A critical section can be as small as a single line of code.

Question

BlackTom AI · Accepted Answer

A critical section is the region of code that accesses a shared resource and must not be executed concurrently by more than one thread or process. It can indeed be as small as a single line of code.

1) Relevant knowledge points and concepts
- Critical section: any contiguous code that requires mutual exclusion to prevent race conditions.
- Mutual exclusion primitives: mutexes, spinlocks, semaphores, atomic instructions.
- Granularity: the size of the critical section affects contention and concurrency (smaller = less blocking).
- Atomic operations: some single instructions (e.g., atomic increment) inherently provide exclusion at hardware level.

2) Step-by-step reasoning
- Definition: Identify the minimal unit that accesses shared state. If a single statement reads/modifies shared memory, that statement is a critical section.
- Example: counter = counter + 1. In many languages this compiles to multiple machine instructions (load, add, store). Without protection, two threads can interleave and corrupt the result, so that single line must be protected — making the critical section one line long.
- Alternatively, if the architecture/language provides an atomic increment instruction (e.g., atomic_fetch_add), that single instruction is itself an atomic critical region implemented by hardware; still, the protected region is one operation/line.

3) Intermediate demonstration
- Thread A executes: load counter (value 5)
- Thread B executes: load counter (value 5)
- A does add→6 and stores 6
- B does add→6 and stores 6 → lost update
This shows the one-line statement requires exclusion.

4) Why the correct answer is correct
Because a critical section is defined by what must be protected, not by code length. A single statement that accesses shared mutable state can constitute the entire critical section. Using locks or atomic primitives around that line enforces mutual exclusion.

5) Why the other option (False) is incorrect
Saying it cannot be a single line ignores common scenarios and hardware-supported atomic operations. Critical sections can be any size—from a single instruction/line up to large code blocks.

Conclusion: The statement is True, which matches the provided answer.

A critical section can be as small as a single line of code.True/False

Similar Questions

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