Merge pull request #2470 from degasus/syncgpu

Common: Blocking Loop (extracted from Fifo.cpp)

Source/Core/Common/BlockingLoop.h

@@ -0,0 +1,214 @@
+// Copyright 2015 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <atomic>
+#include <mutex>
+#include <thread>
+
+#include "Common/Event.h"
+#include "Common/Flag.h"
+
+namespace Common
+{
+
+// This class provides a synchronized loop.
+// It's a thread-safe way to trigger a new iteration without busy loops.
+// It's optimized for high-usage iterations which usually are already running while it's triggered often.
+// Be careful on using Wait() and Wakeup() at the same time. Wait() may block forever while Wakeup() is called regulary.
+class BlockingLoop
+{
+public:
+	BlockingLoop()
+	{
+		m_stopped.Set();
+	}
+
+	~BlockingLoop()
+	{
+		Stop();
+	}
+
+	// Triggers to rerun the payload of the Run() function at least once again.
+	// This function will never block and is designed to finish as fast as possible.
+	void Wakeup()
+	{
+		// Already running, so no need for a wakeup.
+		// This is the common case, so try to get this as fast as possible.
+		if (m_running_state.load() >= STATE_NEED_EXECUTION)
+			return;
+
+		// Mark that new data is available. If the old state will rerun the payload
+		// itself, we don't have to set the event to interrupt the worker.
+		if (m_running_state.exchange(STATE_NEED_EXECUTION) != STATE_SLEEPING)
+			return;
+
+		// Else as the worker thread may sleep now, we have to set the event.
+		m_new_work_event.Set();
+	}
+
+	// Wait for a complete payload run after the last Wakeup() call.
+	// If stopped, this returns immediately.
+	void Wait()
+	{
+		// already done
+		if (m_stopped.IsSet() || m_running_state.load() <= STATE_DONE)
+			return;
+
+		// notifying this event will only wake up one thread, so use a mutex here to
+		// allow only one waiting thread. And in this way, we get an event free wakeup
+		// but for the first thread for free
+		std::lock_guard<std::mutex> lk(m_wait_lock);
+
+		// Wait for the worker thread to finish.
+		while (!m_stopped.IsSet() && m_running_state.load() > STATE_DONE)
+		{
+			m_done_event.Wait();
+		}
+
+		// As we wanted to wait for the other thread, there is likely no work remaining.
+		// So there is no need for a busy loop any more.
+		m_may_sleep.Set();
+	}
+
+	// Half start the worker.
+	// So this object is in a running state and Wait() will block until the worker calls Run().
+	// This may be called from any thread and is supposed to call at least once before Wait() is used.
+	void Prepare()
+	{
+		// There is a race condition if the other threads call this function while
+		// the loop thread is initializing. Using this lock will ensure a valid state.
+		std::lock_guard<std::mutex> lk(m_prepare_lock);
+
+		if (!m_stopped.TestAndClear())
+			return;
+		m_running_state.store(STATE_LAST_EXECUTION); // so the payload will only be executed once without any Wakeup call
+		m_shutdown.Clear();
+		m_may_sleep.Set();
+	}
+
+	// Mainloop of this object.
+	// The payload callback is called at least as often as it's needed to match the Wakeup() requirements.
+	// The optional timeout parameters is a timeout how periodicly the payload should be called.
+	// Use timeout = 0 to run without a timeout at all.
+	template<class F> void Run(F payload, int64_t timeout = 0)
+	{
+		// Asserts that Prepare is called at least once before we enter the loop.
+		// But a good implementation should call this before already.
+		Prepare();
+
+		while (!m_shutdown.IsSet())
+		{
+			payload();
+
+			switch (m_running_state.load())
+			{
+				case STATE_NEED_EXECUTION:
+					// We won't get notified while we are in the STATE_NEED_EXECUTION state, so maybe Wakeup was called.
+					// So we have to assume on finishing the STATE_NEED_EXECUTION state, that there may be some remaining tasks.
+					// To process this tasks, we call the payload again within the STATE_LAST_EXECUTION state.
+					m_running_state--;
+					break;
+
+				case STATE_LAST_EXECUTION:
+					// If we're still in the STATE_LAST_EXECUTION state, than Wakeup wasn't called within the last
+					// execution of payload. This means we should be ready now.
+					// But bad luck, Wakeup might have be called right now. So break and rerun the payload
+					// if the state was touched right now.
+					if (m_running_state-- != STATE_LAST_EXECUTION)
+						break;
+
+					// Else we're likely in the STATE_DONE state now, so wakeup the waiting threads right now.
+					// However, if we're not in the STATE_DONE state any more, the event should also be
+					// triggered so that we'll skip the next waiting call quite fast.
+					m_done_event.Set();
+
+				case STATE_DONE:
+					// We're done now. So time to check if we want to sleep or if we want to stay in a busy loop.
+					if (m_may_sleep.TestAndClear())
+					{
+						// Try to set the sleeping state.
+						if (m_running_state-- != STATE_DONE)
+							break;
+					}
+					else
+					{
+						// Busy loop.
+						break;
+					}
+
+				case STATE_SLEEPING:
+					// Just relax
+					if (timeout > 0)
+					{
+						m_new_work_event.WaitFor(std::chrono::milliseconds(timeout));
+					}
+					else
+					{
+						m_new_work_event.Wait();
+					}
+					break;
+			}
+		}
+
+		// Shutdown down, so get a safe state
+		m_running_state.store(STATE_DONE);
+		m_stopped.Set();
+
+		// Wake up the last Wait calls.
+		m_done_event.Set();
+	}
+
+	// Quits the mainloop.
+	// By default, it will wait until the Mainloop quits.
+	// Be careful to not use the blocking way within the payload of the Run() method.
+	void Stop(bool block = true)
+	{
+		if (m_stopped.IsSet())
+			return;
+
+		m_shutdown.Set();
+
+		// We have to interrupt the sleeping call to let the worker shut down soon.
+		Wakeup();
+
+		if (block)
+			Wait();
+	}
+
+	bool IsRunning() const
+	{
+		return !m_stopped.IsSet() && !m_shutdown.IsSet();
+	}
+
+	// This functions should be triggered by regulary by time. So we will fall back from
+	// the busy loop to the sleeping way.
+	void AllowSleep()
+	{
+		m_may_sleep.Set();
+	}
+
+private:
+	std::mutex m_wait_lock;
+	std::mutex m_prepare_lock;
+
+	Flag m_stopped;  // This one is set, Wait() shall not block.
+	Flag m_shutdown; // If this one is set, the loop shall be quit.
+
+	Event m_new_work_event;
+	Event m_done_event;
+
+	enum RUNNING_TYPE {
+		STATE_SLEEPING = 0,
+		STATE_DONE = 1,
+		STATE_LAST_EXECUTION = 2,
+		STATE_NEED_EXECUTION = 3
+	};
+	std::atomic<int> m_running_state; // must be of type RUNNING_TYPE
+
+	Flag m_may_sleep; // If this one is set, we fall back from the busy loop to an event based synchronization.
+};
+
+}

Source/Core/Common/Common.vcxproj

@@ -40,6 +40,7 @@
     <ClInclude Include="Atomic_Win32.h" />
     <ClInclude Include="BitField.h" />
     <ClInclude Include="BitSet.h" />
+    <ClInclude Include="BlockLoop.h" />
     <ClInclude Include="BreakPoints.h" />
     <ClInclude Include="CDUtils.h" />
     <ClInclude Include="ChunkFile.h" />

Source/Core/Common/Common.vcxproj.filters

@@ -14,6 +14,7 @@
     <ClInclude Include="Atomic_Win32.h" />
     <ClInclude Include="BitField.h" />
     <ClInclude Include="BitSet.h" />
+    <ClInclude Include="BlockingLoop.h" />
     <ClInclude Include="BreakPoints.h" />
     <ClInclude Include="CDUtils.h" />
     <ClInclude Include="ChunkFile.h" />
@@ -126,4 +127,4 @@
   <ItemGroup>
     <Text Include="CMakeLists.txt" />
   </ItemGroup>
-</Project>
+</Project>