From 23cd9febbc63b633f8ef8be25387df21c1c52b7e Mon Sep 17 00:00:00 2001
From: Nick Lockwood <nicklockwood@fb.com>
Date: Thu, 7 Jan 2016 01:29:43 -0800
Subject: [PATCH] Fixed deadlock in RCTModuleData

Summary:
public
Fixed a potential deadlock issue if code attempted to access a module via [bridge moduleForName/Class:] while it was being initialized.

Reviewed By: lry

Differential Revision: D2807827

fb-gh-sync-id: 58cafe9b92c094dde632d17245fb9b342a0fe9e0
---
 React/Base/RCTBatchedBridge.m |  9 +--------
 React/Base/RCTModuleData.h    |  9 ++++++++-
 React/Base/RCTModuleData.m    | 26 ++++++++++++++++----------
 3 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/React/Base/RCTBatchedBridge.m b/React/Base/RCTBatchedBridge.m
index 185d6379e..e619c67d7 100644
--- a/React/Base/RCTBatchedBridge.m
+++ b/React/Base/RCTBatchedBridge.m
@@ -333,14 +333,7 @@ RCT_EXTERN NSArray<Class> *RCTGetModuleClasses(void);
 
   for (RCTModuleData *moduleData in _moduleDataByID) {
     if (moduleData.hasInstance) {
-      [moduleData methodQueue]; // initialize the queue
-    }
-  }
-
-  for (RCTModuleData *moduleData in _moduleDataByID) {
-    if (moduleData.hasInstance) {
-      [self registerModuleForFrameUpdates:moduleData.instance
-                           withModuleData:moduleData];
+      [moduleData finishSetupForInstance];
     }
   }
 
diff --git a/React/Base/RCTModuleData.h b/React/Base/RCTModuleData.h
index bf55892fd..ec922c804 100644
--- a/React/Base/RCTModuleData.h
+++ b/React/Base/RCTModuleData.h
@@ -25,11 +25,18 @@
 
 /**
  * Sets the bridge for the module instance. This is only needed when using the
- * `initWithModuleID:instance:` constructor. Otherwise, the bridge will be set
+ * `initWithModuleInstance:bridge:` constructor. Otherwise, the bridge will be set
  * automatically when the module is first accessed.
  */
 - (void)setBridgeForInstance;
 
+/**
+ * Sets the methodQueue and performs the remaining setup for the module. This is
+ * only needed when using the `initWithModuleInstance:bridge:` constructor.
+ * Otherwise it will be done automatically when the module is first accessed.
+ */
+- (void)finishSetupForInstance;
+
 @property (nonatomic, strong, readonly) Class moduleClass;
 @property (nonatomic, copy, readonly) NSString *name;
 
diff --git a/React/Base/RCTModuleData.m b/React/Base/RCTModuleData.m
index 2e290ce6c..d87edf430 100644
--- a/React/Base/RCTModuleData.m
+++ b/React/Base/RCTModuleData.m
@@ -70,6 +70,18 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init);
   }
 }
 
+- (void)finishSetupForInstance
+{
+  if (!_setupComplete) {
+    _setupComplete = YES;
+    [self setUpMethodQueue];
+    [_bridge registerModuleForFrameUpdates:_instance withModuleData:self];
+    [[NSNotificationCenter defaultCenter] postNotificationName:RCTDidInitializeModuleNotification
+                                                        object:_bridge
+                                                      userInfo:@{@"module": _instance}];
+  }
+}
+
 - (void)setUpMethodQueue
 {
   if (!_methodQueue) {
@@ -90,19 +102,13 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init);
           [(id)_instance setValue:_methodQueue forKey:@"methodQueue"];
         }
         @catch (NSException *exception) {
-          RCTLogError(@"%@ is returning nil for it's methodQueue, which is not "
+          RCTLogError(@"%@ is returning nil for its methodQueue, which is not "
                       "permitted. You must either return a pre-initialized "
                       "queue, or @synthesize the methodQueue to let the bridge "
                       "create a queue for you.", self.name);
         }
       }
     }
-
-    // Needs to be sent after bridge has been set for all module instances.
-    // Makes sense to put it here, since the same rules apply for methodQueue.
-    [[NSNotificationCenter defaultCenter]
-     postNotificationName:RCTDidInitializeModuleNotification
-     object:_bridge userInfo:@{@"module": _instance}];
   }
 }
 
@@ -124,11 +130,11 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init);
     // initialization requires it (View Managers get their queue by calling
     // self.bridge.uiManager.methodQueue)
     [self setBridgeForInstance];
-    [self setUpMethodQueue];
-    [_bridge registerModuleForFrameUpdates:_instance withModuleData:self];
-    _setupComplete = YES;
   }
   [_instanceLock unlock];
+
+  [self finishSetupForInstance];
+
   return _instance;
 }