src: use env->RequestInterrupt() for inspector MainThreadInterface

This simplifies the code significantly, and removes the dependency of
the inspector code on the availability of a `MultiIsolatePlatform`
(by removing the dependency on a platform altogether).

It also fixes a memory leak that occurs when `RequestInterrupt()`
is used, but the interrupt handler is never called before the Isolate
is destroyed.

One downside is that this leads to a slight change in timing, because
inspector messages are not dispatched in a re-entrant way. This means
having to harden one test to account for that possibility by making
sure that the stack is always clear through a `setImmediate()`.
This does not affect the assertion made by the test, which is that
messages will not be delivered synchronously while other code is
executing.

https://github.com/nodejs/node/issues/32415

PR-URL: https://github.com/nodejs/node/pull/32523
Reviewed-By: Matheus Marchini <mat@mmarchini.me>
Reviewed-By: James M Snell <jasnell@gmail.com>

2 files changed, 9 insertions, 37 deletions

diff --git a/src/inspector/main_thread_interface.cc b/src/inspector/main_thread_interface.cc
index 48a964d564f..a15cd52d239 100644
--- a/src/inspector/main_thread_interface.cc
+++ b/src/inspector/main_thread_interface.cc
@@ -1,5 +1,6 @@
 #include "main_thread_interface.h"
 
+#include "env-inl.h"
 #include "node_mutex.h"
 #include "v8-inspector.h"
 #include "util-inl.h"
@@ -85,19 +86,6 @@ class CallRequest : public Request {
   Fn fn_;
 };
 
-class DispatchMessagesTask : public v8::Task {
- public:
-  explicit DispatchMessagesTask(std::weak_ptr<MainThreadInterface> thread)
-                                : thread_(thread) {}
-
-  void Run() override {
-    if (auto thread = thread_.lock()) thread->DispatchMessages();
-  }
-
- private:
-  std::weak_ptr<MainThreadInterface> thread_;
-};
-
 template <typename T>
 class AnotherThreadObjectReference {
  public:
@@ -212,12 +200,7 @@ class ThreadSafeDelegate : public InspectorSessionDelegate {
 }  // namespace
 
 
-MainThreadInterface::MainThreadInterface(Agent* agent, uv_loop_t* loop,
-                                         v8::Isolate* isolate,
-                                         v8::Platform* platform)
-                                         : agent_(agent), isolate_(isolate),
-                                           platform_(platform) {
-}
+MainThreadInterface::MainThreadInterface(Agent* agent) : agent_(agent) {}
 
 MainThreadInterface::~MainThreadInterface() {
   if (handle_)
@@ -225,23 +208,15 @@ MainThreadInterface::~MainThreadInterface() {
 }
 
 void MainThreadInterface::Post(std::unique_ptr<Request> request) {
+  CHECK_NOT_NULL(agent_);
   Mutex::ScopedLock scoped_lock(requests_lock_);
   bool needs_notify = requests_.empty();
   requests_.push_back(std::move(request));
   if (needs_notify) {
-    if (isolate_ != nullptr && platform_ != nullptr) {
-      std::shared_ptr<v8::TaskRunner> taskrunner =
-          platform_->GetForegroundTaskRunner(isolate_);
-      std::weak_ptr<MainThreadInterface>* interface_ptr =
-          new std::weak_ptr<MainThreadInterface>(shared_from_this());
-      taskrunner->PostTask(
-          std::make_unique<DispatchMessagesTask>(*interface_ptr));
-      isolate_->RequestInterrupt([](v8::Isolate* isolate, void* opaque) {
-        std::unique_ptr<std::weak_ptr<MainThreadInterface>> interface_ptr {
-          static_cast<std::weak_ptr<MainThreadInterface>*>(opaque) };
-        if (auto iface = interface_ptr->lock()) iface->DispatchMessages();
-      }, static_cast<void*>(interface_ptr));
-    }
+    std::weak_ptr<MainThreadInterface> weak_self {shared_from_this()};
+    agent_->env()->RequestInterrupt([weak_self](Environment*) {
+      if (auto iface = weak_self.lock()) iface->DispatchMessages();
+    });
   }
   incoming_message_cond_.Broadcast(scoped_lock);
 }
@@ -274,7 +249,7 @@ void MainThreadInterface::DispatchMessages() {
       std::swap(dispatching_message_queue_.front(), task);
       dispatching_message_queue_.pop_front();
 
-      v8::SealHandleScope seal_handle_scope(isolate_);
+      v8::SealHandleScope seal_handle_scope(agent_->env()->isolate());
       task->Call(this);
     }
   } while (had_messages);
diff --git a/src/inspector/main_thread_interface.h b/src/inspector/main_thread_interface.h
index 78337a25e43..3ec5b3db3e1 100644
--- a/src/inspector/main_thread_interface.h
+++ b/src/inspector/main_thread_interface.h
@@ -72,8 +72,7 @@ class MainThreadHandle : public std::enable_shared_from_this<MainThreadHandle> {
 class MainThreadInterface :
     public std::enable_shared_from_this<MainThreadInterface> {
  public:
-  MainThreadInterface(Agent* agent, uv_loop_t*, v8::Isolate* isolate,
-                      v8::Platform* platform);
+  explicit MainThreadInterface(Agent* agent);
   ~MainThreadInterface();
 
   void DispatchMessages();
@@ -98,8 +97,6 @@ class MainThreadInterface :
   ConditionVariable incoming_message_cond_;
   // Used from any thread
   Agent* const agent_;
-  v8::Isolate* const isolate_;
-  v8::Platform* const platform_;
   std::shared_ptr<MainThreadHandle> handle_;
   std::unordered_map<int, std::unique_ptr<Deletable>> managed_objects_;
 };