Crash report

What happened?

It's possible to segfault or abort a no-gil interpreter running withPYTHON_GIL=0 by callingatexit functions from threads:

fromthreadingimportThreadimportatexitdefg():passdeff():forxinrange(100):atexit.register(g)atexit._clear()atexit.register(g)forxinrange(100):Thread(target=f,args=()).start()

Found using fusil by@vstinner.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Output from running 'python -VV' on the command line:

Python 3.14.0a1+ experimental free-threading build (heads/main-dirty:612ac283b81, Nov 16 2024, 01:37:56) [GCC 11.4.0]

Linked PRs

• gh-126907: Lock theatexit state on the free-threaded build #126908
• gh-126907: Use a list foratexit callbacks #127935