Fix PR23293 - Do not unlock shared state before notifying consumers.

Within the shared state methods do not unlock the lock guards manually. This
could cause a race condition where the shared state is destroyed before the
method is complete.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@239577 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/thread/futures/futures.async/async_race.pass.cpp

@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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
+
+// <future>
+
+// template <class F, class... Args>
+//     future<typename result_of<F(Args...)>::type>
+//     async(F&& f, Args&&... args);
+
+// template <class F, class... Args>
+//     future<typename result_of<F(Args...)>::type>
+//     async(launch policy, F&& f, Args&&... args);
+
+// This test is designed to cause and allow TSAN to detect the race condition
+// reported in PR23293. (http://llvm.org/PR23293).
+
+#include <future>
+#include <chrono>
+#include <thread>
+#include <memory>
+#include <cassert>
+
+int f_async() {
+    typedef std::chrono::milliseconds ms;
+    std::this_thread::sleep_for(ms(200));
+    return 42;
+}
+
+bool ran = false;
+
+int f_deferred() {
+    ran = true;
+    return 42;
+}
+
+void test_each() {
+    {
+        std::future<int> f = std::async(f_async);
+        int const result = f.get();
+        assert(result == 42);
+    }
+    {
+        std::future<int> f = std::async(std::launch::async, f_async);
+        int const result = f.get();
+        assert(result == 42);
+    }
+    {
+        ran = false;
+        std::future<int> f = std::async(std::launch::deferred, f_deferred);
+        assert(ran == false);
+        int const result = f.get();
+        assert(ran == true);
+        assert(result == 42);
+    }
+}
+
+int main() {
+    for (int i=0; i < 25; ++i) test_each();
+}