Allow recursive calls to schedulerShouldRenderTransactions without de…

…adlocks (facebook#44725)

Summary:

Changelog: [internal]

## Context

We're currently testing synchronous state updates in Fabric (committing shadow trees for state updates synchronously in the thread where they were dispatched, instead of always scheduling it in the JS thread).

In these experiments we saw a problem caused by a recent change in the Android mounting layer (done to fix a problem with the Event Loop) where we were doing the mount operations inside a mutex lock. The problem is that we didn't have recursive commit+mount operations (because we were dispatching state updates in the JS thread) but now that we do we get a deadlock here.

 {F1659804385} 

These recursive commit+mount operations happen because it's possible to trigger state updates while we mount changes in the host platform (e.g.: we create the scroll view and we update the state to set the content offset). Those state updates trigger more mount operations, which deadlock in the mentioned place.

## Changes

This fixes the described issue by restricting the lock only to access the list of pending operations, but not to apply them. In the current implementation, `mountingManager->executeMount` is protected by the lock, whereas in the new version it isn't (so it can be safely called recursively). The synchronization of the mount operations is done directly at the mounting layer on Android.

Differential Revision: D57968936

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlags.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<84f45a19bf93a62da7ce904a2682fc51>>
+ * @generated SignedSource<<4e30b8a42dfe7e041ecb30a386b54e50>>
  */
 
 /**
@@ -40,6 +40,12 @@ public object ReactNativeFeatureFlags {
   @JvmStatic
   public fun allowCollapsableChildren(): Boolean = accessor.allowCollapsableChildren()
 
+  /**
+   * Adds support for recursively processing commits that mount synchronously (Android only).
+   */
+  @JvmStatic
+  public fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean = accessor.allowRecursiveCommitsWithSynchronousMountOnAndroid()
+
   /**
    * When enabled, the RuntimeScheduler processing the event loop will batch all rendering updates and dispatch them together at the end of each iteration of the loop.
    */

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsCxxAccessor.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<2f84a5455d747e14324f7b79cbbdc763>>
+ * @generated SignedSource<<944fabed27a371ce2e1a86e367312c1f>>
  */
 
 /**
@@ -22,6 +22,7 @@ package com.facebook.react.internal.featureflags
 public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccessor {
   private var commonTestFlagCache: Boolean? = null
   private var allowCollapsableChildrenCache: Boolean? = null
+  private var allowRecursiveCommitsWithSynchronousMountOnAndroidCache: Boolean? = null
   private var batchRenderingUpdatesInEventLoopCache: Boolean? = null
   private var destroyFabricSurfacesInReactInstanceManagerCache: Boolean? = null
   private var enableBackgroundExecutorCache: Boolean? = null
@@ -59,6 +60,15 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
     return cached
   }
 
+  override fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean {
+    var cached = allowRecursiveCommitsWithSynchronousMountOnAndroidCache
+    if (cached == null) {
+      cached = ReactNativeFeatureFlagsCxxInterop.allowRecursiveCommitsWithSynchronousMountOnAndroid()
+      allowRecursiveCommitsWithSynchronousMountOnAndroidCache = cached
+    }
+    return cached
+  }
+
   override fun batchRenderingUpdatesInEventLoop(): Boolean {
     var cached = batchRenderingUpdatesInEventLoopCache
     if (cached == null) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsCxxInterop.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<c82dca47362f4798dfcebda31b2fe2d6>>
+ * @generated SignedSource<<d2ccaef4c75979c26327963aeee0b0ad>>
  */
 
 /**
@@ -32,6 +32,8 @@ public object ReactNativeFeatureFlagsCxxInterop {
 
   @DoNotStrip @JvmStatic public external fun allowCollapsableChildren(): Boolean
 
+  @DoNotStrip @JvmStatic public external fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean
+
   @DoNotStrip @JvmStatic public external fun batchRenderingUpdatesInEventLoop(): Boolean
 
   @DoNotStrip @JvmStatic public external fun destroyFabricSurfacesInReactInstanceManager(): Boolean

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsDefaults.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<1ea3b574063dca0256494361423ce63e>>
+ * @generated SignedSource<<c74b5434945f63cf42551b188b9f7a48>>
  */
 
 /**
@@ -27,6 +27,8 @@ public open class ReactNativeFeatureFlagsDefaults : ReactNativeFeatureFlagsProvi
 
   override fun allowCollapsableChildren(): Boolean = true
 
+  override fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean = false
+
   override fun batchRenderingUpdatesInEventLoop(): Boolean = false
 
   override fun destroyFabricSurfacesInReactInstanceManager(): Boolean = false

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsLocalAccessor.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<a66642e4f6027ab0f5280baa2169d901>>
+ * @generated SignedSource<<3b94757d58e6adb2bccf4ddfb86e2080>>
  */
 
 /**
@@ -26,6 +26,7 @@ public class ReactNativeFeatureFlagsLocalAccessor : ReactNativeFeatureFlagsAcces
 
   private var commonTestFlagCache: Boolean? = null
   private var allowCollapsableChildrenCache: Boolean? = null
+  private var allowRecursiveCommitsWithSynchronousMountOnAndroidCache: Boolean? = null
   private var batchRenderingUpdatesInEventLoopCache: Boolean? = null
   private var destroyFabricSurfacesInReactInstanceManagerCache: Boolean? = null
   private var enableBackgroundExecutorCache: Boolean? = null
@@ -65,6 +66,16 @@ public class ReactNativeFeatureFlagsLocalAccessor : ReactNativeFeatureFlagsAcces
     return cached
   }
 
+  override fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean {
+    var cached = allowRecursiveCommitsWithSynchronousMountOnAndroidCache
+    if (cached == null) {
+      cached = currentProvider.allowRecursiveCommitsWithSynchronousMountOnAndroid()
+      accessedFeatureFlags.add("allowRecursiveCommitsWithSynchronousMountOnAndroid")
+      allowRecursiveCommitsWithSynchronousMountOnAndroidCache = cached
+    }
+    return cached
+  }
+
   override fun batchRenderingUpdatesInEventLoop(): Boolean {
     var cached = batchRenderingUpdatesInEventLoopCache
     if (cached == null) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsProvider.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<7a63b1fc14ccc86efb0929452755744d>>
+ * @generated SignedSource<<68ec2c046868a2cb1d2d88e4fdd9d993>>
  */
 
 /**
@@ -27,6 +27,8 @@ public interface ReactNativeFeatureFlagsProvider {
 
   @DoNotStrip public fun allowCollapsableChildren(): Boolean
 
+  @DoNotStrip public fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean
+
   @DoNotStrip public fun batchRenderingUpdatesInEventLoop(): Boolean
 
   @DoNotStrip public fun destroyFabricSurfacesInReactInstanceManager(): Boolean

packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.cpp

@@ -487,11 +487,28 @@ void Binding::schedulerShouldRenderTransactions(
     return;
   }
 
-  std::unique_lock<std::mutex> lock(pendingTransactionsMutex_);
-  for (auto& transaction : pendingTransactions_) {
-    mountingManager->executeMount(transaction);
+  if (ReactNativeFeatureFlags::
+          allowRecursiveCommitsWithSynchronousMountOnAndroid()) {
+    std::vector<MountingTransaction> pendingTransactions;
+
+    {
+      // Retain the lock to access the pending transactions but not to execute
+      // the mount operations because that method can call into this method
+      // again.
+      std::unique_lock<std::mutex> lock(pendingTransactionsMutex_);
+      pendingTransactions_.swap(pendingTransactions);
+    }
+
+    for (auto& transaction : pendingTransactions) {
+      mountingManager->executeMount(transaction);
+    }
+  } else {
+    std::unique_lock<std::mutex> lock(pendingTransactionsMutex_);
+    for (auto& transaction : pendingTransactions_) {
+      mountingManager->executeMount(transaction);
+    }
+    pendingTransactions_.clear();
   }
-  pendingTransactions_.clear();
 }
 
 void Binding::schedulerDidRequestPreliminaryViewAllocation(

packages/react-native/ReactAndroid/src/main/jni/react/featureflags/JReactNativeFeatureFlagsCxxInterop.cpp

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<82d20aa409496b17df21a077088894a6>>
+ * @generated SignedSource<<318ea35c5b58c968d7026dbe547200e4>>
  */
 
 /**
@@ -51,6 +51,12 @@ class ReactNativeFeatureFlagsProviderHolder
     return method(javaProvider_);
   }
 
+  bool allowRecursiveCommitsWithSynchronousMountOnAndroid() override {
+    static const auto method =
+        getReactNativeFeatureFlagsProviderJavaClass()->getMethod<jboolean()>("allowRecursiveCommitsWithSynchronousMountOnAndroid");
+    return method(javaProvider_);
+  }
+
   bool batchRenderingUpdatesInEventLoop() override {
     static const auto method =
         getReactNativeFeatureFlagsProviderJavaClass()->getMethod<jboolean()>("batchRenderingUpdatesInEventLoop");
@@ -173,6 +179,11 @@ bool JReactNativeFeatureFlagsCxxInterop::allowCollapsableChildren(
   return ReactNativeFeatureFlags::allowCollapsableChildren();
 }
 
+bool JReactNativeFeatureFlagsCxxInterop::allowRecursiveCommitsWithSynchronousMountOnAndroid(
+    facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop> /*unused*/) {
+  return ReactNativeFeatureFlags::allowRecursiveCommitsWithSynchronousMountOnAndroid();
+}
+
 bool JReactNativeFeatureFlagsCxxInterop::batchRenderingUpdatesInEventLoop(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop> /*unused*/) {
   return ReactNativeFeatureFlags::batchRenderingUpdatesInEventLoop();
@@ -286,6 +297,9 @@ void JReactNativeFeatureFlagsCxxInterop::registerNatives() {
       makeNativeMethod(
         "allowCollapsableChildren",
         JReactNativeFeatureFlagsCxxInterop::allowCollapsableChildren),
+      makeNativeMethod(
+        "allowRecursiveCommitsWithSynchronousMountOnAndroid",
+        JReactNativeFeatureFlagsCxxInterop::allowRecursiveCommitsWithSynchronousMountOnAndroid),
       makeNativeMethod(
         "batchRenderingUpdatesInEventLoop",
         JReactNativeFeatureFlagsCxxInterop::batchRenderingUpdatesInEventLoop),

packages/react-native/ReactAndroid/src/main/jni/react/featureflags/JReactNativeFeatureFlagsCxxInterop.h

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<08463d4f487df81332c79c8e85b4dac8>>
+ * @generated SignedSource<<4d557dc4399d46888205165ee7ae4ab2>>
  */
 
 /**
@@ -36,6 +36,9 @@ class JReactNativeFeatureFlagsCxxInterop
   static bool allowCollapsableChildren(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
 
+  static bool allowRecursiveCommitsWithSynchronousMountOnAndroid(
+    facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
+
   static bool batchRenderingUpdatesInEventLoop(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
 

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlags.cpp

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<c51ddd57ad10e748d6e2c5f444ea3765>>
+ * @generated SignedSource<<2a748a0a1b92cb0514fec83668ed8b0f>>
  */
 
 /**
@@ -29,6 +29,10 @@ bool ReactNativeFeatureFlags::allowCollapsableChildren() {
   return getAccessor().allowCollapsableChildren();
 }
 
+bool ReactNativeFeatureFlags::allowRecursiveCommitsWithSynchronousMountOnAndroid() {
+  return getAccessor().allowRecursiveCommitsWithSynchronousMountOnAndroid();
+}
+
 bool ReactNativeFeatureFlags::batchRenderingUpdatesInEventLoop() {
   return getAccessor().batchRenderingUpdatesInEventLoop();
 }

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlags.h

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<705dba656bfb228227399bcda638c404>>
+ * @generated SignedSource<<a75464f590c4f55e64ad2e33cfc52989>>
  */
 
 /**
@@ -47,6 +47,11 @@ class ReactNativeFeatureFlags {
    */
   RN_EXPORT static bool allowCollapsableChildren();
 
+  /**
+   * Adds support for recursively processing commits that mount synchronously (Android only).
+   */
+  RN_EXPORT static bool allowRecursiveCommitsWithSynchronousMountOnAndroid();
+
   /**
    * When enabled, the RuntimeScheduler processing the event loop will batch all rendering updates and dispatch them together at the end of each iteration of the loop.
    */