CS 3733 Operating Systems

This assignment relies on the first three assignments. Modify the runsim from assignment 3 as follows:

• Keep the a record of the processes that are currently being run by runsim in a linked list. For each process you should include:
  • Process ID
  • Time process was last stopped (wall clock time that runsim detects the stop).
  • Total CPU time used by process so far (sum of system time and user time for process as given in the proc file system).

• Write a function called output_list which has prototype:

            void output_list(FILE *fp, list_t *p);
  

  The output_list function outputs the contents of the linked list of processes to the file fp. Use this function to test that your linked list is working.

• Write a function called update_total_time which has prototype:

            void update_total_time(list_t *p, timespec_t t, pid_t pid);
  

  The update_total_timefunction updates the time used by process pid

• Write a function called update_stopped_time which has prototype:

   
            void update_stopped_time(list_t *p, timespec_t t, pid_t pid); 
  

  The update_stopped_timefunction updates the time that the process pid was last stopped.

• Write a function to add a process to the list.

• Write a function to delete a process from the list.

Program Development and Testing Speciification

• Test point 1: (Due October 31, 1997)
  

  Insert the code for adding a process to the list when it is forked and deleting it from the list when the process terminates. Do not update any times in this step. Output the list after each insertion and deletion.

• Test point 2: (Due October 31, 1997)
  Add the code to update the last time stopped when the waitpid detects that the process has stopped. For testing, output the entire list each time you update.

• Test point 3: (Due October 31, 1997)
  Add a signal handler for SIGUSR1 to runsim. The signal handler will print the status information contained in the linked list by calling output_list. At this point you will have to also insert code to block signals to protect critical sections as discussed in class.

• Test point 4: (Due November 5, 1997)
  
  • Add an additional command line argument to runsim that gives the number of seconds between updates of the CPU time.

  • Have the program regularly update the times by having an alarm go off periodically. (You can achieve this by having the SIGALRM signal handler reset the alarm or by using POSIX timers.)

  • The alarm system call generates a SIGALARM signal. Write a signal handler that will update the amount of CPU time for each process that is managed by runsim Read the status in proc as in assignment 2.

• Test point 5: (Due November 5, 1997)
  Add code to restart the child processes by sending SIGCONT to them after outputting their status information and updating the list.