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
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
/* Thread pool
Copyright (C) 2019-2023 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program 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 this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef GDBSUPPORT_THREAD_POOL_H
#define GDBSUPPORT_THREAD_POOL_H
#include <queue>
#include <vector>
#include <functional>
#include <chrono>
#if CXX_STD_THREAD
#include <thread>
#include <mutex>
#include <condition_variable>
#include <future>
#endif
#include "gdbsupport/gdb_optional.h"
namespace gdb
{
#if CXX_STD_THREAD
/* Simply use the standard future. */
template<typename T>
using future = std::future<T>;
/* ... and the standard future_status. */
using future_status = std::future_status;
#else /* CXX_STD_THREAD */
/* A compatibility enum for std::future_status. This is just the
subset needed by gdb. */
enum class future_status
{
ready,
timeout,
};
/* A compatibility wrapper for std::future. Once <thread> and
<future> are available in all GCC builds -- should that ever happen
-- this can be removed. GCC does not implement threading for
MinGW, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93687.
Meanwhile, in this mode, there are no threads. Tasks submitted to
the thread pool are invoked immediately and their result is stored
here. The base template here simply wraps a T and provides some
std::future compatibility methods. The provided methods are chosen
based on what GDB needs presently. */
template<typename T>
class future
{
public:
explicit future (T value)
: m_value (std::move (value))
{
}
future () = default;
future (future &&other) = default;
future (const future &other) = delete;
future &operator= (future &&other) = default;
future &operator= (const future &other) = delete;
void wait () const { }
template<class Rep, class Period>
future_status wait_for (const std::chrono::duration<Rep,Period> &duration)
const
{
return future_status::ready;
}
T get () { return std::move (m_value); }
private:
T m_value;
};
/* A specialization for void. */
template<>
class future<void>
{
public:
void wait () const { }
template<class Rep, class Period>
future_status wait_for (const std::chrono::duration<Rep,Period> &duration)
const
{
return future_status::ready;
}
void get () { }
};
#endif /* CXX_STD_THREAD */
/* A thread pool.
There is a single global thread pool, see g_thread_pool. Tasks can
be submitted to the thread pool. They will be processed in worker
threads as time allows. */
class thread_pool
{
public:
/* The sole global thread pool. */
static thread_pool *g_thread_pool;
~thread_pool ();
DISABLE_COPY_AND_ASSIGN (thread_pool);
/* Set the thread count of this thread pool. By default, no threads
are created -- the thread count must be set first. */
void set_thread_count (size_t num_threads);
/* Return the number of executing threads. */
size_t thread_count () const
{
#if CXX_STD_THREAD
return m_thread_count;
#else
return 0;
#endif
}
/* Post a task to the thread pool. A future is returned, which can
be used to wait for the result. */
future<void> post_task (std::function<void ()> &&func)
{
#if CXX_STD_THREAD
std::packaged_task<void ()> task (std::move (func));
future<void> result = task.get_future ();
do_post_task (std::packaged_task<void ()> (std::move (task)));
return result;
#else
func ();
return {};
#endif /* CXX_STD_THREAD */
}
/* Post a task to the thread pool. A future is returned, which can
be used to wait for the result. */
template<typename T>
future<T> post_task (std::function<T ()> &&func)
{
#if CXX_STD_THREAD
std::packaged_task<T ()> task (std::move (func));
future<T> result = task.get_future ();
do_post_task (std::packaged_task<void ()> (std::move (task)));
return result;
#else
return future<T> (func ());
#endif /* CXX_STD_THREAD */
}
private:
thread_pool () = default;
#if CXX_STD_THREAD
/* The callback for each worker thread. */
void thread_function ();
/* Post a task to the thread pool. A future is returned, which can
be used to wait for the result. */
void do_post_task (std::packaged_task<void ()> &&func);
/* The current thread count. */
size_t m_thread_count = 0;
/* A convenience typedef for the type of a task. */
typedef std::packaged_task<void ()> task_t;
/* The tasks that have not been processed yet. An optional is used
to represent a task. If the optional is empty, then this means
that the receiving thread should terminate. If the optional is
non-empty, then it is an actual task to evaluate. */
std::queue<optional<task_t>> m_tasks;
/* A condition variable and mutex that are used for communication
between the main thread and the worker threads. */
std::condition_variable m_tasks_cv;
std::mutex m_tasks_mutex;
#endif /* CXX_STD_THREAD */
};
}
#endif /* GDBSUPPORT_THREAD_POOL_H */
|
