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worker: reset Isolate stack limit after entering Locker #31593

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addaleax wants to merge 4 commits into from
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worker: reset Isolate stack limit after entering Locker #31593

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a1755e3
worker: reset `Isolate` stack limit after entering `Locker`
addaleax Jan 31, 2020
3f8f3d6
fixup! worker: reset `Isolate` stack limit after entering `Locker`
addaleax Feb 1, 2020
cbb2051
fixup! fixup! worker: reset `Isolate` stack limit after entering `Loc…
addaleax Feb 1, 2020
0d30c30
fixup! worker: reset `Isolate` stack limit after entering `Locker`
addaleax Feb 4, 2020
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worker: reset Isolate stack limit after entering Locker 
It turns out that using `v8::Locker` undoes the effects of
passing an explicit stack limit as part of the `Isolate`’s
resource constraints.

Therefore, reset the stack limit manually after entering a Locker.

Refs: #26049 (comment)
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@addaleax
addaleax committed Jan 31, 2020
commit a1755e3aa1888609b2562351f28fd168c03b6209
7 changes: 7 additions & 0 deletions src/node_worker.cc
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Expand Up @@ -157,6 +157,9 @@ class WorkerThreadData {
{
Locker locker(isolate);
Isolate::Scope isolate_scope(isolate);
// V8 computes its stack limit every time a `Locker` is used based on
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// --stack-size. Reset it to the correct value.
isolate->SetStackLimit(w->stack_base_);

HandleScope handle_scope(isolate);
isolate_data_.reset(CreateIsolateData(isolate,
Expand Down Expand Up @@ -242,6 +245,10 @@ void Worker::Run() {
{
Locker locker(isolate_);
Isolate::Scope isolate_scope(isolate_);
// V8 computes its stack limit every time a `Locker` is used based on
// --stack-size. Reset it to the correct value.
isolate_->SetStackLimit(stack_base_);
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SealHandleScope outer_seal(isolate_);

DeleteFnPtr<Environment, FreeEnvironment> env_;
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40 changes: 40 additions & 0 deletions test/parallel/test-worker-stack-overflow-stack-size.js
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@@ -0,0 +1,40 @@
'use strict';
const common = require('../common');
const assert = require('assert');
const { once } = require('events');
const v8 = require('v8');
const { Worker } = require('worker_threads');

// Verify that Workers don't care about --stack-size, as they have their own
// fixed and known stack sizes.

async function runWorker() {
const empiricalStackDepth = new Uint32Array(new SharedArrayBuffer(4));
const worker = new Worker(`
const { workerData: { empiricalStackDepth } } = require('worker_threads');
function f() {
empiricalStackDepth[0]++;
f();
}
f();`, {
eval: true,
workerData: { empiricalStackDepth }
});

const [ error ] = await once(worker, 'error');

common.expectsError({
constructor: RangeError,
message: 'Maximum call stack size exceeded'
})(error);

return empiricalStackDepth[0];
}

(async function() {
v8.setFlagsFromString('--stack-size=500');
const w1stack = await runWorker();
v8.setFlagsFromString('--stack-size=1000');
const w2stack = await runWorker();
assert.strictEqual(w1stack, w2stack);
})().then(common.mustCall());