Bug report

atexit.unregister() can call the user__eq__() when it searches the callback(s) to remove. If__eq__() returns true, the callback is removed by index. But__eq__() can call arbitrary code, it can release the GIL, andatexit.unregister() can be called in other thread. If it removes the callback at the current index or before current index, the current index will no point to the compared callable, and the following deletion will delete wrong callable.

This issue is similar to#112127, but causes different symptoms.

Linked PRs

• gh-142881: Fix concurrent and reentrant call of atexit.unregister() #142901