heap: Introduce ThreadStateStorage

Splits off the storage parts of ThreadState to allow only including
that in garbage_collected.h which is what users need to define their
GCed objects.

Follow up CLs will remove thread_state.h from anything that doesn't
need to manually invoke GC or set up the heaps.

Bug: chromium:1269227
Change-Id: I191b6fcbf7691ba600ca9567fc741005d6694bad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3298109
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#944879}

third_party/blink/renderer/bindings/core/v8/v8_initializer.cc

@@ -77,6 +77,7 @@
 #include "third_party/blink/renderer/platform/bindings/v8_per_context_data.h"
 #include "third_party/blink/renderer/platform/bindings/v8_per_isolate_data.h"
 #include "third_party/blink/renderer/platform/heap/garbage_collected.h"
+#include "third_party/blink/renderer/platform/heap/thread_state_storage.h"
 #include "third_party/blink/renderer/platform/instrumentation/histogram.h"
 #include "third_party/blink/renderer/platform/instrumentation/tracing/trace_event.h"
 #include "third_party/blink/renderer/platform/runtime_enabled_features.h"
@@ -776,7 +777,7 @@ void V8Initializer::InitializeMainThread(
   // ThreadState::isolate_ needs to be set before setting the EmbedderHeapTracer
   // as setting the tracer indicates that a V8 garbage collection should trace
   // over to Blink.
-  DCHECK(ThreadState::MainThreadState());
+  DCHECK(ThreadStateStorage::MainThreadStateStorage());
 
   InitializeV8Common(isolate);
 

third_party/blink/renderer/platform/heap/BUILD.gn

@@ -52,6 +52,8 @@ blink_platform_sources("heap") {
     "thread_state.cc",
     "thread_state.h",
     "thread_state_scopes.h",
+    "thread_state_storage.cc",
+    "thread_state_storage.h",
     "trace_traits.h",
     "visitor.h",
     "write_barrier.h",

third_party/blink/renderer/platform/heap/garbage_collected.h

@@ -5,11 +5,15 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_GARBAGE_COLLECTED_H_
 #define THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_GARBAGE_COLLECTED_H_
 
-#include "third_party/blink/renderer/platform/heap/thread_state.h"
+#include "third_party/blink/renderer/platform/heap/thread_state_storage.h"
 #include "v8/include/cppgc/allocation.h"
 #include "v8/include/cppgc/garbage-collected.h"
 #include "v8/include/cppgc/type-traits.h"
 
+namespace cppgc {
+class Visitor;
+}  // namespace cppgc
+
 namespace blink {
 
 template <typename T>
@@ -17,12 +21,14 @@ using GarbageCollected = cppgc::GarbageCollected<T>;
 
 using GarbageCollectedMixin = cppgc::GarbageCollectedMixin;
 
+using Visitor = cppgc::Visitor;
+
 // Default MakeGarbageCollected: Constructs an instance of T, which is a garbage
 // collected type.
 template <typename T, typename... Args>
 T* MakeGarbageCollected(Args&&... args) {
   return cppgc::MakeGarbageCollected<T>(
-      ThreadStateFor<ThreadingTrait<T>::kAffinity>::GetState()
+      ThreadStateStorageFor<ThreadingTrait<T>::kAffinity>::GetState()
           ->allocation_handle(),
       std::forward<Args>(args)...);
 }
@@ -34,7 +40,7 @@ using AdditionalBytes = cppgc::AdditionalBytes;
 template <typename T, typename... Args>
 T* MakeGarbageCollected(AdditionalBytes additional_bytes, Args&&... args) {
   return cppgc::MakeGarbageCollected<T>(
-      ThreadStateFor<ThreadingTrait<T>::kAffinity>::GetState()
+      ThreadStateStorageFor<ThreadingTrait<T>::kAffinity>::GetState()
           ->allocation_handle(),
       std::forward<AdditionalBytes>(additional_bytes),
       std::forward<Args>(args)...);

third_party/blink/renderer/platform/heap/heap_allocator_impl.h

@@ -9,6 +9,7 @@
 #include "third_party/blink/renderer/platform/heap/collection_support/heap_vector_backing.h"
 #include "third_party/blink/renderer/platform/heap/garbage_collected.h"
 #include "third_party/blink/renderer/platform/heap/thread_state.h"
+#include "third_party/blink/renderer/platform/heap/thread_state_storage.h"
 #include "third_party/blink/renderer/platform/heap/visitor.h"
 #include "third_party/blink/renderer/platform/heap/write_barrier.h"
 #include "third_party/blink/renderer/platform/platform_export.h"
@@ -60,7 +61,7 @@ class PLATFORM_EXPORT HeapAllocator {
       return;
 
     HeapVectorBacking<T>::FromArray(array)->Free(
-        ThreadStateFor<ThreadingTrait<T>::kAffinity>::GetState()
+        ThreadStateStorageFor<ThreadingTrait<T>::kAffinity>::GetState()
             ->heap_handle());
   }
 
@@ -96,7 +97,7 @@ class PLATFORM_EXPORT HeapAllocator {
       return;
 
     HeapHashTableBacking<HashTable>::FromArray(array)->Free(
-        ThreadStateFor<ThreadingTrait<
+        ThreadStateStorageFor<ThreadingTrait<
             HeapHashTableBacking<HashTable>>::kAffinity>::GetState()
             ->heap_handle());
   }
@@ -109,11 +110,12 @@ class PLATFORM_EXPORT HeapAllocator {
 
   static bool IsAllocationAllowed() {
     return cppgc::subtle::DisallowGarbageCollectionScope::
-        IsGarbageCollectionAllowed(ThreadState::Current()->heap_handle());
+        IsGarbageCollectionAllowed(
+            ThreadStateStorage::Current()->heap_handle());
   }
 
   static bool IsIncrementalMarking() {
-    auto& heap_handle = ThreadState::Current()->heap_handle();
+    auto& heap_handle = ThreadStateStorage::Current()->heap_handle();
     return cppgc::subtle::HeapState::IsMarking(heap_handle) &&
            !cppgc::subtle::HeapState::IsInAtomicPause(heap_handle);
   }
@@ -156,7 +158,7 @@ class PLATFORM_EXPORT HeapAllocator {
     // garbage collected type but may be kept inline.
     switch (HeapConsistency::GetWriteBarrierType(
         slot_in_backing, params, []() -> cppgc::HeapHandle& {
-          return ThreadStateFor<ThreadingTrait<T>::kAffinity>::GetState()
+          return ThreadStateStorageFor<ThreadingTrait<T>::kAffinity>::GetState()
               ->heap_handle();
         })) {
       case HeapConsistency::WriteBarrierType::kMarking:
@@ -181,7 +183,7 @@ class PLATFORM_EXPORT HeapAllocator {
     // garbage collected type but may be kept inline.
     switch (HeapConsistency::GetWriteBarrierType(
         first_element, params, []() -> cppgc::HeapHandle& {
-          return ThreadStateFor<ThreadingTrait<T>::kAffinity>::GetState()
+          return ThreadStateStorageFor<ThreadingTrait<T>::kAffinity>::GetState()
               ->heap_handle();
         })) {
       case HeapConsistency::WriteBarrierType::kMarking:

third_party/blink/renderer/platform/heap/thread_state.cc

@@ -9,6 +9,7 @@
 #include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
 #include "third_party/blink/renderer/platform/bindings/wrapper_type_info.h"
 #include "third_party/blink/renderer/platform/heap/custom_spaces.h"
+#include "third_party/blink/renderer/platform/heap/thread_state_storage.h"
 #include "third_party/blink/renderer/platform/wtf/hash_set.h"
 #include "third_party/blink/renderer/platform/wtf/vector.h"
 #include "v8/include/cppgc/heap-consistency.h"
@@ -86,39 +87,41 @@ class BlinkRootsHandler final : public v8::EmbedderRootsHandler {
 
 }  // namespace
 
-thread_local ThreadState* g_thread_specific_ CONSTINIT
-    __attribute__((tls_model(BLINK_HEAP_THREAD_LOCAL_MODEL))) = nullptr;
-
-// static
-alignas(ThreadState) uint8_t
-    ThreadState::main_thread_state_storage_[sizeof(ThreadState)];
-
-BLINK_HEAP_DEFINE_THREAD_LOCAL_GETTER(ThreadState::Current,
-                                      ThreadState*,
-                                      g_thread_specific_)
-
 // static
 ThreadState* ThreadState::AttachMainThread() {
-  return new (main_thread_state_storage_) ThreadState(gin::V8Platform::Get());
+  auto* thread_state = new ThreadState(gin::V8Platform::Get());
+  ThreadStateStorage::CreateMain(*thread_state,
+                                 thread_state->cpp_heap().GetAllocationHandle(),
+                                 thread_state->cpp_heap().GetHeapHandle());
+  return thread_state;
 }
 
 // static
 ThreadState* ThreadState::AttachMainThreadForTesting(v8::Platform* platform) {
-  ThreadState* thread_state =
+  auto* thread_state = new ThreadState(platform);
-      new (main_thread_state_storage_) ThreadState(platform);
+  ThreadStateStorage::CreateMain(*thread_state,
+                                 thread_state->cpp_heap().GetAllocationHandle(),
+                                 thread_state->cpp_heap().GetHeapHandle());
   thread_state->EnableDetachedGarbageCollectionsForTesting();
   return thread_state;
 }
 
 // static
 ThreadState* ThreadState::AttachCurrentThread() {
-  return new ThreadState(gin::V8Platform::Get());
+  auto* thread_state = new ThreadState(gin::V8Platform::Get());
+  ThreadStateStorage::Create(*thread_state,
+                             thread_state->cpp_heap().GetAllocationHandle(),
+                             thread_state->cpp_heap().GetHeapHandle());
+  return thread_state;
 }
 
 // static
 ThreadState* ThreadState::AttachCurrentThreadForTesting(
     v8::Platform* platform) {
   ThreadState* thread_state = new ThreadState(platform);
+  ThreadStateStorage::Create(*thread_state,
+                             thread_state->cpp_heap().GetAllocationHandle(),
+                             thread_state->cpp_heap().GetHeapHandle());
   thread_state->EnableDetachedGarbageCollectionsForTesting();
   return thread_state;
 }
@@ -153,16 +156,13 @@ ThreadState::ThreadState(v8::Platform* platform)
            v8::WrapperDescriptor(kV8DOMWrapperTypeIndex,
                                  kV8DOMWrapperObjectIndex,
                                  gin::GinEmbedder::kEmbedderBlink)})),
-      allocation_handle_(cpp_heap_->GetAllocationHandle()),
       heap_handle_(cpp_heap_->GetHeapHandle()),
-      thread_id_(CurrentThread()) {
+      thread_id_(CurrentThread()) {}
-  g_thread_specific_ = this;
-}
 
 ThreadState::~ThreadState() {
-  DCHECK(!IsMainThread());
   DCHECK(IsCreationThread());
   cpp_heap_->Terminate();
+  delete ThreadStateStorage::Current();
 }
 
 void ThreadState::SafePoint(StackState stack_state) {

third_party/blink/renderer/platform/heap/thread_state.h

@@ -8,7 +8,7 @@
 #include "base/compiler_specific.h"
 #include "build/build_config.h"
 #include "third_party/blink/renderer/platform/heap/forward.h"
-#include "third_party/blink/renderer/platform/heap/thread_local.h"
+#include "third_party/blink/renderer/platform/heap/thread_state_storage.h"
 #include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
 #include "third_party/blink/renderer/platform/wtf/hash_set.h"
 #include "third_party/blink/renderer/platform/wtf/threading.h"
@@ -22,10 +22,6 @@ namespace v8 {
 class CppHeap;
 }  // namespace v8
 
-namespace cppgc {
-class AllocationHandle;
-}  // namespace cppgc
-
 namespace v8 {
 class EmbedderGraph;
 class EmbedderRootsHandler;
@@ -33,38 +29,10 @@ class EmbedderRootsHandler;
 
 namespace blink {
 
-// ThreadAffinity indicates which threads objects can be used on. We
-// distinguish between objects that can be used on the main thread
-// only and objects that can be used on any thread.
-//
-// For objects that can only be used on the main thread, we avoid going
-// through thread-local storage to get to the thread state. This is
-// important for performance.
-enum ThreadAffinity {
-  kAnyThread,
-  kMainThreadOnly,
-};
-
-template <typename T, typename = void>
-struct ThreadingTrait {
-  STATIC_ONLY(ThreadingTrait);
-  static constexpr ThreadAffinity kAffinity = kAnyThread;
-};
-
-template <ThreadAffinity>
-class ThreadStateFor;
-class ThreadState;
-
 using V8BuildEmbedderGraphCallback = void (*)(v8::Isolate*,
                                               v8::EmbedderGraph*,
                                               void*);
 
-// Storage for all ThreadState objects. This includes the main-thread
-// ThreadState as well. Keep it outside the class so that PLATFORM_EXPORT
-// doesn't apply to it (otherwise, clang-cl complains).
-extern thread_local ThreadState* g_thread_specific_ CONSTINIT
-    __attribute__((tls_model(BLINK_HEAP_THREAD_LOCAL_MODEL)));
-
 class PLATFORM_EXPORT ThreadState final {
  public:
   class NoAllocationScope;
@@ -72,12 +40,8 @@ class PLATFORM_EXPORT ThreadState final {
 
   using StackState = cppgc::EmbedderStackState;
 
-  BLINK_HEAP_DECLARE_THREAD_LOCAL_GETTER(Current,
+  static ALWAYS_INLINE ThreadState* Current() {
-                                         ThreadState*,
+    return &ThreadStateStorage::Current()->thread_state();
-                                         g_thread_specific_)
-
-  static ALWAYS_INLINE ThreadState* MainThreadState() {
-    return reinterpret_cast<ThreadState*>(main_thread_state_storage_);
   }
 
   // Attaches a ThreadState to the main-thread.
@@ -90,16 +54,16 @@ class PLATFORM_EXPORT ThreadState final {
   void AttachToIsolate(v8::Isolate* isolate, V8BuildEmbedderGraphCallback);
   void DetachFromIsolate();
 
-  ALWAYS_INLINE cppgc::AllocationHandle& allocation_handle() const {
-    return allocation_handle_;
-  }
   ALWAYS_INLINE cppgc::HeapHandle& heap_handle() const { return heap_handle_; }
   ALWAYS_INLINE v8::CppHeap& cpp_heap() const { return *cpp_heap_; }
   ALWAYS_INLINE v8::Isolate* GetIsolate() const { return isolate_; }
 
   void SafePoint(StackState);
 
-  bool IsMainThread() const { return this == MainThreadState(); }
+  bool IsMainThread() const {
+    return this ==
+           &ThreadStateStorage::MainThreadStateStorage()->thread_state();
+  }
   bool IsCreationThread() const { return thread_id_ == CurrentThread(); }
 
   void NotifyGarbageCollection(v8::GCType, v8::GCCallbackFlags);
@@ -135,42 +99,17 @@ class PLATFORM_EXPORT ThreadState final {
   static ThreadState* AttachCurrentThreadForTesting(v8::Platform*);
 
  private:
-  // Main-thread ThreadState avoids TLS completely by using a regular global.
-  // The object is manually managed and should not rely on global ctor/dtor.
-  static uint8_t main_thread_state_storage_[];
-
   explicit ThreadState(v8::Platform*);
   ~ThreadState();
 
   std::unique_ptr<v8::CppHeap> cpp_heap_;
   std::unique_ptr<v8::EmbedderRootsHandler> embedder_roots_handler_;
-  cppgc::AllocationHandle& allocation_handle_;
   cppgc::HeapHandle& heap_handle_;
   v8::Isolate* isolate_ = nullptr;
   base::PlatformThreadId thread_id_;
   bool forced_scheduled_gc_for_testing_ = false;
 };
 
-template <>
-class ThreadStateFor<kMainThreadOnly> {
-  STATIC_ONLY(ThreadStateFor);
-
- public:
-  static ALWAYS_INLINE ThreadState* GetState() {
-    return ThreadState::MainThreadState();
-  }
-};
-
-template <>
-class ThreadStateFor<kAnyThread> {
-  STATIC_ONLY(ThreadStateFor);
-
- public:
-  static ALWAYS_INLINE ThreadState* GetState() {
-    return ThreadState::Current();
-  }
-};
-
 }  // namespace blink
 
 #endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_THREAD_STATE_H_

third_party/blink/renderer/platform/heap/thread_state_storage.cc

@@ -0,0 +1,52 @@
+// Copyright 2020 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/thread_state_storage.h"
+
+#include <new>
+
+namespace blink {
+
+thread_local ThreadStateStorage* g_thread_specific_ CONSTINIT
+    __attribute__((tls_model(BLINK_HEAP_THREAD_LOCAL_MODEL))) = nullptr;
+
+// static
+alignas(ThreadStateStorage) uint8_t
+    ThreadStateStorage::main_thread_state_storage_[sizeof(ThreadStateStorage)];
+
+BLINK_HEAP_DEFINE_THREAD_LOCAL_GETTER(ThreadStateStorage::Current,
+                                      ThreadStateStorage*,
+                                      g_thread_specific_)
+
+// static
+void ThreadStateStorage::CreateMain(ThreadState& thread_state,
+                                    cppgc::AllocationHandle& allocation_handle,
+                                    cppgc::HeapHandle& heap_handle) {
+  new (main_thread_state_storage_)
+      ThreadStateStorage(thread_state, allocation_handle, heap_handle);
+}
+
+// static
+void ThreadStateStorage::Create(ThreadState& thread_state,
+                                cppgc::AllocationHandle& allocation_handle,
+                                cppgc::HeapHandle& heap_handle) {
+  new ThreadStateStorage(thread_state, allocation_handle, heap_handle);
+}
+
+ThreadStateStorage::ThreadStateStorage(
+    ThreadState& thread_state,
+    cppgc::AllocationHandle& allocation_handle,
+    cppgc::HeapHandle& heap_handle)
+    : allocation_handle_(allocation_handle),
+      heap_handle_(heap_handle),
+      thread_state_(thread_state) {
+  g_thread_specific_ = this;
+}
+
+ThreadStateStorage::~ThreadStateStorage() {
+  DCHECK(!IsMainThread());
+  g_thread_specific_ = nullptr;
+}
+
+}  // namespace blink

third_party/blink/renderer/platform/heap/thread_state_storage.h

@@ -0,0 +1,123 @@
+// Copyright 2020 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.
+
+#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_THREAD_STATE_STORAGE_H_
+#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_THREAD_STATE_STORAGE_H_
+
+#include <cstdint>
+
+#include "base/compiler_specific.h"
+#include "third_party/blink/renderer/platform/heap/thread_local.h"
+#include "third_party/blink/renderer/platform/platform_export.h"
+#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
+
+namespace cppgc {
+class AllocationHandle;
+class HeapHandle;
+}  // namespace cppgc
+
+namespace blink {
+
+class ThreadState;
+class ThreadStateStorage;
+
+// ThreadAffinity indicates which threads objects can be used on. We
+// distinguish between objects that can be used on the main thread
+// only and objects that can be used on any thread.
+//
+// For objects that can only be used on the main thread, we avoid going
+// through thread-local storage to get to the thread state. This is
+// important for performance.
+enum ThreadAffinity {
+  kAnyThread,
+  kMainThreadOnly,
+};
+
+template <typename T, typename = void>
+struct ThreadingTrait {
+  STATIC_ONLY(ThreadingTrait);
+  static constexpr ThreadAffinity kAffinity = kAnyThread;
+};
+
+// Storage for all ThreadState objects. This includes the main-thread
+// ThreadState as well. Keep it outside the class so that PLATFORM_EXPORT
+// doesn't apply to it (otherwise, clang-cl complains).
+extern thread_local ThreadStateStorage* g_thread_specific_ CONSTINIT
+    __attribute__((tls_model(BLINK_HEAP_THREAD_LOCAL_MODEL)));
+
+// ThreadStateStorage is the explicitly managed TLS- and global-backed storage
+// for ThreadState.
+class PLATFORM_EXPORT ThreadStateStorage final {
+ public:
+  static ALWAYS_INLINE ThreadStateStorage* MainThreadStateStorage() {
+    return reinterpret_cast<ThreadStateStorage*>(main_thread_state_storage_);
+  }
+
+  BLINK_HEAP_DECLARE_THREAD_LOCAL_GETTER(Current,
+                                         ThreadStateStorage*,
+                                         g_thread_specific_)
+
+  ALWAYS_INLINE cppgc::AllocationHandle& allocation_handle() const {
+    return allocation_handle_;
+  }
+
+  ALWAYS_INLINE cppgc::HeapHandle& heap_handle() const { return heap_handle_; }
+
+  ALWAYS_INLINE ThreadState& thread_state() const { return thread_state_; }
+
+  ALWAYS_INLINE bool IsMainThread() const {
+    return this == MainThreadStateStorage();
+  }
+
+ private:
+  static void CreateMain(ThreadState&,
+                         cppgc::AllocationHandle&,
+                         cppgc::HeapHandle&);
+  static void Create(ThreadState&,
+                     cppgc::AllocationHandle&,
+                     cppgc::HeapHandle&);
+
+  // Main-thread ThreadStateStorage avoids TLS completely by using a regular
+  // global. The object is manually managed and should not rely on global
+  // ctor/dtor.
+  static uint8_t main_thread_state_storage_[];
+
+  ThreadStateStorage(ThreadState&,
+                     cppgc::AllocationHandle&,
+                     cppgc::HeapHandle&);
+  ~ThreadStateStorage();
+
+  cppgc::AllocationHandle& allocation_handle_;
+  cppgc::HeapHandle& heap_handle_;
+  ThreadState& thread_state_;
+
+  friend class ThreadState;
+};
+
+template <ThreadAffinity>
+class ThreadStateStorageFor;
+
+template <>
+class ThreadStateStorageFor<kMainThreadOnly> {
+  STATIC_ONLY(ThreadStateStorageFor);
+
+ public:
+  static ALWAYS_INLINE ThreadStateStorage* GetState() {
+    return ThreadStateStorage::MainThreadStateStorage();
+  }
+};
+
+template <>
+class ThreadStateStorageFor<kAnyThread> {
+  STATIC_ONLY(ThreadStateStorageFor);
+
+ public:
+  static ALWAYS_INLINE ThreadStateStorage* GetState() {
+    return ThreadStateStorage::Current();
+  }
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_THREAD_STATE_STORAGE_H_

third_party/blink/renderer/platform/testing/run_all_tests.cc

@@ -37,7 +37,7 @@
 #include "mojo/core/embedder/embedder.h"
 #include "mojo/core/embedder/scoped_ipc_support.h"
 #include "skia/ext/test_fonts.h"
-#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
+#include "third_party/blink/renderer/platform/heap/thread_state.h"
 #include "third_party/blink/renderer/platform/testing/testing_platform_support.h"
 
 namespace {