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// Copyright 2025 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#include <gtest/gtest.h>
#include <algorithm>
#include <chrono>
#include <mutex>
#include <shared_mutex>
#include <thread>
#include "Common/Mutex.h"
#include "Common/TransferableSharedMutex.h"
template <typename MutexType>
static void DoAtomicMutexTests(const char mutex_name[])
{
MutexType work_mutex;
bool worker_done = false;
static constexpr auto SLEEP_TIME = std::chrono::microseconds{1};
// lock() on main thread, unlock() on worker thread.
std::thread thread{[&, lk = std::unique_lock{work_mutex}] {
std::this_thread::sleep_for(SLEEP_TIME);
worker_done = true;
}};
// lock() waits for the thread to unlock().
{
std::lock_guard lk{work_mutex};
EXPECT_TRUE(worker_done);
}
thread.join();
// Prevent below workers from incrementing `done_count`.
MutexType done_mutex;
std::unique_lock done_lk{done_mutex};
// try_lock() fails when holding a lock.
EXPECT_FALSE(done_mutex.try_lock());
static constexpr int THREAD_COUNT = 4;
static constexpr int REPEAT_COUNT = 100;
static constexpr int TOTAL_ITERATIONS = THREAD_COUNT * REPEAT_COUNT;
int done_count = 0;
int work_count = 0;
std::atomic<int> try_lock_fail_count{};
std::vector<std::thread> threads(THREAD_COUNT);
for (auto& t : threads)
{
t = std::thread{[&] {
// lock() blocks until main thread unlock()s.
{
std::lock_guard lk{done_mutex};
++done_count;
}
// Contesting lock() and try_lock() doesn't explode.
for (int i = 0; i != REPEAT_COUNT; ++i)
{
{
std::lock_guard lk{work_mutex};
++work_count;
}
// Try lock in a loop.
while (!work_mutex.try_lock())
{
try_lock_fail_count.fetch_add(1, std::memory_order_relaxed);
}
std::lock_guard lk{work_mutex, std::adopt_lock};
++work_count;
}
}};
}
std::this_thread::sleep_for(SLEEP_TIME);
// The threads are still blocking on done_mutex.
EXPECT_EQ(done_count, 0);
done_lk.unlock();
std::ranges::for_each(threads, &std::thread::join);
// The threads finished.
EXPECT_EQ(done_count, THREAD_COUNT);
EXPECT_EQ(work_count, TOTAL_ITERATIONS * 2);
GTEST_LOG_(INFO) << mutex_name << "::try_lock() failure %: "
<< (try_lock_fail_count * 100.0 / (TOTAL_ITERATIONS + try_lock_fail_count));
// Things are still sane after contesting in worker threads.
std::lock_guard lk{work_mutex};
}
TEST(Mutex, AtomicMutex)
{
DoAtomicMutexTests<Common::AtomicMutex>("AtomicMutex");
DoAtomicMutexTests<Common::SpinMutex>("SpinMutex");
}
TEST(Mutex, TransferableSharedMutex)
{
Common::TransferableSharedMutex work_mutex;
bool worker_done = false;
static constexpr auto SLEEP_TIME = std::chrono::microseconds{1};
// lock() on main thread, unlock() on worker thread.
std::thread thread{[&, lk = std::unique_lock{work_mutex}] {
std::this_thread::sleep_for(SLEEP_TIME);
worker_done = true;
}};
// lock() waits for the thread to unlock().
{
std::lock_guard lk{work_mutex};
EXPECT_TRUE(worker_done);
}
thread.join();
// Prevent below workers from incrementing `done_count`.
Common::TransferableSharedMutex done_mutex;
std::unique_lock done_lk{done_mutex};
// try_*() fails when holding an exclusive lock.
EXPECT_FALSE(done_mutex.try_lock());
EXPECT_FALSE(done_mutex.try_lock_shared());
static constexpr int THREAD_COUNT = 4;
static constexpr int REPEAT_COUNT = 100;
static constexpr int TOTAL_ITERATIONS = THREAD_COUNT * REPEAT_COUNT;
std::atomic<int> work_count = 0;
std::atomic<int> done_count = 0;
int additional_work_count = 0;
std::atomic<int> try_lock_fail_count = 0;
std::atomic<int> try_lock_shared_fail_count = 0;
std::vector<std::thread> threads(THREAD_COUNT);
for (auto& t : threads)
{
// lock_shared() multiple times on main thread.
t = std::thread{[&, work_lk = std::shared_lock{work_mutex}]() mutable {
std::this_thread::sleep_for(SLEEP_TIME);
// try_lock() fails after lock_shared().
EXPECT_FALSE(work_mutex.try_lock());
// Main thread already holds done_mutex.
EXPECT_FALSE(done_mutex.try_lock());
EXPECT_FALSE(done_mutex.try_lock_shared());
++work_count;
// Signal work is done.
work_lk.unlock();
// lock_shared() blocks until main thread unlock()s.
{
std::shared_lock lk{done_mutex};
++done_count;
}
// Contesting all of [try_]lock[_shared] doesn't explode.
for (int i = 0; i != REPEAT_COUNT; ++i)
{
while (!work_mutex.try_lock())
{
try_lock_fail_count.fetch_add(1, std::memory_order_relaxed);
}
work_mutex.unlock();
while (!work_mutex.try_lock_shared())
{
try_lock_shared_fail_count.fetch_add(1, std::memory_order_relaxed);
}
work_mutex.unlock_shared();
{
std::lock_guard lk{work_mutex};
++additional_work_count;
}
std::shared_lock lk{work_mutex};
}
}};
}
// lock() waits for threads to unlock_shared().
{
std::lock_guard lk{work_mutex};
EXPECT_EQ(work_count.load(std::memory_order_relaxed), THREAD_COUNT);
}
std::this_thread::sleep_for(SLEEP_TIME);
// The threads are still blocking on done_mutex.
EXPECT_EQ(done_count, 0);
done_lk.unlock();
std::ranges::for_each(threads, &std::thread::join);
// The threads finished.
EXPECT_EQ(done_count, THREAD_COUNT);
EXPECT_EQ(additional_work_count, TOTAL_ITERATIONS);
GTEST_LOG_(INFO) << "try_lock() failure %: "
<< (try_lock_fail_count * 100.0 / (TOTAL_ITERATIONS + try_lock_fail_count));
GTEST_LOG_(INFO) << "try_lock_shared() failure %: "
<< (try_lock_shared_fail_count * 100.0 /
(TOTAL_ITERATIONS + try_lock_shared_fail_count));
// Things are still sane after contesting in worker threads.
done_lk.lock();
std::lock_guard lk{work_mutex};
}
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