Python 2.4 changed ntpath.abspath to do an import
inside the function. As a result, due to Python's
import lock, anything calling abspath on Windows
(directly, or indirectly like tempfile.TemporaryFile)
hung when it was called from a thread spawned as a
side effect of importing a module.
This is a depressingly frequent problem, and
deserves a more general fix. I'm settling for
a micro-fix here because this specific one accounts
for a report of Zope Corp's ZEO hanging on Windows,
and it was an odd way to change abspath to begin
with (ntpath needs a different implementation
depending on whether we're actually running on
Windows, and the _obvious_ way to arrange for that
is not to bury a possibly-failing import _inside_
the function).
Note that if/when other micro-fixes of this kind
get made, the new Lib/test/threaded_import_hangers.py
is a convenient place to add tests for them.
imports e.g. test_support must do so using an absolute package name
such as "import test.test_support" or "from test import test_support".
This also updates the README in Lib/test, and gets rid of the
duplicate data dirctory in Lib/test/data (replaced by
Lib/email/test/data).
Now Tim and Jack can have at it. :)
Fix exit races in test_thread.py and test_threaded_import.py.
I suspect the bug is provokable only under Linux (where child threads
seem to get lots of cycles before they get killed after the main thread
exits), or on multi-processor machines running other OSes.
Bugfix candidate.
When regrtest.py finds an attribute "test_main" in a test it imports,
regrtest runs the test's test_main after the import. test_threaded_import
needs this else the cross-thread import lock prevents it from making
progress. Other tests can use this hack too, but I doubt it will ever be
popular.
ICK ALERT: read the long comment block before run_the_test(). It was
almost impossible to get this to run without instant deadlock, and the
solution here sucks on several counts. If you can dream up a better way,
let me know!
Georg Brandl
Benjamin Peterson
Tim Peters
Michael W. Hudson
Barry Warsaw
Jack Jansen