--- /dev/null
+++ libmalloc/libmalloc-409.40.6/src/locking.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2015 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#ifndef __LOCKING_H
+#define __LOCKING_H
+
+#if OS_UNFAIR_LOCK_INLINE
+#define os_unfair_lock_lock_with_options(lock, options) \
+		os_unfair_lock_lock_with_options_inline(lock, options)
+#define os_unfair_lock_trylock(lock) \
+		os_unfair_lock_trylock_inline(lock)
+#define os_unfair_lock_unlock(lock) \
+		os_unfair_lock_unlock_inline(lock)
+#endif // OS_UNFAIR_LOCK_INLINE
+
+typedef os_unfair_lock _malloc_lock_s;
+#define _MALLOC_LOCK_INIT OS_UNFAIR_LOCK_INIT
+
+__attribute__((always_inline))
+static inline void
+_malloc_lock_init(_malloc_lock_s *lock) {
+    *lock = OS_UNFAIR_LOCK_INIT;
+}
+
+MALLOC_ALWAYS_INLINE
+static inline void
+_malloc_lock_lock(_malloc_lock_s *lock) {
+	return os_unfair_lock_lock_with_options(lock, OS_UNFAIR_LOCK_ADAPTIVE_SPIN |
+			OS_UNFAIR_LOCK_DATA_SYNCHRONIZATION);
+}
+
+MALLOC_ALWAYS_INLINE
+static inline bool
+_malloc_lock_trylock(_malloc_lock_s *lock) {
+    return os_unfair_lock_trylock(lock);
+}
+
+MALLOC_ALWAYS_INLINE
+static inline void
+_malloc_lock_unlock(_malloc_lock_s *lock) {
+    return os_unfair_lock_unlock(lock);
+}
+
+MALLOC_ALWAYS_INLINE
+static inline void
+_malloc_lock_assert_owner(_malloc_lock_s *lock) {
+	os_unfair_lock_assert_owner(lock);
+}
+
+#endif // __LOCKING_H