In Linux, a mutual exclusion applies the one of following cases.

Question

BlackTom AI · Accepted Answer

Mutual exclusion requires that when one process is executing in its critical section, no other process may be executing in its critical section at the same time.

1. Relevant knowledge points and concepts
- Critical section: the portion of code where a process accesses shared resources and must not be concurrently accessed by others.
- Mutual exclusion: a property ensuring exclusive access to a shared resource or critical section.
- Additional requirements for correct concurrency: progress (system makes a decision if no one is in critical sections) and bounded waiting (no indefinite starvation).
- Linux implementations: mutexes, semaphores, spinlocks, and futexes enforce mutual exclusion at user and kernel levels.

2. Complete reasoning process step by step
- Identify the goal: prevent concurrent access to shared data that could cause inconsistency.
- Mutual exclusion definition: enforce that at most one process is in its critical section at any time.
- Therefore, if Process A is in its critical section, any other Process B must be prevented from entering until A leaves.
- Mechanisms (locks, semaphores) block or spin other processes until the section is free; they do not require blocking of all system resources nor mandate that others must also be executing.

3. Intermediate logical steps
- Step 1: Two or more processes may attempt to enter the same critical section.
- Step 2: Mutual exclusion enforces a protocol so only one proceeds.
- Step 3: Others are either blocked or wait (suspended or spinning) until the lock is released.
- Step 4: After release, one of the waiting processes may enter.

4. Why the correct answer is correct
The statement "if a process is executing in its critical section, then no other process must be executing in their critical sections" exactly matches the standard definition of mutual exclusion: exclusive access to the critical section.

5. Why other options are incorrect
- "None of the mentioned": incorrect because a precise definition exists.
- "If a process is executing..., then other processes must be executing...": opposite of mutual exclusion; would permit concurrent access and data races.
- "If a process is executing..., then all the resources of the system must be blocked...": too strong and incorrect; mutual exclusion only blocks access to the shared resource(s) or critical section, not all system resources.

6. Conclusion
The correct choice is: "if a process is executing in its critical section, then no other process must be executing in their critical sections," which matches the provided answer.

In Linux, a mutual exclusion applies the one of following cases.单项选择题

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