CS 3733 Operating Systems, Spring 2003 Assignment 4 Comments

The assignment was graded on a basis of 40 points.
If there is anything you don't understand, see me.

• Some people still do not understand how to tell whether Part 1 is working. For a maximum of 3 processes, the output would often look like:
        Start
        Start
        Start
        End
        Start
        End
        Start
        ...
        End
        End
        End
• Do not block the signals during the readline. This can indefinitely delay a signal from being caught
• A signal handler must have either 1 or three arguments depending on whether it is set with SA_SIGACTION clear or set.
• Do not use the argument in the signal handler just to eliminate the lint warning message.
• In Part 2 your program has a critical section in the signal handler and the main program when the data structure holding the list is modified.
• The simplest way to protect this critical section is to block the SIGUSR1 signal before modifying the structure. Unblock the signal when the modification is complete.
• You should save and restore errno in the signal handler.
• When testing, be sure to test the case in which signals are delivered before the last process starts.
• Don't allocate a pointer and malloc memory unless necessary. Normally, malloc is used when the amount of memory needed is not known during compile time.
• The simplest implementation of Part 2 is to allocate an array of structures of n entries, where n is the maximum number of running processes. If instead, you use a linked list, it makes Part 4 almost trivial. Instead of deleting entires, mark them as finished.
• readline should not use global variables.
• You don't have to test with very long lines if you make your initial buffer have a small size.
• readline should not exit the program under any circumstances.
• For Part 5, write a function:
        int int2str(int n, char *buf)
  That creates a string in buf corresponding to the integer, n. Return the length of the string. You function can assume that buf is large enough.