On Thu, 16 Aug 2007, Paul Mackerras wrote:

It seems that there could be a lot of places where atomic_t is used in
a non-atomic fashion, and that those uses are either buggy, or there
is some lock held at the time which guarantees that other CPUs aren't
changing the value.  In both cases there is no point in using
atomic_t; we might as well just use an ordinary int.

The point of atomic_t is to do atomic *changes* to the variable.