When I switched my installation from kernel 2.4 to 2.6 I recognized that
the ISDN module dss1_divert was marked incompilable (config option
CONFIG_CLEAN_COMPILE must be turned off). 

The compile problem was the obsolete using of kernel 2.4 critical
sections.  I replaced the cli() stuff with spinlocks as explained in the
Documentation/spinlocks.txt file.  After that the module compiles and
runs as expected. 
Signed-off-by: Steffen A. Mork <linux-dev@morknet.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>