem during class, so no late submissions are accepted.

The Dining Savages. A tribe of savages eats communal dinners

from a large pot that can hold M servings of stewed missionary. When a savage wants to eat, he helps himself from the pot, unless it is empty. If the pot is empty, the savage wakes up the cook and then waits until the cook has refilled the pot. The behavior of the savages and cook is defined by the following processes:

Savagei: while (1) { get serving from pot; eat; }
Cook: while (1) { sleep; put M servings in pot; }

Develop psuedocode (along the lines of the in-class Sleeping Barber solution) for the actions of the savages and the cook. Use semaphores for synchronization. The only operations permitted on the semaphores are initialization, wait, and signal. You may assume the semaphores are fair. Your solution should avoid deadlock and awaken the cook only when the pot is empty. You do not need to implement C code, just a list of shared variables and pseudocode describing the actions of the savages and the cook.