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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_timed_mutex;
// template <class Clock, class Duration>
// bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
#include <mutex>
#include <atomic>
#include <cassert>
#include <chrono>
#include <thread>
#include "make_test_thread.h"
bool is_lockable(std::recursive_timed_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;
}
template <class Function>
std::chrono::microseconds measure(Function f) {
std::chrono::high_resolution_clock::time_point start = std::chrono::high_resolution_clock::now();
f();
std::chrono::high_resolution_clock::time_point end = std::chrono::high_resolution_clock::now();
return std::chrono::duration_cast<std::chrono::microseconds>(end - start);
}
int main(int, char**) {
// Try to lock a mutex that is not locked yet. This should succeed immediately.
{
std::recursive_timed_mutex m;
bool succeeded = m.try_lock_until(std::chrono::steady_clock::now() + std::chrono::milliseconds(1));
assert(succeeded);
m.unlock();
}
// Lock a mutex that is already locked by this thread. This should succeed immediately and the mutex
// should only be unlocked after a matching number of calls to unlock() on the same thread.
{
std::recursive_timed_mutex m;
int lock_count = 0;
for (int i = 0; i != 10; ++i) {
assert(m.try_lock_until(std::chrono::steady_clock::now() + std::chrono::milliseconds(1)));
++lock_count;
}
while (lock_count != 0) {
assert(!is_lockable(m));
m.unlock();
--lock_count;
}
assert(is_lockable(m));
}
// Try to lock an already-locked mutex for a long enough amount of time and succeed.
// This is technically flaky, but we use such long durations that it should pass even
// in slow or contended environments.
{
std::chrono::milliseconds const wait_time(500);
std::chrono::milliseconds const tolerance = wait_time * 3;
std::atomic<bool> ready(false);
std::recursive_timed_mutex m;
m.lock();
std::thread t = support::make_test_thread([&] {
auto elapsed = measure([&] {
ready = true;
bool succeeded = m.try_lock_until(std::chrono::steady_clock::now() + wait_time);
assert(succeeded);
m.unlock();
});
// Ensure we didn't wait significantly longer than our timeout. This is technically
// flaky and non-conforming because an implementation is free to block for arbitrarily
// long, but any decent quality implementation should pass this test.
assert(elapsed - wait_time < tolerance);
});
// Wait for the thread to be ready to take the lock before we unlock it from here, otherwise
// there's a high chance that we're not testing the "locking an already locked" mutex use case.
// There is still technically a race condition here.
while (!ready)
/* spin */;
std::this_thread::sleep_for(wait_time / 5);
m.unlock(); // this should allow the thread to lock 'm'
t.join();
}
// Try to lock an already-locked mutex for a short amount of time and fail.
// Again, this is technically flaky but we use such long durations that it should work.
{
std::chrono::milliseconds const wait_time(10);
std::chrono::milliseconds const tolerance(750); // in case the thread we spawned goes to sleep or something
std::recursive_timed_mutex m;
m.lock();
std::thread t = support::make_test_thread([&] {
auto elapsed = measure([&] {
bool succeeded = m.try_lock_until(std::chrono::steady_clock::now() + wait_time);
assert(!succeeded);
});
// Ensure we failed within some bounded time.
assert(elapsed - wait_time < tolerance);
});
t.join();
m.unlock();
}
return 0;
}
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