mirror of https://github.com/python/cpython
SF bug #1473760 TempFile can hang on Windows.
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.
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@ -481,27 +481,28 @@ def normpath(path):
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# Return an absolute path.
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def abspath(path):
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"""Return the absolute version of a path"""
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try:
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from nt import _getfullpathname
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except ImportError: # Not running on Windows - mock up something sensible.
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global abspath
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def _abspath(path):
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if not isabs(path):
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path = join(os.getcwd(), path)
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return normpath(path)
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abspath = _abspath
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return _abspath(path)
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try:
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from nt import _getfullpathname
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if path: # Empty path must return current working directory.
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try:
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path = _getfullpathname(path)
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except WindowsError:
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pass # Bad path - return unchanged.
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else:
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path = os.getcwd()
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return normpath(path)
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except ImportError: # not running on Windows - mock up something sensible
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def abspath(path):
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"""Return the absolute version of a path."""
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if not isabs(path):
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path = join(os.getcwd(), path)
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return normpath(path)
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else: # use native Windows method on Windows
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def abspath(path):
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"""Return the absolute version of a path."""
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if path: # Empty path must return current working directory.
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try:
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path = _getfullpathname(path)
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except WindowsError:
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pass # Bad path - return unchanged.
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else:
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path = os.getcwd()
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return normpath(path)
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# realpath is a no-op on systems without islink support
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realpath = abspath
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@ -6,7 +6,7 @@
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# randrange, and then Python hangs.
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import thread
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from test.test_support import verbose, TestSkipped
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from test.test_support import verbose, TestSkipped, TestFailed
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critical_section = thread.allocate_lock()
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done = thread.allocate_lock()
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@ -25,6 +25,23 @@ def task():
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if finished:
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done.release()
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def test_import_hangers():
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import sys
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if verbose:
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print "testing import hangers ...",
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from test import threaded_import_hangers
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try:
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if threaded_import_hangers.errors:
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raise TestFailed(threaded_import_hangers.errors)
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elif verbose:
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print "OK."
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finally:
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# In case this test is run again, make sure the helper module
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# gets loaded from scratch again.
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del sys.modules['test.threaded_import_hangers']
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# Tricky: When regrtest imports this module, the thread running regrtest
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# grabs the import lock and won't let go of it until this module returns.
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# All other threads attempting an import hang for the duration. Since
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@ -53,5 +70,7 @@ def test_main(): # magic name! see above
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print "OK."
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done.release()
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test_import_hangers()
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if __name__ == "__main__":
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test_main()
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@ -0,0 +1,42 @@
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# This is a helper module for test_threaded_import. The test imports this
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# module, and this module tries to run various Python library functions in
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# their own thread, as a side effect of being imported. If the spawned
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# thread doesn't complete in TIMEOUT seconds, an "appeared to hang" message
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# is appended to the module-global `errors` list. That list remains empty
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# if (and only if) all functions tested complete.
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TIMEOUT = 10
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import threading
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import tempfile
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import os.path
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errors = []
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# This class merely runs a function in its own thread T. The thread importing
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# this module holds the import lock, so if the function called by T tries
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# to do its own imports it will block waiting for this module's import
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# to complete.
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class Worker(threading.Thread):
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def __init__(self, function, args):
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threading.Thread.__init__(self)
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self.function = function
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self.args = args
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def run(self):
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self.function(*self.args)
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for name, func, args in [
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# Bug 147376: TemporaryFile hung on Windows, starting in Python 2.4.
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("tempfile.TemporaryFile", tempfile.TemporaryFile, ()),
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# The real cause for bug 147376: ntpath.abspath() caused the hang.
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("os.path.abspath", os.path.abspath, ('.',)),
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]:
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t = Worker(func, args)
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t.start()
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t.join(TIMEOUT)
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if t.isAlive():
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errors.append("%s appeared to hang" % name)
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@ -86,6 +86,9 @@ Extension Modules
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Library
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-------
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- Bug #1473760: ``tempfile.TemporaryFile()`` could hang on Windows, when
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called from a thread spawned as a side effect of importing a module.
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- New modules: setuptools, easy_install, and pkg_resources, to support
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building, installing, and using Python eggs, respectively.
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