diff --git a/source/common/putilimp.h b/source/common/putilimp.h
index e3da340..90bae92 100644
--- a/source/common/putilimp.h
+++ b/source/common/putilimp.h
@@ -1,7 +1,7 @@
 /*
 ******************************************************************************
 *
-*   Copyright (C) 1997-2014, International Business Machines
+*   Copyright (C) 1997-2015, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *
 ******************************************************************************
@@ -229,6 +229,26 @@ typedef size_t uintptr_t;
 #endif
 
 
+/**
+ *  \def U_HAVE_CLANG_ATOMICS
+ *  Defines whether Clang c11 style built-in atomics are avaialable.
+ *  These are used in preference to gcc atomics when both are available.
+ */
+#ifdef U_HAVE_CLANG_ATOMICS
+    /* Use the predefined value. */
+#elif !defined(__clang__)
+#    define U_HAVE_CLANG_ATOMICS 0
+#else
+#if __has_builtin(__c11_atomic_load) && \
+    __has_builtin(__c11_atomic_store) && \
+    __has_builtin(__c11_atomic_fetch_add) && \
+    __has_builtin(__c11_atomic_fetch_sub)
+#    define U_HAVE_CLANG_ATOMICS 1
+#else
+#    define U_HAVE_CLANG_ATOMICS 0
+#endif
+#endif
+
 /*===========================================================================*/
 /** @{ Code alignment                                                        */
 /*===========================================================================*/
diff --git a/source/common/umutex.cpp b/source/common/umutex.cpp
index 0c1fdc8..581f2b9 100644
--- a/source/common/umutex.cpp
+++ b/source/common/umutex.cpp
@@ -349,8 +349,8 @@ umtx_atomic_dec(u_atomic_int32_t *p) {
 
 U_COMMON_API int32_t U_EXPORT2
 umtx_loadAcquire(u_atomic_int32_t &var) {
-    int32_t val = var;
     umtx_lock(&gIncDecMutex);
+    int32_t val = var;
     umtx_unlock(&gIncDecMutex);
     return val;
 }
@@ -358,8 +358,8 @@ umtx_loadAcquire(u_atomic_int32_t &var) {
 U_COMMON_API void U_EXPORT2
 umtx_storeRelease(u_atomic_int32_t &var, int32_t val) {
     umtx_lock(&gIncDecMutex);
-    umtx_unlock(&gIncDecMutex);
     var = val;
+    umtx_unlock(&gIncDecMutex);
 }
 
 U_NAMESPACE_END
diff --git a/source/common/umutex.h b/source/common/umutex.h
index e0ad0d3..0e4d118 100644
--- a/source/common/umutex.h
+++ b/source/common/umutex.h
@@ -1,6 +1,6 @@
 /*
 **********************************************************************
-*   Copyright (C) 1997-2014, International Business Machines
+*   Copyright (C) 1997-2015, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 **********************************************************************
 *
@@ -118,6 +118,33 @@ inline int32_t umtx_atomic_dec(u_atomic_int32_t *var) {
 U_NAMESPACE_END
 
 
+#elif U_HAVE_CLANG_ATOMICS
+/*
+ *  Clang __c11 atomic built-ins
+ */
+
+U_NAMESPACE_BEGIN
+typedef _Atomic(int32_t) u_atomic_int32_t;
+#define ATOMIC_INT32_T_INITIALIZER(val) val
+
+inline int32_t umtx_loadAcquire(u_atomic_int32_t &var) {
+     return __c11_atomic_load(&var, __ATOMIC_ACQUIRE);
+}
+
+inline void umtx_storeRelease(u_atomic_int32_t &var, int32_t val) {
+   return __c11_atomic_store(&var, val, __ATOMIC_RELEASE);
+}
+
+inline int32_t umtx_atomic_inc(u_atomic_int32_t *var) {
+    return __c11_atomic_fetch_add(var, 1, __ATOMIC_SEQ_CST) + 1;
+}
+
+inline int32_t umtx_atomic_dec(u_atomic_int32_t *var) {
+    return __c11_atomic_fetch_sub(var, 1, __ATOMIC_SEQ_CST) - 1;
+}
+U_NAMESPACE_END
+
+
 #elif U_HAVE_GCC_ATOMICS
 /*
  * gcc atomic ops. These are available on several other compilers as well.