In a system where threads must both mutually exclude access to a critical section and also wait for specific events, which synchronization design best avoids deadlocks and ensures correctness?

hard🎤 Interviewer Follow-up Q10 of Q15

Operating Systems - Semaphore vs Mutex - When to Use Which

AUse mutexes combined with condition variables to wait and signal events safely

BUse binary semaphores for both mutual exclusion and event signaling

CUse only mutexes for mutual exclusion and busy-wait for events

DUse counting semaphores for mutual exclusion and event notification

Step-by-Step Solution

Solution:

Step 1: Identify synchronization needs
Mutual exclusion plus waiting for events requires both locking and waiting mechanisms.
Step 2: Analyze options
Mutex alone with busy-wait (A) wastes CPU and risks deadlock. Binary semaphores (B) do not enforce ownership and can cause race conditions. Counting semaphores (D) do not provide atomic release-and-wait semantics.
Step 3: Correct design
Mutex combined with condition variables (C) allows atomic release of mutex while waiting and safe event signaling, avoiding deadlocks.
Final Answer:
Option A -> Option A
Quick Check:
Mutex + condition variables enable safe wait/signal [OK]

Quick Trick: Mutex + condition variables avoid deadlock and enable event waits [OK]

Common Mistakes:

MISTAKES

Using busy-wait loops with mutexes
Confusing semaphores with condition variables for event waits
Assuming counting semaphores handle mutual exclusion and events atomically

Trap Explanation:

PITFALL

Candidates often misuse semaphores for event waiting, missing condition variable semantics.

Interviewer Note:

CONTEXT

Tests deep understanding of synchronization primitives and deadlock avoidance in complex scenarios.

Master "Semaphore vs Mutex - When to Use Which" in Operating Systems

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More Operating Systems Quizzes

In a system where threads must both mutually exclude access to a critical section and also wait for specific events, which synchronization design best avoids deadlocks and ensures correctness?

Step 1: Identify synchronization needs

Step 2: Analyze options

Step 3: Correct design

Final Answer:

Quick Check:

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