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 // <mutex>
13 
14 // template <class Mutex> class unique_lock;
15 
16 // unique_lock(mutex_type& m, try_to_lock_t);
17 
18 #include <mutex>
19 #include <thread>
20 #include <cstdlib>
21 #include <cassert>
22 
23 std::mutex m;
24 
25 typedef std::chrono::system_clock Clock;
26 typedef Clock::time_point time_point;
27 typedef Clock::duration duration;
28 typedef std::chrono::milliseconds ms;
29 typedef std::chrono::nanoseconds ns;
30 
f()31 void f()
32 {
33     time_point t0 = Clock::now();
34     {
35         std::unique_lock<std::mutex> lk(m, std::try_to_lock);
36         assert(lk.owns_lock() == false);
37     }
38     {
39         std::unique_lock<std::mutex> lk(m, std::try_to_lock);
40         assert(lk.owns_lock() == false);
41     }
42     {
43         std::unique_lock<std::mutex> lk(m, std::try_to_lock);
44         assert(lk.owns_lock() == false);
45     }
46     while (true)
47     {
48         std::unique_lock<std::mutex> lk(m, std::try_to_lock);
49         if (lk.owns_lock())
50             break;
51     }
52     time_point t1 = Clock::now();
53     ns d = t1 - t0 - ms(250);
54     assert(d < ms(200));  // within 200ms
55 }
56 
main()57 int main()
58 {
59     m.lock();
60     std::thread t(f);
61     std::this_thread::sleep_for(ms(250));
62     m.unlock();
63     t.join();
64 }
65