How to execute atomic 64b read on x86 (Pentium and above)?

Question

I would like to perform atomic reading of 64-bit 64b data on the x86 platform (guaranteed by Pentium or higher).

Is there any way to do this? (And no, I don’t want to use a critical section or a mutex for this, I want it to be locked).

Answer 1

Use lock operations, here is a sample code:

LONGLONG AtomicRead(LONGLONG* p)
{
    return InterlockedCompareExchange64(p, 0, 0);
}

This compares the exchange with zero and sets p to zero if it is already zero - this is noop. InterlockedCompareExchange returns the original 64-bit value pointed to by p.

Answer 2

, . lock cmpxchg8b.

Answer 3

Use the lock functions * ().

There is no reading per se, but you can create Add () where you add 0.