cmpxchg / atomic_cmpset_int emulation for userland (i386) ?

Hi,
I have some list manipulation algorithm that I would like to use
that relies rather centrally on atomic_cmpset_int().

This is an atomic instruction on 486+, but not available on 386
and maybe other platforms. i386/atomic.h has a replacement
but it uses "pushfl; cli; ... popfl;" so it cannot run in userland.

I was wondering if there is a good emulation for that instruction
on the i386 that is suitable for userland (other architectures
we support have a CPU instruction that does it, or in the case of ARM,
a usable emulation for userland).

	cheers
	luigi