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Title: segfault with gunicorn and a library made with cython bindings
Type: crash Stage: resolved
Components: Versions: Python 3.8
Status: closed Resolution: third party
Dependencies: Superseder:
Assigned To: Nosy List: amirouche, vstinner
Priority: normal Keywords:

Created on 2021-01-11 14:48 by amirouche, last changed 2022-04-11 14:59 by admin. This issue is now closed.

Messages (7)
msg384836 - (view) Author: Amirouche Boubekki (amirouche) Date: 2021-01-11 14:48
Here is a simple way to reproduce:

from lsm import LSM

db = LSM('db.sqlite')

def app(environ, start_response):
    """Simplest possible application object"""

    for (index, (key, value)) in enumerate(db[b'\x00':b'\xFF']):

    start_response(b'200', {})
    return b''


In my real program, if I add 'global db' in the function `app`, it does not segfault.

msg384838 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2021-01-11 14:55
I put the code in a "bla.p" script and I ran it with Python 3.8 on Fedora 33:

python3.8 -m venv env
env/bin/python -m pip install lsm-db

It doesn't crash. Please provide a script reproducing the issue.

Note: lsm-db cannot be installed in Python 3.9 (errors about the removed PyTypeObject.tp_print member in C).
msg384839 - (view) Author: Amirouche Boubekki (amirouche) Date: 2021-01-11 15:01
You need to run the program with the following:

  python -X dev -c "from import run; run()" --workers=1 foobar:app

where is the code from the previous message.

The crash happen when, the function `app` is executed, hence you need to call in another console:

curl http://localhost:8000

note: lsm package can be installed with pip install lsm-db
note2: lsm db can not be installed with py3.9
msg384840 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2021-01-11 15:16
I get a crash without any code, just by running gunicorn. It looks like a bug in gunicorn.

$ python3.8 -m venv env
$ env/bin/python -m pip install gunicorn
Successfully installed gunicorn-20.0.4

$ ./env/bin/python -X dev -c 'from import run; run()' foobar:app 

[2021-01-11 16:14:11 +0100] [32107] [ERROR] Exception in worker process
Traceback (most recent call last):
  File "/home/vstinner/z/env/lib64/python3.8/site-packages/gunicorn/app/", line 39, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/home/vstinner/z/env/lib64/python3.8/site-packages/gunicorn/", line 358, in import_app
    mod = importlib.import_module(module)
ModuleNotFoundError: No module named 'foobar'

[2021-01-11 16:14:11 +0100] [32107] [INFO] Worker exiting (pid: 32107)
sys:1: ResourceWarning: unclosed <socket.socket fd=5, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('', 8000)>
ResourceWarning: Enable tracemalloc to get the object allocation traceback
Debug memory block at address p=0x55cfa92154a0: API '1'
    3271705103877500672 bytes originally requested
    The 7 pad bytes at p-7 are not all FORBIDDENBYTE (0xfd):
        at p-7: 0x00 *** OUCH
        at p-6: 0x00 *** OUCH
        at p-5: 0x00 *** OUCH
        at p-4: 0x00 *** OUCH
        at p-3: 0x00 *** OUCH
        at p-2: 0x00 *** OUCH
        at p-1: 0x00 *** OUCH
    Because memory is corrupted at the start, the count of bytes requested
       may be bogus, and checking the trailing pad bytes may segfault.
    The 8 pad bytes at tail=0x2d67c444d794c3a0 are [2021-01-11 16:14:11 +0100] [32113] [INFO] Booting worker with pid: 32113


You should report the issue to gunicorn:
msg384843 - (view) Author: Amirouche Boubekki (amirouche) Date: 2021-01-11 15:39
> ModuleNotFoundError: No module named 'foobar'

That is not a segfault. The problem I am reporting is a segfault.

It can be reproduced with uvicorn as follow:

from lsm import LSM

db = LSM('db.sqlite')

async def app(scope, receive, send):
    assert scope['type'] == 'http'
    global db
    for (index, (key, value)) in enumerate(db[b'\x00':b'\xFF']):

    await send({
        'type': 'http.response.start',
        'status': 200,
        'headers': [
            [b'content-type', b'text/plain'],
    await send({
        'type': 'http.response.body',
        'body': b'Hello, world!',


Run the above program with: python -X dev -m uvicorn bobo:app

Then in another console: curl http://localhost:8000/

Here is the output:

$ python -X dev -m uvicorn bobo:app
INFO:     Started server process [3580316]
INFO:     Waiting for application startup.
INFO:     ASGI 'lifespan' protocol appears unsupported.
INFO:     Application startup complete.
INFO:     Uvicorn running on (Press CTRL+C to quit)
Fatal Python error: Segmentation fault

Current thread 0x00007fbb6e49b740 (most recent call first):
  File "./", line 10 in app
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/uvicorn/middleware/", line 45 in __call__
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/uvicorn/protocols/http/", line 394 in run_asgi
  File "/usr/lib/python3.8/asyncio/", line 81 in _run
  File "/usr/lib/python3.8/asyncio/", line 1851 in _run_once
  File "/usr/lib/python3.8/asyncio/", line 570 in run_forever
  File "/usr/lib/python3.8/asyncio/", line 603 in run_until_complete
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/uvicorn/", line 48 in run
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/uvicorn/", line 386 in run
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/uvicorn/", line 362 in main
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/click/", line 610 in invoke
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/click/", line 1066 in invoke
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/click/", line 782 in main
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/click/", line 829 in __call__
  File "/home/amirouche/.cache/pypoetry/virtualenvs/lsmdb-cTe2806J-py3.8/lib/python3.8/site-packages/uvicorn/", line 4 in <module>
  File "/usr/lib/python3.8/", line 87 in _run_code
  File "/usr/lib/python3.8/", line 194 in _run_module_as_main
Segmentation fault (core dumped)
msg384845 - (view) Author: Amirouche Boubekki (amirouche) Date: 2021-01-11 16:22
I tried to reduce the program by replacing gunicorn / uvicorn dependency with threading.Thread and multiprocess.Pool without success.
msg384852 - (view) Author: Amirouche Boubekki (amirouche) Date: 2021-01-11 18:07
The problem is prolly in lsm-db.


Sorry for the noise.
Date User Action Args
2022-04-11 14:59:40adminsetgithub: 87057
2021-01-11 18:07:31amirouchesetstatus: open -> closed
resolution: third party
messages: + msg384852
2021-01-11 16:22:17amirouchesetmessages: + msg384845
2021-01-11 15:39:41amirouchesetstatus: closed -> open
resolution: third party -> (no value)
messages: + msg384843
2021-01-11 15:16:34vstinnersetstatus: open -> closed
resolution: third party
messages: + msg384840

stage: resolved
2021-01-11 15:01:04amirouchesetmessages: + msg384839
2021-01-11 14:55:47vstinnersetnosy: + vstinner
messages: + msg384838
2021-01-11 14:48:27amirouchecreate