I'm seeing:
 `acpiphp_glue_exit' referenced in section `.init.text' of
drivers/built-in.o: defined in discarded section `.exit.text' of
drivers/built-in.o
when trying to compile an IA64 kernel with PCI hotplug enabled.
I suggest this patch:
Signed-off-by: Peter Chubb <peterc@gelato.unsw.edu.au>
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  *
  * This function frees all data allocated in acpiphp_glue_init()
  */
-void __exit acpiphp_glue_exit(void)
+void  acpiphp_glue_exit(void)
 {
        acpi_pci_unregister_driver(&acpi_pci_hp_driver);
 }