From 322d9e1537a3687ae3925cdcf0ea8f571b9fa24d Mon Sep 17 00:00:00 2001
From: Pieter De Baets <pieterdb@fb.com>
Date: Thu, 30 Nov 2023 02:52:42 -0800
Subject: [PATCH] Clarify threading of OnViewAttach mount items (#41704)

Summary:

`mOnViewAttachItems` was set to be be concurrent, but this would be unexpected, as all mount item operations occur solely on the main thread.

Simplify this to be just a LinkedList and annotate the methods as being UI thread only.

Changelog: [Internal]

Reviewed By: NickGerleman

Differential Revision: D51662154
---
 .../fabric/mounting/MountItemDispatcher.java  |  2 +-
 .../mounting/SurfaceMountingManager.java      | 19 ++++++++++---------
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/MountItemDispatcher.java b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/MountItemDispatcher.java
index 7a083c9870b322..3261a598b041f3 100644
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/MountItemDispatcher.java
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/MountItemDispatcher.java
@@ -362,7 +362,7 @@ private void executeOrEnqueue(MountItem item) {
       }
       SurfaceMountingManager surfaceMountingManager =
           mMountingManager.getSurfaceManager(item.getSurfaceId());
-      surfaceMountingManager.executeOnViewAttach(item);
+      surfaceMountingManager.scheduleMountItemOnViewAttach(item);
     } else {
       item.execute(mMountingManager);
     }
diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/SurfaceMountingManager.java b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/SurfaceMountingManager.java
index 87b15e454f3127..90267da55b369a 100644
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/SurfaceMountingManager.java
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/SurfaceMountingManager.java
@@ -52,6 +52,7 @@
 import com.facebook.react.uimanager.events.EventCategoryDef;
 import com.facebook.react.views.view.ReactMapBufferViewManager;
 import com.facebook.react.views.view.ReactViewManagerWrapper;
+import java.util.ArrayDeque;
 import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.Map;
@@ -59,7 +60,6 @@
 import java.util.Set;
 import java.util.Stack;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentLinkedQueue;
 
 public class SurfaceMountingManager {
   public static final String TAG = SurfaceMountingManager.class.getSimpleName();
@@ -74,7 +74,7 @@ public class SurfaceMountingManager {
   // These are all non-null, until StopSurface is called
   private ConcurrentHashMap<Integer, ViewState> mTagToViewState =
       new ConcurrentHashMap<>(); // any thread
-  private ConcurrentLinkedQueue<MountItem> mOnViewAttachItems = new ConcurrentLinkedQueue<>();
+  private Queue<MountItem> mOnViewAttachMountItems = new ArrayDeque<>();
   private JSResponderHandler mJSResponderHandler;
   private ViewManagerRegistry mViewManagerRegistry;
   private RootViewManager mRootViewManager;
@@ -181,9 +181,10 @@ public boolean getViewExists(int tag) {
     return mTagToViewState.containsKey(tag);
   }
 
-  @AnyThread
-  public void executeOnViewAttach(MountItem item) {
-    mOnViewAttachItems.add(item);
+  @UiThread
+  @ThreadConfined(UI)
+  public void scheduleMountItemOnViewAttach(MountItem item) {
+    mOnViewAttachMountItems.add(item);
   }
 
   @AnyThread
@@ -233,7 +234,7 @@ private void addRootView(@NonNull final View rootView) {
           }
           mRootViewAttached = true;
 
-          executeViewAttachMountItems();
+          executeMountItemsOnViewAttach();
         };
 
     if (UiThreadUtil.isOnUiThread()) {
@@ -245,8 +246,8 @@ private void addRootView(@NonNull final View rootView) {
 
   @UiThread
   @ThreadConfined(UI)
-  private void executeViewAttachMountItems() {
-    mMountItemExecutor.executeItems(mOnViewAttachItems);
+  private void executeMountItemsOnViewAttach() {
+    mMountItemExecutor.executeItems(mOnViewAttachMountItems);
   }
 
   /**
@@ -319,7 +320,7 @@ public void stopSurface() {
           mRootViewManager = null;
           mMountItemExecutor = null;
           mThemedReactContext = null;
-          mOnViewAttachItems.clear();
+          mOnViewAttachMountItems.clear();
 
           if (ReactFeatureFlags.enableViewRecycling) {
             mViewManagerRegistry.onSurfaceStopped(mSurfaceId);