Files
ppsspp/Common/Thread/ParallelLoop.h
T
libretroadmin f1208a7a5a Make threading lock-free
The core and the headless tools no longer use mutexes, condition variables,
spinlocks, std::atomic, std::thread or volatile flags. Threads hand off through
libretro-common's retro_atomic and rthreads plus a few small pieces on top of
them in Common/Thread: Thread, MpscQueue, EventCounter, ParkingLot waits and
ReaderGate. Every wait blocks until it's woken; nothing polls on a timer.

State that only one thread touches just loses its lock. The PSP filesystem,
sceIo and the savedata dialog now belong to the emulation thread: async reads
and writes run when they're queued and complete later in emulated time, and
the IO and savedata threads are gone. The friend finder only talks to the
adhoc server and hands what it gets to the emulation thread. GPU init always
runs on the thread that starts the game.

The Vulkan render and compile queues, pipeline and render pass caches, delete
list and SPIR-V cache, the GL render queue, the software renderer's jit caches,
the file loader caches, the web debugger, UPnP, input, savestates, logging and
the GE debugger all hand off through queues and atomics. The IR jit's spinning
profiler thread goes.

A CPU thread with nothing to run now sleeps until work is queued instead of
spinning. Headless with --debugger waits for a client while stopped, and ends
the run once every client that connected has left. Web server shutdown keeps
servicing the CPU queue until the server has finished.
2026-10-09 04:56:16 +02:00

104 lines
2.8 KiB
C++

#pragma once
#include <functional>
#include <retro_atomic.h>
#include "Common/Thread/ParkingLot.h"
#include "Common/Thread/ThreadManager.h"
// Same as the latch from C++20.
struct WaitableCounter : public Waitable {
public:
WaitableCounter(int count) {
retro_atomic_int_init(&count_, count);
}
void Count() {
for (;;) {
const int count = retro_atomic_load_acquire_int(&count_);
if (count == 0)
return;
if (retro_atomic_cas_int(&count_, count, count - 1)) {
if (count == 1) {
// We were the last one; the waiter may free us as soon as it sees zero.
ParkingLotNotify(this);
}
return;
}
}
}
void Wait() override {
ParkingLotWait(this, [this] { return retro_atomic_load_acquire_int(&count_) == 0; });
}
retro_atomic_int_t count_;
};
// Note that upper bounds are non-inclusive: range is [lower, upper)
WaitableCounter *ParallelRangeLoopWaitable(ThreadManager *threadMan, const std::function<void(int, int)> &loop, int lower, int upper, int minSize, TaskPriority priority);
// Note that upper bounds are non-inclusive: range is [lower, upper)
void ParallelRangeLoop(ThreadManager *threadMan, const std::function<void(int, int)> &loop, int lower, int upper, int minSize, TaskPriority priority = TaskPriority::NORMAL);
// Common utilities for large (!) memory copies.
// Will only fall back to threads if it seems to make sense.
void ParallelMemcpy(ThreadManager *threadMan, void *dst, const void *src, size_t bytes, TaskPriority priority = TaskPriority::NORMAL);
template<class T>
class SimpleParallelTask : public Task {
public:
SimpleParallelTask(WaitableCounter *counter, T func, int index, int count, TaskPriority p)
: counter_(counter), func_(func), index_(index), count_(count), priority_(p) {
}
TaskType Type() const override {
return TaskType::CPU_COMPUTE;
}
TaskPriority Priority() const override {
return priority_;
}
void Run() override {
func_(index_, count_);
counter_->Count();
}
// Cancellable so a Teardown() racing with an in-flight parallel loop still
// counts down the waiter's counter instead of leaving it blocked forever.
bool Cancellable() const override {
return true;
}
void Cancel() override {
counter_->Count();
}
T func_;
WaitableCounter *counter_;
int index_;
int count_;
const TaskPriority priority_;
};
template<class T>
WaitableCounter *RunParallel(ThreadManager *threadMan, T func, int count, TaskPriority priority = TaskPriority::NORMAL) {
if (count == 1) {
func(0, 1);
return nullptr;
}
WaitableCounter *counter = new WaitableCounter(count);
for (int i = 0; i < count; i++) {
threadMan->EnqueueTaskOnThread(i, new SimpleParallelTask<T>(counter, func, i, count, priority));
}
return counter;
}
// To wait for all tasks to finish: if (counter) counter->WaitAndRelease();