[pylucene-dev] finalizing the deadly embrace

Andi Vajda vajda at osafoundation.org
Thu Jan 17 12:38:47 PST 2008


Thinking about this some more, I believe that Anurag's finalizer proxy idea 
is on the right track. It provides the "trick" needed to break the deadly 
embrace when the ref count of the python object is down to 1, that is, down 
to when the only reference is the one from the Java parent wrapper.

When the finalizer proxy's refcount goes to zero, it is safe to assume that 
only Java _may_ still be needing the object. This is enough then to replace 
the strong global reference to the Java parent wrapper with a weak global 
reference thereby breaking the deadly embrace and letting Java garbage 
collect it when its time has come. When that time comes, the finalize() 
method on it is normally called by the Java garbage collector and the python 
ref count to the Python extension instance is brought to zero and the object 
is finally freed.

This assumes, of course, that when such an extension object is instantiated, 
the finalizer proxy is actually returned.

I should be able to implement this in C/C++ so that the performance hit 
is minimal and in a way that is transparent to PyLucene users.

More on this in the next few days....

Andi..


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