26. Concurrency. An introduction

Question 1

What does thread have its own and what does it share?

Answer 1

Thread has own program counter, stack and private set of registers, but they share a single address space.

Question 2

Does context switch occur for threads?

Answer 2

Yes, but there is no need in switching page table with threads. The state is also saved to TCB instead of PCB.

Question 3

How is stack for thread sometimes called?

Answer 3

Thread-local storage.

Question 4

What is race condition?

Answer 4

It’s when multiple threads are updating the same shared data, but in a way that is not atomic and indeterministic

Question 5

What is critical section?

Answer 5

Piece of code that accesses a shared variable and can be run only by 1 thread at a time

Question 6

How to avoid race condition?

Answer 6

With atomic operations which can be atomic either by design (pre-made hardware instruction) or that can be atomic with help of some synchronization primitives