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Fix set___name__ and set___qualname__ deadlock #5956

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Merged
merged 1 commit into from
Jul 12, 2025
Merged

Fix set___name__ and set___qualname__ deadlock #5956

merged 1 commit into from
Jul 12, 2025

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@youknowone youknowone commented Jul 12, 2025 •
edited by coderabbitai bot
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close #5940 by different approach

cc @ShaharNaveh

Summary by CodeRabbit

  • Refactor
    • Improved the way type names are updated internally to enhance reliability and consistency. No changes to user-facing behavior.

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coderabbitai bot commented Jul 12, 2025 •
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Walkthrough

The changes update the implementation of the set___qualname__ and set___name__ methods in the PyType struct. Instead of directly overwriting the qualname and name fields under a write lock, the code now uses std::mem::replace to swap values, ensuring the old value is dropped after releasing the lock.

Changes

File(s) Change Summary
vm/src/builtins/type.rs Refactored set___qualname__ and set___name__ to use std::mem::replace for field updates, ensuring old values are dropped after lock release. No signature changes.

Sequence Diagram(s)

sequenceDiagram
    participant User
    participant PyType
    participant Lock

    User->>PyType: set___name__(new_value)
    PyType->>Lock: acquire write lock
    PyType->>Lock: replace name with new_value (mem::replace)
    Lock-->>PyType: release lock
    PyType->>User: return result
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Assessment against linked issues

Objective (Issue #) Addressed Explanation
Improved handling when setting the __name__ attribute of types to ensure proper internal updates and consistency (#5940) ✅

Poem

A rabbit hopped to type-land’s den,
Swapped names with care, then swapped again.
With mem::replace the lock was freed,
No evil hangs or buggy deed.
The fields now change without a fuss—
Type rabbits cheer, “No deadlocks for us!”
🐇✨

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Reviewing files that changed from the base of the PR and between ac20b00 and 746f7a3.

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  • Lib/test/test_descr.py is excluded by !Lib/**
📒 Files selected for processing (1)
  • vm/src/builtins/type.rs (2 hunks)
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**/*.rs

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🔇 Additional comments (2)
vm/src/builtins/type.rs (2)

683-691: Excellent deadlock fix implementation!

The use of std::mem::replace with proper scoping correctly addresses the deadlock issue. This pattern ensures the write lock is released before the old value's destructor runs, preventing potential deadlocks during Python object cleanup.

The implementation mirrors CPython's Py_SETREF semantics and is well-documented.

848-854: Consistent and correct deadlock fix implementation.

This follows the same safe pattern as the set___qualname__ method, using std::mem::replace to ensure the lock is released before destructors run. The comment correctly references CPython's Py_SETREF pattern.

Both implementations are consistent and should resolve the deadlock issue mentioned in the PR.

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@youknowone youknowone merged commit e21ec55 into RustPython:main Jul 12, 2025
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@youknowone youknowone deleted the fix-name-deadlock branch July 12, 2025 15:22
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