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Signal handling machinery still relies on "pending calls". #79604

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ericsnowcurrently opened this issue Dec 6, 2018 · 4 comments
Closed

Signal handling machinery still relies on "pending calls". #79604

ericsnowcurrently opened this issue Dec 6, 2018 · 4 comments
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3.8 (EOL) end of life interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error

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@ericsnowcurrently
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BPO 35423
Nosy @pitrou, @vstinner, @ericsnowcurrently, @emilyemorehouse
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  • bpo-35423: Stop using the "pending calls" machinery for signals. #10972
  • 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/ericsnowcurrently'
    closed_at = <Date 2019-01-11.21:50:36.931>
    created_at = <Date 2018-12-06.00:12:39.591>
    labels = ['interpreter-core', 'type-bug', '3.8']
    title = 'Signal handling machinery still relies on "pending calls".'
    updated_at = <Date 2019-01-11.21:50:36.931>
    user = 'https://github.com/ericsnowcurrently'

    bugs.python.org fields:

    activity = <Date 2019-01-11.21:50:36.931>
    actor = 'eric.snow'
    assignee = 'eric.snow'
    closed = True
    closed_date = <Date 2019-01-11.21:50:36.931>
    closer = 'eric.snow'
    components = ['Interpreter Core']
    creation = <Date 2018-12-06.00:12:39.591>
    creator = 'eric.snow'
    dependencies = []
    files = []
    hgrepos = []
    issue_num = 35423
    keywords = ['patch']
    message_count = 4.0
    messages = ['331196', '331197', '331654', '333507']
    nosy_count = 4.0
    nosy_names = ['pitrou', 'vstinner', 'eric.snow', 'emilyemorehouse']
    pr_nums = ['10972']
    priority = 'normal'
    resolution = 'fixed'
    stage = 'resolved'
    status = 'closed'
    superseder = None
    type = 'behavior'
    url = 'https://bugs.python.org/issue35423'
    versions = ['Python 3.8']

    @ericsnowcurrently
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    For a while now the signal handling machinery has piggy-backed on ceval's "pending calls" machinery (e.g. Py_AddPendingCall). This is a bit confusing. It also increases the risk with unrelated changes to the pending calls code.

    @ericsnowcurrently ericsnowcurrently added the 3.8 (EOL) end of life label Dec 6, 2018
    @ericsnowcurrently ericsnowcurrently self-assigned this Dec 6, 2018
    @ericsnowcurrently ericsnowcurrently added the type-bug An unexpected behavior, bug, or error label Dec 6, 2018
    @vstinner
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    vstinner commented Dec 6, 2018

    In the master branch, the signal handler only uses pending calls to report error on writing into the "wakeup_fd" (fd or socket handle):

    commit c08177a
    Author: Antoine Pitrou <pitrou@free.fr>
    Date: Wed Jun 28 23:29:29 2017 +0200

    bpo-30703: Improve signal delivery (bpo-2415)
    

    @ericsnowcurrently
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    Correct. The remaining call to Py_AddPendingCall in the signal-handling code is fine.

    This issue is only indirectly related. I suppose you could consider it a follow-up to bpo-30703. The PR for that issue (GH-2415) switches from using pending calls for signal handlers to using the pending calls machinery without actual pending calls.

    So here I want to address taking the next step: deal with pending signals separately from pending calls. That separation helps simplify efforts to adapt the pending calls machinery for use in arbitrary threads (rather than the main thread). See bpo-33608.

    @ericsnowcurrently ericsnowcurrently added the interpreter-core (Objects, Python, Grammar, and Parser dirs) label Dec 11, 2018
    @ericsnowcurrently
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    New changeset fdf282d by Eric Snow in branch 'master':
    bpo-35423: Stop using the "pending calls" machinery for signals. (gh-10972)
    fdf282d

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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