napi: finalize an aborted threadsafe function without waiting for the other threads' references - #40671
napi: finalize an aborted threadsafe function without waiting for the other threads' references#40671robobun wants to merge 4 commits into
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… other threads' references An aborted threadsafe function only ran its finalizer and dropped its event-loop keepalive once thread_count reached zero. Node finalizes from the abort's dispatch and keeps only the allocation alive for the threads that still hold a reference, since after an abort they are told to make no further calls and may never release. The addon's finalizer now runs before anything is released, while the handle is still valid. The finalizer of the blocked-producers test depended on two producer threads being scheduled within the test's 1000 setImmediate turns, which made it flaky under CI load.
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Included review availability: Your plan provides up to 5 included reviews per hour; 0 remain after this review. WalkthroughChangesThreadSafeFunction finalization now separates JavaScript resource release from allocation destruction. Abort and teardown paths support outstanding thread references, with Node-API tests covering finalization and late release. ThreadSafeFunction finalization
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Suggested reviewers: Merge Risk: 🟡 Moderate · up to The change finalizes aborted threadsafe functions while other references remain, but the new regression test can report success even if its finalization wait times out. Merge readiness is therefore not established until the test asserts the wait completed or the risk is explicitly accepted. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Beyond the inline nit, I also checked the two non-obvious deletions: the self_.unref() dropped from the old destroy path is covered because maybe_queue_finalizer already calls poll_ref.disable() before enqueueing the finalize task; and the removed else if prev_remaining == 1 { schedule_dispatch() } branch in release_locked is subsumed by the new Closed early-return plus dispatch_one finalizing regardless of thread_count. Given this reworks cross-thread allocation ownership for TSFN, a human pass on the lock/ordering in finalize vs. concurrent release_locked would still be worthwhile.
Extended reasoning...
The confirmed finding is a nit-level stale SAFETY comment. Beyond it, two deletions in the diff looked like potential regressions and were checked: (1) the old destroy called unref() before anything else, and finalize does not — but maybe_queue_finalizer (the only path that enqueues the task landing in finalize) already runs poll_ref.disable() first, so the event-loop keepalive is dropped at the same point as before; (2) the else if prev_remaining == 1 { schedule_dispatch() } last-release branch is gone — but a Closed/Closing function now finalizes from the abort's own dispatch, and the new Closed guard in release_locked routes the last releaser to free_orphaned via resources_released instead of scheduling again. The change is a substantive rework of cross-thread ownership and finalization ordering in memory-safety-critical N-API code, so it warrants human review of the finalize lock section against a concurrent release_locked on another thread.
Additional findings (outside the current diff — GitHub can't attach inline comments there):
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src/runtime/napi/napi_body.rs— nit: stale SAFETY comment still referencesdestroy, which this PR removed/renamed tofinalizeExtended reasoning...
src/CLAUDE.md requires SAFETY comments to be accurate; after this change the registry entry is removed by
finalize(andenv_teardown), notdestroy, so the comment names a function that no longer exists — a future reader grepping fordestroyto understand the registry-unregister invariant will find nothing. Update the comment to sayfinalize(the sibling comments at lines 2871 and 3147 that say "env_teardownalready released everything it owned" are also now slightly stale sincefinalizecan be the releaser too).Verification: nit — src/runtime/napi/napi_body.rs:3205-3207 reads: "SAFETY: the registry only holds live TSFN pointers —
destroyandenv_teardownboth remove the entry before freeing." This PR removesThreadSafeFunction::destroy(the diff replacesunsafe fn destroy(this: *mut ThreadSafeFunction)withunsafe fn finalize(this: *mut ThreadSafeFunction)at line 2957; grep confirms the only remaining…
…till said destroy or env_teardown
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Updated the stale comments in 19fa03e: the registry SAFETY note at On the lock ordering between |
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aa71092 shortens the ownership comments the comment check flagged. The ones that remain are the ownership invariant on the struct, the |
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Actionable comments posted: 2
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Inline comments:
In `@test/napi/napi-app/standalone_tests.cpp`:
- Around line 214-222: Update tsfn_abort_outstanding_holder so timing out while
tsfn_abort_outstanding_finalized remains false is published through observable
state, such as a dedicated atomic flag or the existing release-status accessor.
Ensure the JavaScript-side test asserts this state, distinguishing release after
finalization from the timeout case.
In `@test/napi/napi.test.ts`:
- Around line 721-724: Update the test named “runs the finalizer on abort while
another thread still holds a reference” to set an explicit timeout exceeding the
driver’s possible 10-second wait, while preserving its existing checkSameOutput
invocation and assertions.
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Fix all unresolved CodeRabbit comments on this PR:
- Push a commit to this branch (recommended)
- Create a new PR with the fixes
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… its release, and keep the driver under the test timeout
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9d88ba1 addresses the two review findings on the new test:
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Updated 3:42 PM PT - Aug 27th, 2026
❌ @robobun, your commit 9d88ba1 has 3 failures in
🧪 To try this PR locally: bunx bun-pr 40671That installs a local version of the PR into your bun-40671 --bun |
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CI status for 9d88ba1 (build 107054): 177 of 181 jobs passed.
All three are reported to main-break triage. The diff is ready for review. |
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Folded into #39848, which now carries this change together with the |
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Thanks. One check on the fold: the head of #39848 as of 61ebbe8 still gates the closing dispatch on |
…safe functions (#39848) ### Problem - An addon's `napi_finalize` segfaults under `napi_body::Finalizer::run`: Sentry BUN-4MXA and BUN-4NJZ on 1.4.0, and #41055 (libsql under `bun test --parallel`). - `NapiRef::callFinalizer` (`napi.h`) copied the finalizer into the task that runs after the GC, so `napi_delete_reference` in between did not cancel it and it ran on freed memory. Node dequeues it. - `ThreadSafeFunction::destroy` (`napi_body.rs`) freed the function before its finalizer ran. After `napi_tsfn_abort` it also waited for every other thread's reference (#40671), so a holder that never releases pinned the process. ### Fix - `NapiEnv::m_pendingRefFinalizers` (Node's `pending_finalizers`): the GC adds the ref and queues a drain if the set was empty. Each drain takes the first ref, requeues if any remain, then runs its finalizer. `~NapiRef` removes itself, so a deleted reference never finalizes. - `ThreadSafeFunction::finalize` (was `destroy`) runs from the closing dispatch whatever `thread_count` is: the finalizer first, then the JS-thread release under the lock. It frees the allocation if no thread reference is left, else the last release does (Node's `Finalize` + `MaybeDelete`). - Verified: four new tests in `test/napi/napi.test.ts`, compared with Node 26. ### Background - A `NapiRef` backs a `napi_ref`. `napi_wrap` creates one that holds the JS object weakly, and JSC calls it when it sweeps the object. - Outside `NAPI_EXPERIMENTAL` a finalizer may not run inside the GC, so it is queued on the event loop. Node never finalizes a reference deleted before then. - Node finalizes a threadsafe function on the JS thread when it closes and deletes it after the callback, or at the last `thread_count` release. <details><summary>Notes</summary> Branch history. The first version kept a `HashSet` of refs with a queued task each; the maintainer push on this branch replaced it with the `ListHashSet` drain (`NapiEnv::drainOneRefFinalizer`, one ref per event-loop task, the next drain queued before the finalizer runs so a finalizer that deletes or enqueues other refs is plain) and merged #40671 (threadsafe function: finalize on abort without waiting for the other threads, `finalize` replaces `destroy`, `env_teardown_done` renamed `resources_released`). That PR is closed in favour of this one. A `napi_wrap` without a result keeps the copying `callFinalizer()` path: its runtime-owned reference (`NapiRefSelfDeletingWeakHandleOwner`) is deleted right after, so nothing can delete it while the copy is queued. The four tests: `napi_wrap` and `napi_add_finalizer` references deleted in the same turn as the GC, a parent finalizer that deletes children collected by the same GC (in both creation orders), a tsfn finalizer that uses its handle, and (from #40671) a tsfn aborted while another thread still holds a reference. The last one waits for the holder thread by deadline (3 s, the holder gives up after 2 s) so it stays under the default test timeout. Fail before, on release 1.4.0 and on an unfixed ASAN debug build. The fixture's native objects are static and record a finalizer that runs after the delete instead of reading freed memory, so the failure is a clean output mismatch with Node: ``` - napi_wrap: collected before delete: true, finalized after delete: 0 - napi_add_finalizer: collected before delete: true, finalized after delete: 0 + napi_wrap: collected before delete: true, finalized after delete: 1 + napi_add_finalizer: collected before delete: true, finalized after delete: 2 ``` Parent and children (the shape from the report): with the parent created after the children, JSC sweeps the parent's weak handle first, so the parent's queued finalizer ran first and then all 8 child finalizers ran on deleted children (`children finalized after delete: 8`). Created before the children, the children's finalizers ran first and the parent's deletes were plain. The fixture runs both orders. `Bun.gc(true)` is `collectNow(Sync)`, which sweeps synchronously, so the task is queued before `Bun.gc` returns and the same-turn delete is deterministic. A conservative scan can keep an object alive, so each attempt uses a fresh object and the output does not depend on the attempt count. BUN-4NJZ (Windows x64, `bun test`): eight frames inside `index.node`, then `napi_body::Finalizer::run` (`napi_body.rs:2405`, the return address after the callback, which symbolizes as the inlined `napi_internal_remove_finalizer` / `NapiEnv::removeFinalizer` / `BoundFinalizer::BoundFinalizer`), `NapiFinalizerTask::run_on_js_thread`, `dispatch::run_task`. Same shape as BUN-4MXA: the addon's finalizer is what is executing. Drains queued during VM shutdown become cleanup hooks (`NapiFinalizerTask::schedule`); `VirtualMachine::run_cleanup_hooks` repeats while hooks push more, so a chain of drains still runs at exit. The tsfn test on an unfixed ASAN build: ``` ERROR: AddressSanitizer: heap-use-after-free #0 napi_get_threadsafe_function_context src/runtime/napi/napi_body.rs:3290 #1 napitests::tsfn_finalizer_uses_handle standalone_tests.cpp #2 <napi_body::Finalizer>::run napi_body.rs:2403 #3 <NapiFinalizerTask>::run_on_js_thread #4 bun_runtime::dispatch::run_task freed by: ThreadSafeFunction::destroy ``` On a release build the stale read still returns the old context, so that test only fails under ASAN. The two reference tests fail on every build. Experimental modules are unchanged: `callFinalizerFromGC` runs the finalizer during the GC for them, as before. The runtime-owned reference is `NapiRefSelfDeletingWeakHandleOwner` in `napi.cpp`. Other paths checked: - Finalizer deletes its own reference (node-addon-api `ObjectWrap`): `runQueuedFinalizer` takes the ref out of the set before calling, so the delete inside the callback is plain. `test/napi/napi-finalizer-delete-ref.test.ts` covers the experimental variant. - Env cleanup while a finalizer is queued: `wrap_cleanup` runs it at once and clears it. The task later finds the cleared callback and does nothing, so it still runs once. - Task dropped at VM teardown (`has_run_cleanup_hooks`): the entry stays in the set until `~NapiRef` or the env goes away. The set holds the pointer as a key only. - A reused address: set membership means a finalizer is owed, so a drain that reaches a new ref at the same address runs a finalizer that is owed anyway, and the set holds each ref once. - `~NapiRef` does one `ListHashSet::remove`, which returns at once while the env never queued anything. `napi_create_reference` refs never enter the set. - Re-entry from the tsfn finalizer into the function it belongs to: `destroy` holds no borrow and no lock while the callback runs. `napi_release_threadsafe_function` returns `napi_invalid_arg` (`thread_count` is 0) and `napi_unref_threadsafe_function` returns `napi_ok` in both runtimes (asserted by the test). `napi_acquire_threadsafe_function` returns `napi_closing` (`closing` is `Closed`), `napi_call_threadsafe_function` returns `napi_invalid_arg` for the same reason, and `napi_ref_threadsafe_function` is a no-op because `maybe_queue_finalizer` disabled the keepalive. None of them frees the function or schedules it, and `finalizer_fun` was taken, so nothing runs the finalizer twice. Suites run with the debug build: `test/napi/napi.test.ts`, `napi-finalizer-delete-ref.test.ts`, `napi-value-ffi.test.ts`, and the node-napi-tests suites `6_object_wrap`, `7_factory_wrap`, `8_passing_wrapped`, `test_finalizer`, `test_reference`, `test_reference_double_free`, `test_general` (both), `test_instance_data` (both), `test_threadsafe_function`, `test_reference_by_node_api_version`, `test_env_teardown_gc`, `test_worker_terminate_finalization`, `test_buffer`. All pass (a CI-like `--timeout` is needed locally, the default 5 s is too short for the ASAN build). #38506 changes `NapiEnv::inGC()`. `callFinalizerFromGC` calls it, so the two compose. Closes #41055. </details> <!-- robobun:evidence:begin --> --- **no test proof** · iteration 1 · Platform-specific test(s) that do not run on this machine. Deferring to CI, which covers all platforms: test/napi/napi.test.ts <!-- robobun:evidence:end --> --------- Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
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Problem
test/napi/napi.test.ts"wakes blocked producers, runs the finalizer and exits when aborted with a bounded queue" is the most frequent retry-passed failure of that file in CI (30 builds in the last 24 hours, every Linux lane):- "finalized: true/+ "finalized: false.napi_release_threadsafe_function(tsfn, napi_tsfn_abort)in bun ran the finalizer and dropped the event-loop keepalive only oncethread_countreached zero (dispatch_one,src/runtime/napi/napi_body.rs:2713). Node finalizes from the abort's own dispatch (DispatchOne->CloseHandlesAndMaybeDelete->Finalize) and keeps only the allocation alive for the threads that still hold a reference. In the test, the finalizer waited for two producer threads to be scheduled, and the fixture's 1000setImmediateturns (about 3 ms) do not cover that under load.Fix
thread_countis.finalize(replacesdestroy) runs the addon's finalizer while the handle is still valid, then releases the JS-thread resources under the lock, and frees the allocation only if no thread reference is left. Otherwise the lastnapi_release_threadsafe_functionornapi_closingcall frees it, through the same pathenv_teardownalready used (env_teardown_done, renamedresources_released).release_lockednever schedules a dispatch once the function isClosed: the JS thread owns the finalization, so no task can reach the allocation after it is freed.test/napi/napi.test.ts(new test "runs the finalizer on abort while another thread still holds a reference" fails on main withfinalized: false, passes with the fix; all 189 tests pass). The blocked-producers fixture: 1 of 60 runs printedfinalized: falseunder CPU load with the release build, 0 of 160 with the fix.Background
thread_countis the number of threads that hold a reference;napi_tsfn_abortmarks it closing so that further calls reportnapi_closing.poll_ref) keeps the process alive until the function finalizes. The finalizer is the addon callback that frees the context.Finalizeruns the finalizer, thenMaybeDeletereleases the JS resources (ReleaseResources, statekClosed) and deletes the object only whenthread_count == 0; a laterReleaseorPushfrom a remaining thread deletes it otherwise. Bun'sresources_releasedis Node'skClosed.Notes
napi.test.tsappeared in the retry-passed list of 131 builds; the tsfn signature above is 30 of them (Debian 13 x64 16, Debian 13 aarch64 8, Ubuntu 25.04 x64 5, Alpine x64 1). The other two signatures in that file arenapi_wrap has the right lifetime(Windows only, GC observation) andnapi_get_value_string_*timeouts under ASAN.test/napi/napi-app/main.js test_threadsafe_function_abort_blocked_producersin a loop with 32 busy-loop processes, release bun 1.4.1-canary: 1 of 60 runsfinalized: false. Without load 1000setImmediateturns take 3.4 ms in bun.Release(abort)usescond->Signal, so only one blocked producer wakes there; bun keeps itsbroadcast. Node's owntest_threadsafe_functionjoins the producer threads inside the finalizer, which requires the finalizer to run while they are still blocked, as this change does.else if prev_remaining == 1 { schedule_dispatch() }branch ofrelease_lockedis gone: aClosingfunction always has the abort's dispatch pending or running, and that dispatch now finalizes on its own.test/napi/node-napi-tests/test/node-api/test_threadsafe_function/do.test.ts(same result as main:test.jsis todo because ofuv_thread_create).destroytoo (run the finalizer before the free). This change keeps that ordering infinalize; the two will need a manual merge innapi_body.rs.no test proof · iteration 1 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/napi/napi.test.ts