1 //===----------------------------------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // UNSUPPORTED: libcpp-has-no-threads
11 
12 // FLAKY_TEST
13 
14 // <mutex>
15 
16 // template <class Mutex> class lock_guard;
17 
18 // lock_guard(mutex_type& m, adopt_lock_t);
19 
20 #include <mutex>
21 #include <thread>
22 #include <cstdlib>
23 #include <cassert>
24 
25 std::mutex m;
26 
27 typedef std::chrono::system_clock Clock;
28 typedef Clock::time_point time_point;
29 typedef Clock::duration duration;
30 typedef std::chrono::milliseconds ms;
31 typedef std::chrono::nanoseconds ns;
32 
f()33 void f()
34 {
35     time_point t0 = Clock::now();
36     time_point t1;
37     {
38     m.lock();
39     std::lock_guard<std::mutex> lg(m, std::adopt_lock);
40     t1 = Clock::now();
41     }
42     ns d = t1 - t0 - ms(250);
43     assert(d < ms(50));  // within 50ms
44 }
45 
main()46 int main()
47 {
48     m.lock();
49     std::thread t(f);
50     std::this_thread::sleep_for(ms(250));
51     m.unlock();
52     t.join();
53 }
54