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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: no-threads, c++03
// <condition_variable>
// class condition_variable_any;
// template <class Lock, class Rep, class Period>
// cv_status
// wait_for(Lock& lock, const chrono::duration<Rep, Period>& rel_time);
#include <condition_variable>
#include <atomic>
#include <cassert>
#include <chrono>
#include <mutex>
#include <thread>
#include "make_test_thread.h"
#include "test_macros.h"
template <class Mutex>
struct MyLock : std::unique_lock<Mutex> {
using std::unique_lock<Mutex>::unique_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);
}
template <class Lock>
void test() {
using Mutex = typename Lock::mutex_type;
// Test unblocking via a call to notify_one() in another thread.
//
// To test this, we set a very long timeout in wait_for() and we wait
// again in case we get awoken spuriously. Note that it can actually
// happen that we get awoken spuriously and fail to recognize it
// (making this test useless), but the likelihood should be small.
{
std::atomic<bool> ready(false);
std::atomic<bool> likely_spurious(true);
auto timeout = std::chrono::seconds(3600);
std::condition_variable_any cv;
Mutex mutex;
std::thread t1 = support::make_test_thread([&] {
Lock lock(mutex);
auto elapsed = measure([&] {
ready = true;
do {
std::cv_status result = cv.wait_for(lock, timeout);
assert(result == std::cv_status::no_timeout);
} while (likely_spurious);
});
// This can technically fail if we have many spurious awakenings, but in practice the
// tolerance is so high that it shouldn't be a problem.
assert(elapsed < timeout);
});
std::thread t2 = support::make_test_thread([&] {
while (!ready) {
// spin
}
// Acquire the same mutex as t1. This blocks the condition variable inside its wait call
// so we can notify it while it is waiting.
Lock lock(mutex);
cv.notify_one();
likely_spurious = false;
lock.unlock();
});
t2.join();
t1.join();
}
// Test unblocking via a timeout.
//
// To test this, we create a thread that waits on a condition variable
// with a certain timeout, and we never awaken it. To guard against
// spurious wakeups, we wait again whenever we are awoken for a reason
// other than a timeout.
{
auto timeout = std::chrono::milliseconds(250);
std::condition_variable_any cv;
Mutex mutex;
std::thread t1 = support::make_test_thread([&] {
Lock lock(mutex);
std::cv_status result;
do {
auto elapsed = measure([&] { result = cv.wait_for(lock, timeout); });
if (result == std::cv_status::timeout)
assert(elapsed >= timeout);
} while (result != std::cv_status::timeout);
});
t1.join();
}
}
int main(int, char**) {
test<std::unique_lock<std::mutex>>();
test<std::unique_lock<std::timed_mutex>>();
test<MyLock<std::mutex>>();
test<MyLock<std::timed_mutex>>();
return 0;
}
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