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//===----------------------------------------------------------------------===//
//
// 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 recursive_mutex;
// bool try_lock();
#include <mutex>
#include <atomic>
#include <cassert>
#include <chrono>
#include <thread>
#include "make_test_thread.h"
bool is_lockable(std::recursive_mutex& m) {
bool did_lock;
std::thread t = support::make_test_thread([&] {
did_lock = m.try_lock();
if (did_lock)
m.unlock(); // undo side effects
});
t.join();
return did_lock;
}
int main(int, char**) {
// Try to lock a mutex that is not locked yet. This should succeed.
{
std::recursive_mutex m;
bool succeeded = m.try_lock();
assert(succeeded);
m.unlock();
}
// Try to lock a mutex that is already locked by this thread. This should succeed and the mutex should only
// be unlocked after a matching number of calls to unlock() on the same thread.
{
std::recursive_mutex m;
int lock_count = 0;
for (int i = 0; i != 10; ++i) {
assert(m.try_lock());
++lock_count;
}
while (lock_count != 0) {
assert(!is_lockable(m));
m.unlock();
--lock_count;
}
assert(is_lockable(m));
}
// Try to lock a mutex that is already locked by another thread. This should fail.
{
std::recursive_mutex m;
m.lock();
std::thread t = support::make_test_thread([&] {
for (int i = 0; i != 10; ++i) {
bool succeeded = m.try_lock();
assert(!succeeded);
}
});
t.join();
m.unlock();
}
return 0;
}
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