DEFINE_IDR() and the layer cache

Hi all,

while the idr discussion is still hot, there's another thing that caught my
eye recently:

As to my reading of idr.h, I have two choices of initializing a global idr:
 a) static struct idr foo; /* ... */ idr_init(&foo);
 b) static DEFINE_IDR(foo);

idr_init(), when called for the first time, sets up the layer
cache. idr_get_new() and friends expect the cache to exist. Now, what happens
if the first call to idr_get_new() targets an idr initialized using
DEFINE_IDR() before idr_init() has been called at least once? Could this
happen?

My $0.02,
  Joachim