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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "third_party/blink/renderer/platform/heap/marking_visitor.h"
#include "third_party/blink/renderer/platform/heap/heap.h"
#include "third_party/blink/renderer/platform/heap/thread_state.h"
namespace blink {
std::unique_ptr<MarkingVisitor> MarkingVisitor::Create(ThreadState* state,
MarkingMode mode) {
return std::make_unique<MarkingVisitor>(state, mode);
}
MarkingVisitor::MarkingVisitor(ThreadState* state, MarkingMode marking_mode)
: Visitor(state),
marking_worklist_(Heap().GetMarkingWorklist(),
WorklistTaskId::MainThread),
not_fully_constructed_worklist_(Heap().GetNotFullyConstructedWorklist(),
WorklistTaskId::MainThread),
weak_callback_worklist_(Heap().GetWeakCallbackWorklist(),
WorklistTaskId::MainThread),
marking_mode_(marking_mode) {
DCHECK(state->InAtomicMarkingPause());
#if DCHECK_IS_ON()
DCHECK(state->CheckThread());
#endif // DCHECK_IS_ON
}
MarkingVisitor::~MarkingVisitor() = default;
void MarkingVisitor::ConservativelyMarkAddress(BasePage* page,
Address address) {
#if DCHECK_IS_ON()
DCHECK(page->Contains(address));
#endif
HeapObjectHeader* const header =
page->IsLargeObjectPage()
? static_cast<LargeObjectPage*>(page)->GetHeapObjectHeader()
: static_cast<NormalPage*>(page)->FindHeaderFromAddress(address);
if (!header)
return;
ConservativelyMarkHeader(header);
}
#if DCHECK_IS_ON()
void MarkingVisitor::ConservativelyMarkAddress(
BasePage* page,
Address address,
MarkedPointerCallbackForTesting callback) {
DCHECK(page->Contains(address));
HeapObjectHeader* const header =
page->IsLargeObjectPage()
? static_cast<LargeObjectPage*>(page)->GetHeapObjectHeader()
: static_cast<NormalPage*>(page)->FindHeaderFromAddress(address);
if (!header)
return;
if (!callback(header))
ConservativelyMarkHeader(header);
}
#endif // DCHECK_IS_ON
namespace {
#if DCHECK_IS_ON()
bool IsUninitializedMemory(void* object_pointer, size_t object_size) {
// Scan through the object's fields and check that they are all zero.
Address* object_fields = reinterpret_cast<Address*>(object_pointer);
for (size_t i = 0; i < object_size / sizeof(Address); ++i) {
if (object_fields[i])
return false;
}
return true;
}
#endif
} // namespace
void MarkingVisitor::ConservativelyMarkHeader(HeapObjectHeader* header) {
const GCInfo* gc_info = ThreadHeap::GcInfo(header->GcInfoIndex());
if (gc_info->HasVTable() && !VTableInitialized(header->Payload())) {
// We hit this branch when a GC strikes before GarbageCollected<>'s
// constructor runs.
//
// class A : public GarbageCollected<A> { virtual void f() = 0; };
// class B : public A {
// B() : A(foo()) { };
// };
//
// If foo() allocates something and triggers a GC, the vtable of A
// has not yet been initialized. In this case, we should mark the A
// object without tracing any member of the A object.
MarkHeaderNoTracing(header);
#if DCHECK_IS_ON()
DCHECK(IsUninitializedMemory(header->Payload(), header->PayloadSize()));
#endif
} else {
MarkHeader(header, gc_info->trace_);
}
}
void MarkingVisitor::RegisterWeakCallback(void* object, WeakCallback callback) {
// We don't want to run weak processings when taking a snapshot.
if (marking_mode_ == kSnapshotMarking)
return;
weak_callback_worklist_.Push({object, callback});
}
void MarkingVisitor::RegisterBackingStoreReference(void* slot) {
if (marking_mode_ != kGlobalMarkingWithCompaction)
return;
Heap().RegisterMovingObjectReference(
reinterpret_cast<MovableReference*>(slot));
}
void MarkingVisitor::RegisterBackingStoreCallback(void* backing_store,
MovingObjectCallback callback,
void* callback_data) {
if (marking_mode_ != kGlobalMarkingWithCompaction)
return;
Heap().RegisterMovingObjectCallback(
reinterpret_cast<MovableReference>(backing_store), callback,
callback_data);
}
bool MarkingVisitor::RegisterWeakTable(const void* closure,
EphemeronCallback iteration_callback) {
Heap().RegisterWeakTable(const_cast<void*>(closure), iteration_callback);
return true;
}
} // namespace blink
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