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++98, c++03, c++11
12 
13 // FLAKY_TEST.
14 
15 // <shared_mutex>
16 
17 // class shared_timed_mutex;
18 
19 // void lock_shared();
20 
21 #include <shared_mutex>
22 #include <thread>
23 #include <vector>
24 #include <cstdlib>
25 #include <cassert>
26 
27 #include "test_macros.h"
28 
29 std::shared_timed_mutex m;
30 
31 typedef std::chrono::system_clock Clock;
32 typedef Clock::time_point time_point;
33 typedef Clock::duration duration;
34 typedef std::chrono::milliseconds ms;
35 typedef std::chrono::nanoseconds ns;
36 
37 
38 ms WaitTime = ms(250);
39 
40 // Thread sanitizer causes more overhead and will sometimes cause this test
41 // to fail. To prevent this we give Thread sanitizer more time to complete the
42 // test.
43 #if !defined(TEST_HAS_SANITIZERS)
44 ms Tolerance = ms(50);
45 #else
46 ms Tolerance = ms(50 * 5);
47 #endif
48 
49 
f()50 void f()
51 {
52     time_point t0 = Clock::now();
53     m.lock_shared();
54     time_point t1 = Clock::now();
55     m.unlock_shared();
56     ns d = t1 - t0 - WaitTime;
57     assert(d < Tolerance);  // within tolerance
58 }
59 
g()60 void g()
61 {
62     time_point t0 = Clock::now();
63     m.lock_shared();
64     time_point t1 = Clock::now();
65     m.unlock_shared();
66     ns d = t1 - t0;
67     assert(d < Tolerance);  // within tolerance
68 }
69 
70 
main()71 int main()
72 {
73     m.lock();
74     std::vector<std::thread> v;
75     for (int i = 0; i < 5; ++i)
76         v.push_back(std::thread(f));
77     std::this_thread::sleep_for(WaitTime);
78     m.unlock();
79     for (auto& t : v)
80         t.join();
81     m.lock_shared();
82     for (auto& t : v)
83         t = std::thread(g);
84     std::thread q(f);
85     std::this_thread::sleep_for(WaitTime);
86     m.unlock_shared();
87     for (auto& t : v)
88         t.join();
89     q.join();
90 }
91