python / python/cpython

[Windows] multiprocessing handle leak when child process is killed during startup/unpickling

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3.10 3.8 (EOL) 3.9 (EOL) OS-windows stdlib topic-multiprocessing type-bug
Dominant language
Python
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Description

BPO 42968
Nosy @pfmoore, @tjguk, @zware, @eryksun, @zooba, @dgrunwald
Files
  • deadlock.py
  • 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 2021-01-19.18:24:16.409>
    labels = ['type-bug', '3.8', '3.9', '3.10', 'library', 'OS-windows']
    title = '[Windows] multiprocessing handle leak when child process is killed during startup/unpickling'
    updated_at = <Date 2021-03-30.18:31:06.717>
    user = 'https://github.com/dgrunwald'
    

    bugs.python.org fields:

    activity = <Date 2021-03-30.18:31:06.717>
    actor = 'eryksun'
    assignee = 'none'
    closed = False
    closed_date = None
    closer = None
    components = ['Library (Lib)', 'Windows']
    creation = <Date 2021-01-19.18:24:16.409>
    creator = 'dgrunwald'
    dependencies = []
    files = ['49751']
    hgrepos = []
    issue_num = 42968
    keywords = []
    message_count = 3.0
    messages = ['385283', '385284', '385380']
    nosy_count = 6.0
    nosy_names = ['paul.moore', 'tim.golden', 'zach.ware', 'eryksun', 'steve.dower', 'dgrunwald']
    pr_nums = []
    priority = 'normal'
    resolution = None
    stage = None
    status = 'open'
    superseder = None
    type = 'behavior'
    url = 'https://bugs.python.org/issue42968'
    versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']
    

    Contributor guide

    Open the contributing guide

    First steps

    1. Read the whole issue, then the project's contributing guide.
    2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
    3. Fork the repository and make your change on a branch.
    4. Open a pull request that references the issue number.

    Research direction

    Start with the attached deadlock.py reproducer and the Windows multiprocessing startup/unpickling path. Reproduce the case where a child is killed during startup, then investigate whether the process handle remains open. Done means the reproducer no longer leaks a handle on supported Python versions.

    Written by the indexing model from the issue text.

    Assessment

    Tech stack
    python
    Domain
    backend, operating-systems
    Issue type
    Bug
    Difficulty
    4/5
    Estimated time
    3-5 days
    Activity status
    Stale
    Clarity
    Needs clarification
    Newbie friendliness
    35/100

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