From 178e3d69f1e6db7df05f546c660c87fc47d75e16 Mon Sep 17 00:00:00 2001
From: Paul Beusterien <paulbeusterien@google.com>
Date: Thu, 27 Nov 2025 16:00:56 -0800
Subject: [PATCH 1/3] Fix UnfairLock deadlock

---
 FirebaseCore/CHANGELOG.md                     |  2 ++
 .../Sources/Utilities/UnfairLock.swift        | 36 +++++--------------
 Gemfile                                       |  1 +
 3 files changed, 12 insertions(+), 27 deletions(-)

diff --git a/FirebaseCore/CHANGELOG.md b/FirebaseCore/CHANGELOG.md
index 49629fa233b..b87251e28b5 100644
--- a/FirebaseCore/CHANGELOG.md
+++ b/FirebaseCore/CHANGELOG.md
@@ -3,6 +3,8 @@
   resolves build failures when using static linking
   (`use_frameworks! :linkage => :static`) in projects using frameworks like
   React Native (#15506).
+- [fixed] Fix UnfairLock deadlock that is known to occur from Crashlytics or
+  Performance. (#15394)
 
 # Firebase 12.0.0
 - [changed] **Breaking change**: Firebase's minimum supported versions have
diff --git a/FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift b/FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift
index 9028029763c..26c918793cf 100644
--- a/FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift
+++ b/FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift
@@ -1,3 +1,4 @@
+
 // Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
@@ -13,54 +14,35 @@
 // limitations under the License.
 
 import Foundation
-private import os.lock
 
-/// A reference wrapper around `os_unfair_lock`. Replace this class with
-/// `OSAllocatedUnfairLock` once we support only iOS 16+. For an explanation
-/// on why this is necessary, see the docs:
-/// https://developer.apple.com/documentation/os/osallocatedunfairlock
+/// A thread-safe wrapper around a value.
 public final class UnfairLock<Value>: @unchecked Sendable {
-  private var lockPointer: UnsafeMutablePointer<os_unfair_lock>
+  private var lock: NSRecursiveLock = .init()
   private var _value: Value
 
   public init(_ value: consuming sending Value) {
-    lockPointer = UnsafeMutablePointer<os_unfair_lock>
-      .allocate(capacity: 1)
-    lockPointer.initialize(to: os_unfair_lock())
     _value = value
   }
 
-  deinit {
-    lockPointer.deallocate()
-  }
-
   public func value() -> Value {
-    lock()
-    defer { unlock() }
+    lock.lock()
+    defer { lock.unlock() }
     return _value
   }
 
   @discardableResult
   public borrowing func withLock<Result>(_ body: (inout sending Value) throws
     -> sending Result) rethrows -> sending Result {
-    lock()
-    defer { unlock() }
+    lock.lock()
+    defer { lock.unlock() }
     return try body(&_value)
   }
 
   @discardableResult
   public borrowing func withLock<Result>(_ body: (inout sending Value) -> sending Result)
     -> sending Result {
-    lock()
-    defer { unlock() }
+    lock.lock()
+    defer { lock.unlock() }
     return body(&_value)
   }
-
-  private func lock() {
-    os_unfair_lock_lock(lockPointer)
-  }
-
-  private func unlock() {
-    os_unfair_lock_unlock(lockPointer)
-  }
 }
diff --git a/Gemfile b/Gemfile
index cc267b2e746..7143ab933f1 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,5 +1,6 @@
 # To update, change version below, run bundle install, test,
 # commit Gemfile and Gemfile.lock.
+#touch 
 source 'https://rubygems.org'
 
 # To test CocoaPods pre-releases, update to a relevant commit or tag like below

From c0b947a47ce247295bc7a49a2233c2aecfae4ca0 Mon Sep 17 00:00:00 2001
From: Paul Beusterien <paulbeusterien@google.com>
Date: Thu, 27 Nov 2025 16:30:49 -0800
Subject: [PATCH 2/3] Restore Gemfile after good test run

---
 Gemfile | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Gemfile b/Gemfile
index 7143ab933f1..cc267b2e746 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,6 +1,5 @@
 # To update, change version below, run bundle install, test,
 # commit Gemfile and Gemfile.lock.
-#touch 
 source 'https://rubygems.org'
 
 # To test CocoaPods pre-releases, update to a relevant commit or tag like below

From 5a9c7b6ae73f27177a0c8a907973eb4eb4a509fb Mon Sep 17 00:00:00 2001
From: Paul Beusterien <paulbeusterien@google.com>
Date: Fri, 28 Nov 2025 07:23:35 -0800
Subject: [PATCH 3/3] Remove extra blank line

---
 FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift | 1 -
 1 file changed, 1 deletion(-)

diff --git a/FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift b/FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift
index 26c918793cf..b3c0f53a4c0 100644
--- a/FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift
+++ b/FirebaseCore/Internal/Sources/Utilities/UnfairLock.swift
@@ -1,4 +1,3 @@
-
 // Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");