Concurrency_Quiz1

What is a thread?

• A set of instructions loaded into memory.

• A security mechanism used to control access to shared resources.

• A unit of execution within a process.

• A running program.

Match the following

• Processor

• Instance of a running program.

• Amit Chopra

• 
• Thread

• A set of instructions to be executed.

• Program

• Hardware component that executes instructions.

• Process

• The smallest unit of execution within a process.

What are the methods a lock should have?

• wait(), signal()

• acquire(), release()

• start(), exit()

• lock(), unlock()

What does the Semaphore's count represent?

• Total number of threads that can be created.

• Number of locks a thread can have.

• Number of permits to enter a critical section available.

• Number of total critical section accesses allowed.

Which are TRUE about Spinlocks?

• Resource intensive.

• Effective for small critical sections.

• Allow multiple threads to access a critical section.

• Do not require a context switch as the thread never sleeps (just like us).

What causes a Race Condition?

• Two or more threads accessing a shared resource at the same time.

• Mismatched data types in a program.

• Creating multiple threads at the same time within a process.

• Operating System scheduler.

Consider the following psuedocode:

lock.acquire()

Critical section (some piece of code)

lock.release()

Which of the following statements are true?

• The critical section cannot be executed by any thread.

• Whenever a thread acquires the lock, the number of permits available is decremented.

• The critical section is atomic.

• Mutual exclusion of threads is guaranteed in the critical section.

Which of the following statements are true about semaphores?

• Locks are called semaphores in Java.

• Semaphores were first introduced in ancient Greek temples for queue management.

• Semaphores can be used to guarantee mutual exclusion.

• Semaphores cannot be initialised with a value of 0 or less.

• At any point, a semaphore's value (the value of its counter) represents the number of permits that are available to threads.

A thread cannot enter a synchronized block without acquiring a lock in Java.

• True

• False

What is wrong with this code in a multithreaded environment?