ITPEC FE Morning April 2019 Question 20
ITPEC FE Morning April 2019 — Question 20 of 80
Preemptive Priority Scheduling — higher-priority task preempts the running lower-priority task.
Given: Task A has higher priority than *B`, real-time OS uses preemptive scheduling.
Key rule: When a higher-priority task arrives, it immediately preempts the current task.
- •A launched during B's execution → A preempts B
- •B goes to ready state (not "waiting" — it's ready to run, just yielding CPU)
- •A executes immediately
Why not others:
- (b) — says B gets "waiting" status; preempted tasks go to "ready", not "waiting" (waiting = blocked on I/O)
- (c) — says B launched during A, A gets "ready", B executes — wrong, lower-priority B cannot preempt A
- (d) — says B launched during A, A gets "waiting", B executes — wrong for the same reason
Key rule: Preempted process → ready state. Waiting = blocked on resource/I/O, not preemption.
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