Assignment: Delta Queues

From Embedded Xinu
Jump to navigation Jump to search

Delta Queues

This assignment is a Xinu assignment allowing the student to grow a more firm understanding of how an operating system works. This assignment is part of the Student Built Xinu track for professors that are Teaching With Xinu. Your entire working directory containing your Xinu operating system will be submission for this assignment.


First, make a fresh copy of your work thus far.

  cp -R <old Xinu directory> <new Xinu directory>

Untar the new project files on top of this new directory:

  tar xvzf <tar-ball location>

You should now see the new project files in with your old files. Be certain to make clean before compiling for the first time.


Modify system/sleep.c, system/wakeup.c, system/insertd.c, and system/clockintr.c to add the sleep() system call to the operating system. A process that calls sleep(n) should enter the PRSLEEP state for n clock ticks. A clock "tick" is one millisecond in our current system. It corresponds to the raising of the timer interrupt request when interrupts are not disabled. When the clock interrupt handler detects that a process has slept for long enough, the wakeup function should move the process back to the ready list.

The appropriate data structure for maintaining a list of sleeping processes is a delta queue, as described in lecture. Add a delta queue to the system by increasing the QENT constant in include/queue.h, declaring a queue called "sleepq" in include/clock.h, and and defining and initializing sleepq in system/clockinit.c. Make sure to test your delta queue in isolation before testing the sleep() function.


Project credit will be weighted evenly between delta queue maintenance, sleeping, and waking processes. By now, you should be aware that rigorous testing is the key to success in these projects. Our test cases will include at least:

  • Checking your delta queue insert function with a variety of parameters
  • Checking your sleeping and waking functions independently and in concert.