Back-port rn81 performance fix

This is based on two commits from the React Native upstream project:

1st: dd12edf35f89aed4872ba40e54fc9caaabfac0bf
2nd: cb20a1cd32c5a9fa79e12223d03b7ade18a890c8

These commits touch a lot of files, but we just need these two:

packages/react-native/ReactCommon/react/renderer/mounting/ShadowTree.cpp
packages/react-native/ReactCommon/react/renderer/mounting/ShadowTree.h

The other files implement the new feature flag, but we can ignore those
and just hard-code the change to "on".

Author: swansontec

package.json

@@ -266,5 +266,10 @@
   },
   "engines": {
     "node": ">=18"
+  },
+  "reanimated": {
+    "staticFeatureFlags": {
+      "DISABLE_COMMIT_PAUSING_MECHANISM": true
+    }
   }
 }

patches/react-native+0.79.2.patch

@@ -0,0 +1,133 @@
+diff --git a/node_modules/react-native/ReactCommon/react/renderer/mounting/ShadowTree.cpp b/node_modules/react-native/ReactCommon/react/renderer/mounting/ShadowTree.cpp
+index 522ec57..e6ad1df 100644
+--- a/node_modules/react-native/ReactCommon/react/renderer/mounting/ShadowTree.cpp
++++ b/node_modules/react-native/ReactCommon/react/renderer/mounting/ShadowTree.cpp
+@@ -22,6 +22,10 @@
+ 
+ namespace facebook::react {
+ 
++namespace {
++const int MAX_COMMIT_ATTEMPTS_BEFORE_LOCKING = 3;
++} // namespace
++
+ using CommitStatus = ShadowTree::CommitStatus;
+ using CommitMode = ShadowTree::CommitMode;
+ 
+@@ -207,7 +211,8 @@ void ShadowTree::setCommitMode(CommitMode commitMode) const {
+   auto revision = ShadowTreeRevision{};
+ 
+   {
+-    std::unique_lock lock(commitMutex_);
++    ShadowTree::UniqueLock lock = uniqueCommitLock();
++
+     if (commitMode_ == commitMode) {
+       return;
+     }
+@@ -224,7 +229,7 @@ void ShadowTree::setCommitMode(CommitMode commitMode) const {
+ }
+ 
+ CommitMode ShadowTree::getCommitMode() const {
+-  std::shared_lock lock(commitMutex_);
++  SharedLock lock = sharedCommitLock();
+   return commitMode_;
+ }
+ 
+@@ -238,17 +243,17 @@ CommitStatus ShadowTree::commit(
+     const CommitOptions& commitOptions) const {
+   [[maybe_unused]] int attempts = 0;
+ 
+-  while (true) {
+-    attempts++;
+-
++  while (attempts < MAX_COMMIT_ATTEMPTS_BEFORE_LOCKING) {
+     auto status = tryCommit(transaction, commitOptions);
+     if (status != CommitStatus::Failed) {
+       return status;
+     }
++    attempts++;
++  }
+ 
+-    // After multiple attempts, we failed to commit the transaction.
+-    // Something internally went terribly wrong.
+-    react_native_assert(attempts < 1024);
++  {
++    std::unique_lock lock(commitMutexRecursive_);
++    return tryCommit(transaction, commitOptions);
+   }
+ }
+ 
+@@ -266,7 +271,7 @@ CommitStatus ShadowTree::tryCommit(
+ 
+   {
+     // Reading `currentRevision_` in shared manner.
+-    std::shared_lock lock(commitMutex_);
++    SharedLock lock = sharedCommitLock();
+     commitMode = commitMode_;
+     oldRevision = currentRevision_;
+   }
+@@ -307,7 +312,7 @@ CommitStatus ShadowTree::tryCommit(
+ 
+   {
+     // Updating `currentRevision_` in unique manner if it hasn't changed.
+-    std::unique_lock lock(commitMutex_);
++    UniqueLock lock = uniqueCommitLock();
+ 
+     if (currentRevision_.number != oldRevision.number) {
+       return CommitStatus::Failed;
+@@ -345,7 +350,7 @@ CommitStatus ShadowTree::tryCommit(
+ }
+ 
+ ShadowTreeRevision ShadowTree::getCurrentRevision() const {
+-  std::shared_lock lock(commitMutex_);
++  SharedLock lock = sharedCommitLock();
+   return currentRevision_;
+ }
+ 
+@@ -392,4 +397,12 @@ void ShadowTree::notifyDelegatesOfUpdates() const {
+   delegate_.shadowTreeDidFinishTransaction(mountingCoordinator_, true);
+ }
+ 
++inline ShadowTree::UniqueLock ShadowTree::uniqueCommitLock() const {
++  return std::unique_lock{commitMutexRecursive_};
++}
++
++inline ShadowTree::SharedLock ShadowTree::sharedCommitLock() const {
++  return std::unique_lock{commitMutexRecursive_};
++}
++
+ } // namespace facebook::react
+diff --git a/node_modules/react-native/ReactCommon/react/renderer/mounting/ShadowTree.h b/node_modules/react-native/ReactCommon/react/renderer/mounting/ShadowTree.h
+index ae9d005..c3bef0b 100644
+--- a/node_modules/react-native/ReactCommon/react/renderer/mounting/ShadowTree.h
++++ b/node_modules/react-native/ReactCommon/react/renderer/mounting/ShadowTree.h
+@@ -8,6 +8,8 @@
+ #pragma once
+ 
+ #include <memory>
++#include <mutex>
++#include <shared_mutex>
+ 
+ #include <react/renderer/components/root/RootComponentDescriptor.h>
+ #include <react/renderer/components/root/RootShadowNode.h>
+@@ -139,10 +141,21 @@ class ShadowTree final {
+   const SurfaceId surfaceId_;
+   const ShadowTreeDelegate& delegate_;
+   mutable std::shared_mutex commitMutex_;
++  mutable std::recursive_mutex commitMutexRecursive_;
+   mutable CommitMode commitMode_{
+       CommitMode::Normal}; // Protected by `commitMutex_`.
+   mutable ShadowTreeRevision currentRevision_; // Protected by `commitMutex_`.
+   std::shared_ptr<const MountingCoordinator> mountingCoordinator_;
++
++  using UniqueLock = std::variant<
++      std::unique_lock<std::shared_mutex>,
++      std::unique_lock<std::recursive_mutex>>;
++  using SharedLock = std::variant<
++      std::shared_lock<std::shared_mutex>,
++      std::unique_lock<std::recursive_mutex>>;
++
++  inline UniqueLock uniqueCommitLock() const;
++  inline SharedLock sharedCommitLock() const;
+ };
+ 
+ } // namespace facebook::react