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Fixed critical shutdown race in _Database._commit.

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Related to SF patch 723231 (which pointed out the problem, but didn't
fix it, just shut up the warning msg -- which was pointing out a dead-
serious bug!).

Bugfix candidate.
This commit is contained in:
Tim Peters 2003-07-13 02:22:03 +00:00
parent 5c5fca9844
commit d7472ec13a
2 changed files with 27 additions and 5 deletions
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24
Lib/dumbdbm.py
View file

@ -33,6 +33,17 @@ error = IOError # For anydbm
class _Database(UserDict.DictMixin):
# The on-disk directory and data files can remain in mutually
# inconsistent states for an arbitrarily long time (see comments
# at the end of __setitem__). This is only repaired when _commit()
# gets called. One place _commit() gets called is from __del__(),
# and if that occurs at program shutdown time, module globals may
# already have gotten rebound to None. Since it's crucial that
# _commit() finish sucessfully, we can't ignore shutdown races
# here, and _commit() must not reference any globals.
_os = _os # for _commit()
_open = _open # for _commit()
def __init__(self, filebasename, mode):
self._mode = mode
@ -78,17 +89,20 @@ class _Database(UserDict.DictMixin):
# file (if any) is renamed with a .bak extension first. If a .bak
# file currently exists, it's deleted.
def _commit(self):
# CAUTION: It's vital that _commit() succeed, and _commit() can
# be called from __del__(). Therefore we must never reference a
# global in this routine.
try:
_os.unlink(self._bakfile)
except _os.error:
self._os.unlink(self._bakfile)
except self._os.error:
pass
try:
_os.rename(self._dirfile, self._bakfile)
except _os.error:
self._os.rename(self._dirfile, self._bakfile)
except self._os.error:
pass
f = _open(self._dirfile, 'w', self._mode)
f = self._open(self._dirfile, 'w', self._mode)
for key, pos_and_siz_pair in self._index.iteritems():
f.write("%r, %r\n" % (key, pos_and_siz_pair))
f.close()