Calling ShareableList.count in threads aborts: Assertion 'self->exports == 0' failed

[devdanzin]

Crash report

What happened?

It's possible to abort the interpreter by calling multiprocessing.shared_memory.ShareableList.count in threads with PYTHON_GIL=0 in a debug build:

import gc
import multiprocessing.shared_memory
from threading import Thread

obj = multiprocessing.shared_memory.ShareableList("Uq..SeDAmB+EBrkLl.SG.Z+Z.ZdsV..wT+zLxKwdN\b")

for x in range(10):
    Thread(target=obj.count, args=(1,)).start()

del obj
gc.collect()

Result:

Exception ignored in: <function SharedMemory.__del__ at 0x200006bbfb0>
Traceback (most recent call last):
  File "/home/danzin/projects/mycpython/Lib/multiprocessing/shared_memory.py", line 189, in __del__
    self.close()
  File "/home/danzin/projects/mycpython/Lib/multiprocessing/shared_memory.py", line 229, in close
    self._buf.release()
BufferError: memoryview has 2 exported buffers
python: Objects/memoryobject.c:1143: memory_dealloc: Assertion `self->exports == 0' failed.
Aborted

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 3.14.0a2+ experimental free-threading build (heads/main-dirty:c9b399fbdb0, Nov 19 2024, 20:12:48) [GCC 11.4.0]

[LindaSummer]

Hi @devdanzin ,

I'm a newbie of CPython and want to have a try on this issue.

Could it be assigned to me?😊

Best Regards,
Edward

[JelleZijlstra]

@LindaSummer you don't need to be assigned an issue to work on it. If you're interested in this issue, I suggest you read through the code where the crash happens to understand it. If you feel you found something useful, you can post on this issue with your findings. If you find a possible solution, you can open a PR with your fix.

[LindaSummer]

@LindaSummer you don't need to be assigned an issue to work on it. If you're interested in this issue, I suggest you read through the code where the crash happens to understand it. If you feel you found something useful, you can post on this issue with your findings. If you find a possible solution, you can open a PR with your fix.

Hi @JelleZijlstra ,

Got it! Thanks very much for your warm guidance! 😊

I will try to go through the code and search for the root cause.

Best Regards,
Edward