kernel patch question

[Richard Kimber <rkimber@ntlworld.com>]

I have been experimenting with the low latency and preempt patches.

http://newbiedoc.sourceforge.net/system/kernel-pkg.html
says that after the kernel is built, make-kpkg reverses the patches you
applied, so that each new build starts with an unpatched source tree.

However, whenever I try to re-build a kernel, the patch application always
fails the second time round (i.e. it works from a newly installed
tree but not if make-kpkg has been run already) with the message
" ... patch for 2.4.22 does not apply cleanly"

Is the above document correct? How can I tell whether the patches have in
fact been removed properly? And how should I proceed?  Do I really have to
delete the tree and start over again?

- Richard.
-- 
Richard Kimber