1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
|
// SPDX-FileCopyrightText: 2010 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#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, bool with_stop_token = false>
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::move(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;
++size;
// cv_mutex must be held or else there will be a missed wakeup if the other thread is in the
// line before cv.wait
// 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.
std::scoped_lock 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;
}
T PopWait(std::stop_token stop_token) {
if (Empty()) {
std::unique_lock lock{cv_mutex};
cv.wait(lock, stop_token, [this] { return !Empty(); });
}
if (stop_token.stop_requested()) {
return T{};
}
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::conditional_t<with_stop_token, std::condition_variable_any, std::condition_variable> cv;
};
// a simple thread-safe,
// single reader, multiple writer queue
template <typename T, bool with_stop_token = false>
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::scoped_lock 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();
}
T PopWait(std::stop_token stop_token) {
return spsc_queue.PopWait(stop_token);
}
// not thread-safe
void Clear() {
spsc_queue.Clear();
}
private:
SPSCQueue<T, with_stop_token> spsc_queue;
std::mutex write_lock;
};
} // namespace Common
|
