| 1 | /* Thread pool |
| 2 | |
| 3 | Copyright (C) 2019-2020 Free Software Foundation, Inc. |
| 4 | |
| 5 | This file is part of GDB. |
| 6 | |
| 7 | This program is free software; you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation; either version 3 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 19 | |
| 20 | #ifndef GDBSUPPORT_THREAD_POOL_H |
| 21 | #define GDBSUPPORT_THREAD_POOL_H |
| 22 | |
| 23 | #include <queue> |
| 24 | #include <thread> |
| 25 | #include <vector> |
| 26 | #include <functional> |
| 27 | #include <mutex> |
| 28 | #include <condition_variable> |
| 29 | #include <future> |
| 30 | #include "gdbsupport/gdb_optional.h" |
| 31 | |
| 32 | namespace gdb |
| 33 | { |
| 34 | |
| 35 | /* A thread pool. |
| 36 | |
| 37 | There is a single global thread pool, see g_thread_pool. Tasks can |
| 38 | be submitted to the thread pool. They will be processed in worker |
| 39 | threads as time allows. */ |
| 40 | class thread_pool |
| 41 | { |
| 42 | public: |
| 43 | /* The sole global thread pool. */ |
| 44 | static thread_pool *g_thread_pool; |
| 45 | |
| 46 | ~thread_pool (); |
| 47 | DISABLE_COPY_AND_ASSIGN (thread_pool); |
| 48 | |
| 49 | /* Set the thread count of this thread pool. By default, no threads |
| 50 | are created -- the thread count must be set first. */ |
| 51 | void set_thread_count (size_t num_threads); |
| 52 | |
| 53 | /* Return the number of executing threads. */ |
| 54 | size_t thread_count () const |
| 55 | { |
| 56 | return m_thread_count; |
| 57 | } |
| 58 | |
| 59 | /* Post a task to the thread pool. A future is returned, which can |
| 60 | be used to wait for the result. */ |
| 61 | std::future<void> post_task (std::function<void ()> func); |
| 62 | |
| 63 | private: |
| 64 | |
| 65 | thread_pool () = default; |
| 66 | |
| 67 | /* The callback for each worker thread. */ |
| 68 | void thread_function (); |
| 69 | |
| 70 | /* The current thread count. */ |
| 71 | size_t m_thread_count = 0; |
| 72 | |
| 73 | /* A convenience typedef for the type of a task. */ |
| 74 | typedef std::packaged_task<void ()> task; |
| 75 | |
| 76 | /* The tasks that have not been processed yet. An optional is used |
| 77 | to represent a task. If the optional is empty, then this means |
| 78 | that the receiving thread should terminate. If the optional is |
| 79 | non-empty, then it is an actual task to evaluate. */ |
| 80 | std::queue<optional<task>> m_tasks; |
| 81 | |
| 82 | /* A condition variable and mutex that are used for communication |
| 83 | between the main thread and the worker threads. */ |
| 84 | std::condition_variable m_tasks_cv; |
| 85 | std::mutex m_tasks_mutex; |
| 86 | }; |
| 87 | |
| 88 | } |
| 89 | |
| 90 | #endif /* GDBSUPPORT_THREAD_POOL_H */ |