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: c++03
10 // UNSUPPORTED: no-threads
11 
12 // <mutex>
13 
14 // class recursive_timed_mutex;
15 
16 // bool try_lock();
17 
18 #include <mutex>
19 #include <atomic>
20 #include <cassert>
21 #include <chrono>
22 #include <thread>
23 
24 #include "make_test_thread.h"
25 
26 bool is_lockable(std::recursive_timed_mutex& m) {
27   bool did_lock;
28   std::thread t = support::make_test_thread([&] {
29     did_lock = m.try_lock();
30     if (did_lock)
31       m.unlock(); // undo side effects
32   });
33   t.join();
34 
35   return did_lock;
36 }
37 
38 int main(int, char**) {
39   // Try to lock a mutex that is not locked yet. This should succeed.
40   {
41     std::recursive_timed_mutex m;
42     bool succeeded = m.try_lock();
43     assert(succeeded);
44     m.unlock();
45   }
46 
47   // Try to lock a mutex that is already locked by this thread. This should succeed and the mutex should only
48   // be unlocked after a matching number of calls to unlock() on the same thread.
49   {
50     std::recursive_timed_mutex m;
51     int lock_count = 0;
52     for (int i = 0; i != 10; ++i) {
53       assert(m.try_lock());
54       ++lock_count;
55     }
56     while (lock_count != 0) {
57       assert(!is_lockable(m));
58       m.unlock();
59       --lock_count;
60     }
61     assert(is_lockable(m));
62   }
63 
64   // Try to lock a mutex that is already locked by another thread. This should fail.
65   {
66     std::recursive_timed_mutex m;
67     m.lock();
68 
69     std::thread t = support::make_test_thread([&] {
70       for (int i = 0; i != 10; ++i) {
71         bool succeeded = m.try_lock();
72         assert(!succeeded);
73       }
74     });
75     t.join();
76 
77     m.unlock();
78   }
79 
80   return 0;
81 }
82