Add NPTL support to uClibc for some architecture: where to start?

Question

linux

Hello. Got a task: to add nptl support to uClibc for some architecture.
I see that now the following architectures definitely do not have it: arc, avr32, bfin, c6x, cris, e1, frv, h8300, hppa, i960, ia64, m68k, microblaze, nios, v850, vax, xtensa. The most recent ones are arc, avr32, c6x and frv. There is support in qemu for cris, m68k, microblaze and xtensa, I think this is more important.
My rough plan is:
1. understand how the selected architectures deal with NPTL support in Linux (I suspect that everyone is equally good, but can anyone know for sure?);
2. understand whether something needs to be done in the toolchain to support NPTL;
3. look at the code (libpthread/nptl/sysdeps) of some architecture in which support is implemented;
...
4. get the tests to pass (test/nptl);
5. PROFIT?
For which of these architectures do you think it would be easier to do this? And what is the best place to start?