From c9fbc05bbca803032914be4b38ac4c9608852963 Mon Sep 17 00:00:00 2001
From: Benoit Girard <bgirard@meta.com>
Date: Mon, 8 Jul 2024 12:20:11 -0700
Subject: [PATCH] Register Thread For Hermes Sampling (#45331)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/45331

Let's add the a new JSRuntime API  to register the thread. This allows Hermes sampling to correctly work in Bridgeless/Activity.

## Changelog:
[General][Added] - Add experimental api to JSRuntimeFactory to initialize runtime on js thread

Reviewed By: RSNara

Differential Revision: D58787655

fbshipit-source-id: 2202271b9ad88cf8ba2145fb4e9e7bfd6e0c09fa
---
 .../src/main/jni/react/runtime/jni/JReactInstance.cpp     | 1 +
 .../ReactCommon/react/runtime/JSRuntimeFactory.h          | 8 ++++++++
 .../ReactCommon/react/runtime/ReactInstance.cpp           | 2 ++
 .../ReactCommon/react/runtime/hermes/HermesInstance.cpp   | 4 ++++
 4 files changed, 15 insertions(+)

diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactInstance.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactInstance.cpp
index 61c48351584d82..43c10f563ecf8e 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactInstance.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactInstance.cpp
@@ -74,6 +74,7 @@ JReactInstance::JReactInstance(
   timerManager->setRuntimeExecutor(bufferedRuntimeExecutor);
 
   ReactInstance::JSRuntimeFlags options = {.isProfiling = isProfiling};
+  // TODO T194671568 Consider moving runtime init to the JS thread.
   instance_->initializeRuntime(options, [this](jsi::Runtime& runtime) {
     react::Logger androidLogger =
         static_cast<void (*)(const std::string&, unsigned int)>(
diff --git a/packages/react-native/ReactCommon/react/runtime/JSRuntimeFactory.h b/packages/react-native/ReactCommon/react/runtime/JSRuntimeFactory.h
index dca9c1ac25c7b0..c60a46ab9bc25b 100644
--- a/packages/react-native/ReactCommon/react/runtime/JSRuntimeFactory.h
+++ b/packages/react-native/ReactCommon/react/runtime/JSRuntimeFactory.h
@@ -30,6 +30,14 @@ class JSRuntime {
    */
   virtual jsinspector_modern::RuntimeTargetDelegate& getRuntimeTargetDelegate();
 
+  /**
+   * Run initialize work that must happen on the runtime's JS thread. Used for
+   * initializing TLS and registering profiling.
+   *
+   * TODO T194671568 Move the runtime constructor to the JsThread
+   */
+  virtual void unstable_initializeOnJsThread() {}
+
  private:
   /**
    * Initialized by \c getRuntimeTargetDelegate if not overridden, and then
diff --git a/packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp b/packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp
index 5a1d10fdaaa362..0b8128c586f4b0 100644
--- a/packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp
+++ b/packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp
@@ -346,6 +346,8 @@ void ReactInstance::initializeRuntime(
     RuntimeSchedulerBinding::createAndInstallIfNeeded(
         runtime, runtimeScheduler_);
 
+    runtime_->unstable_initializeOnJsThread();
+
     defineReactInstanceFlags(runtime, options);
 
     defineReadOnlyGlobal(
diff --git a/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp b/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp
index 25f877a401e167..0a42996a11e391 100644
--- a/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp
+++ b/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp
@@ -109,6 +109,10 @@ class HermesJSRuntime : public JSRuntime {
     return *targetDelegate_;
   }
 
+  void unstable_initializeOnJsThread() override {
+    runtime_->registerForProfiling();
+  }
+
  private:
   std::shared_ptr<HermesRuntime> runtime_;
   std::optional<jsinspector_modern::HermesRuntimeTargetDelegate>