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WalkthroughWorker shutdown now forbids script execution before VM termination, discards pending microtasks and ChangesWorker shutdown
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Reproduced on main (74c2457) and on the 1.4.0 canary: the worker entry Fix and tests are in this PR (#38016). The ten new tests fail on main and pass with the change; the worker_threads fixtures print the expected results under Node v26. |
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I reviewed this PR and didn't find any bugs. Because it changes worker VM termination semantics — setting JSC's execution-forbidden flag earlier and reordering set_requested_terminate vs exit_called in WebWorker::exit() — a human look at the lifecycle/race implications would still be worthwhile.
Checked: stop_script() runs after 'exit' handlers on both the process.exit() and on_unhandled_rejection paths, so those handlers aren't blocked by the new execution-forbidden flag. Verified node_process.rs is the sole caller of WebWorker::exit(), so the return-type change is contained. Traced the nested process.exit(7)-inside-process.exit(3) case through the new first gate — inner call reaches reallyExit first, stores 7, outer returns false and doesn't overwrite. Noted that exit_called is now only set when the worker's exit is the first stop request, which changes stopped_by_parent() in the parent-terminate()-wins-then-worker-calls-process.exit() race — this appears intentional per the "first request wins" reasoning and symmetric with request_termination.
Extended reasoning...
Overview
Adds VirtualMachine::stop_script() (VmHandle gate + JSC's setExecutionForbidden), calls it from the two worker self-stop sites (WebWorker::exit, on_unhandled_rejection) instead of a bare handle().stop(), and gates the exit-code store in Bun__Process__exit on WebWorker::exit()'s new bool return (whether this call is the first stop request). WebWorker::exit() now swaps requested_terminate before setting exit_called, and only sets exit_called when it wins that swap. VmHandle.rs is a comment-only change. Eight new tests across worker_threads and Web Worker.
Security risks
None identified. This is worker-thread lifecycle/exit-code plumbing; no auth, crypto, untrusted-input parsing, or path handling touched.
Level of scrutiny
High. Worker termination is concurrency-sensitive and shares state (requested_terminate, exit_called, terminated_by_parent) between the parent thread's request_termination and the worker thread's exit(). Setting JSC's execution-forbidden flag earlier is a one-way VM-wide state change now applied while user script is still on the stack; the PR's argument that the only in-JSC consumer is the microtask checkpoint is load-bearing and worth a maintainer confirming.
Other factors
- The
exit_calledsemantics shift (from "any process.exit() ran" to "process.exit() made the first stop request") flows intostopped_by_parent()and thence into what exit code the parent observes whenterminate()andprocess.exit()race. The PR calls this out as intentional symmetry withrequest_termination, and it does look more Node-consistent, but it is an observable change in a race not directly covered by the new tests. - Tests are thorough (eval/CJS/ESM entries, event-callback path, promise-reaction path, uncaught error, nested exit) and use SharedArrayBuffer to record what actually ran rather than relying on stdout ordering. All stated to fail on main and match Node v26.
- The one existing consumer of
exit_calledI traced (spin()'s "don't clobber process.exit's code on load failure") is unaffected: it readsexit_calledonly after the entry-point load returned an error, on the worker thread, where no parent-terminate race applies to that check's purpose. - No CODEOWNER file conflicts noted; CI build was still in progress at review time.
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robobun
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I reviewed this PR and didn't find any bugs. The fix is well-reasoned and thoroughly tested (ten new subprocess tests covering eval/CJS/ESM entries, event-callback and promise-reaction stops, parent-side terminate(), and nested process.exit(), all cross-checked against Node), but it touches the worker VM's stop path and GlobalObject::drainMicrotasks() — the checkpoint every callback goes through, on the main thread as well as workers — so a maintainer familiar with the VmHandle gate / JSC execution-forbidden interaction should still take a look.
What was reviewed:
drainMicrotasks()early-discard: confirmedclientData(vm)->scriptAllowed()andexecutionForbidden()only go false on the main thread during teardown, so the new branch is worker-only in practice;JSNextTickQueue::discardanddefaultMicrotaskQueue().clear()are the same operationsprepareForDestructionperforms.WebWorker::exit()now gatingexit_calledon being the first stop request: traced the effect onstopped_by_parent()— aprocess.exit()that runs after a parent'sterminate()already claimedrequested_terminateno longer marksexit_called, so the worker reports as parent-stopped, which matches Node (that script would not have run there).Bun__Process__exitno longer overwritingexit_handler.exit_codeon repeat calls; the main-thread branch is unchanged.
Extended reasoning...
Overview
The PR fixes two Node-compat defects in worker termination: (1) microtasks / process.nextTick callbacks queued before a worker's stop request (its own process.exit(), an uncaught error, or a parent's terminate()) still ran after it, and (2) a nested process.exit(n) from an 'exit' handler was overwritten by the outer call's code. It adds VirtualMachine::stop_script() (stop the VmHandle gate + set JSC's executionForbidden) and calls it from both worker-side stop sites before firing the termination trap; adds an early-discard branch to GlobalObject::drainMicrotasks() gated on the same two flags; and makes WebWorker::exit() return whether it was the first stop request so Bun__Process__exit only stores the code then.
Security risks
None. No untrusted-input parsing, no auth/crypto, no new external surface.
Level of scrutiny
High. drainMicrotasks() is the microtask checkpoint that runs after every callback on every thread, including the main thread — a wrong condition there would silently drop microtasks in normal operation. The worker stop path is cross-thread (parent's request_termination and the worker's own exit() share requested_terminate), and the change alters when exit_called is set, which flows into stopped_by_parent() and thence into whether 'exit' handlers run and what exit code is reported. I traced these and found the change consistent with the stated Node semantics, but this is exactly the class of change where a maintainer who owns the #37075 gate design should confirm the intent.
Other factors
- The comment-cop bot fired on comment length; the author shortened them in 6cf00a0 and all threads are resolved.
- Test coverage is strong: subprocess-based (so uncaught-error paths are the worker's parent's 'error' event, not the test file's), records what ran in a
SharedArrayBufferread after 'exit', covers eval /.cjs/.mjs, top-level / event-callback / promise-reaction / uncaught-error / parent-terminate stop points, and the nested-exit code case. All stated to fail on main and match Node v26. - CI build #94612 was still building at the time the timeline was captured; result not visible here.
- #32386 (linked as a possible duplicate) is called out in the description as an earlier attempt against pre-#37075 code that no longer applies.
…rocess.exit() / uncaught error) (#38483) ### Problem - In a `worker_threads` Worker (or Web `Worker`) whose loop is kept alive by something like a `parentPort` `'message'` listener, `process.exit()` called from a `setImmediate` callback (or from a `nextTick`/microtask that callback queued), and likewise an uncaught exception thrown from one, does not end the worker promptly. The parent's `'exit'` event arrives about 680ms later on 1.4.0 release (about 900ms on a debug build); the same exit from a `setTimeout` callback or a message listener takes ~3ms. - The delay is "until something unrelated wakes the worker's loop": by default that is the idle GC timer (1s period, 30s once it has backed off after 30 idle fires). With `BUN_GC_TIMER_DISABLE=1` the worker never exits at all; the parent process hangs. - Cause: the worker's two self-stop sites, `WebWorker::exit()` (`src/jsc/web_worker.rs:1088`, reached from `Bun__Process__exit`) and the uncaught-error hook `on_unhandled_rejection` (`src/jsc/web_worker.rs:1282`), set `requested_terminate`, stop the VM handle and arm the JSC termination trap, but do not wake the loop. A parent's `worker.terminate()` goes through `VmHandle::request_termination()` (`src/jsc/VmHandle.rs:387`), which does the same three things plus `wakeup()`. - Why only immediates: `spin()` (`web_worker.rs:933`) checks `requested_terminate` after `tick()` and after `auto_tick_active()`. Immediates run at the top of `auto_tick_active()` (`src/runtime/jsc_hooks.rs:1134`), which then computes the poll timeout from the timer heaps and blocks in `tick_with_timeout()`; the flag is only re-read once that poll returns. Timer and I/O callbacks run after the poll, so their exits are seen right away. With a keep-alive and an empty timer heap, `get_timeout()` asks for an unbounded wait. ### Fix - Both self-stop sites call `handle_ref().request_termination()`, the same request a parent's `terminate()` makes: stop the handle, arm the trap, wake the loop. The wake is a write to the loop's wakeup fd (eventfd / mach port / `uv_async_send`), so the poll that follows returns at once and `spin()` sees the flag. Nothing else about the stop changes: `stop()` and `notify_need_termination()` are what these sites already did, in the same order. - Correct because the wake goes through the mechanism the parent-side stop has always used (the worker's loop is already woken from another thread on `terminate()`); waking the loop from its own thread is the same eventfd write, and a wake that turns out to be unnecessary (no keep-alive, so the poll was non-blocking anyway) is harmless, exactly as it is today for a `terminate()` that lands while the worker is idle. - Debug build, `BUN_GC_TIMER_DISABLE=1`: exit from an immediate went from never exiting to ~165ms (the same as an exit from a timer callback, i.e. plain teardown cost); with the GC timer on, ~900ms to ~165ms. Release numbers in the details below. - Verified: - `test/js/node/worker_threads/worker_threads.test.ts`, new `describe` "a worker that stops itself from an immediate exits right away" (3 rows: `process.exit()`, `process.exit()` from a `nextTick` the immediate queued, an uncaught exception). Each runs with `BUN_GC_TIMER_DISABLE=1`, so without the `src/` change the worker never exits and all three rows time out (confirmed on a build without it); with it they pass. Whole file: 132 pass. - `test/js/web/workers/worker.test.ts`, `worker-terminate-lifetime.test.ts`, `worker-terminate-funnels.test.ts`, `worker-late-completion.test.ts`, `worker_destruction.test.ts`, `worker-top-level-await.test.ts`, `worker-async-dispose.test.ts`, `worker-shutdown-post-leak.test.ts`: the only failures are identical on a build without this change (the fs `Binding` LSan report that #35159 addresses, and 5s timeouts of tests that boot many workers on a debug/ASAN build). - 24 upstream `test-worker-*` exit / uncaught / terminate tests under `test/js/node/test/parallel`: all pass. - Not covered here: a promise rejected (not thrown) inside an immediate is still only reported after the next loop wakeup, on the main thread as well. That has a different cause (rejections are not examined between the immediate phase and the poll) and is tracked separately; #37981 is adjacent to it. - #38016 edits the same two sites for a different bug (discarding queued work after the stop); the two changes compose, whichever lands second just calls both. ### Background - Worker run loop: `WebWorker::spin()` loops `tick()` (runs queued tasks and microtasks) then `auto_tick_active()` (runs the immediates queued for this turn, computes how long the loop may sleep from the timer heaps, blocks in the uSockets/libuv poll, then runs due timers). It breaks out and tears the VM down when `requested_terminate` is set; that flag is checked between those two calls, never inside them. - `requested_terminate` and `VmHandle`: a worker is stopped by setting the `WebWorker`'s `requested_terminate` flag (what `spin()` polls) and making the VM stop running script: `VmHandle::stop()` closes the gate every native-to-JS entry consults, and `notify_need_termination()` arms JSC's trap so script already on the stack unwinds with a `TerminationException`. `VmHandle::request_termination()` bundles those two with a loop wakeup, and is what the parent thread's `terminate()` calls; this PR makes the worker's own exit paths call it too. - Loop wakeup: every uSockets loop has an async handle (an eventfd on Linux, a mach port on macOS, a `uv_async_t` on Windows) registered in its poll set. `wakeup()` signals it, so a blocked poll returns immediately and a poll entered afterwards returns without blocking. It works the same whether signalled from another thread or from the loop's own thread before it polls. - Idle GC timer (`GarbageCollectionController`): a per-VM repeating timer that runs a GC every 1s (30s after the heap has been stable for 30 fires); `BUN_GC_TIMER_DISABLE=1` turns it off. It is normally what bounded this bug at about a second, which is why the new tests disable it: without it a worker stuck in the poll stays stuck, so the tests hang rather than pass slowly on a build without the fix. <details> <summary>Measurements (time from the worker's postMessage right before the stop to the parent's 'exit' event)</summary> Release 1.4.0, linux x64, worker kept alive by a `parentPort` listener, before this change: | shape | default | `BUN_GC_TIMER_DISABLE=1` | |---|---|---| | `process.exit()` from an immediate scheduled 300ms in | 679ms | never exits | | `throw` from that immediate | 679ms (code 1) | never exits | | `process.exit()` from a nextTick queued by that immediate | 680ms | never exits | | `process.exit()` from a microtask queued by that immediate | 682ms | never exits | | `process.exit()` from a `setTimeout` callback | 4ms | 3ms | | `throw` from a `setTimeout` callback | 4ms | 5ms | | `process.exit()` from a `parentPort` message listener | 4ms | 4ms | | immediate scheduled synchronously at startup | ~104ms | ~103ms (a JSC startup timer happens to fire then) | Scanning the immediate's scheduling delay with the GC timer disabled (release): 0ms to 100ms after startup the exit piggybacks on a one-shot startup timer (106ms, 79ms, 54ms, 32ms, 4ms), from 150ms on it never exits. The debug build behaves the same (last startup timer at about 150ms), which is what the 300ms in the new tests is sized against. Debug build after this change, all immediate shapes: 162ms to 195ms, the same as the timer shapes (161ms to 168ms) on that build. The `Promise.reject` shape is unchanged (910ms / never), see the last Fix bullet. </details> --------- Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
…xit() wins A worker's own stop request (WebWorker::exit, on_unhandled_rejection) closed the VmHandle gate but left JSC's execution-forbidden flag clear. JSC's microtask checkpoints consult only that flag, so the promise reactions and queueMicrotask callbacks queued before the request still ran: at the checkpoint inside the request itself (JSC__VM__notifyNeedTermination releases the API lock to fire the trap, and the release drains), and at the dispatcher's post-callback drain once it had caught and cleared the termination that unwound the callback. Node runs nothing queued before Stop(env). Add VirtualMachine::stop_script(), which stops the handle and sets the flag, and use it at both sites, so every checkpoint from the request on discards the queue, as teardown's forbid_script() already does. Bun__Process__exit also stored the code on every call in a worker, so the reallyExit of an outer process.exit(3) overwrote the process.exit(7) an 'exit' handler made inside it (Node: 7). WebWorker::exit() now reports whether it made the first stop request and only that call's code is stored; it still stops script on every call.
…op was requested The execution-forbidden flag covers JSC's own checkpoints, but Bun's checkpoint drains the nextTick queue itself, through a plain JSC::call, and is reached with no termination pending after an event listener requested the stop (its dispatcher caught and cleared the termination that unwound it) or when a parent's terminate() unwound the listener: a nextTick queued before process.exit() in an onmessage handler still ran, and everything queued before a terminate() that landed inside a handler still ran. Gate the drain on the flag and on the VM handle, discarding both queues as prepareForDestruction() does, and return the ordinary "nothing ran" result. Tests now queue a nextTick as well, cover terminate() landing inside an event callback, and the Web Worker case also exits from an onmessage handler.
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Inline comments:
In `@test/js/web/workers/worker.test.ts`:
- Around line 456-461: Bound the polling loop around received in the worker test
with an explicit deadline or iteration limit, and assert clearly when the limit
is exceeded before continuing. Preserve the existing polling behavior and
subsequent timer-interleaving check when a message arrives.
- Around line 1-10: Update the timeout configuration near setDefaultTimeout to
import isASAN and use isASAN || isDebug when selecting the 90-second timeout,
preserving the existing 10-second default for other builds.
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Inline comments:
In `@test/js/web/workers/worker.test.ts`:
- Around line 458-462: Update the polling deadline logic around the received
check to use performance.now() for both deadline creation and timeout
comparison, preserving the existing debug/ASAN durations and polling behavior.
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| // nothing here depends on the dying thread delivering anything; the parent is | ||
| // a subprocess so that the worker's uncaught error is its parent's 'error' | ||
| // event and not this test's. The fixtures print the same results under Node. | ||
| describe("stopping a worker discards what it queued before the request", () => { |
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🔴 Commit 9f16c5e ("monotonic clock for the flood poll deadline") silently reverted the entire src/ implementation — stop_script(), the drainMicrotasks guard, the WebWorker::exit() return, and the Bun__Process__exit change are all gone; git diff <merge-base>..HEAD -- src/ is now empty and only the two test files remain. The ten new tests here assert behavior the PR description says fails on main, so merging as-is will break CI. Restore the src/ portion of caa9afd + 1630718 + 695be75 (or revert the src/ deletions in 9f16c5e).
Extended reasoning...
What the bug is
The final commit on this branch, 9f16c5e, has the message "worker.test.ts: monotonic clock for the flood poll deadline" and does make that two-line change (Date.now() → performance.now() in worker.test.ts). But its diffstat also shows five src/ files touched with net-negative deltas:
src/jsc/VirtualMachine.rs | 11 -----------
src/jsc/VmHandle.rs | 10 +++++-----
src/jsc/bindings/ZigGlobalObject.cpp | 11 -----------
src/jsc/web_worker.rs | 35 ++++++-----------------------------
src/runtime/node/node_process.rs | 9 ++++-----
test/js/web/workers/worker.test.ts | 4 ++--
Those deletions are exactly the implementation added in caa9afd, 1630718 and 695be75: VirtualMachine::stop_script(), the vm.executionForbidden() || !clientData(vm)->scriptAllowed() guard in GlobalObject::drainMicrotasks(), the WebWorker::exit() -> bool change with its stop_script() calls, and the first-request-wins store in Bun__Process__exit. The commit message gives no hint that source was touched — this looks like an accidental git checkout <base> -- src/ (or a bad rebase/amend) folded into the two-line clock tweak.
Step-by-step proof
git show --stat 9f16c5e3lists 6 files: the 2-line test change plus 5src/files with 63 lines deleted / 17 added.git diff 3cf31495..HEAD --stat -- src/(3cf3149 is the merge base) prints nothing —src/is byte-identical to main.git diff 3cf31495..HEAD --name-onlylists onlytest/js/node/worker_threads/worker_threads.test.tsandtest/js/web/workers/worker.test.ts.git grep -n stop_script src/finds nothing — the method the PR description says it adds does not exist in the tree.- GitHub's PR diff API agrees: only the two test files are changed.
So the PR as it will merge is ten new tests + zero implementation.
Why existing code doesn't prevent it
The PR description itself states that all eight cases in the new describe("stopping a worker discards what it queued before the request") block fail on main (as [1,4,2,3] / [4,2,3] / [1,2,3] / exit code 3), and that both test.each cases in worker.test.ts fail on main. Since src/ at HEAD is now identical to src/ at the merge base, those tests will fail exactly the same way after merge. Robobun's own comment on this PR ("Reproduced on main… The ten new tests fail on main and pass with the change") confirms the tests need the implementation.
Impact
Merging this PR will land ten failing tests on main and turn CI red. The runtime behavior the PR title and description promise (discard queued work at worker stop; first process.exit() wins) will not ship — nothing outside the test suite changes.
How to fix
Restore the source changes. Either:
git revert --no-commit 9f16c5e3 -- src/(keep the two-line test tweak, drop only the accidentalsrc/reverts), or- re-apply the
src/portion of caa9afd + 1630718 + 695be75 on top of HEAD.
Then re-verify git diff <merge-base>..HEAD -- src/ shows the five files, rg stop_script src/ finds the method, and bun bd test worker_threads.test.ts worker.test.ts passes.
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Heads up for whoever picks this branch up again: the last push, 9f16c5e ("worker.test.ts: monotonic clock for the flood poll deadline"), also removed the src/ half of this PR ( For reference, the behaviour this PR targets (nothing queued before a worker's |
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Superseded by the fix that landed on main in #38660 (worker teardown round 3). It stops a worker's VM with take-at-landing termination, and |
Problem
worker_threadsfile, CJS,eval: true, and WebWorkeralike), what was queued beforeprocess.exit()still runs after it. Repro, as the worker's entry:ran after exitand the parent's'exit'event gets42; Node prints nothing and reports0. Same for microtasks queued before an uncaught error in a callback, forprocess.nextTickqueued before aprocess.exit()made inside an event listener, and for everything queued before a parent'sterminate()that lands while a listener is running (Node: nothing runs afterStop(env)). The main thread already behaves like Node; Worker / worker_threads: WebCore-shaped lifetimes, joined threads, one ordered VM teardown #37075 intended workers to as well.WebWorker::exit()andon_unhandled_rejection,src/jsc/web_worker.rs) callshandle().stop(), which closes the gate Bun's native to JS entries consult, but leaves JSC's execution-forbidden flag clear, and JSC's microtask checkpoints consult only that flag. The first such checkpoint is inside the request itself:JSC__VM__notifyNeedTermination(src/jsc/bindings/bindings.cpp) releases the API lock to fire the trap, andJSLock::willReleaseLockdrains when that is the outermost lock (top-level code, timers, promise reactions).GlobalObject::drainMicrotasks()(src/jsc/bindings/ZigGlobalObject.cpp), consults neither the gate nor the flag for the nextTick queue, which it runs through a plainJSC::call. Event dispatch (MessagePort,parentPort,self.onmessage) runs it after each listener, by which time the listener's dispatcher has caught and cleared the termination that unwound the listener, so nothing stops it: a nextTick queued beforeprocess.exit()in a listener ran, and after aterminate()that unwound a listener, nextTicks and microtasks both ran.Bun__Process__exit(src/runtime/node/node_process.rs) stores the code on every call. In a worker it returns, so the outerprocess.exit(3)still reaches its ownreallyExitafter an'exit'handler calledprocess.exit(7)inside it, and the worker exits 3. Node exits 7: the thread stops at the firstreallyExit.Fix
VirtualMachine::stop_script()(new,src/jsc/VirtualMachine.rs): stop the handle and set JSC's execution-forbidden flag; both worker stop sites use it, before firing the trap. This is what teardown'sforbid_script()already does to the VM, applied when the worker commits to stopping, minus the module-registry teardown that has to wait for the stack to unwind. Inside JSC the flag is consulted only by the microtask checkpoints, which then clear their queue, so this is exactly the wanted change and nothing else; Bun's other readers of it (Bun__JSValue__call,isJSExecutionForbidden) already refuse on the stopped handle. WebCore likewise forbids execution on the VM when a worker is told to stop.GlobalObject::drainMicrotasks(): when the flag is set or the handle is stopped, discard the nextTick queue and clear the microtask queue (the same two operationsprepareForDestruction()performs at teardown) and return the ordinary result. The handle is the Worker / worker_threads: WebCore-shaped lifetimes, joined threads, one ordered VM teardown #37075 gate every other native to JS entry already tests (one byte load); the drain was the one entry that did not, which is also why the parent-terminate()case leaked. Returning the ordinary result is deliberate: the "terminated" result promises callers a pending termination exception and makesEventLoop::exit_maybe_drain_microtasksskip its bookkeeping, and nothing was terminated here. The handle never reopens and the flag is one-way, so discarding at this point is the same state teardown would reach.'exit'handlers are unaffected:process.exit()runs them before reaching this point, and the uncaught-error path runs them before it too; a terminated worker runs none, as before.WebWorker::exit()returns whether it made the first stop request (the same flag a parent'sterminate()claims inrequest_termination, so the two directions are symmetric), andBun__Process__exitstores the code only then. It still stops script on every call, since a later call that did run (the outerprocess.exit()above) has to be unwound as well. Matches Node's exit code in the nested case. The other order, aprocess.exit()after the parent'sterminate()already claimed the stop, normally never gets this far (the first exception check insideprocess.exit()fires the pending trap); if a native caller does get here, theterminate()keeps its exit code, as in Node, where that script would not have run at all. Not separately testable without instrumentation, hence no test for it.test/js/node/worker_threads/worker_threads.test.ts, newdescribe("stopping a worker discards what it queued before the request"): each fixture queues a promise reaction, aqueueMicrotaskcallback and anextTick, then stops the worker:process.exit()at the top level of eval /.cjs/.mjsentries, inside an event callback, inside a promise reaction, an uncaught error inside a callback, a parentterminate()landing inside an event callback, and the nestedprocess.exit()exit code. Fixtures run in a subprocess and record what ran in aSharedArrayBuffer; all eight fail on main (the event rows as[1,4,2,3]/[4,2,3], the others as[1,2,3]or exit code 3) and produce the expected output under Node v26 (the same fixtures run withnode).test/js/web/workers/worker.test.ts: the WebWorkerflavour, exiting from the top level and fromself.onmessage; both fail on main.worker_threads.test.ts(130),worker-terminate-funnels,worker-refused-completion,message-port-pipe,message-channel,vm.test.ts,process.test.js, the main-thread teardown tests that setBUN_DESTRUCT_VM_ON_EXIT, and 26 vendoredtest-worker-*exit / uncaught / terminate tests pass. The remaining local failures are the same with and without the change on a debug build: tests sitting at their 5 s budget with debug worker startup, the knownnode:fsbinding LSan leak onterminate(), andUSERbeing unset here.request_termination()(which wakes the loop) right afterstop_script(), instead of a rawnotifyNeedTermination; nothing else about the fix changed.worker.test.tswere flaking on slow debug/ASAN machines with or without this change: the file now sets the same debug-aware default timeoutworker_threads.test.tsuses, and the message-flood test polls until the flood reaches the parent instead of counting three fixed timer turns (worker startup outlasts them under ASAN).process.exitCode = nassigned inside an'exit'handler duringprocess.exit(m)still exitsmon the main thread and in workers (Node re-reads it); that is process: match Node exit code semantics; fix node:events captureRejections #32814's. worker: drop queued microtasks after an uncaught error or process.exit #32386 was an earlier attempt at the first half against the pre-Worker / worker_threads: WebCore-shaped lifetimes, joined threads, one ordered VM teardown #37075 worker code and no longer applies.Background
VmHandlegate (VmHandle::stop()/script_allowed(), added by Worker / worker_threads: WebCore-shaped lifetimes, joined threads, one ordered VM teardown #37075) is Bun's: every native to JS entry Bun controls (timers, listeners, completions) checks it, any thread may close it, and C++ reads it as one byte throughclientData(vm)->scriptAllowed(). The execution-forbidden flag is JSC's own (VM::setExecutionForbidden(), one-way); inside JSC it is what makes a microtask checkpoint clear its queue rather than run it. Teardown (forbid_script()) sets both; until this change the worker's own stop request set only the gate, and the drain read neither.queueMicrotaskcallbacks run.GlobalObject::drainMicrotasks()is Bun's: it runs theprocess.nextTickqueue (a Bun structure,JSNextTickQueue, drained by calling into JS) and then JSC's queue; Bun's event loop and its event dispatchers run it after every callback. JSC additionally runs a checkpoint of its own whenever the outermost API lock is released.notifyNeedTermination) makes the running script throw an uncatchable termination exception at its next check. Forprocess.exit()that check is the one right afterreallyExitreturns insideprocess.exit()itself, so the calling script is unwound at once; forterminate()it is the next loop iteration or call. Code that catches exceptions from a callback (event dispatch, the emitter that runs'exit'handlers) clears that exception like any other and carries on with its post-callback work, which is how a checkpoint can run after the stop with nothing pending.process.exit(code)issetExitCode+ emit'exit'+reallyExit(code);reallyExitisBun__Process__exit, which exits the process on the main thread and, in a worker, requests the thread's stop and returns.