[WIP] bpo-40533: Make PyObject.ob_refcnt atomic in subinterpreters#19958
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When Python is built with experimental isolated interpreters, declare PyObject.ob_refcnt and _dictkeysobject.dk_refcnt as atomic variables. Temporary workaround until subinterpreters stop sharing Python objects.
vstinner commented May 6, 2020
aeros commented May 6, 2020
Based on the discussion at https://mail.python.org/archives/list/python-committers@python.org/thread/2WHQBHFK7UQ7OYAJV5S2QCINODVVKGJY/#2WHQBHFK7UQ7OYAJV5S2QCINODVVKGJY, I think we should leave a |
vstinner commented May 6, 2020
Right, thanks. I converted this PR into a draft to ensure that nobody merges it by mistake. |
vstinner changed the title 
| #ifdefEXPERIMENTAL_ISOLATED_SUBINTERPRETERS | ||
| /* bpo-40533: Use an atomic variable for PyObject.ob_refcnt, to ensure that | ||
| Py_INCREF() and Py_DECREF() are safe when called in parallel, until | ||
| subinterpreters stop sharing Python objects. */ | ||
| _Atomic Py_ssize_tob_refcnt; |
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Perhaps this is somewhat emphasized by the "experimental" part, but could we possibly make it a bit more crystal clear that this is only a temporary stopgap measure? I personally find that "until subinterpreters stop sharing Python objects" could be interpreted as a near indefinite amount of time; I'm not confident that most readers will go over the full context in the bpo issue and related discussions.
Normally, this wouldn't be a huge concern, but I think object.h is likely one of the most public-facing header files in CPython, so it seems important to communicate this as clearly as possible.
vstinner commented Mar 17, 2021
The current plan is to not share any object between two interpreters, so this PR is not needed. I close it. |
4 participants
When Python is built with experimental isolated interpreters, declare
PyObject.ob_refcnt and _dictkeysobject.dk_refcnt as atomic variables.
Temporary workaround until subinterpreters stop sharing Python
objects.
https://bugs.python.org/issue40533