2.5.68: SMP for arch/sparc broken?

Hi,
I'm currently trying to get linux running on my old (but it's my own :-) Tatung SparcStation 20 clone, mainly for acting as a dsl-router / firewall. Kind of exotic I guess, but funny. I must confess that I'm pretty new to linux on sparc while running linux on i386 for nearly 8 years.

The device has two processors (high speed 85MHz). I installed a debian distro and now trying to bring it on actual (or rather bleeding edge) software revisions.

While trying to compile a 2.5.68 kernel I stumbled into a problem: the function "cpu_possible":
while being defined for other architectures in include/asm-i386/smp.h or similar it is missing in include/asm-sparc/smp.h.
Unfortunately it seems to be needed to successfully compile a kernel because several other things depend on it. Also unfortunately I don't have the slightest idea on how to fix it because I'm not that deep in the sparc system architecture (or the linux kernel architecture).

Any suggestions (besides to stay with a (successfully for SMP compiled) 2.4.20 kernel)?

Regards
Schwarzseher

P.S.: When already at the topic, now offtopic for this list: any ideas on why swapon /dev/sdc2 throws a core since I updated the kernel to 2.4.20? The swapon systemcall is called and the swapspace is added but afterwards the swapon utility makes a segfault.