[Python-bugs-list] [ python-Bugs-834461 ] simple bsddb interface potential for deadlock with threads

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Bugs item #834461, was opened at 2003-11-02 01:30
Message generated for change (Comment added) made by greg
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Category: Extension Modules
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Gregory P. Smith (greg)
Assigned to: Gregory P. Smith (greg)
Summary: simple bsddb interface potential for deadlock with threads

Initial Comment:
>From Lib/bsddb/__init__.py

        # FIXME-20031101-greg: I believe there is still the potential
        # for deadlocks in a multithreaded environment if someone
        # attempts to use the any of the cursor interfaces in one
        # thread while doing a put or delete in another thread.  The
        # reason is that _checkCursor and _closeCursors are not atomic
        # operations.  Doing our own locking around self.dbc,
        # self.saved_dbc_key and self._iter_cursors could prevent this.
        # TODO: A test case demonstrating the problem needs to be written.


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>Comment By: Gregory P. Smith (greg)
Date: 2003-11-02 01:47

Message:
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While I'm at it, I think there might be a memory leak in my
__iter__ and iteritems() implementation when the resulting
generator objects are destroyed without completing their
iteration (as will happen in UserDict.DictMixIn.popitem
among other things).

They add their DBCursor to _DBWithCursor._iter_cursors but
only ever delete it from that hash before a return rather
than a yield.  The solution to this should be simple: have
_closeCursors() empty the _iter_cursors hash after calling
close() on all of the cursors.  __iter__ and iteritems()
already ignore a KeyError when trying to remove their cursor
from the map when returning.

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