Eric Snow <ericsnowcurren...@gmail.com> added the comment:
On Sun, Feb 2, 2020 at 3:32 PM Raymond Hettinger <rep...@bugs.python.org> wrote: > Random idea (not carefully thought-out): Would it be simpler to have these > objects just > ignore their refcount by having dealloc() be a null operation or having it > set the refcount > back to a positive number). That would let sub-interpreters share the > objects without > worrying about race-conditions on incref/decref operations. This is pretty much one of the two approaches I have been considering. :) Just to be clear, singletons normally won't end up with a refcount of 0, by design. However, if there's a incref race between two interpreters (that don't share a GIL) then you *can* end up triggering dealloc (via Py_DECREF) and even get negative refcounts (which cause Py_FatalError() on debug builds). Here are some mitigations: * (as noted above) make dealloc() for singletons a noop * (as noted above) in dealloc() set the refcount back to some positive value * make the initial refcount sufficiently large such that it is unlikely to reach 0 even with races * incref each singleton once during each interpreter initiialization (and decref once during interp. finalization) We would have to special-case refleak checks for singletons, to avoid false positives. Also note that currently extension authors (and CPython contributors) can rely on the runtime to identify when then accidentally incref/decref a singleton too much (or forget to do so). So it may make sense to do something in the "singleton dealloc()" in debug builds to provide similar checks. > To make this work, the objects can register themselves as permanent, shared, > objects; > then, during shutdown, we could explicitly call a hard dealloc on those > objects. great point ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue39511> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
