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rework weakref#6916

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youknowone merged 2 commits into
RustPython:mainfrom
youknowone:weakref
Feb 1, 2026
Merged

rework weakref#6916
youknowone merged 2 commits into
RustPython:mainfrom
youknowone:weakref

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@youknowone

@youknowone youknowone commented Jan 31, 2026 •
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Summary by CodeRabbit

  • Refactor

    • Reorganized weak reference handling to use an optimized locking mechanism for improved concurrency management.
    • Adjusted internal method visibility to enhance code structure and maintainability.

  • Chores

    • Updated spell-check dictionary with new vocabulary entries.
    • Updated documentation comments for consistency.

✏️ Tip: You can customize this high-level summary in your review settings.

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coderabbitai Bot commented Jan 31, 2026 •
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📝 Walkthrough

Walkthrough

This pull request refactors the weakref locking mechanism in the VM from per-object mutex guards to a stripe-based locking approach, inlines the weakref list representation, and adds a direct referent pointer to PyWeak. Additionally, four pointer accessor methods are exposed as public, and a dictionary entry is added for spelling.

Changes

Cohort / File(s) Summary
Spell Check Dictionary
.cspell.dict/cpython.txt		 Added "weakrefobject" entry to CPython dictionary for improved lexical coverage.
API Visibility
crates/common/src/linked_list.rs		 Elevated visibility of four Pointers<T> accessor methods (get_prev, get_next, set_prev, set_next) from private to pub const fn.
Weakref Locking Refactor
crates/vm/src/object/core.rs		 Introduced stripe-based locking mechanism (weakref_lock) replacing per-object mutex; inlined WeakRefList with atomic head/generic cache pointers; added wr_object field to PyWeak for direct referent access; reworked upgrade, is_dead, and drop_inner operations; updated get_weak_references and weak_count signatures to pass owning object context; added unsafe unlink helper for list manipulation.
Documentation Update
crates/vm/src/object/traverse_object.rs		 Updated comments describing weak list tracing rationale in PyInner without altering traversal behavior.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~50 minutes

Poem

🐰 With stripes and locks, the weakrefs dance,
No mutex chains—a pointers' prance!
Cache generic, reference tight,
Dead detection burning bright. ✨

🚥 Pre-merge checks | ✅ 1 | ❌ 2
❌ Failed checks (1 warning, 1 inconclusive)
Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 71.88% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
Title check ❓ Inconclusive The title 'rework weakref' is vague and generic, using non-descriptive language that doesn't convey meaningful details about the substantial architectural changes in the changeset. Provide a more specific title that highlights the key change, such as 'Replace weakref per-object mutexes with stripe-based locking' or 'Refactor weakref locking mechanism to use stripe locks'.
✅ Passed checks (1 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

✨ Finishing touches
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@github-actions

github-actions Bot commented Jan 31, 2026

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Code has been automatically formatted

The code in this PR has been formatted using:

  • cargo fmt --all
    Please pull the latest changes before pushing again:
git pull origin weakref

@youknowone youknowone marked this pull request as ready for review February 1, 2026 01:42
@youknowone
Replace WeakListInner with inline atomic weakref list and stripe locks
c383586 
Remove heap-allocated WeakListInner (OncePtr<PyMutex<WeakListInner>>).
WeakRefList now holds two inline atomic pointers (head, generic).
PyWeak.parent replaced with wr_object pointing directly to referent.
Add weakref_lock module with AtomicU8 spinlock array for thread safety.
Rewrite upgrade/clear/drop_inner/count/get_weak_references with stripe lock.
Make Pointers methods public in linked_list.rs.
Remove expectedFailure from test_subclass_refs_dont_replace_standard_refs.
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github-actions Bot commented Feb 1, 2026

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📦 Library Dependencies

The following Lib/ modules were modified. Here are their dependencies:

[x] lib: cpython/Lib/weakref.py
[x] lib: cpython/Lib/_weakrefset.py
[x] test: cpython/Lib/test/test_weakref.py (TODO: 22)

dependencies:

  • weakref

dependent tests: (147 tests)

  • weakref: test_array test_ast test_asyncio test_code test_concurrent_futures test_context test_contextlib test_copy test_deque test_descr test_dict test_exceptions test_file test_fileio test_functools test_generators test_genericalias test_importlib test_inspect test_io test_ipaddress test_itertools test_logging test_memoryview test_mmap test_ordered_dict test_pickle test_picklebuffer test_queue test_re test_scope test_set test_slice test_socket test_sqlite3 test_ssl test_struct test_tempfile test_thread test_threading test_threading_local test_types test_typing test_unittest test_uuid test_weakref test_weakset test_xml_etree
    • asyncio: test_asyncio test_builtin test_contextlib_async test_os test_sys_settrace test_unittest
    • concurrent.futures.process: test_concurrent_futures
    • copy: test_bytes test_codecs test_collections test_coroutines test_csv test_defaultdict test_dictviews test_email test_enum test_fractions test_http_cookies test_opcache test_optparse test_platform test_plistlib test_posix test_site test_statistics test_sysconfig test_tomllib test_xml_dom_minicompat test_zlib
      • dataclasses: test__colorize test_patma test_pprint test_regrtest test_zoneinfo
      • email.generator: test_email
      • http.cookiejar: test_http_cookiejar
      • http.server: test_httpservers test_robotparser test_urllib2_localnet
      • mailbox: test_mailbox
      • smtplib: test_smtplib test_smtpnet
      • tarfile: test_shutil test_tarfile
    • inspect: test_abc test_argparse test_asyncgen test_decimal test_grammar test_ntpath test_operator test_posixpath test_signal test_traceback test_yield_from test_zipimport
      • bdb: test_bdb
      • importlib.metadata: test_importlib
      • rlcompleter: test_rlcompleter
      • trace: test_trace
      • xmlrpc.server: test_docxmlrpc test_xmlrpc
    • multiprocessing: test_concurrent_futures test_fcntl test_multiprocessing_main_handling
    • symtable: test_symtable
    • tempfile: test_bz2 test_cmd_line test_compile test_compileall test_dis test_doctest test_ensurepip test_faulthandler test_filecmp test_fileinput test_importlib test_linecache test_pathlib test_pkg test_pkgutil test_py_compile test_runpy test_selectors test_string_literals test_subprocess test_support test_tabnanny test_threadedtempfile test_urllib test_urllib2 test_urllib_response test_venv test_zipapp test_zipfile test_zipfile64 test_zstd
      • urllib.request: test_urllib2net test_urllibnet

Legend:

  • [+] path exists in CPython
  • [x] up-to-date, [ ] outdated

@youknowone youknowone merged commit 60bec8a into RustPython:main Feb 1, 2026
14 checks passed
@youknowone youknowone deleted the weakref branch February 1, 2026 03:12
This was referenced Mar 4, 2026
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