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 // UNSUPPORTED: c++03, c++98, c++11, c++14
12 
13 // <shared_mutex>
14 
15 // class shared_mutex;
16 
17 // bool try_lock_shared();
18 
19 #include <shared_mutex>
20 #include <thread>
21 #include <vector>
22 #include <cstdlib>
23 #include <cassert>
24 
25 std::shared_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     assert(!m.try_lock_shared());
37     assert(!m.try_lock_shared());
38     assert(!m.try_lock_shared());
39     while(!m.try_lock_shared())
40         ;
41     time_point t1 = Clock::now();
42     m.unlock_shared();
43     ns d = t1 - t0 - ms(250);
44     assert(d < ms(200));  // within 200ms
45 }
46 
47 
main()48 int main()
49 {
50     m.lock();
51     std::vector<std::thread> v;
52     for (int i = 0; i < 5; ++i)
53         v.push_back(std::thread(f));
54     std::this_thread::sleep_for(ms(250));
55     m.unlock();
56     for (auto& t : v)
57         t.join();
58 }
59