Problem 3: Interrupt Service Routine Scheduling

• Suppose that we have the following interrupt tasks to perform.

  Task	Priority	Run Time	Dead- line	Event Freq.	Event Period	CPU Load
  A	1	2 ms	5 ms	200 Hz
  B	2		9 ms	100 Hz		40 %
  C	4	1 ms	13 ms		100 ms

  As with the homework, assume that:

  • All requests are buffered. If multiple tasks occur while the CPU is busy, they will be sequentially processed when the task is scheduled until either:
    1. The CPU is interrupted with a higher priority interrupt -or-
    2. There are no more tasks to process.
  • Write infinity if the task will eventually have an infinite worst-case delay.
  • Interrupts with lower-numbered priorities are always serviced before higher-numbered priorities.
  • The time to switch between interrupts is negligable.
    
  • All numbers are specified in decimal (base 10).

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• Carefully complete the empty boxes for run-time, deadline, event period, and CPU load in the table above. Double-check your answers for avoid errors in other parts of this problem. (6 pts)

• What is the total CPU load ? (1 pt)

• Suppose that all routines are preemtive. Determine the worst-case completion time for each of the tasks. Show your work to receive partial credit. (3 pts/each)
  • Task A:

  • Task B:

  • Task C:

• Suppose that all routines are non-preemtive. Determine the worst-case completion time for each of the tasks. Show your work to receive partial credit. (3 pts/each)
  • Task A:

  • Task B:

  • Task C: