My annoying, non-google-able problem of the day: Say you want to build the source tree for a RHEL/CentOS 5.4 kernel (2.6.18-164.11.1.el5 in my case) and you are running a recent Debian or Fedora system. You might get patch failure errors that look like this:
Patch #212 (linux-2.6-x86-support-rdtscp-for-gtod.patch): + + /bin/cat /Users/david/rpmbuild/SOURCES/linux-2.6-x86-support-rdtscp-for-gtod.patch /usr/bin/patch -s -p1 --fuzz=0 1 out of 7 hunks FAILED -- saving rejects to file arch/x86_64/kernel/time.c.rej error: Bad exit status from /var/tmp/rpm-tmp.5n4IVi (%prep)
This is caused by newer versions of rpmbuild passing --fuzz=0 to patch. You can fix it by putting this line in the kernel-2.6.spec file:
%define _default_patch_fuzz 2
That’s it. I just saved you 8 hours of screwing around and looking for pre-patched kernels sources. 
I can’t possibly thank you enough for your work here in making the non-googl-able googl-able. Worked like a charm.