The data array / buffer doesn't need to be atomic. Once the atomic load/store on indices has justified access to the data you're good. C puts atomic on the typ

The data array / buffer doesn't need to be atomic. Once the atomic load/store on indices has justified access to the data you're good. C puts atomic on the type, not the operation. That's conservative and occasionally very annoying (can't use normal stores in some parts of the program and atomic in others, thanks to aliasing rules) but doesn't hurt this particular application.