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Seqfault in on_trait_change #162
Description
With the release of Traitlets 4.1 I am seeing some random seqfaults when restarting the Jupyter notebook and as part of the Matplotlib docs build which seems to point to the Traitlets tear down steps.
Im not sure this is related to Traitlets 4.1 but it does seem to correlate. Perhaps we are doing something wrong in Matplotlib which is causing this.
Locally:
Fatal Python error: PyImport_GetModuleDict: no module dictionary!
Thread 0x0000700001113000 (most recent call first):
File "/usr/local/lib/python3.5/site-packages/ipykernel/parentpoller.py", line 37 in run
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/threading.py", line 914 in _bootstrap_inner
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/threading.py", line 882 in _bootstrap
Thread 0x0000700000607000 (most recent call first):
File "/usr/local/lib/python3.5/site-packages/ipykernel/heartbeat.py", line 61 in run
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/threading.py", line 914 in _bootstrap_inner
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/threading.py", line 882 in _bootstrap
Current thread 0x00007fff7844b000 (most recent call first):
File "/usr/local/lib/python3.5/site-packages/traitlets/traitlets.py", line 1136 in on_trait_change
File "/usr/local/lib/python3.5/site-packages/IPython/core/extensions.py", line 64 in __del__
and in the Matplotlib docs build which uses the IPython Sphinx extension:
Error in atexit._run_exitfuncs:
Traceback (most recent call last):
File "/home/travis/build/matplotlib/matplotlib/venv/lib/python3.5/site-packages/IPython/core/history.py", line 547, in end_session
len(self.input_hist_parsed)-1, self.session_number))
sqlite3.OperationalError: disk I/O error
Fatal Python error: PyImport_GetModuleDict: no module dictionary!
Current thread 0x00007ff58684b700 (most recent call first):
File "/home/travis/build/matplotlib/matplotlib/venv/lib/python3.5/site-packages/traitlets/traitlets.py", line 1136 in on_trait_change
File "/home/travis/build/matplotlib/matplotlib/venv/lib/python3.5/site-packages/IPython/core/extensions.py", line 64 in __del__
Aborted (core dumped)
The sql error is old and fixed already in IPython master see ipython/ipython#8850
Activity
jenshnielsen commentedon Jan 19, 2016
BTW the Matplotlib build log is in https://travis-ci.org/matplotlib/matplotlib/jobs/103175772
jenshnielsen commentedon Jan 19, 2016
Looking over Matplotlib log we only seem to see it with python 3 (Specifically python 3.5) On the branches where the docs are build with python 2.7 this doesn't happen.
jenshnielsen commentedon Jan 19, 2016
Im also seeing it in a fresh conda environment
minrk commentedon Jan 19, 2016
I can see this, too sometimes. Seems like it has to be a bug in Python 3.5, even if it's triggered by a change in traitlets. I'll try to see if I can figure out what caused it.
Build the docs with python 3.4 which should fix the Traitlets/IPython…
jenshnielsen commentedon Jan 19, 2016
@minrk Thanks, It sounds plausible that it's a bug in Python 3.5
minrk commentedon Jan 19, 2016
I just need to narrow it down to what's the exact cause. I've seen it, but I cannot reproduce it reliably, which makes it harder to find what is the relevant change. I can only reproduce the error about 1% of the time, which suggests to me that it might be threading related.
minrk commentedon Jan 19, 2016
I think I found it: the cause appears to be the deprecation warning that we throw, since
on_trait_changeis deprecated. I'm guessing it's the inspection used to show the warning message that's failing.Unfortunately, I don't know a way to fix this in traitlets, since it seems like the only thing we are doing is a simple warning.
Fortunately, though, the
__del__call here that's the direct cause is unnecessary and already removed in master (ipython/ipython#9040). My proposal is to backport this fix and immediately release IPython 4.0.3, while we work with CPython to figure out the upstream bug.jenshnielsen commentedon Jan 19, 2016
@minrk Sounds good to me
minrk commentedon Jan 19, 2016
Released IPython 4.0.3 with the patch. Hopefully that should tide us over while we work out what's up with Python 3.5.
jenshnielsen commentedon Jan 20, 2016
@minrk Thanks, I will upgrade and see what happens.