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worker: move JoinThread() back into exit callback #31468

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worker: move JoinThread() back into exit callback #31468

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d55fac1
worker: move JoinThread() back into exit callback
addaleax Jan 22, 2020
ff3cd57
src: harden running native `SetImmediate()`s slightly
addaleax Jan 22, 2020
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worker: move JoinThread() back into exit callback 
de2c68c moved this call to
the destructor, under the assumption that that would essentially
be equivalent to running it as part of the callback since the
worker would be destroyed along with the callback.

However, the actual code in
`Environment::RunAndClearNativeImmediates()` comes with the subtlety
that testing whether a JS exception has been thrown
happens between the invocation of the callback and its destruction,
leaving a possible exception from `JoinThread()` potentially
unhandled (and unintentionally silenced through the `TryCatch`).

This affected exceptions thrown from the `'exit'` event of the
Worker, and made the `parallel/test-worker-message-type-unknown`
test flaky, as the invalid message was sometimes only received
during the Worker thread’s exit handler.

Fix this by moving the `JoinThread()` call back to where it was
before.

Refs: #31386
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@addaleax
addaleax committed Jan 22, 2020
commit d55fac1fff942695dc34d18b999312d7881d1a8e
3 changes: 1 addition & 2 deletions src/node_worker.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -438,8 +438,6 @@ void Worker::JoinThread() {
}

Worker::~Worker() {
JoinThread();

Mutex::ScopedLock lock(mutex_);

CHECK(stopped_);
Expand Down Expand Up @@ -599,6 +597,7 @@ void Worker::StartThread(const FunctionCallbackInfo<Value>& args) {
[w = std::unique_ptr<Worker>(w)](Environment* env) {
if (w->has_ref_)
env->add_refs(-1);
w->JoinThread();
// implicitly delete w
});
}, static_cast<void*>(w)), 0);
Expand Down
8 changes: 8 additions & 0 deletions test/parallel/test-worker-exit-event-error.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
'use strict';
const common = require('../common');
const { Worker } = require('worker_threads');

process.on('uncaughtException', common.mustCall());

new Worker('', { eval: true })
.on('exit', common.mustCall(() => { throw new Error('foo'); }));