On two machines I have seen test_threading hang in ...
HPUX 11.22 ia64,
Solaris 5.8 sparc

The attached file contains the output of running

./apy/bin/python2.5 ./apy/lib/python2.5/test/regrtest.py -v test_threading

on the problematic machines.

It is necessary to kill one of the subprocesses to force forward
progress. A partial output of 'ps -ef' on the HPUX machine is

andreask 26601 26552  0 12:13:50 pts/1     0:00 ./apy/bin/python2.5
./apy/lib/python2.5/test/regrtest.py -v tes
andreask 26657 26601  0 12:14:26 pts/1     0:00
/home/andreask/tmp/autotest/apy/bin/python2.5 -c if 1:^J
andreask 26658 26657  0 12:14:26 pts/1     0:00
/home/andreask/tmp/autotest/apy/bin/python2.5 -c if 1:^J

And I usually kill the bottom most process.

I can confirm the same exact issue exists in python2.6 on:
Solaris 5.8 sparc

Killing the bottom process worked for me as well

Platform: Solaris 5.8 sparc
Compiler: gcc version 4.2.4

make test reported back the following on the initial test:
test test_threading failed -- Traceback (most recent call last):
  File
"/tools/webapps/local/src/Python-2.6.2/Lib/test/test_threading.py", line
419, in test_3_join_in_forked_from_thread
    self._run_and_join(script)
  File
"/tools/webapps/local/src/Python-2.6.2/Lib/test/test_threading.py", line
355, in _run_and_join
    self.assertEqual(data, "end of main\nend of thread\n")
AssertionError: '' != 'end of main\nend of thread\n'

**********

Same type of issue further on in the testing:

test_1_join_on_shutdown (test.test_threading.ThreadJoinOnShutdown) ... ok
test_2_join_in_forked_process (test.test_threading.ThreadJoinOnShutdown)
... ok
test_3_join_in_forked_from_thread
(test.test_threading.ThreadJoinOnShutdown) ... 
<hangs here>

$ ps -ef | grep -i 'python'
 xuserx 24669 17424  0 11:36:01 pts/18   5:44 ./python -E -tt
./Lib/test/regrtest.py -l
 xuserx 27539 27528  0 12:00:29 pts/18   0:00
/tools/webapps/local/src/Python-2.6.2/python -c if 1:            import
sys, o
 xuserx 27528 24669  0 12:00:28 pts/18   0:00
/tools/webapps/local/src/Python-2.6.2/python -c if 1:            import
sys, o
 xuserx 27660 29318  0 12:07:16 pts/18   0:00 grep -i python
$ kill 27539
<test continues then reports:>
test_3_join_in_forked_from_thread
(test.test_threading.ThreadJoinOnShutdown) ... FAIL

======================================================================
FAIL: test_3_join_in_forked_from_thread
(test.test_threading.ThreadJoinOnShutdown)
----------------------------------------------------------------------
Traceback (most recent call last):
  File
"/tools/webapps/local/src/Python-2.6.2/Lib/test/test_threading.py", line
419, in test_3_join_in_forked_from_thread
    self._run_and_join(script)
  File
"/tools/webapps/local/src/Python-2.6.2/Lib/test/test_threading.py", line
355, in _run_and_join
    self.assertEqual(data, "end of main\nend of thread\n")
AssertionError: '' != 'end of main\nend of thread\n'

I'll keep digging and see if I can find a solution, but know that while
I have extensive programming experience in other languages, I have none
in python (yet).

FWIW it hangs on Solaris 9 also (sparc + x86)

Still an issue in 2.7 or 3.1/2?

Yes, this problem persists on Solaris 9 (SPARC) even with Python 2.7.1.
The problematic processes are:

ssahmed@blade:[~]$ ps -ef|grep -i python
 ssahmed   480   418  0 15:30:25 pts/1    9:14 ./python -Wd -3 -E -tt ./Lib/test/regrtest.py -l
 ssahmed  3062   480  0 15:43:22 pts/1    0:00 /space/home/ssahmed/Python-2.7.1/python -c if 1:            import sys, os, ti
 ssahmed  3063  3062  0 15:43:22 pts/1    0:00 /space/home/ssahmed/Python-2.7.1/python -c if 1:            import sys, os, ti

I was able to workaround the problem by killing the bottom-most process in the list.

Hmm.
I think this was probably fixed by Gregory in issue #6643 (it's not in Python 2.7.1).
Could you try with Python 3.2, or a current snapshot?

I'm closing.
Feel free to re-open if this fails with 2.7 or 3.2.