Kernel version 3.6.0-rc2, and probably -rc1 as well.  I get the
following compile-time error on alpha architecture:

(...)
  CC      net/core/sock.o
net/core/sock.c:274:36: error: initializer element is not constant
net/core/sock.c:274:36: error: (near initialization for "memalloc_socks")
net/core/sock.c:274:36: error: initializer element is not constant
make[2]: *** [net/core/sock.o] Error 1
make[1]: *** [net/core] Error 2
make: *** [net] Error 2

Compiler is gcc-4.6.3.

Line 274 of net/core/sock.c is

struct static_key memalloc_socks = STATIC_KEY_INIT_FALSE;

which made its first appearance in 3.6.0-rc1.

--Bob