94 lines
2.5 KiB
C++
94 lines
2.5 KiB
C++
// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_
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#define ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_
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#include <cassert>
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#include <cstddef>
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#include <functional>
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#include <queue>
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#include <thread> // NOLINT(build/c++11)
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#include <vector>
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#include "absl/base/thread_annotations.h"
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#include "absl/synchronization/mutex.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace synchronization_internal {
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// A simple ThreadPool implementation for tests.
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class ThreadPool {
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public:
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explicit ThreadPool(int num_threads) {
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for (int i = 0; i < num_threads; ++i) {
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threads_.push_back(std::thread(&ThreadPool::WorkLoop, this));
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}
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}
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ThreadPool(const ThreadPool &) = delete;
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ThreadPool &operator=(const ThreadPool &) = delete;
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~ThreadPool() {
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{
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absl::MutexLock l(&mu_);
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for (size_t i = 0; i < threads_.size(); i++) {
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queue_.push(nullptr); // Shutdown signal.
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}
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}
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for (auto &t : threads_) {
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t.join();
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}
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}
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// Schedule a function to be run on a ThreadPool thread immediately.
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void Schedule(std::function<void()> func) {
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assert(func != nullptr);
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absl::MutexLock l(&mu_);
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queue_.push(std::move(func));
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}
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private:
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bool WorkAvailable() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_) {
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return !queue_.empty();
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}
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void WorkLoop() {
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while (true) {
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std::function<void()> func;
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{
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absl::MutexLock l(&mu_);
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mu_.Await(absl::Condition(this, &ThreadPool::WorkAvailable));
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func = std::move(queue_.front());
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queue_.pop();
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}
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if (func == nullptr) { // Shutdown signal.
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break;
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}
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func();
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}
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}
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absl::Mutex mu_;
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std::queue<std::function<void()>> queue_ ABSL_GUARDED_BY(mu_);
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std::vector<std::thread> threads_;
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};
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} // namespace synchronization_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_
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