[New-bugs-announce] [issue6147] multithreading.Pool.map() crashes Windows computer

[Alex James]

New submission from Alex James <ac.james at shaw.ca>:

When calling multithreading.Pool().map() to distribute computational
load I've recently got system crashes.  

The attached minimalist script exhibits this issue.  
On a Windows Vista home premium sp1 running Python 2.6.2 on a dual-core
laptop, the script stops executing at
threading.Condition(threading.Lock()).wait() called from
multithreading.ApplyResult().wait() called from
multithreading.ApplyResult().get() called from
multithreading.Pool().map() and then compiles the original script as it
starts the script form the beggining twice simultaneously.  The printed
output gets mixed content and both new instances of the script hit the
same problem and spawn more instances.  All old processes are still
active in memory so this leads to system resources being fully consumed.  

This behavior started occurring recently, immediately after attempting
to install a Python .Egg package.  I have uninstalled python an all
extensions, restarted windows, deleted all orphan files and registry
keys I could find, restarted windows, and then re-installed a fresh
download of 2.6.2, but the problem remains.  

The error output retrievable from Keyboard Interrupt (which only works
when script was started on commandline) contains several copies of """
Traceback:
file "<string>", line 1, in <module>
'import site' failed: use -v for traceback
script opening print statement
script opening print statement
'import site' failed: use -v for traceback
File "C:\Python26\lib\multiprocessing\forking.py", line 341, in main
prepare(preparation_data)
File "C:\Python26\lib\multiprocessing\forking.py", line 456, in prepare
'__parents_main__', file, path_name, etc
File "H:\builder26\test_a6.py", line 1, in <module>
Traceback:
from custom_module import *
"""
amoung many pieces thereof stuffed bytewise into other pieces thereof.  

Identical code running in Unix operates just fine, and the identical
code worked on my machine last week.  Reproducability of this error is
thus doubtful.  Repeatability is perfect however.  

Any possible workarounds and/or understanding of root cause is
appreciated for this very rare extreme error.

----------
components: Windows
files: test_a10.py
messages: 88557
nosy: ac.james
severity: normal
status: open
title: multithreading.Pool.map() crashes Windows computer
type: crash
versions: Python 2.6
Added file: http://bugs.python.org/file14119/test_a10.py

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue6147>
_______________________________________