yuzu/src/common/threadsafe_queue.h
Markus Wick 4aec060f6d common/threadsafe_queue: Provide Wait() method.
It shall block until there is something to consume in the queue.

And use it for the GPU emulation instead of the spin loop.
This is only in booting the emulator, however in BOTW this is the case for about 1 second.
2021-04-07 22:38:52 +02:00

181 lines
3.9 KiB
C++

// Copyright 2010 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.
#pragma once
// a simple lockless thread-safe,
// single reader, single writer queue
#include <atomic>
#include <condition_variable>
#include <cstddef>
#include <mutex>
#include <utility>
namespace Common {
template <typename T>
class SPSCQueue {
public:
SPSCQueue() {
write_ptr = read_ptr = new ElementPtr();
}
~SPSCQueue() {
// this will empty out the whole queue
delete read_ptr;
}
[[nodiscard]] std::size_t Size() const {
return size.load();
}
[[nodiscard]] bool Empty() const {
return Size() == 0;
}
[[nodiscard]] T& Front() const {
return read_ptr->current;
}
template <typename Arg>
void Push(Arg&& t) {
// create the element, add it to the queue
write_ptr->current = std::forward<Arg>(t);
// set the next pointer to a new element ptr
// then advance the write pointer
ElementPtr* new_ptr = new ElementPtr();
write_ptr->next.store(new_ptr, std::memory_order_release);
write_ptr = new_ptr;
const size_t previous_size{size++};
// Acquire the mutex and then immediately release it as a fence.
// TODO(bunnei): This can be replaced with C++20 waitable atomics when properly supported.
// See discussion on https://github.com/yuzu-emu/yuzu/pull/3173 for details.
if (previous_size == 0) {
std::lock_guard lock{cv_mutex};
}
cv.notify_one();
}
void Pop() {
--size;
ElementPtr* tmpptr = read_ptr;
// advance the read pointer
read_ptr = tmpptr->next.load();
// set the next element to nullptr to stop the recursive deletion
tmpptr->next.store(nullptr);
delete tmpptr; // this also deletes the element
}
bool Pop(T& t) {
if (Empty())
return false;
--size;
ElementPtr* tmpptr = read_ptr;
read_ptr = tmpptr->next.load(std::memory_order_acquire);
t = std::move(tmpptr->current);
tmpptr->next.store(nullptr);
delete tmpptr;
return true;
}
void Wait() {
if (Empty()) {
std::unique_lock lock{cv_mutex};
cv.wait(lock, [this]() { return !Empty(); });
}
}
T PopWait() {
Wait();
T t;
Pop(t);
return t;
}
// not thread-safe
void Clear() {
size.store(0);
delete read_ptr;
write_ptr = read_ptr = new ElementPtr();
}
private:
// stores a pointer to element
// and a pointer to the next ElementPtr
class ElementPtr {
public:
ElementPtr() {}
~ElementPtr() {
ElementPtr* next_ptr = next.load();
if (next_ptr)
delete next_ptr;
}
T current;
std::atomic<ElementPtr*> next{nullptr};
};
ElementPtr* write_ptr;
ElementPtr* read_ptr;
std::atomic_size_t size{0};
std::mutex cv_mutex;
std::condition_variable cv;
};
// a simple thread-safe,
// single reader, multiple writer queue
template <typename T>
class MPSCQueue {
public:
[[nodiscard]] std::size_t Size() const {
return spsc_queue.Size();
}
[[nodiscard]] bool Empty() const {
return spsc_queue.Empty();
}
[[nodiscard]] T& Front() const {
return spsc_queue.Front();
}
template <typename Arg>
void Push(Arg&& t) {
std::lock_guard lock{write_lock};
spsc_queue.Push(t);
}
void Pop() {
return spsc_queue.Pop();
}
bool Pop(T& t) {
return spsc_queue.Pop(t);
}
void Wait() {
spsc_queue.Wait();
}
T PopWait() {
return spsc_queue.PopWait();
}
// not thread-safe
void Clear() {
spsc_queue.Clear();
}
private:
SPSCQueue<T> spsc_queue;
std::mutex write_lock;
};
} // namespace Common