I'm on os x 10.6 where threadboom.py doesn't segfault anymore at least
on the system provided python. The problem that I see is that it
shouldn't be segfaulting on mac os x 10.5 with the default recursion
limit (I think it is 1000) with 2 threads. IIRC in a simple recursive
function (not on object __init__ like you did) I could put 10000 or more
as a recursion limit and still get a traceback, so I thought that 2
threads each with 1000 recursion limit should not be using the whole
stack. Also I think I did try to raise the stack limit with ulimit, but
I could be wrong.

Nick Coghlan, did you do your experments on os x 10.5? Can you try
threadboom.py on a python before the corrected mimetype lib landed
(somewhere between 2.6.2 and 2.6.3) or with an old version of the
mimetype lib?

I got the same errors both on my old white macbook core duo machine and
with a macbook pro core 2 duo and with both python 2.6.2 or 2.6.3 with
the old mimetypes lib.

I was worried with this bug because I guessed that maybe there is a race
condition of some sort on object creation on python 2.6. If someone can
reproduce the bug and understand the bug tell me it is a problem of
stack size I would rest my case and be happy with the segfault :).

ps: I will try to compile python2.6.2 here and reproduce the errors, if
I can I will reply with more info.