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255 lines
8.1 KiB
C++
255 lines
8.1 KiB
C++
// SPDX-FileCopyrightText: 2002-2024 PCSX2 Dev Team
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// SPDX-License-Identifier: GPL-3.0+
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#pragma once
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#include "common/Pcsx2Defs.h"
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#if defined(__APPLE__)
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#include <mach/semaphore.h>
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#elif !defined(_WIN32)
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#include <semaphore.h>
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#endif
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#include <atomic>
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#include <functional>
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namespace Threading
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{
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// --------------------------------------------------------------------------------------
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// Platform Specific External APIs
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// --------------------------------------------------------------------------------------
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// The following set of documented functions have Linux/Win32 specific implementations,
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// which are found in WinThreads.cpp and LnxThreads.cpp
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extern u64 GetThreadCpuTime();
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extern u64 GetThreadTicksPerSecond();
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/// Set the name of the current thread
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extern void SetNameOfCurrentThread(const char* name);
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// Releases a timeslice to other threads.
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extern void Timeslice();
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// For use in spin/wait loops.
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extern void SpinWait();
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// Optional implementation to enable hires thread/process scheduler for the operating system.
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// Needed by Windows, but might not be relevant to other platforms.
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extern void EnableHiresScheduler();
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extern void DisableHiresScheduler();
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// sleeps the current thread for the given number of milliseconds.
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extern void Sleep(int ms);
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// sleeps the current thread until the specified time point, or later.
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extern void SleepUntil(u64 ticks);
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// --------------------------------------------------------------------------------------
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// ThreadHandle
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// --------------------------------------------------------------------------------------
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// Abstracts an OS's handle to a thread, closing the handle when necessary. Currently,
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// only used for getting the CPU time for a thread.
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//
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class ThreadHandle
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{
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public:
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ThreadHandle();
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ThreadHandle(ThreadHandle&& handle);
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ThreadHandle(const ThreadHandle& handle);
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~ThreadHandle();
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/// Returns a new handle for the calling thread.
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static ThreadHandle GetForCallingThread();
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ThreadHandle& operator=(ThreadHandle&& handle);
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ThreadHandle& operator=(const ThreadHandle& handle);
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operator void*() const { return m_native_handle; }
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operator bool() const { return (m_native_handle != nullptr); }
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/// Returns the amount of CPU time consumed by the thread, at the GetThreadTicksPerSecond() frequency.
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u64 GetCPUTime() const;
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/// Sets the affinity for a thread to the specified processors.
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/// Obviously, only works up to 64 processors.
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bool SetAffinity(u64 processor_mask) const;
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protected:
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void* m_native_handle = nullptr;
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// We need the thread ID for affinity adjustments on Linux.
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#if defined(__linux__)
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unsigned int m_native_id = 0;
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#endif
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};
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// --------------------------------------------------------------------------------------
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// Thread
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// --------------------------------------------------------------------------------------
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// Abstracts a native thread in a lightweight manner. Provides more functionality than
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// std::thread (allowing stack size adjustments).
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//
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class Thread : public ThreadHandle
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{
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public:
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using EntryPoint = std::function<void()>;
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Thread();
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Thread(Thread&& thread);
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Thread(const Thread&) = delete;
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Thread(EntryPoint func);
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~Thread();
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ThreadHandle& operator=(Thread&& thread);
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ThreadHandle& operator=(const Thread& handle) = delete;
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__fi bool Joinable() const { return (m_native_handle != nullptr); }
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__fi u32 GetStackSize() const { return m_stack_size; }
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/// Sets the stack size for the thread. Do not call if the thread has already been started.
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void SetStackSize(u32 size);
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bool Start(EntryPoint func);
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void Detach();
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void Join();
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protected:
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#ifdef _WIN32
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static unsigned __stdcall ThreadProc(void* param);
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#else
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static void* ThreadProc(void* param);
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#endif
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u32 m_stack_size = 0;
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};
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/// A semaphore that may not have a fast userspace path
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/// (Used in other semaphore-based algorithms where the semaphore is just used for its thread sleep/wake ability)
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class KernelSemaphore
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{
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#if defined(_WIN32)
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void* m_sema;
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#elif defined(__APPLE__)
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semaphore_t m_sema;
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#else
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sem_t m_sema;
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#endif
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public:
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KernelSemaphore();
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~KernelSemaphore();
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void Post();
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void Wait();
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bool TryWait();
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};
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/// A semaphore for notifying a work-processing thread of new work in a (separate) queue
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///
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/// Usage:
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/// - Processing thread loops on `WaitForWork()` followed by processing all work in the queue
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/// - Threads adding work first add their work to the queue, then call `NotifyOfWork()`
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class WorkSema
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{
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/// Semaphore for sleeping the worker thread
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KernelSemaphore m_sema;
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/// Semaphore for sleeping thread waiting on worker queue empty
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KernelSemaphore m_empty_sema;
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/// Current state (see enum below)
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std::atomic<s32> m_state{0};
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// Expected call frequency is NotifyOfWork > WaitForWork > WaitForEmpty
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// So optimize states for fast NotifyOfWork
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enum
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{
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/* Any <-2 state: STATE_DEAD: Thread has crashed and is awaiting revival */
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STATE_SPINNING = -2, ///< Worker thread is spinning waiting for work
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STATE_SLEEPING = -1, ///< Worker thread is sleeping on m_sema
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STATE_RUNNING_0 = 0, ///< Worker thread is processing work, but no work has been added since it last checked for new work
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/* Any >0 state: STATE_RUNNING_N: Worker thread is processing work, and work has been added since it last checked for new work */
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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)
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};
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bool IsDead(s32 state)
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{
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return state < STATE_SPINNING;
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}
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bool IsReadyForSleep(s32 state)
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{
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s32 waiting_empty_cleared = state & (STATE_FLAG_WAITING_EMPTY - 1);
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return waiting_empty_cleared == STATE_RUNNING_0;
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}
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s32 NextStateWaitForWork(s32 current)
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{
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s32 new_state = IsReadyForSleep(current) ? STATE_SLEEPING : STATE_RUNNING_0;
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return new_state | (current & STATE_FLAG_WAITING_EMPTY); // Preserve waiting empty flag for RUNNING_N → RUNNING_0
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}
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public:
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/// Notify the worker thread that you've added new work to its queue
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void NotifyOfWork()
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{
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// State change:
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// DEAD: Stay in DEAD (starting DEAD state is INT_MIN so we can assume we won't flip over to anything else)
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// SPINNING: Change state to RUNNING. Thread will notice and process the new data
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// SLEEPING: Change state to RUNNING and wake worker. Thread will wake up and process the new data.
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// RUNNING_0: Change state to RUNNING_N.
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// RUNNING_N: Stay in RUNNING_N
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s32 old = m_state.fetch_add(2, std::memory_order_release);
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if (old == STATE_SLEEPING)
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m_sema.Post();
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}
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/// Checks if there's any work in the queue
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bool CheckForWork();
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/// Wait for work to be added to the queue
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void WaitForWork();
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/// Wait for work to be added to the queue, spinning for a bit before sleeping the thread
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void WaitForWorkWithSpin();
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/// Wait for the worker thread to finish processing all entries in the queue or die
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/// Returns false if the thread is dead
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bool WaitForEmpty();
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/// Wait for the worker thread to finish processing all entries in the queue or die, spinning a bit before sleeping the thread
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/// Returns false if the thread is dead
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bool WaitForEmptyWithSpin();
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/// Called by the worker thread to notify others of its death
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/// Dead threads don't process work, and WaitForEmpty will return instantly even though there may be work in the queue
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void Kill();
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/// Reset the semaphore to the initial state
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/// Should be called by the worker thread if it restarts after dying
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void Reset();
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};
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/// A semaphore that definitely has a fast userspace path
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class UserspaceSemaphore
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{
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KernelSemaphore m_sema;
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std::atomic<int32_t> m_counter{0};
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public:
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UserspaceSemaphore() = default;
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~UserspaceSemaphore() = default;
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void Post()
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{
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if (m_counter.fetch_add(1, std::memory_order_release) < 0)
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m_sema.Post();
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}
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void Wait()
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{
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if (m_counter.fetch_sub(1, std::memory_order_acquire) <= 0)
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m_sema.Wait();
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}
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bool TryWait()
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{
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int32_t counter = m_counter.load(std::memory_order_relaxed);
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while (counter > 0 && !m_counter.compare_exchange_weak(counter, counter - 1, std::memory_order_acquire, std::memory_order_relaxed))
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;
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return counter > 0;
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}
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};
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} // namespace Threading
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