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// Copyright 2017 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once
#include <atomic>
#include <functional>
#include <mutex>
#include <string>
#include <thread>
#include "Common/Event.h"
#include "Common/SPSCQueue.h"
#include "Common/Thread.h"
// A thread that executes the given function for every item placed into its queue.
namespace Common
{
namespace detail
{
template <typename T, bool IsSingleProducer>
class WorkQueueThreadBase final
{
public:
WorkQueueThreadBase() = default;
WorkQueueThreadBase(std::string name, std::function<void(T)> 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, std::function<void(T)> function)
{
auto lg = GetLockGuard();
Shutdown();
m_run_thread.store(true, std::memory_order_relaxed);
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();
if (IsRunning())
{
m_skip_work.store(true, std::memory_order_relaxed);
WaitForCompletion();
m_skip_work.store(false, std::memory_order_relaxed);
}
else
{
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() { StopThread(true); }
// 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() { StopThread(false); }
// 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();
}
private:
void StopThread(bool wait_for_completion)
{
auto lg = GetLockGuard();
if (wait_for_completion)
WaitForCompletion();
if (m_run_thread.exchange(false, std::memory_order_relaxed))
{
m_event.Set();
m_thread.join();
}
}
auto GetLockGuard()
{
struct DummyLockGuard
{
// Silences unused variable warning.
~DummyLockGuard() { void(); }
};
if constexpr (IsSingleProducer)
return DummyLockGuard{};
else
return std::lock_guard{m_mutex};
}
bool IsRunning() { return m_thread.joinable(); }
void ThreadLoop(const std::string& thread_name, const std::function<void(T)>& function)
{
Common::SetCurrentThreadName(thread_name.c_str());
while (m_run_thread.load(std::memory_order_relaxed))
{
if (m_items.Empty())
{
m_event.Wait();
continue;
}
if (m_skip_work.load(std::memory_order_relaxed))
{
m_items.Clear();
continue;
}
function(std::move(m_items.Front()));
m_items.Pop();
}
}
std::thread m_thread;
Common::WaitableSPSCQueue<T> m_items;
Common::Event m_event;
std::atomic_bool m_skip_work = false;
std::atomic_bool m_run_thread = false;
using DummyMutex = std::type_identity<void>;
using ProducerMutex = std::conditional_t<IsSingleProducer, DummyMutex, std::recursive_mutex>;
ProducerMutex m_mutex;
};
} // 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>;
} // namespace Common
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