CSI 3131
Assignment 3
Question 1
A university computer science department has a teaching assistant (TA) who helps
undergraduate students with their programming assignments during regular office hours.
The TA’s office is rather small and has room for only one desk with a chair and
computer. There are three chairs in the hallway outside the office where students can sit
and wait if the TA is currently helping another student. When there are no students who
need help during office hours, the TA sits at the desk and takes a nap. If a student arrives
during office hours and finds the TA sleeping, the student must awaken the TA to ask for
help. If a student arrives and finds the TA currently helping another student, the student
sits on one of the chairs in the hallway and waits. If no chairs are available, the student
will come back at a later time.
Using POSIX threads, mutex locks, and semaphores, implement a solution that
coordinates the activities of the TA and the students. Details for this assignment are
provided below.
The Students and the TA
Using Pthreads, begin by creating n students. Each will run as a separate thread. The TA
will run as a separate thread as well. Student threads will alternate between programming
for a period of time and seeking help from the TA. If the TA is available, they will obtain
help. Otherwise, they will either sit in a chair in the hallway or, if no chairs are available,
will resume programming and will seek help at a later time. If a student arrives and
notices that the TA is sleeping, the student must notify the TA using a semaphore. When
the TA finishes helping a student, the TA must check to see if there are students waiting
for help in the hallway. If so, the TA must help each of these students in turn. If no
students are present, the TA may return to napping.
Perhaps the best option for simulating students programming—as well as the TA
providing help to a student—is to have the appropriate threads sleep for a random period
of time.
