Hello,
  The following error occurred while compiling 2.4.0-ac6..The strange
thing is that I checked mm/vmalloc.c (line 188, and the entire file) and
didn't see PKMAP_BASE mentioned. My guess is that there is a problem with
one of the header files.

Regards,
Frank
 
vmalloc.c: In function `get_vm_area':
vmalloc.c:188: `PKMAP_BASE' undeclared (first use in this function)
vmalloc.c:188: (Each undeclared identifier is reported only once
vmalloc.c:188: for each function it appears in.)
make[2]: *** [vmalloc.o] Error 1
make[2]: Leaving directory `/usr/src/linux/mm'
make[1]: *** [first_rule] Error 2
make[1]: Leaving directory `/usr/src/linux/mm'
make: *** [_dir_mm] Error 2