I've recently started seeing occasional regression test error messages 
on OS X from test_thread.  The test reports running OK but tracebacks 
are displayed.  It's not reproducible at will but has shown up on both 
10.5 Intel and 10.5 PPC machines with various recent top of py3k builds.  
Here are two examples:

nad@pbg4:/Library/Frameworks/Python.framework/Versions/3.1$ 
./bin/python3.1 -S ./lib/python3.1/test/regrtest.py -w test_thread
test_thread
Unhandled exception in thread started by <bound method 
ThreadRunningTests.task of <test.test_thread.ThreadRunningTests 
testMethod=test_stack_size>>
Traceback (most recent call last):
  File 
"/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/test/te
st_thread.py", line 49, in task
    self.done_mutex.release()
_thread.error: release unlocked lock
Unhandled exception in thread started by <bound method 
ThreadRunningTests.task of <test.test_thread.ThreadRunningTests 
testMethod=test_stack_size>>
Traceback (most recent call last):
  File 
"/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/test/te
st_thread.py", line 49, in task
    self.done_mutex.release()
_thread.error: release unlocked lock
Unhandled exception in thread started by <bound method 
ThreadRunningTests.task of <test.test_thread.ThreadRunningTests 
testMethod=test_stack_size>>
Traceback (most recent call last):
  File 
"/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/test/te
st_thread.py", line 49, in task
    self.done_mutex.release()
_thread.error: release unlocked lock
Unhandled exception in thread started by <bound method 
ThreadRunningTests.task of <test.test_thread.ThreadRunningTests 
testMethod=test_stack_size>>
Traceback (most recent call last):
  File 
"/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/test/te
st_thread.py", line 49, in task
    self.done_mutex.release()
_thread.error: release unlocked lock
Unhandled exception in thread started by <bound method 
ThreadRunningTests.task of <test.test_thread.ThreadRunningTests 
testMethod=test_starting_threads>>
Traceback (most recent call last):
  File 
"/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/test/te
st_thread.py", line 49, in task
    self.done_mutex.release()
_thread.error: release unlocked lock
1 test OK.

and

nad@fimt:/Library/Frameworks/Python.framework/Versions/3.1$ 
./bin/python3.1 -S ./lib/python3.1/test/regrtest.py -w test_thread
test_thread
Unhandled exception in thread started by <bound method 
ThreadRunningTests.task of <test.test_thread.ThreadRunningTests 
testMethod=test_stack_size>>
Traceback (most recent call last):
  File 
"/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/test/te
st_thread.py", line 49, in task
    self.done_mutex.release()
_thread.error: release unlocked lock
Unhandled exception in thread started by <bound method 
ThreadRunningTests.task of <test.test_thread.ThreadRunningTests 
testMethod=test_starting_threads>>
Traceback (most recent call last):
  File 
"/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/test/te
st_thread.py", line 49, in task
    self.done_mutex.release()
_thread.error: release unlocked lock
1 test OK.


Are the tracebacks from a harmless race condition and, if so, can the 
test be modified to eliminate them?  Or is there some new real problem?