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// Copyright (c) 2020-2025 Andrey Semashev
//
// Distributed under the Boost Software License, Version 1.0.
// See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// This is a fuzzing test for waiting and notifying operations.
// The test creates a number of threads exceeding the number of hardware threads, each of which
// blocks on the atomic object. The main thread then notifies one or all threads repeatedly,
// while incrementing the atomic object. The test ends when the atomic counter reaches the predefined limit.
// The goal of the test is to verify that (a) it doesn't crash and (b) all threads get unblocked in the end.
#include <boost/memory_order.hpp>
#include <boost/atomic/atomic.hpp>
#include <chrono>
#include <thread>
#include <memory>
#include <iostream>
#include <boost/config.hpp>
#include "test_barrier.hpp"
boost::atomic< unsigned int > g_atomic(0u);
constexpr unsigned int loop_count = 4096u;
void thread_func(test_barrier* barrier)
{
barrier->arrive_and_wait();
unsigned int old_count = 0u;
while (true)
{
unsigned int new_count = g_atomic.wait(old_count, boost::memory_order_relaxed);
if (new_count >= loop_count)
break;
old_count = new_count;
}
}
int main()
{
const unsigned int thread_count = std::thread::hardware_concurrency() + 4u;
test_barrier barrier(thread_count + 1u);
std::unique_ptr< std::thread[] > threads(new std::thread[thread_count]);
for (unsigned int i = 0u; i < thread_count; ++i)
threads[i] = std::thread([&barrier]() { thread_func(&barrier); });
barrier.arrive_and_wait();
// Let the threads block on the atomic counter
std::this_thread::sleep_for(std::chrono::milliseconds(100));
while (true)
{
for (unsigned int i = 0u; i < thread_count; ++i)
{
g_atomic.opaque_add(1u, boost::memory_order_relaxed);
g_atomic.notify_one();
}
unsigned int old_count = g_atomic.fetch_add(1u, boost::memory_order_relaxed);
g_atomic.notify_all();
if ((old_count + 1u) >= loop_count)
break;
}
for (unsigned int i = 0u; i < thread_count; ++i)
threads[i].join();
return 0u;
}
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