Task Communication – Real-time Systems MCQs

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1. What is the main purpose of task communication in real-time systems?
(A) To share information between tasks safely and efficiently
(B) To increase CPU idle time
(C) To extend task periods
(D) To reduce execution time automatically

2. Which of the following is a common mechanism for task communication?
(A) Deadlines only
(B) CPU scheduling only
(C) WCET calculation
(D) Message passing and shared memory

3. In shared memory communication, tasks communicate by:
(A) Executing sequentially without interaction
(B) Sending emails
(C) Using separate CPUs only
(D) Reading and writing common variables or memory regions

4. A major challenge of shared memory communication is:
(A) Reduced WCET
(B) Increased task periods
(C) Race conditions and data inconsistency
(D) Random task selection

5. Message passing communication involves:
(A) Writing to shared memory directly
(B) Ignoring deadlines
(C) Sending data from one task to another via messages or buffers
(D) Executing tasks non-preemptively

6. Which synchronization mechanism is often needed for shared memory communication?
(A) Task period adjustments
(B) CPU idle cycles
(C) Aperiodic servers only
(D) Mutexes or semaphores

7. What is a mailbox in task communication?
(A) A scheduling algorithm
(B) A type of periodic task
(C) A buffer used to hold messages between tasks
(D) A type of semaphore

8. Task communication must ensure:
(A) Extended WCET
(B) Random execution
(C) CPU idle time
(D) Data consistency and timely delivery

9. What is the difference between direct and indirect communication?
(A) Direct: non-preemptive; Indirect: preemptive
(B) Direct: sender writes to receiver; Indirect: via buffer or mailbox
(C) Direct: periodic tasks; Indirect: aperiodic tasks
(D) No difference

10. Which type of task communication is easier to implement but harder to synchronize?
(A) EDF scheduling
(B) Message passing
(C) Sporadic server
(D) Shared memory

11. Which type of task communication naturally enforces mutual exclusion?
(A) WCET analysis
(B) Shared memory
(C) Background tasks only
(D) Message passing

12. A common problem in task communication is:
(A) WCET reduction
(B) Periodic task deadline extension
(C) Race condition when multiple tasks access shared data concurrently
(D) CPU idle time increase

13. Which task communication mechanism is suitable for distributed real-time systems?
(A) Message passing
(B) Mutex only
(C) Shared memory only
(D) Cyclic executive

14. In real-time systems, communication latency should be:
(A) Minimized to ensure timely response
(B) Ignored
(C) Maximized
(D) Equal to WCET

15. Task communication can be blocking or non-blocking. Blocking means:
(A) Deadlines are ignored
(B) Task executes without preemption
(C) CPU remains idle always
(D) Sender or receiver waits until message is delivered or received

16. Which of the following ensures safe communication in shared memory?
(A) Increased WCET
(B) Random task execution
(C) Critical sections protected by mutexes or semaphores
(D) Ignoring deadlines

17. Which statement about message queues is TRUE?
(A) They increase race conditions
(B) They buffer messages between tasks to decouple sender and receiver
(C) They reduce task periods
(D) They are used for WCET only

18. Priority inversion may occur during task communication when:
(A) All tasks are periodic
(B) A high-priority task waits for a resource held by a low-priority task
(C) Tasks communicate via messages only
(D) CPU is idle

19. Which protocol can help avoid priority inversion during communication?
(A) Round-robin only
(B) RMS only
(C) Priority Inheritance Protocol (PIP)
(D) LLF only

20. Task communication is essential in real-time systems to:
(A) Increase CPU idle time
(B) Ensure correct and timely exchange of data between tasks
(C) Ignore shared resources
(D) Reduce deadlines