fix finalizing and atexit timing#6626

youknowone

Summary by CodeRabbit

Bug Fixes
- Improved interpreter shutdown handling and suppressed unraisable hook invocations during VM finalization to ensure cleaner interpreter shutdown.

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📝 Walkthrough

Walkthrough

The interpreter finalization sequence is restructured to dynamically import the threading module and call threading._shutdown() during shutdown. Additionally, unraisable exception handling is suppressed when the VM is finalizing by checking the finalizing flag.

Changes

Cohort / File(s)	Summary
Finalization Sequencing `crates/vm/src/vm/interpreter.rs`	Replaced direct non-daemon thread wait with conditional dynamic threading module import and `threading._shutdown()` invocation. Updated finalization flag timing and documentation to reflect Py_FinalizeEx semantics.
Exception Handling During Shutdown `crates/vm/src/vm/mod.rs`	Added early-return guard in `run_unraisable()` to suppress unraisable hook handling when VM is finalizing.

Sequence Diagram

sequenceDiagram
    participant VM as Virtual Machine
    participant Threading as Threading Module
    participant Atexit as Atexit System

    VM->>Threading: Attempt dynamic import
    alt Import Successful
        VM->>Threading: Call threading._shutdown()
        Threading-->>VM: Shutdown complete
    else Import Failed
        VM-->>VM: Continue
    end
    VM->>VM: Set finalizing flag = true
    VM->>Atexit: Run atexit functions
    Atexit-->>VM: Cleanup complete

Estimated Code Review Effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly Related PRs

Fix test_runpy #6409: Modifies Interpreter::finalize with changes to shutdown sequencing and return type handling, directly overlapping with main PR's finalization restructuring.
Add PythonFinallizationError and upgrade multiprocessing #6592: Adds VM finalizing flag guards to suppress behaviors during shutdown, sharing the same suppression pattern and finalization state management as this PR.
Upgrade threading to 3.13.11; sys.setprofile & impl more threading #6691: Introduces threading _shutdown implementation and VM threading state management, which directly implements the threading shutdown mechanism called by this PR's finalization logic.

Suggested Reviewers

fanninpm

🐰 The VM winds down with grace and care,
Threading module bids farewell in the air,
Atexit functions tidy up the floor,
Finalization flags mark the door,
A shutdown sequence, crisp and fair! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix atexit' directly relates to the main changes in the PR, which involve fixing atexit and finalization timing issues in the interpreter shutdown sequence.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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fanninpm

You may want to take a look in test_bdb for 31 tests that can be un-skipped.

youknowone

let me check this again when #6718 is done

youknowone

@fanninpm they are downgraded to expectedFailure (@terryluan12 thanks!)
And this patch doesn't seem to be enough for that

coderabbitai

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@crates/vm/src/vm/mod.rs`:
- Around line 552-562: The finalizing flag is set before calling
atexit::_run_exitfuncs, causing run_unraisable to early-return and suppress
atexit handler exceptions; either move the store to state.finalizing to after
atexit::_run_exitfuncs(vm) so finalization suppression happens post-atexit, or
add a small atexit bypass: introduce an atexit-running marker on VM state (e.g.,
vm.state.atexit_running) set around atexit::_run_exitfuncs and change
run_unraisable to allow reporting when that marker is true (while still
suppressing in other finalization contexts). Ensure references are to
run_unraisable, atexit::_run_exitfuncs, and state.finalizing (or the new
state.atexit_running) so reviewers can find and apply the change.

fanninpm

they are downgraded to expectedFailure

That's better than nothing!

fanninpm mentioned this pull request Jan 13, 2026

Downgraded skips in tests #6716

Merged

youknowone force-pushed the atexit branch from 96e9080 to ab5fde2 Compare January 17, 2026 12:24

youknowone marked this pull request as ready for review January 17, 2026 12:25

coderabbitai Bot reviewed Jan 17, 2026

View reviewed changes

youknowone marked this pull request as draft January 17, 2026 14:31

youknowone added 2 commits January 17, 2026 23:41

fix finalizing and atexit timing

cdf4c6f

fix shutdown

0b8ce97

youknowone force-pushed the atexit branch from ab5fde2 to 0b8ce97 Compare January 17, 2026 14:41

youknowone marked this pull request as ready for review January 17, 2026 16:25

youknowone deleted the atexit branch January 17, 2026 16:54

youknowone changed the title ~~fix atexit~~ Jan 17, 2026

coderabbitai Bot mentioned this pull request Feb 1, 2026

dealloc and finalize_modules #6934

Merged

This was referenced Mar 4, 2026

Stop non-main threads during interpreter finalization #7349

Merged

Fix atexit unraisable exception message format #7399

Merged

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fix finalizing and atexit timing#6626