pcsx2/common/Threading.h

/*  PCSX2 - PS2 Emulator for PCs
 *  Copyright (C) 2002-2010  PCSX2 Dev Team
 *
 *  PCSX2 is free software: you can redistribute it and/or modify it under the terms
 *  of the GNU Lesser General Public License as published by the Free Software Found-
 *  ation, either version 3 of the License, or (at your option) any later version.
 *
 *  PCSX2 is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 *  PURPOSE.  See the GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along with PCSX2.
 *  If not, see <http://www.gnu.org/licenses/>.
 */

#pragma once

#include <wx/datetime.h>
#ifdef _WIN32
// thanks I hate it.
#include <wx/filefn.h>
#define HAVE_MODE_T
#endif
#include <semaphore.h>
#include <errno.h> // EBUSY
#include <pthread.h>
#ifdef __APPLE__
#include <mach/semaphore.h>
#endif
#include "common/Pcsx2Defs.h"
#include "common/TraceLog.h"
#include "common/General.h"
#include <atomic>

// --------------------------------------------------------------------------------------
//  PCSX2_THREAD_LOCAL - Defines platform/operating system support for Thread Local Storage
// --------------------------------------------------------------------------------------
//
// TLS is enabled by default. It will be disabled at compile time for Linux plugin.
// If you link SPU2X/ZZOGL with a TLS library, you will consume a DVT slots. Slots
// are rather limited and it ends up to "impossible to dlopen the library"
// None of the above plugin uses TLS variable in a multithread context
#ifndef PCSX2_THREAD_LOCAL
#define PCSX2_THREAD_LOCAL 1
#endif

#if PCSX2_THREAD_LOCAL
#define DeclareTls(x) thread_local x
#else
#define DeclareTls(x) x
#endif

namespace Threading
{
	class ThreadHandle;
	class pxThread;
	class RwMutex;

	extern void pxTestCancel();
	extern void YieldToMain();

	extern u64 GetThreadCpuTime();
	extern u64 GetThreadTicksPerSecond();

	/// Set the name of the current thread
	extern void SetNameOfCurrentThread(const char* name);

	extern const wxTimeSpan def_yieldgui_interval;
} // namespace Threading

namespace Threading
{
	// --------------------------------------------------------------------------------------
	//  Platform Specific External APIs
	// --------------------------------------------------------------------------------------
	// The following set of documented functions have Linux/Win32 specific implementations,
	// which are found in WinThreads.cpp and LnxThreads.cpp

	// Releases a timeslice to other threads.
	extern void Timeslice();

	// For use in spin/wait loops.
	extern void SpinWait();

	// Optional implementation to enable hires thread/process scheduler for the operating system.
	// Needed by Windows, but might not be relevant to other platforms.
	extern void EnableHiresScheduler();
	extern void DisableHiresScheduler();

	// sleeps the current thread for the given number of milliseconds.
	extern void Sleep(int ms);

	// --------------------------------------------------------------------------------------
	//  ThreadHandle
	// --------------------------------------------------------------------------------------
	// Abstracts an OS's handle to a thread, closing the handle when necessary. Currently,
	// only used for getting the CPU time for a thread.
	//
	class ThreadHandle
	{
	public:
		ThreadHandle();
		ThreadHandle(ThreadHandle&& handle);
		ThreadHandle(const ThreadHandle& handle);
		~ThreadHandle();

		/// Returns a new handle for the calling thread.
		static ThreadHandle GetForCallingThread();

		ThreadHandle& operator=(ThreadHandle&& handle);
		ThreadHandle& operator=(const ThreadHandle& handle);

		operator void*() const { return m_native_handle; }
		operator bool() const { return (m_native_handle != nullptr); }

		/// Returns the amount of CPU time consumed by the thread, at the GetThreadTicksPerSecond() frequency.
		u64 GetCPUTime() const;

		/// Sets the affinity for a thread to the specified processors.
		/// Obviously, only works up to 64 processors.
		bool SetAffinity(u64 processor_mask) const;

	private:
		void* m_native_handle = nullptr;

		// We need the thread ID for affinity adjustments on Linux.
#if defined(__linux__)
		unsigned int m_native_id = 0;
#endif
	};

	// --------------------------------------------------------------------------------------
	//  NonblockingMutex
	// --------------------------------------------------------------------------------------
	// This is a very simple non-blocking mutex, which behaves similarly to pthread_mutex's
	// trylock(), but without any of the extra overhead needed to set up a structure capable
	// of blocking waits.  It basically optimizes to a single InterlockedExchange.
	//
	// Simple use: if TryAcquire() returns false, the Bool is already interlocked by another thread.
	// If TryAcquire() returns true, you've locked the object and are *responsible* for unlocking
	// it later.
	//
	class NonblockingMutex
	{
	protected:
		std::atomic_flag val;

	public:
		NonblockingMutex() { val.clear(); }
		virtual ~NonblockingMutex() = default;

		bool TryAcquire() noexcept
		{
			return !val.test_and_set();
		}

		// Can be done with a TryAcquire/Release but it is likely better to do it outside of the object
		bool IsLocked()
		{
			pxAssertMsg(0, "IsLocked isn't supported for NonblockingMutex");
			return false;
		}

		void Release()
		{
			val.clear();
		}
	};

	/// A semaphore that may not have a fast userspace path
	/// (Used in other semaphore-based algorithms where the semaphore is just used for its thread sleep/wake ability)
	class KernelSemaphore
	{
#if defined(_WIN32)
		void* m_sema;
#elif defined(__APPLE__)
		semaphore_t m_sema;
#else
		sem_t m_sema;
#endif
	public:
		KernelSemaphore();
		~KernelSemaphore();
		void Post();
		void Wait();
		bool TryWait();
	};

	/// A semaphore for notifying a work-processing thread of new work in a (separate) queue
	///
	/// Usage:
	/// - Processing thread loops on `WaitForWork()` followed by processing all work in the queue
	/// - Threads adding work first add their work to the queue, then call `NotifyOfWork()`
	class WorkSema
	{
		/// Semaphore for sleeping the worker thread
		KernelSemaphore m_sema;
		/// Semaphore for sleeping thread waiting on worker queue empty
		KernelSemaphore m_empty_sema;
		/// Current state (see enum below)
		std::atomic<s32> m_state{0};

		// Expected call frequency is NotifyOfWork > WaitForWork > WaitForEmpty
		// So optimize states for fast NotifyOfWork
		enum
		{
			/* Any <-2 state: STATE_DEAD: Thread has crashed and is awaiting revival */
			STATE_SPINNING = -2, ///< Worker thread is spinning waiting for work
			STATE_SLEEPING = -1, ///< Worker thread is sleeping on m_sema
			STATE_RUNNING_0 = 0, ///< Worker thread is processing work, but no work has been added since it last checked for new work
			/* Any >0 state: STATE_RUNNING_N: Worker thread is processing work, and work has been added since it last checked for new work */
			STATE_FLAG_WAITING_EMPTY = 1 << 30, ///< Flag to indicate that a thread is sleeping on m_empty_sema (can be applied to any STATE_RUNNING)
		};

		bool IsDead(s32 state)
		{
			return state < STATE_SPINNING;
		}

		bool IsReadyForSleep(s32 state)
		{
			s32 waiting_empty_cleared = state & (STATE_FLAG_WAITING_EMPTY - 1);
			return waiting_empty_cleared == STATE_RUNNING_0;
		}

		s32 NextStateWaitForWork(s32 current)
		{
			s32 new_state = IsReadyForSleep(current) ? STATE_SLEEPING : STATE_RUNNING_0;
			return new_state | (current & STATE_FLAG_WAITING_EMPTY); // Preserve waiting empty flag for RUNNING_N → RUNNING_0
		}

	public:
		/// Notify the worker thread that you've added new work to its queue
		void NotifyOfWork()
		{
			// State change:
			// DEAD: Stay in DEAD (starting DEAD state is INT_MIN so we can assume we won't flip over to anything else)
			// SPINNING: Change state to RUNNING.  Thread will notice and process the new data
			// SLEEPING: Change state to RUNNING and wake worker.  Thread will wake up and process the new data.
			// RUNNING_0: Change state to RUNNING_N.
			// RUNNING_N: Stay in RUNNING_N
			s32 old = m_state.fetch_add(2, std::memory_order_release);
			if (old == STATE_SLEEPING)
				m_sema.Post();
		}

		/// Wait for work to be added to the queue
		void WaitForWork();
		/// Wait for work to be added to the queue, spinning for a bit before sleeping the thread
		void WaitForWorkWithSpin();
		/// Wait for the worker thread to finish processing all entries in the queue or die
		/// Returns false if the thread is dead
		bool WaitForEmpty();
		/// Wait for the worker thread to finish processing all entries in the queue or die, spinning a bit before sleeping the thread
		/// Returns false if the thread is dead
		bool WaitForEmptyWithSpin();
		/// Called by the worker thread to notify others of its death
		/// Dead threads don't process work, and WaitForEmpty will return instantly even though there may be work in the queue
		void Kill();
		/// Reset the semaphore to the initial state
		/// Should be called by the worker thread if it restarts after dying
		void Reset();
	};

	class Mutex
	{
	protected:
		pthread_mutex_t m_mutex;

	public:
		Mutex();
		virtual ~Mutex();
		virtual bool IsRecursive() const { return false; }

		void Recreate();
		bool RecreateIfLocked();
		void Detach();

		void Acquire();
		bool Acquire(const wxTimeSpan& timeout);
		bool TryAcquire();
		void Release();

		void AcquireWithoutYield();
		bool AcquireWithoutYield(const wxTimeSpan& timeout);

		void Wait();
		void WaitWithSpin();
		bool Wait(const wxTimeSpan& timeout);
		void WaitWithoutYield();
		bool WaitWithoutYield(const wxTimeSpan& timeout);

	protected:
		// empty constructor used by MutexLockRecursive
		Mutex(bool) {}
	};

	class MutexRecursive : public Mutex
	{
	public:
		MutexRecursive();
		virtual ~MutexRecursive();
		virtual bool IsRecursive() const { return true; }
	};

	// --------------------------------------------------------------------------------------
	//  ScopedLock
	// --------------------------------------------------------------------------------------
	// Helper class for using Mutexes.  Using this class provides an exception-safe (and
	// generally clean) method of locking code inside a function or conditional block.  The lock
	// will be automatically released on any return or exit from the function.
	//
	// Const qualification note:
	//  ScopedLock takes const instances of the mutex, even though the mutex is modified
	//  by locking and unlocking.  Two rationales:
	//
	//  1) when designing classes with accessors (GetString, GetValue, etc) that need mutexes,
	//     this class needs a const hack to allow those accessors to be const (which is typically
	//     *very* important).
	//
	//  2) The state of the Mutex is guaranteed to be unchanged when the calling function or
	//     scope exits, by any means.  Only via manual calls to Release or Acquire does that
	//     change, and typically those are only used in very special circumstances of their own.
	//
	class ScopedLock
	{
		DeclareNoncopyableObject(ScopedLock);

	protected:
		Mutex* m_lock;
		bool m_IsLocked;

	public:
		virtual ~ScopedLock();
		explicit ScopedLock(const Mutex* locker = NULL);
		explicit ScopedLock(const Mutex& locker);
		void AssignAndLock(const Mutex& locker);
		void AssignAndLock(const Mutex* locker);

		void Assign(const Mutex& locker);
		void Assign(const Mutex* locker);

		void Release();
		void Acquire();

		bool IsLocked() const { return m_IsLocked; }

	protected:
		// Special constructor used by ScopedTryLock
		ScopedLock(const Mutex& locker, bool isTryLock);
	};
} // namespace Threading