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Fix CppGc leak. #2146

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merged 1 commit into from
May 21, 2024
Merged

Fix CppGc leak. #2146

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24 changes: 16 additions & 8 deletions src/workerd/jsg/setup.c++
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Original file line number Diff line number Diff line change
Expand Up @@ -276,10 +276,8 @@ bool HeapTracer::TryResetRoot(const v8::TracedReference<v8::Value>& handle) {
}

namespace {
static v8::Isolate* newIsolate(
V8PlatformWrapper* system,
v8::Isolate::CreateParams&& params) {
return jsg::runInV8Stack([&](jsg::V8StackScope& stackScope) -> v8::Isolate* {
std::unique_ptr<v8::CppHeap> newCppHeap(V8PlatformWrapper* system) {
return jsg::runInV8Stack([&](jsg::V8StackScope& stackScope) {
v8::CppHeapCreateParams heapParams {
{},
v8::WrapperDescriptor(
Expand All @@ -289,6 +287,13 @@ namespace {
};
heapParams.marking_support = cppgc::Heap::MarkingType::kAtomic;
heapParams.sweeping_support = cppgc::Heap::SweepingType::kAtomic;
return v8::CppHeap::Create(system, heapParams);
});
}
static v8::Isolate* newIsolate(
v8::Isolate::CreateParams&& params,
v8::CppHeap* cppHeap) {
return jsg::runInV8Stack([&](jsg::V8StackScope& stackScope) -> v8::Isolate* {
// We currently don't attempt to support incremental marking or sweeping. We probably could
// support them, but it will take some careful investigation and testing. It's not clear if
// this would be a win anyway, since Worker heaps are relatively small and therefore doing a
Expand All @@ -300,8 +305,10 @@ namespace {
// fully utilized. This differs from browser environments, where a user is typically doing
// only one thing at a time and thus likely has CPU cores to spare.

// v8 takes ownership of the v8::CppHeap when passed this way.
params.cpp_heap = v8::CppHeap::Create(system, heapParams).release();
// V8 *claims* to take ownership of the v8::CppHeap but actually releases ownership of it
// during v8::Isolate::Dispose.
// TODO(soon): submit a bug report/patch to v8.
params.cpp_heap = cppHeap;

if (params.array_buffer_allocator == nullptr &&
params.array_buffer_allocator_shared == nullptr) {
Expand All @@ -316,8 +323,8 @@ namespace {
IsolateBase::IsolateBase(const V8System& system, v8::Isolate::CreateParams&& createParams,
kj::Own<IsolateObserver> observer)
: system(system),
ptr(newIsolate(const_cast<V8PlatformWrapper*>(&system.platformWrapper),
kj::mv(createParams))),
cppHeap(newCppHeap(const_cast<V8PlatformWrapper*>(&system.platformWrapper))),
ptr(newIsolate(kj::mv(createParams), cppHeap.get())),
heapTracer(ptr),
observer(kj::mv(observer)) {
jsg::runInV8Stack([&](jsg::V8StackScope& stackScope) {
Expand Down Expand Up @@ -382,6 +389,7 @@ IsolateBase::IsolateBase(const V8System& system, v8::Isolate::CreateParams&& cre
IsolateBase::~IsolateBase() noexcept(false) {
jsg::runInV8Stack([&](jsg::V8StackScope& stackScope) {
ptr->Dispose();
cppHeap.reset();;
});
}

Expand Down
1 change: 1 addition & 0 deletions src/workerd/jsg/setup.h
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Expand Up @@ -187,6 +187,7 @@ class IsolateBase {
using Item = kj::OneOf<v8::Global<v8::Data>, RefToDelete>;

const V8System& system;
std::unique_ptr<class v8::CppHeap> cppHeap;
v8::Isolate* ptr;
kj::Maybe<kj::String> uuid;
bool evalAllowed = false;
Expand Down
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