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subprocess: child_exec() uses _Py_set_inheritable() which is not async-signal-safe #76958
Description
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = 'https://github.com/gpshead'
closed_at = <Date 2018-02-06.06:52:35.951>
created_at = <Date 2018-02-06.01:34:02.804>
labels = ['extension-modules', 'type-bug', 'library', '3.7']
title = 'subprocess: child_exec() uses _Py_set_inheritable() which is not async-signal-safe'
updated_at = <Date 2018-02-06.07:25:34.347>
user = 'https://github.com/izbyshev'bugs.python.org fields:
activity = <Date 2018-02-06.07:25:34.347>
actor = 'izbyshev'
assignee = 'gregory.p.smith'
closed = True
closed_date = <Date 2018-02-06.06:52:35.951>
closer = 'gregory.p.smith'
components = ['Extension Modules', 'Library (Lib)']
creation = <Date 2018-02-06.01:34:02.804>
creator = 'izbyshev'
dependencies = []
files = []
hgrepos = []
issue_num = 32777
keywords = ['patch']
message_count = 6.0
messages = ['311699', '311706', '311707', '311708', '311709', '311712']
nosy_count = 3.0
nosy_names = ['gregory.p.smith', 'vstinner', 'izbyshev']
pr_nums = ['5560', '5562', '5563']
priority = 'normal'
resolution = 'fixed'
stage = 'commit review'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue32777'
versions = ['Python 3.6', 'Python 3.7']
Activity
izbyshev commentedon Feb 6, 2018
_Py_set_inheritable() raises a Python-level exception on error and thus is not async-signal-safe, but child_exec() must use only async-signal-safe functions because it's executed between fork() and exec().
Since a non-raising version is already implemented in Python/fileutils.c for internal use (set_inheritable), I suggest to simply expose it via another public function (similar to _Py_open_noraise(), etc.).
gpshead commentedon Feb 6, 2018
out of curiosity, did you actually diagnose a process deadlocked due to this or was it noted via code inspection?
this issue has been around since 3.4 and the file descriptor inheritance changes from the looks of things.
gpshead commentedon Feb 6, 2018
New changeset c1e46e9 by Gregory P. Smith (Alexey Izbyshev) in branch 'master':
bpo-32777: Fix _Py_set_inheritable async-safety in subprocess (GH-5560)
c1e46e9
gpshead commentedon Feb 6, 2018
New changeset 2bb0bfa by Gregory P. Smith (Miss Islington (bot)) in branch '3.7':
bpo-32777: Fix _Py_set_inheritable async-safety in subprocess (GH-5560) (GH-5562)
2bb0bfa
gpshead commentedon Feb 6, 2018
New changeset b90c685 by Gregory P. Smith (Miss Islington (bot)) in branch '3.6':
bpo-32777: Fix _Py_set_inheritable async-safety in subprocess (GH-5560) (GH-5563)
b90c685
izbyshev commentedon Feb 6, 2018
The latter. I noted it while working on another issue. While it was easy to trigger a malloc() in child_exec() by e.g. specifying an invalid fd in pass_fds for Popen, I haven't tried to arrange a deadlock.