Concurrency: Atomic and volatile in C++11 memory model

Question

A global variable is shared across 2 concurrently running threads on 2 different cores. The threads writes to and read from the variables. For the atomic variable can one th

Answer 1

Volatile and Atomic serve different purposes.

Volatile : Informs the compiler to avoid optimization. This keyword is used for variables that shall change unexpectedly. So, it can be used to represent the Hardware status registers, variables of ISR, Variables shared in a multi-threaded application.

Atomic : It is also used in case of multi-threaded application. However, this ensures that there is no lock/stall while using in a multi-threaded application. Atomic operations are free of races and indivisble. Few of the key scenario of usage is to check whether a lock is free or used, atomically add to the value and return the added value etc. in multi-threaded application.