Question

Given below are two statements :
one is labelled as
Assertion (A) and the other is labelled as
Reason (R).
Assertion (A) :
Preemptive scheduling can lead to race conditions in critical section.
Reason (R) :
Preemption allows multiple processes to access shared data simultaneously.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

In a non-preemptive environment, a process stays in its critical section until it finishes. In a preemptive environment, the OS can "kick" it out mid-calculation, which is why we need Mutexes!

Answer 1

The Correct Option is C

Concept:
• A race condition occurs when multiple processes access and manipulate the same data concurrently.
• The outcome of the execution depends on the particular order in which the access takes place.
• Preemptive scheduling allows the operating system to interrupt a process at any time to assign the CPU to another process.

Step 1: Evaluate the Assertion (A)
Preemptive scheduling can interrupt a process while it is in its critical section.
If a process is modifying shared data and is preempted, the data may be in an inconsistent state.
The next process scheduled might then access this inconsistent data, causing a race condition.
Thus, Assertion (A) is correct.

Step 2: Evaluate the Reason (R)
Preemption facilitates "concurrency" by allowing multiple processes to be in a state of execution at the same time.
In a broad sense, this allows processes to access shared data "simultaneously" (overlapping in time).
Without preemption, a process would finish its critical section before another could start.
Thus, Reason (R) is correct in the context of concurrent system theory.

Step 3: Determine the relationship
The reason why race conditions happen under preemption is exactly because processes can be interleaved.
This interleaving creates the situation where multiple processes attempt to access the same resource at once.
Therefore, (R) explains (A).