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_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
26bool is_lockable(std::recursive_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
38int main(int, char**) {
39 // Try to lock a mutex that is not locked yet. This should succeed.
40 {
41 std::recursive_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_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_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

source code of libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/try_lock.pass.cpp