1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
|
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03
// UNSUPPORTED: no-threads
// <mutex>
// class mutex;
// void lock();
#include <mutex>
#include <atomic>
#include <cassert>
#include <thread>
#include <vector>
#include "make_test_thread.h"
int main(int, char**) {
// Lock a mutex that is not locked yet. This should succeed.
{
std::mutex m;
m.lock();
m.unlock();
}
// Lock a mutex that is already locked. This should block until it is unlocked.
{
std::atomic<bool> ready(false);
std::mutex m;
m.lock();
std::atomic<bool> is_locked_from_main(true);
std::thread t = support::make_test_thread([&] {
ready = true;
m.lock();
assert(!is_locked_from_main);
m.unlock();
});
while (!ready)
/* spin */;
// We would rather signal this after we unlock, but that would create a race condition.
// We instead signal it before we unlock, which means that it's technically possible for
// the thread to take the lock while main is still holding it yet for the test to still pass.
is_locked_from_main = false;
m.unlock();
t.join();
}
// Make sure that at most one thread can acquire the mutex concurrently.
{
std::atomic<int> counter(0);
std::mutex mutex;
std::vector<std::thread> threads;
for (int i = 0; i != 10; ++i) {
threads.push_back(support::make_test_thread([&] {
mutex.lock();
counter++;
assert(counter == 1);
counter--;
mutex.unlock();
}));
}
for (auto& t : threads)
t.join();
}
return 0;
}
|
