1 files changed, 48 insertions, 0 deletions
diff --git a/libcxx/test/std/thread/thread.mutex/thread.once/thread.once.callonce/race.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.once/thread.once.callonce/race.pass.cpp
new file mode 100644
index 00000000000..33215819f58
--- /dev/null
+++ b/libcxx/test/std/thread/thread.mutex/thread.once/thread.once.callonce/race.pass.cpp
@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: libcpp-has-no-threads
+
+// <mutex>
+
+// struct once_flag;
+
+// template<class Callable, class ...Args>
+//   void call_once(once_flag& flag, Callable&& func, Args&&... args);
+
+// This test is supposed to be run with ThreadSanitizer and verifies that
+// call_once properly synchronizes user state, a data race that was fixed
+// in r280621.
+
+#include <mutex>
+#include <thread>
+#include <cassert>
+
+std::once_flag flg0;
+long global = 0;
+
+void init0()
+{
+    ++global;
+}
+
+void f0()
+{
+    std::call_once(flg0, init0);
+    assert(global == 1);
+}
+
+int main()
+{
+    std::thread t0(f0);
+    std::thread t1(f0);
+    t0.join();
+    t1.join();
+    assert(global == 1);
+}