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// Copyright 2017 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once
#include <functional>
#include <future>
#include <mutex>
#include <string>
#include <thread>
#include "Common/Event.h"
#include "Common/SPSCQueue.h"
#include "Common/Thread.h"
namespace Common
{
namespace detail
{
template <typename T, bool IsSingleProducer>
class WorkQueueThreadBase final
{
public:
using FunctionType = std::function<void(T)>;
WorkQueueThreadBase() = default;
WorkQueueThreadBase(std::string name, FunctionType function)
{
Reset(std::move(name), std::move(function));
}
~WorkQueueThreadBase() { Shutdown(); }
// Shuts the current work thread down (if any) and starts a new thread with the given function
// Note: Some consumers of this API push items to the queue before starting the thread.
void Reset(std::string name, FunctionType function)
{
auto lg = GetLockGuard();
Shutdown();
m_thread = std::thread(std::bind_front(&WorkQueueThreadBase::ThreadLoop, this), std::move(name),
std::move(function));
}
// Adds an item to the work queue
template <typename... Args>
void EmplaceItem(Args&&... args)
{
auto lg = GetLockGuard();
m_items.Emplace(std::forward<Args>(args)...);
m_event.Set();
}
void Push(T&& item) { EmplaceItem(std::move(item)); }
void Push(const T& item) { EmplaceItem(item); }
// Empties the queue, skipping all work.
// Blocks until the current work is cancelled.
void Cancel()
{
auto lg = GetLockGuard();
// Fast path avoids round trip thread communication and saves ~20us.
if (m_items.Empty())
return;
RunCommand([&] { m_items.Clear(); });
}
// Tells the worker thread to stop when its queue is empty.
// Blocks until the worker thread exits. Does nothing if thread isn't running.
void Shutdown()
{
auto lg = GetLockGuard();
WaitForCompletion();
StopThread();
}
// Tells the worker thread to stop immediately, potentially leaving work in the queue.
// Blocks until the worker thread exits. Does nothing if thread isn't running.
void Stop()
{
auto lg = GetLockGuard();
StopThread();
}
// Stops the worker thread ASAP and empties the queue.
void StopAndCancel()
{
auto lg = GetLockGuard();
Stop();
Cancel();
}
// Blocks until all items in the queue have been processed (or cancelled)
// Does nothing if thread isn't running.
void WaitForCompletion()
{
auto lg = GetLockGuard();
if (IsRunning())
m_items.WaitForEmpty();
}
bool IsRunning() { return m_thread.joinable(); }
private:
using CommandFunction = std::function<void()>;
// Blocking.
void RunCommand(CommandFunction cmd)
{
if (!IsRunning())
{
std::invoke(cmd);
return;
}
m_commands.Emplace(std::move(cmd));
m_event.Set();
m_commands.WaitForEmpty();
}
// Stop immediately.
void StopThread()
{
if (!m_thread.joinable())
return;
// empty-function shutdown signal.
m_commands.Emplace(CommandFunction{});
m_event.Set();
m_thread.join();
m_commands.Clear();
}
auto GetLockGuard()
{
struct DummyLockGuard
{
// Silences unused variable warning.
~DummyLockGuard() { void(); }
};
if constexpr (IsSingleProducer)
return DummyLockGuard{};
else
return std::lock_guard{m_mutex};
}
void ThreadLoop(const std::string& thread_name, const FunctionType& function)
{
Common::SetCurrentThreadName(thread_name.c_str());
while (true)
{
while (!m_commands.Empty())
{
CommandFunction& command = m_commands.Front();
// empty-function shutdown signal.
if (!command)
return;
std::invoke(command);
m_commands.Pop();
}
if (m_items.Empty())
{
m_event.Wait();
continue;
}
function(std::move(m_items.Front()));
m_items.Pop();
}
}
std::thread m_thread;
Common::WaitableSPSCQueue<T> m_items;
Common::WaitableSPSCQueue<CommandFunction> m_commands;
Common::Event m_event;
using DummyMutex = std::type_identity<void>;
using ProducerMutex = std::conditional_t<IsSingleProducer, DummyMutex, std::recursive_mutex>;
ProducerMutex m_mutex;
};
// A WorkQueueThread-like class that takes functions to invoke.
template <template <typename> typename WorkThread>
class AsyncWorkThreadBase
{
public:
using FuncType = std::function<void()>;
AsyncWorkThreadBase() = default;
explicit AsyncWorkThreadBase(std::string thread_name) { Reset(std::move(thread_name)); }
void Reset(std::string thread_name)
{
m_worker.Reset(std::move(thread_name), std::invoke<FuncType>);
}
void Push(FuncType func) { m_worker.Push(std::move(func)); }
auto PushBlocking(FuncType func)
{
std::packaged_task task{std::move(func)};
m_worker.EmplaceItem([&] { task(); });
return task.get_future().get();
}
void Cancel() { m_worker.Cancel(); }
void Shutdown() { m_worker.Shutdown(); }
void WaitForCompletion() { m_worker.WaitForCompletion(); }
private:
WorkThread<FuncType> m_worker;
};
} // namespace detail
// Multiple threads may use the public interface.
template <typename T>
using WorkQueueThread = detail::WorkQueueThreadBase<T, false>;
// A "Single Producer" WorkQueueThread.
// It uses no mutex but only one thread can safely manipulate the queue.
template <typename T>
using WorkQueueThreadSP = detail::WorkQueueThreadBase<T, true>;
using AsyncWorkThread = detail::AsyncWorkThreadBase<WorkQueueThread>;
using AsyncWorkThreadSP = detail::AsyncWorkThreadBase<WorkQueueThreadSP>;
} // namespace Common
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