Image.open: dictionary changed size during iteration (race condition) #7717
Description
What did you do?
We are running a Django server with Gunicorn, with a view that is returning a thumbnail from an existing PNG image.
We open it from a BytesIO with PIL.Image.open.
What did you expect to happen?
The Image instance is returned by open.
What actually happened?
Python interpreter raised RuntimeError(dictionary changed size during iteration) on this line :
File "PIL/Image.py", line 3258, in open
preinit()
File "PIL/Image.py", line 320, in preinit
from . import GifImagePlugin
File "PIL/GifImagePlugin.py", line 34, in <module>
from . import (
File "PIL/ImageMath.py", line 217, in <module>
for k, v in list(globals().items()):What are your OS, Python and Pillow versions?
- OS: Ubuntu 22.04 AArch64
- Python: 3.9.13 (CPython)
- Pillow: 10.2.0
Unfortunately, it looks like it is a race condition on globals() with another lazy-loaded dependency, I don't have a minimal code that can reproduce this bug consistently. It is highly unlikely to happen, but is has happened once on our servers.
# in a Django view
pil_image = Image.open(raw_image_bytes)