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 
11 // FLAKY_TEST.
12 
13 // <condition_variable>
14 
15 // class condition_variable;
16 
17 // template <class Clock, class Duration, class Predicate>
18 //     bool
19 //     wait_until(unique_lock<mutex>& lock,
20 //                const chrono::time_point<Clock, Duration>& abs_time,
21 //                Predicate pred);
22 
23 #include <condition_variable>
24 #include <mutex>
25 #include <thread>
26 #include <chrono>
27 #include <cassert>
28 
29 struct Clock
30 {
31     typedef std::chrono::milliseconds duration;
32     typedef duration::rep             rep;
33     typedef duration::period          period;
34     typedef std::chrono::time_point<Clock> time_point;
35     static const bool is_steady =  true;
36 
37     static time_point now()
38     {
39         using namespace std::chrono;
40         return time_point(duration_cast<duration>(
41                 steady_clock::now().time_since_epoch()
42                                                  ));
43     }
44 };
45 
46 class Pred
47 {
48     int& i_;
49 public:
50     explicit Pred(int& i) : i_(i) {}
51 
52     bool operator()() {return i_ != 0;}
53 };
54 
55 std::condition_variable cv;
56 std::mutex mut;
57 
58 int test1 = 0;
59 int test2 = 0;
60 
61 int runs = 0;
62 
63 void f()
64 {
65     std::unique_lock<std::mutex> lk(mut);
66     assert(test2 == 0);
67     test1 = 1;
68     cv.notify_one();
69     Clock::time_point t0 = Clock::now();
70     Clock::time_point t = t0 + Clock::duration(250);
71     bool r = cv.wait_until(lk, t, Pred(test2));
72     Clock::time_point t1 = Clock::now();
73     if (runs == 0)
74     {
75         assert(t1 - t0 < Clock::duration(250));
76         assert(test2 != 0);
77         assert(r);
78     }
79     else
80     {
81         assert(t1 - t0 - Clock::duration(250) < Clock::duration(50));
82         assert(test2 == 0);
83         assert(!r);
84     }
85     ++runs;
86 }
87 
88 int main()
89 {
90     {
91         std::unique_lock<std::mutex>lk(mut);
92         std::thread t(f);
93         assert(test1 == 0);
94         while (test1 == 0)
95             cv.wait(lk);
96         assert(test1 != 0);
97         test2 = 1;
98         lk.unlock();
99         cv.notify_one();
100         t.join();
101     }
102     test1 = 0;
103     test2 = 0;
104     {
105         std::unique_lock<std::mutex>lk(mut);
106         std::thread t(f);
107         assert(test1 == 0);
108         while (test1 == 0)
109             cv.wait(lk);
110         assert(test1 != 0);
111         lk.unlock();
112         t.join();
113     }
114 }
115