Which scheduling policy is typical for a mission computer's real-time operating system, and what does priority inheritance accomplish?

Which scheduling policy is typical for a mission computer's real-time operating system, and what does priority inheritance accomplish?

• A. Dynamic priority with earliest deadline first; priority inheritance deprioritizes blocked tasks.
• B. Round-robin; priority inheritance cancels priorities when a resource is contended.
• C. Fixed-priority or rate-monotonic scheduling; priority inheritance temporarily raises a lower-priority task holding a resource to the higher priority to avoid blocking.
• D. First-come first-served; priority inheritance is not used in mission computers.

Answer: (C)

In mission computers, timing predictability is essential, so real-time operating systems typically use fixed-priority scheduling (often rate-monotonic, where shorter-period tasks get higher priority). This approach makes worst-case timing easier to analyze and guarantees timing isolation between tasks. Priority inheritance is used to prevent priority inversion: when a high-priority task needs a resource held by a lower-priority task, the lower-priority task temporarily takes on the higher priority. This lets the resource be released sooner, so the high-priority task can continue, and once the resource is released, the lower-priority task goes back to its original priority.

In mission computers, timing predictability is essential, so real-time operating systems typically use fixed-priority scheduling (often rate-monotonic, where shorter-period tasks get higher priority). This approach makes worst-case timing easier to analyze and guarantees timing isolation between tasks. Priority inheritance is used to prevent priority inversion: when a high-priority task needs a resource held by a lower-priority task, the lower-priority task temporarily takes on the higher priority. This lets the resource be released sooner, so the high-priority task can continue, and once the resource is released, the lower-priority task goes back to its original priority.