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Bug 1745894 - subprocess module fails under mod_wsgi: fork not supported for subinterpreters
Summary: subprocess module fails under mod_wsgi: fork not supported for subinterpreters
Keywords:
Status: CLOSED RAWHIDE
Alias: None
Product: Fedora
Classification: Fedora
Component: python3
Version: rawhide
Hardware: Unspecified
OS: Unspecified
unspecified
high
Target Milestone: ---
Assignee: Charalampos Stratakis
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks: 1706238 1745450
TreeView+ depends on / blocked
 
Reported: 2019-08-27 07:32 UTC by Christian Heimes
Modified: 2019-09-02 08:54 UTC (History)
12 users (show)

Fixed In Version: python3-3.8.0~b4-1.fc32
Doc Type: If docs needed, set a value
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Clone Of:
Environment:
Last Closed: 2019-09-02 07:56:32 UTC
Type: Bug
Embargoed:

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System ID Private Priority Status Summary Last Updated
Python 34651 0 None None None 2019-08-27 07:32:04 UTC
Python 37951 0 None None None 2019-08-27 07:32:04 UTC
Red Hat Bugzilla 1745450 0 unspecified CLOSED ipa-server-install fails with RuntimeError: fork not supported for subinterpreters 2022-05-16 11:32:56 UTC

Description Christian Heimes 2019-08-27 07:32:04 UTC 
Description of problem:
Python 3.8 started to prohibit fork() calls in subinterpreters (see bpo-34651). This also affects subprocess.Popen() calls. Only under some cases subprocess.Popen() uses posix_spawn() instead of fork() + exec(). The new restriction breaks software that executes external commands from a subinterpreter like mod_wsgi applications.

For example FreeIPA server is affected by the regression. It's no longer possible to install FreeIPA on Fedora rawhide.

Version-Release number of selected component (if applicable):
Python 3.8b3

How reproducible:
always

Steps to Reproduce:
1. Execute a subprocess under mod_wsgi (e.g. ipa-server-install)

Actual results:
...
  File "/usr/lib64/python3.8/subprocess.py", line 829, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib64/python3.8/subprocess.py", line 1608, in _execute_child
    self.pid = _posixsubprocess.fork_exec(
RuntimeError: fork not supported for subinterpreters

Expected results:
No error

Additional info:
https://bugs.python.org/issue37951
Comment 1 Christian Heimes 2019-08-27 08:17:00 UTC 
Upstream PR https://github.com/python/cpython/pull/15544
Comment 2 Christian Heimes 2019-08-27 21:59:20 UTC 
Fix has landed in upstream's 3.8 branch, https://github.com/python/cpython/commit/03c52f2f63a8abeb4afb75e9da46c7d6c0a8afd5

Please apply the fix to 3.8 package on rawhide.
Comment 3 Miro Hrončok 2019-08-28 04:33:54 UTC 
Thanks Christian. I've been trying to say this in https://bugs.python.org/issue34651#msg343364 but nothing happened. Thanks for tackling this down. Any chance the fix will be in 3.8.0b4?
Comment 4 Christian Heimes 2019-08-28 05:33:39 UTC 
You are welcome, Miro.

I saw your comment after I started digging into the issue, excellent deduction! :) I assume that the consequences were not fully clear to Victor and Eric. Almost nobody uses subinterpreters -- except for some embedded cases and mod_wsgi.

I forgot that 3.8b4 release is imminent. The fix has landed in 3.8 and 3.8b4 is scheduled to be released yesterday. I dropped Łukasz a mail and informed him that 3.8b4 is unblocked again. You are right, let's wait for 3.8b4.
Comment 5 Miro Hrončok 2019-09-02 07:56:32 UTC 
Python was updated to 3.8.0b4. Reopen if it doesn't fix the issue.
Comment 6 Christian Heimes 2019-09-02 08:54:46 UTC 
Confirmed, 3.8b4 fixed the problem with subinterpreters for FreeIPA and KDCProxy.

Thanks for getting the new build into rawhide so fast.
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