From 7929551623d4e3fbd849500d795755d0c41fdbbd Mon Sep 17 00:00:00 2001
From: Lulu Wu <luluwu@fb.com>
Date: Mon, 26 Jul 2021 02:02:19 -0700
Subject: [PATCH] Make mHybridData thread safe for EventEmitterWrapper

Summary:
In T94154173, when calling ```EventEmitterWrapper->invoke()```, hybrid function ```invokeEvent``` is null, even if we checked that ```mHybridData``` is valid before calling ```invokeEvent```.

**Theory:**

```invoke()``` is called from ```mqt_js``` thread, ```desotry()``` is called from ```main``` thread, which cause multi-thread access of```mHybridData```.

So if ```desotry()``` is called after ```isValid()``` check and before calling ```invokeEvent()```, ```invokeEvent``` could be destroyed and is null.

I can reproduce with above theory:

{F633411001}

**Fix:**

Make functions synchronized so ```mHybridData``` can be thread safe.

Changelog:
[Android][Fixed] - Make mHybridData thread safe

Reviewed By: RSNara

Differential Revision: D29792453

fbshipit-source-id: 8b4c754d53ece933be7b2cf99c6cd026b39e24ad
---
 .../facebook/react/fabric/events/EventEmitterWrapper.java   | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/ReactAndroid/src/main/java/com/facebook/react/fabric/events/EventEmitterWrapper.java b/ReactAndroid/src/main/java/com/facebook/react/fabric/events/EventEmitterWrapper.java
index 69d0e1c8a8aecd..e1652a4f2bdd45 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/fabric/events/EventEmitterWrapper.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/fabric/events/EventEmitterWrapper.java
@@ -47,7 +47,7 @@ private native void invokeUniqueEvent(
    * @param eventName {@link String} name of the event to execute.
    * @param params {@link WritableMap} payload of the event
    */
-  public void invoke(@NonNull String eventName, @Nullable WritableMap params) {
+  public synchronized void invoke(@NonNull String eventName, @Nullable WritableMap params) {
     if (!isValid()) {
       return;
     }
@@ -62,7 +62,7 @@ public void invoke(@NonNull String eventName, @Nullable WritableMap params) {
    * @param eventName {@link String} name of the event to execute.
    * @param params {@link WritableMap} payload of the event
    */
-  public void invokeUnique(
+  public synchronized void invokeUnique(
       @NonNull String eventName, @Nullable WritableMap params, int customCoalesceKey) {
     if (!isValid()) {
       return;
@@ -71,7 +71,7 @@ public void invokeUnique(
     invokeUniqueEvent(eventName, payload, customCoalesceKey);
   }
 
-  public void destroy() {
+  public synchronized void destroy() {
     if (mHybridData != null) {
       mHybridData.resetNative();
     }