Use the same lock for fields cleared on Fabric native binding uninstall

Summary:
Scheduler and JavaUIManager mutexes share the lifetime (between install-uninstall), so we can use singular shared lock to ensure that both sections are locked exclusively for install/uninstall and in shared mode for access.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D33130686

fbshipit-source-id: bf283fd5410e386d2635645e17680a9f4cb7f288

ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.cpp

@@ -223,13 +223,13 @@ jni::local_ref<Binding::jhybriddata> Binding::initHybrid(
 
 // Thread-safe getter
 jni::global_ref<jobject> Binding::getJavaUIManager() {
-  std::lock_guard<std::mutex> uiManagerLock(javaUIManagerMutex_);
+  std::shared_lock<better::shared_mutex> lock(installMutex_);
   return javaUIManager_;
 }
 
 // Thread-safe getter
 std::shared_ptr<Scheduler> Binding::getScheduler() {
-  std::lock_guard<std::mutex> lock(schedulerMutex_);
+  std::shared_lock<better::shared_mutex> lock(installMutex_);
   return scheduler_;
 }
 
@@ -521,10 +521,7 @@ void Binding::installFabricUIManager(
 
   // Use std::lock and std::adopt_lock to prevent deadlocks by locking mutexes
   // at the same time
-  std::lock(schedulerMutex_, javaUIManagerMutex_);
-  std::lock_guard<std::mutex> schedulerLock(schedulerMutex_, std::adopt_lock);
-  std::lock_guard<std::mutex> uiManagerLock(
-      javaUIManagerMutex_, std::adopt_lock);
+  std::unique_lock<better::shared_mutex> lock(installMutex_);
 
   javaUIManager_ = make_global(javaUIManager);
 
@@ -625,13 +622,8 @@ void Binding::uninstallFabricUIManager() {
     LOG(WARNING) << "Binding::uninstallFabricUIManager() was called (address: "
                  << this << ").";
   }
-  // Use std::lock and std::adopt_lock to prevent deadlocks by locking mutexes
-  // at the same time
-  std::lock(schedulerMutex_, javaUIManagerMutex_);
-  std::lock_guard<std::mutex> schedulerLock(schedulerMutex_, std::adopt_lock);
-  std::lock_guard<std::mutex> uiManagerLock(
-      javaUIManagerMutex_, std::adopt_lock);
 
+  std::unique_lock<better::shared_mutex> lock(installMutex_);
   animationDriver_ = nullptr;
   scheduler_ = nullptr;
   javaUIManager_ = nullptr;

ReactAndroid/src/main/java/com/facebook/react/fabric/jni/Binding.h

@@ -178,8 +178,9 @@ class Binding : public jni::HybridClass<Binding>,
   void uninstallFabricUIManager();
 
   // Private member variables
+  better::shared_mutex installMutex_;
   jni::global_ref<jobject> javaUIManager_;
-  std::mutex javaUIManagerMutex_;
+  std::shared_ptr<Scheduler> scheduler_;
 
   // LayoutAnimations
   void onAnimationStarted() override;
@@ -187,9 +188,6 @@ class Binding : public jni::HybridClass<Binding>,
   std::shared_ptr<LayoutAnimationDriver> animationDriver_;
   std::unique_ptr<JBackgroundExecutor> backgroundExecutor_;
 
-  std::shared_ptr<Scheduler> scheduler_;
-  std::mutex schedulerMutex_;
-
   better::map<SurfaceId, SurfaceHandler> surfaceHandlerRegistry_{};
   better::shared_mutex
       surfaceHandlerRegistryMutex_; // Protects `surfaceHandlerRegistry_`.