New submission from Thomas D.:
Hi,
to demonstrate the problem you need >=systemd-217:
# python3.4
Python 3.4.2 (default, Oct 12 2014, 20:09:43)
[GCC 4.8.3] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import subprocess
>>> sp = subprocess.Popen(["/sbin/udevd", "--daemon"], stdout=subprocess.PIPE,
>>> stderr=subprocess.PIPE)
>>> out, err = sp.communicate()
[hangs]
"ps" will show
root 9619 0.0 0.1 23340 5404 pts/5 Ss Jan09 0:00 \_ -bash
root 13291 0.0 0.2 45352 9784 pts/5 S+ 00:34 0:00 \_
python3.4
root 13311 0.0 0.0 0 0 pts/5 Z+ 00:34 0:00 \_
[udevd] <defunct>
Calling "/sbin/udevd --daemon" from the shell works fine.
>>> errorlog = open("/tmp/stderr.log", "wb")
>>> sp = subprocess.Popen(["/sbin/udevd", "--daemon"], stdout=subprocess.PIPE,
>>> stderr=errorlog)
works, too.
The problem first appeared in systemd-217. I bisected systemd's source code and
the commit since when Python's subprocess module is unable to start udevd is
https://github.com/systemd/systemd/commit/5c67cf2774a8b964f4d7cd92a4c447da81ac6087
This is not a systemd/udev only problem. The problem was first seen with the
php-fpm daemon from PHP (but only when using "error_log = syslog").
Please see the original bug report at
https://github.com/saltstack/salt/issues/14957 for more details.
Because Salt is still at Python 2.7, the problem can be reproduced with Python
2.7, too.
Is it a bug in subprocess? In systemd/PHP? Are we (salt) using subprocess the
wrong way?
Thanks!
PS:
On your system, "/sbin/udevd" will be probably "/lib/systemd/systemd-udevd"
Not sure if this is related to http://bugs.python.org/issue12786 in some ways.
----------
components: Library (Lib)
messages: 233788
nosy: whissi
priority: normal
severity: normal
status: open
title: subprocess communicate() hangs when stderr isn't closed
type: behavior
versions: Python 2.7, Python 3.4
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue23213>
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