Most recent kernel where this bug did not occur: 2.6.14-rc5
Distribution: Debian testing/unstable (with a kernel.org kernel)
Hardware Environment: Alphaserver 4100 5/466, 3 CPUs, 4GB
Software Environment: gcc "4.0.2 (Debian 4.0.2-2", binutils from unstable
Problem Description: kernel build fails with:
[...]
  LD      init/built-in.o
  LD      .tmp_vmlinux1
drivers/built-in.o: In function `kcopyd_exit':
: undefined reference to `barrier'
drivers/built-in.o: In function `kcopyd_exit':
: undefined reference to `barrier'
drivers/built-in.o: In function `kcopyd_exit':
: undefined reference to `barrier'
drivers/built-in.o: In function `kcopyd_exit':
: undefined reference to `barrier'
drivers/built-in.o: In function `kcopyd_exit':
: undefined reference to `barrier'
drivers/built-in.o:: more undefined references to `barrier' follow
make[2]: *** [.tmp_vmlinux1] Error 1
make[1]: *** [deb-pkg] Error 2
make: *** [deb-pkg] Error 2

Steps to reproduce:
tar xjf linux-2.6.14.tar.bz2
cd linux-2.6.14
zcat /proc/config.gz > .config # This is my 2.6.14-rc5 configuration
make oldconfig
fakeroot make deb-pkg