Why is volatile keyword not needed for thread synchronisation?

Question

I am reading that the volatile keyword is not suitable for thread synchronisation and in fact it is not needed for these purposes at all.

While I unders

Answer 1

Shortening the answer already given, you do not need to use volatile with mutexes for a simple reason:

• If compiler knows what mutex operations are (by recognizing pthread_* functions or because you used std::mutex), it well knows how to handle access in regards to optimization (which is even required for std::mutex)
• If compiler does not recognize them, pthread_* functions are completely opaque to it, and no optimizations involving any sort of non-local duration objects can go across opaque functions