1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // UNSUPPORTED: libcpp-has-no-threads
10 // UNSUPPORTED: c++98, c++03, c++11
11 
12 // FLAKY_TEST.
13 
14 // <shared_mutex>
15 
16 // template <class Mutex> class shared_lock;
17 
18 // explicit shared_lock(mutex_type& m);
19 
20 // template<class _Mutex> shared_lock(shared_lock<_Mutex>)
21 //     -> shared_lock<_Mutex>;  // C++17
22 
23 #include <shared_mutex>
24 #include <thread>
25 #include <vector>
26 #include <cstdlib>
27 #include <cassert>
28 
29 #include "test_macros.h"
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 ms WaitTime = ms(250);
38 
39 // Thread sanitizer causes more overhead and will sometimes cause this test
40 // to fail. To prevent this we give Thread sanitizer more time to complete the
41 // test.
42 #if !defined(TEST_HAS_SANITIZERS)
43 ms Tolerance = ms(50);
44 #else
45 ms Tolerance = ms(50 * 5);
46 #endif
47 
48 std::shared_timed_mutex m;
49 
50 void f()
51 {
52     time_point t0 = Clock::now();
53     time_point t1;
54     {
55     std::shared_lock<std::shared_timed_mutex> ul(m);
56     t1 = Clock::now();
57     }
58     ns d = t1 - t0 - WaitTime;
59     assert(d < Tolerance);  // within tolerance
60 }
61 
62 void g()
63 {
64     time_point t0 = Clock::now();
65     time_point t1;
66     {
67     std::shared_lock<std::shared_timed_mutex> ul(m);
68     t1 = Clock::now();
69     }
70     ns d = t1 - t0;
71     assert(d < Tolerance);  // within tolerance
72 }
73 
74 int main(int, char**)
75 {
76     std::vector<std::thread> v;
77     {
78         m.lock();
79         for (int i = 0; i < 5; ++i)
80             v.push_back(std::thread(f));
81         std::this_thread::sleep_for(WaitTime);
82         m.unlock();
83         for (auto& t : v)
84             t.join();
85     }
86     {
87         m.lock_shared();
88         for (auto& t : v)
89             t = std::thread(g);
90         std::thread q(f);
91         std::this_thread::sleep_for(WaitTime);
92         m.unlock_shared();
93         for (auto& t : v)
94             t.join();
95         q.join();
96     }
97 
98 #ifdef __cpp_deduction_guides
99     std::shared_lock sl(m);
100     static_assert((std::is_same<decltype(sl), std::shared_lock<decltype(m)>>::value), "" );
101 #endif
102 
103   return 0;
104 }
105