CS240 Spring 2011:LAB08

Signals, Setjmp/Longjmp

Goal

In this lab you have to write a simple scheduler that executes a sequence of tasks and handle exceptions that may occur while executing these tasks. The tasks to be executed are passed as argument to the scheduler using an array of function pointers. Some of the tasks may run in an infinite loop while others may throw exceptions like segmentation fault.

Introduction

Instructions

1. Download the source files for the lab can be downloaded from here. Extract the files using the following command: tar -xpvf lab08.tar


2. This folder contains 3 source files: my_scheduler.h, my_scheduler.c and main.c. It also contains a Makefile that you should use for compiling.
   
   
3. Your code should be written only in my_scheduler.c. We will replace main.c with our own main.c to grade the project. You should use the same function prototypes as specified in my_scheduler.h. Implement the following functionality:
   
   

   Function name	Functionality
   void scheduler(void (*func[])(), int len);	Schedules  multiple tasks one after the other. These tasks are supplied as the func argument (array of function pointers) to the scheduler. The scheduler runs in an infinite loop scheduling the tasks in a round robin manner. The len argument specifies the number of tasks in the array of function pointers.
   void handle_signal(int signo);	Defines the behavior of handler when a signal is received. This is supposed to handle 4 kinds of signals: SIGINT, SIGFPE, SIGSEGV, SIGALRM. In case of SIGINT, the handler prints a message and exits. For the other three signals, you need to print a message and return the control back to the scheduler. (Hint: Use longjmp) The following messages are printed for various signals: For SIGINT:             SIG: Interrupt received. Exiting For SIGFPE:             SIG: Floating point exception encountered For SIGSEGV:             SIG: Segmentation fault encountered For SIGALRM:             SIG: Alarm went off! Note: some signals are reset to default after each call. You will need to reset the signal handler each time.
   void initHandlers();	Initializes the signal handling. That is, for each of the signals SIGINT, SIGFPE, SIGSEGV and SIGALRM, it sets up signal handling by specifying the handle_signal(int signo) as the handler function.

   
   
4. The reference program scheduler.ref can be executed to see the expected behavior of the scheduler.

Submit

Before you submit make sure to test your implementation on LORE using the Makefile provided.
Your code must compile using the provided Makefile and run on LORE for you to earn points for this lab.

Type cd .. in lab08 and change working directory to the parent directory of lab08.

In the parent directory of lab08, type turnin -v -c cs240=XXX -p lab08 lab08 to turnin your work. Replace XXX with your section number.

Now, you may use the command, turnin -c cs240=XXX -p lab08 -v to verify your submission.

This lab is due on Monday, April 25 by 11:59 pm