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/* Thread pool
Copyright (C) 2019-2020 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 <thread>
#include <vector>
#include <functional>
#include <mutex>
#include <condition_variable>
#include <future>
#include "gdbsupport/gdb_optional.h"
namespace gdb
{
/* 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
{
return m_thread_count;
}
/* Post a task to the thread pool. A future is returned, which can
be used to wait for the result. */
std::future<void> post_task (std::function<void ()> func);
private:
thread_pool () = default;
/* The callback for each worker thread. */
void thread_function ();
/* 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;
/* 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>> 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 /* GDBSUPPORT_THREAD_POOL_H */
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