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[Windows] subprocess: close the handle when the process completes #81591

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vstinner opened this issue Jun 26, 2019 · 6 comments
Closed

[Windows] subprocess: close the handle when the process completes #81591

vstinner opened this issue Jun 26, 2019 · 6 comments
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3.12 bugs and security fixes OS-windows performance Performance or resource usage stdlib Python modules in the Lib dir

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@vstinner
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BPO 37410
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PRs
  • bpo-37410: subprocess closes the process handle when done #14391
    		•

    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 = None
closed_at = None
created_at = <Date 2019-06-26.11:53:14.562>
labels = ['3.8', '3.7', 'library', '3.9', 'performance']
title = '[Windows] subprocess: close the handle when the process completes'
updated_at = <Date 2019-06-26.13:40:23.561>
user = 'https://github.com/vstinner'

    bugs.python.org fields:

    activity = <Date 2019-06-26.13:40:23.561>
actor = 'vstinner'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-06-26.11:53:14.562>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 37410
keywords = ['patch']
message_count = 5.0
messages = ['346603', '346604', '346607', '346617', '346618']
nosy_count = 1.0
nosy_names = ['vstinner']
pr_nums = ['14391']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'resource usage'
url = 'https://bugs.python.org/issue37410'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']
    @vstinner
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    subprocess.Popen uses _winapi.CreateProcess() to spawn a child process. It stores the process handle using a Handle class. Popen never explicitly releases the handle, it rely on Handle.__del__ when the Popen object is detroyed (when Popen._handle attribute is cleared).

    As discussed in bpo-37380, we could call explicitly CloseHandle(handle) as soon as the child process completes, to release resources in the Windows kernel.

    Attached PR implements this fix.

    @vstinner vstinner added 3.9 only security fixes stdlib Python modules in the Lib dir performance Performance or resource usage labels Jun 26, 2019
    @vstinner
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    IMHO it's safe to backport PR 14391 to Python 3.7 and 3.8.

    @vstinner vstinner added 3.7 (EOL) end of life 3.8 only security fixes labels Jun 26, 2019
    @vstinner
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    See also bpo-37380: subprocess.Popen._cleanup() "The handle is invalid" error when some old process is gone.

    @vstinner
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    We may backport the change to Python 2.7 as well, but in this case terminate() must be changed to test returncode:

            def terminate(self):
            """Terminates the process."""
            # Don't terminate a process that we know has already died.
            if self.returncode is not None:
                return
            ...

    @vstinner
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    terminate() was changed by:

    commit a0c9caa
    Author: Gregory P. Smith <greg@krypto.org>
    Date: Sun Nov 15 18:19:10 2015 -0800

    Fix issue bpo-6973: When we know a subprocess.Popen process has died, do
not allow the send_signal(), terminate(), or kill() methods to do
anything as they could potentially signal a different process.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
    @iritkatriel iritkatriel added OS-windows 3.12 bugs and security fixes and removed 3.9 only security fixes 3.8 only security fixes 3.7 (EOL) end of life labels Sep 12, 2022
    @vstinner
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    vstinner commented Nov 3, 2022

    Sadly, I don't have the bandwidth to work on this issue, I just close it.

    @vstinner vstinner closed this as completed Nov 3, 2022
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