src: prepare v8 platform for multi-isolate support

This splits the task queue used for asynchronous tasks scheduled
by V8 in per-isolate queues, so that multiple threads can be supported.

Original-PR-URL: ayojs/ayo#89
Original-Reviewed-By: Timothy Gu <timothygu99@gmail.com>
PR-URL: #16700
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: addaleax

src/env-inl.h

@@ -37,41 +37,9 @@
 
 namespace node {
 
-inline IsolateData::IsolateData(v8::Isolate* isolate, uv_loop_t* event_loop,
-                                uint32_t* zero_fill_field) :
-
-// Create string and private symbol properties as internalized one byte strings.
-//
-// Internalized because it makes property lookups a little faster and because
-// the string is created in the old space straight away.  It's going to end up
-// in the old space sooner or later anyway but now it doesn't go through
-// v8::Eternal's new space handling first.
-//
-// One byte because our strings are ASCII and we can safely skip V8's UTF-8
-// decoding step.  It's a one-time cost, but why pay it when you don't have to?
-#define V(PropertyName, StringValue)                                          \
-    PropertyName ## _(                                                        \
-        isolate,                                                              \
-        v8::Private::New(                                                     \
-            isolate,                                                          \
-            v8::String::NewFromOneByte(                                       \
-                isolate,                                                      \
-                reinterpret_cast<const uint8_t*>(StringValue),                \
-                v8::NewStringType::kInternalized,                             \
-                sizeof(StringValue) - 1).ToLocalChecked())),
-  PER_ISOLATE_PRIVATE_SYMBOL_PROPERTIES(V)
-#undef V
-#define V(PropertyName, StringValue)                                          \
-    PropertyName ## _(                                                        \
-        isolate,                                                              \
-        v8::String::NewFromOneByte(                                           \
-            isolate,                                                          \
-            reinterpret_cast<const uint8_t*>(StringValue),                    \
-            v8::NewStringType::kInternalized,                                 \
-            sizeof(StringValue) - 1).ToLocalChecked()),
-    PER_ISOLATE_STRING_PROPERTIES(V)
-#undef V
-    event_loop_(event_loop), zero_fill_field_(zero_fill_field) {}
+inline v8::Isolate* IsolateData::isolate() const {
+  return isolate_;
+}
 
 inline uv_loop_t* IsolateData::event_loop() const {
   return event_loop_;
@@ -81,6 +49,10 @@ inline uint32_t* IsolateData::zero_fill_field() const {
   return zero_fill_field_;
 }
 
+inline MultiIsolatePlatform* IsolateData::platform() const {
+  return platform_;
+}
+
 inline Environment::AsyncHooks::AsyncHooks(v8::Isolate* isolate)
     : isolate_(isolate),
       fields_(isolate, kFieldsCount),

src/env.cc

@@ -16,10 +16,62 @@ namespace node {
 using v8::Context;
 using v8::FunctionTemplate;
 using v8::HandleScope;
+using v8::Isolate;
 using v8::Local;
 using v8::Message;
+using v8::Private;
 using v8::StackFrame;
 using v8::StackTrace;
+using v8::String;
+
+IsolateData::IsolateData(Isolate* isolate,
+                         uv_loop_t* event_loop,
+                         MultiIsolatePlatform* platform,
+                         uint32_t* zero_fill_field) :
+
+// Create string and private symbol properties as internalized one byte strings.
+//
+// Internalized because it makes property lookups a little faster and because
+// the string is created in the old space straight away.  It's going to end up
+// in the old space sooner or later anyway but now it doesn't go through
+// v8::Eternal's new space handling first.
+//
+// One byte because our strings are ASCII and we can safely skip V8's UTF-8
+// decoding step.  It's a one-time cost, but why pay it when you don't have to?
+#define V(PropertyName, StringValue)                                          \
+    PropertyName ## _(                                                        \
+        isolate,                                                              \
+        Private::New(                                                         \
+            isolate,                                                          \
+            String::NewFromOneByte(                                           \
+                isolate,                                                      \
+                reinterpret_cast<const uint8_t*>(StringValue),                \
+                v8::NewStringType::kInternalized,                             \
+                sizeof(StringValue) - 1).ToLocalChecked())),
+  PER_ISOLATE_PRIVATE_SYMBOL_PROPERTIES(V)
+#undef V
+#define V(PropertyName, StringValue)                                          \
+    PropertyName ## _(                                                        \
+        isolate,                                                              \
+        String::NewFromOneByte(                                               \
+            isolate,                                                          \
+            reinterpret_cast<const uint8_t*>(StringValue),                    \
+            v8::NewStringType::kInternalized,                                 \
+            sizeof(StringValue) - 1).ToLocalChecked()),
+    PER_ISOLATE_STRING_PROPERTIES(V)
+#undef V
+    isolate_(isolate),
+    event_loop_(event_loop),
+    zero_fill_field_(zero_fill_field),
+    platform_(platform) {
+  if (platform_ != nullptr)
+    platform_->RegisterIsolate(this, event_loop);
+}
+
+IsolateData::~IsolateData() {
+  if (platform_ != nullptr)
+    platform_->UnregisterIsolate(this);
+}
 
 void Environment::Start(int argc,
                         const char* const* argv,

src/env.h

@@ -344,10 +344,13 @@ struct node_async_ids {
 
 class IsolateData {
  public:
-  inline IsolateData(v8::Isolate* isolate, uv_loop_t* event_loop,
-                     uint32_t* zero_fill_field = nullptr);
+  IsolateData(v8::Isolate* isolate, uv_loop_t* event_loop,
+              MultiIsolatePlatform* platform = nullptr,
+              uint32_t* zero_fill_field = nullptr);
+  ~IsolateData();
   inline uv_loop_t* event_loop() const;
   inline uint32_t* zero_fill_field() const;
+  inline MultiIsolatePlatform* platform() const;
 
 #define VP(PropertyName, StringValue) V(v8::Private, PropertyName)
 #define VS(PropertyName, StringValue) V(v8::String, PropertyName)
@@ -360,6 +363,7 @@ class IsolateData {
 #undef VP
 
   std::unordered_map<nghttp2_rcbuf*, v8::Eternal<v8::String>> http2_static_strs;
+  inline v8::Isolate* isolate() const;
 
  private:
 #define VP(PropertyName, StringValue) V(v8::Private, PropertyName)
@@ -372,8 +376,10 @@ class IsolateData {
 #undef VS
 #undef VP
 
+  v8::Isolate* const isolate_;
   uv_loop_t* const event_loop_;
   uint32_t* const zero_fill_field_;
+  MultiIsolatePlatform* platform_;
 
   DISALLOW_COPY_AND_ASSIGN(IsolateData);
 };

src/inspector_agent.cc

@@ -309,7 +309,7 @@ class NodeInspectorClient : public V8InspectorClient {
     terminated_ = false;
     running_nested_loop_ = true;
     while (!terminated_ && channel_->waitForFrontendMessage()) {
-      platform_->FlushForegroundTasksInternal();
+      platform_->FlushForegroundTasks(env_->isolate());
     }
     terminated_ = false;
     running_nested_loop_ = false;

src/node.cc

@@ -262,10 +262,10 @@ node::DebugOptions debug_options;
 
 static struct {
 #if NODE_USE_V8_PLATFORM
-  void Initialize(int thread_pool_size, uv_loop_t* loop) {
+  void Initialize(int thread_pool_size) {
     tracing_agent_ =
         trace_enabled ? new tracing::Agent() : nullptr;
-    platform_ = new NodePlatform(thread_pool_size, loop,
+    platform_ = new NodePlatform(thread_pool_size,
         trace_enabled ? tracing_agent_->GetTracingController() : nullptr);
     V8::InitializePlatform(platform_);
     tracing::TraceEventHelper::SetTracingController(
@@ -280,8 +280,8 @@ static struct {
     tracing_agent_ = nullptr;
   }
 
-  void DrainVMTasks() {
-    platform_->DrainBackgroundTasks();
+  void DrainVMTasks(Isolate* isolate) {
+    platform_->DrainBackgroundTasks(isolate);
   }
 
 #if HAVE_INSPECTOR
@@ -306,12 +306,16 @@ static struct {
     tracing_agent_->Stop();
   }
 
+  NodePlatform* Platform() {
+    return platform_;
+  }
+
   tracing::Agent* tracing_agent_;
   NodePlatform* platform_;
 #else  // !NODE_USE_V8_PLATFORM
-  void Initialize(int thread_pool_size, uv_loop_t* loop) {}
+  void Initialize(int thread_pool_size) {}
   void Dispose() {}
-  void DrainVMTasks() {}
+  void DrainVMTasks(Isolate* isolate) {}
   bool StartInspector(Environment *env, const char* script_path,
                       const node::DebugOptions& options) {
     env->ThrowError("Node compiled with NODE_USE_V8_PLATFORM=0");
@@ -323,6 +327,10 @@ static struct {
                     "so event tracing is not available.\n");
   }
   void StopTracingAgent() {}
+
+  NodePlatform* Platform() {
+    return nullptr;
+  }
 #endif  // !NODE_USE_V8_PLATFORM
 
 #if !NODE_USE_V8_PLATFORM || !HAVE_INSPECTOR
@@ -4769,7 +4777,14 @@ int EmitExit(Environment* env) {
 
 
 IsolateData* CreateIsolateData(Isolate* isolate, uv_loop_t* loop) {
-  return new IsolateData(isolate, loop);
+  return new IsolateData(isolate, loop, nullptr);
+}
+
+IsolateData* CreateIsolateData(
+    Isolate* isolate,
+    uv_loop_t* loop,
+    MultiIsolatePlatform* platform) {
+  return new IsolateData(isolate, loop, platform);
 }
 
 
@@ -4854,7 +4869,7 @@ inline int Start(Isolate* isolate, IsolateData* isolate_data,
     do {
       uv_run(env.event_loop(), UV_RUN_DEFAULT);
 
-      v8_platform.DrainVMTasks();
+      v8_platform.DrainVMTasks(isolate);
 
       more = uv_loop_alive(env.event_loop());
       if (more)
@@ -4875,7 +4890,7 @@ inline int Start(Isolate* isolate, IsolateData* isolate_data,
   RunAtExit(&env);
   uv_key_delete(&thread_local_env);
 
-  v8_platform.DrainVMTasks();
+  v8_platform.DrainVMTasks(isolate);
   WaitForInspectorDisconnect(&env);
 #if defined(LEAK_SANITIZER)
   __lsan_do_leak_check();
@@ -4918,7 +4933,11 @@ inline int Start(uv_loop_t* event_loop,
     Locker locker(isolate);
     Isolate::Scope isolate_scope(isolate);
     HandleScope handle_scope(isolate);
-    IsolateData isolate_data(isolate, event_loop, allocator.zero_fill_field());
+    IsolateData isolate_data(
+        isolate,
+        event_loop,
+        v8_platform.Platform(),
+        allocator.zero_fill_field());
     exit_code = Start(isolate, &isolate_data, argc, argv, exec_argc, exec_argv);
   }
 
@@ -4965,7 +4984,7 @@ int Start(int argc, char** argv) {
   V8::SetEntropySource(crypto::EntropySource);
 #endif  // HAVE_OPENSSL
 
-  v8_platform.Initialize(v8_thread_pool_size, uv_default_loop());
+  v8_platform.Initialize(v8_thread_pool_size);
   // Enable tracing when argv has --trace-events-enabled.
   if (trace_enabled) {
     fprintf(stderr, "Warning: Trace event is an experimental feature "

src/node.h

@@ -61,6 +61,7 @@
 #endif
 
 #include "v8.h"  // NOLINT(build/include_order)
+#include "v8-platform.h"  // NOLINT(build/include_order)
 #include "node_version.h"  // NODE_MODULE_VERSION
 
 #define NODE_MAKE_VERSION(major, minor, patch)                                \
@@ -209,8 +210,27 @@ NODE_EXTERN void Init(int* argc,
 class IsolateData;
 class Environment;
 
-NODE_EXTERN IsolateData* CreateIsolateData(v8::Isolate* isolate,
-                                           struct uv_loop_s* loop);
+class MultiIsolatePlatform : public v8::Platform {
+ public:
+  virtual ~MultiIsolatePlatform() { }
+  virtual void DrainBackgroundTasks(v8::Isolate* isolate) = 0;
+
+  // These will be called by the `IsolateData` creation/destruction functions.
+  virtual void RegisterIsolate(IsolateData* isolate_data,
+                               struct uv_loop_s* loop) = 0;
+  virtual void UnregisterIsolate(IsolateData* isolate_data) = 0;
+};
+
+// If `platform` is passed, it will be used to register new Worker instances.
+// It can be `nullptr`, in which case creating new Workers inside of
+// Environments that use this `IsolateData` will not work.
+NODE_EXTERN IsolateData* CreateIsolateData(
+    v8::Isolate* isolate,
+    struct uv_loop_s* loop);
+NODE_EXTERN IsolateData* CreateIsolateData(
+    v8::Isolate* isolate,
+    struct uv_loop_s* loop,
+    MultiIsolatePlatform* platform);
 NODE_EXTERN void FreeIsolateData(IsolateData* isolate_data);
 
 NODE_EXTERN Environment* CreateEnvironment(IsolateData* isolate_data,