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a0b57563b1
This adds a simple thread pool to gdb. In the end, this seemed preferable to the approach taken in an earlier version of this series; namely, starting threads in the parallel-foreach implementation. This approach reduces the overhead of starting new threads, and also lets the user control (in a subsequent patch) exactly how many worker threads are running. gdb/ChangeLog 2019-11-26 Christian Biesinger <cbiesinger@google.com> Tom Tromey <tom@tromey.com> * gdbsupport/thread-pool.h: New file. * gdbsupport/thread-pool.c: New file. * Makefile.in (COMMON_SFILES): Add thread-pool.c. (HFILES_NO_SRCDIR): Add thread-pool.h. Change-Id: I597bb642780cb9d578ca92373d2a638efb44fe52
91 lines
2.6 KiB
C++
91 lines
2.6 KiB
C++
/* Thread pool
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Copyright (C) 2019 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef GDBSUPPORT_THREAD_POOL_H
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#define GDBSUPPORT_THREAD_POOL_H
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#include <queue>
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#include <thread>
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#include <vector>
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#include <functional>
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#include <mutex>
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#include <condition_variable>
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#include <future>
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#include "gdbsupport/gdb_optional.h"
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namespace gdb
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{
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/* A thread pool.
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There is a single global thread pool, see g_thread_pool. Tasks can
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be submitted to the thread pool. They will be processed in worker
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threads as time allows. */
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class thread_pool
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{
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public:
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/* The sole global thread pool. */
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static thread_pool *g_thread_pool;
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~thread_pool ();
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DISABLE_COPY_AND_ASSIGN (thread_pool);
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/* Set the thread count of this thread pool. By default, no threads
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are created -- the thread count must be set first. */
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void set_thread_count (size_t num_threads);
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/* Return the number of executing threads. */
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size_t thread_count () const
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{
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return m_thread_count;
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}
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/* Post a task to the thread pool. A future is returned, which can
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be used to wait for the result. */
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std::future<void> post_task (std::function<void ()> func);
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private:
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thread_pool () = default;
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/* The callback for each worker thread. */
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void thread_function ();
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/* The current thread count. */
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size_t m_thread_count = 0;
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/* A convenience typedef for the type of a task. */
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typedef std::packaged_task<void ()> task;
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/* The tasks that have not been processed yet. An optional is used
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to represent a task. If the optional is empty, then this means
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that the receiving thread should terminate. If the optional is
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non-empty, then it is an actual task to evaluate. */
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std::queue<optional<task>> m_tasks;
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/* A condition variable and mutex that are used for communication
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between the main thread and the worker threads. */
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std::condition_variable m_tasks_cv;
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std::mutex m_tasks_mutex;
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};
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}
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#endif /* GDBSUPPORT_THREAD_POOL_H */
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