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
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
//===----------------------------------------------------------------------===//
//
// 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: no-threads
// notify_all_at_thread_exit(...) requires move semantics to transfer the unique_lock.
// UNSUPPORTED: c++03
// This test requires the fix for LWG3343 (64fc3cd), which is done in the dylib
// and landed in LLVM 16. Due to the nature of the test, testing on a broken
// system does not guarantee that the test fails, so we use UNSUPPORTED instead
// of XFAIL.
// UNSUPPORTED: using-built-library-before-llvm-16
// This is a regression test for LWG3343.
//
// <condition_variable>
//
// void notify_all_at_thread_exit(condition_variable& cond, unique_lock<mutex> lk);
#include "make_test_thread.h"
#include "test_macros.h"
#include <condition_variable>
#include <cassert>
#include <chrono>
#include <memory>
#include <mutex>
#include <thread>
int condition_variable_lock_skipped_counter = 0;
TEST_DIAGNOSTIC_PUSH
// MSVC warning C4583: 'X::cv_': destructor is not implicitly called
TEST_MSVC_DIAGNOSTIC_IGNORED(4583)
union X {
X() : cv_() {}
~X() {}
std::condition_variable cv_;
unsigned char bytes_[sizeof(std::condition_variable)];
};
TEST_DIAGNOSTIC_POP
void test()
{
constexpr int N = 3;
X x;
std::mutex m;
int threads_active = N;
for (int i = 0; i < N; ++i) {
std::thread t = support::make_test_thread([&] {
// Emulate work being done.
std::this_thread::sleep_for(std::chrono::milliseconds(1));
// Signal thread completion.
std::unique_lock<std::mutex> lk(m);
--threads_active;
std::notify_all_at_thread_exit(x.cv_, std::move(lk));
});
t.detach();
}
// Wait until all threads complete, i.e. until they've all
// decremented `threads_active` and then unlocked `m` at thread exit.
// It is possible that this `wait` may spuriously wake up,
// but it won't be able to continue until the last thread
// unlocks `m`.
{
std::unique_lock<std::mutex> lk(m);
// Due to OS scheduling the workers might have terminated when this
// code is reached. In that case the wait will not sleep and the call
// to notify_all_at_thread_exit has no effect; the condition variable
// will not be used here.
//
// Keep track of how often that happens, if too often the test needs
// to be improved.
if(threads_active == 0)
++condition_variable_lock_skipped_counter;
x.cv_.wait(lk, [&]() { return threads_active == 0; });
}
// Destroy the condition_variable and shred the bytes.
// Simulate reusing the memory for something else.
x.cv_.~condition_variable();
for (unsigned char& c : x.bytes_) {
c = 0xcd;
}
DoNotOptimize(x.bytes_);
// Check that the bytes still have the same value we just wrote to them.
// If any thread wrongly unlocked `m` before calling cv.notify_all(), and
// cv.notify_all() writes to the memory of the cv, then we have a chance
// to detect the problem here.
int sum = 0;
for (unsigned char c : x.bytes_) {
sum += c;
}
DoNotOptimize(sum);
assert(sum == (0xcd * sizeof(std::condition_variable)));
}
int main(int, char**)
{
for (int i = 0; i < 1000; ++i) {
test();
}
// The threshold is arbitrary, it just makes sure the notification is
// tested a reasonable number of times.
assert(condition_variable_lock_skipped_counter < 250);
return 0;
}
|
