Process Synchronization (Race Condition, Mutex, Semaphores) : MCQs & PYQs with Explanation

Option B

In Linux, a critical section is a part of the code that accesses shared resources, such as variables, files, or hardware, that must not be used by more than one process or thread at a time. To prevent data corruption or race conditions, Linux uses synchronization mechanisms to protect these critical sections. The most common technique used in the Linux kernel for this purpose is the spinlock.

A spinlock is a lightweight lock used in Linux to protect a critical section. It makes a process “spin” in a loop until it can enter the section, ensuring that only one process accesses the shared resource at a time without using heavy context switching.

Option C

A Semaphore is a synchronization tool used in operating systems to control access to shared resources in a multiprogramming or multitasking environment. It helps prevent problems such as race conditions, where multiple processes try to access the same resource simultaneously.
A semaphore works like a signaling mechanism between processes or threads. It maintains an integer value that is modified using two special operations:

• Wait (P operation): Decreases the semaphore value. If the resource is unavailable, the process waits.
• Signal (V operation): Increases the semaphore value and allows waiting processes to continue execution.

Semaphores are mainly used for:

• Process synchronization.
• Resource sharing.
• Avoiding critical section problems.

There are two main types of semaphores:

A Semaphore can be implemented using both software and hardware methods. Software Implementation uses operating system algorithms, while Hardware Implementation uses special atomic instructions such as Test-and-Set or Compare-and-Swap.
For example, if only one printer is available in a system, a semaphore ensures that only one process uses the printer at a time while other processes wait for their turn.

Option C

A Race Condition occurs when multiple processes or threads access and modify shared data concurrently, and the final outcome depends on the order in which the operations are executed. Since the execution order may vary, it can lead to inconsistent or unexpected results.

Option B

Semaphore is a synchronization tool used to control access to shared resources in concurrent systems. There are two types of semaphores:

1. Counting Semaphore: Can take any non-negative integer value; used for controlling access to multiple instances of a resource.
2. Binary Semaphore: Can take only 0 or 1; used to provide mutual exclusion (like a lock) when only one process can access a resource at a time.

Mutex locks are specialized locks for mutual exclusion, but if they are not available, a binary semaphore can perform the same function.

Option B

A binary semaphore is a synchronization mechanism that can take only two values, 0 or 1. It is used to control access to a critical section so that only one process can enter at a time.
When the semaphore is initialized to 1:

• Value 1 : Resource is free, one process can enter.
• When a process enters, value becomes 0 : Other processes are blocked.
• When the process exits, it again becomes 1.

This ensures Mutual Exclusion, meaning only one process is in the critical section at any time. So, Binary semaphore acts like a lock (mutex (Mutual Exclusion)).

Option C