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: no-threads
10 // UNSUPPORTED: c++03, c++11
11 
12 // dylib support for shared_mutex was added in macosx10.12
13 // XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11}}
14 
15 // <shared_mutex>
16 
17 // class timed_mutex;
18 
19 // template <class Rep, class Period>
20 //   shared_lock(mutex_type& m, const chrono::duration<Rep, Period>& rel_time);
21 
22 #include <thread>
23 
24 #include <atomic>
25 #include <cassert>
26 #include <cstdlib>
27 #include <shared_mutex>
28 #include <vector>
29 
30 #include "make_test_thread.h"
31 #include "test_macros.h"
32 
33 std::shared_timed_mutex m;
34 
35 typedef std::chrono::steady_clock Clock;
36 typedef Clock::time_point time_point;
37 typedef Clock::duration duration;
38 typedef std::chrono::milliseconds ms;
39 typedef std::chrono::nanoseconds ns;
40 
41 ms LongTime = ms(5000);
42 ms ShortTime = ms(50);
43 
44 static const unsigned Threads = 5;
45 
46 std::atomic<unsigned> CountDown(Threads);
47 
48 void f1()
49 {
50   // Preemptive scheduling means that one cannot make assumptions about when
51   // code executes and therefore we cannot assume anthing about when the mutex
52   // starts waiting relative to code in the main thread. We can however prove
53   // that a timeout occured and that implies that this code is waiting.
54   // See f2() below.
55   //
56   // Nevertheless, we should at least try to ensure that the mutex waits and
57   // therefore we use an atomic variable to signal to the main thread that this
58   // code is just a few instructions away from waiting.
59   --CountDown;
60   std::shared_lock<std::shared_timed_mutex> lk(m, LongTime);
61   assert(lk.owns_lock() == true);
62 }
63 
64 void f2()
65 {
66   time_point t0 = Clock::now();
67   std::shared_lock<std::shared_timed_mutex> lk(m, ShortTime);
68   time_point t1 = Clock::now();
69   assert(lk.owns_lock() == false);
70   assert(t1 - t0 >= ShortTime);
71 }
72 
73 int main(int, char**)
74 {
75   {
76     m.lock();
77     std::vector<std::thread> v;
78     for (unsigned i = 0; i < Threads; ++i)
79       v.push_back(support::make_test_thread(f1));
80     while (CountDown > 0)
81       std::this_thread::yield();
82     // Give one more chance for threads to block and wait for the mutex.
83     std::this_thread::yield();
84     std::this_thread::sleep_for(ShortTime);
85     m.unlock();
86     for (auto& t : v)
87       t.join();
88   }
89   {
90     m.lock();
91     std::vector<std::thread> v;
92     for (unsigned i = 0; i < Threads; ++i)
93       v.push_back(support::make_test_thread(f2));
94     for (auto& t : v)
95       t.join();
96     m.unlock();
97   }
98 
99   return 0;
100 }
101