grpc/src/cpp/server/thread_pool.cc

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#include "src/cpp/server/thread_pool.h"

namespace grpc {

ThreadPool::ThreadPool(int num_threads) : shutdown_(false) {
  for (int i = 0; i < num_threads; i++) {
    threads_.push_back(std::thread([this]() {
      for (;;) {
        // Wait until work is available or we are shutting down.
        auto have_work = [this]() { return shutdown_ || !callbacks_.empty(); };
        std::unique_lock<std::mutex> lock(mu_);
        if (!have_work()) {
          cv_.wait(lock, have_work);
        }
        // Drain callbacks before considering shutdown to ensure all work
        // gets completed.
        if (!callbacks_.empty()) {
          auto cb = callbacks_.front();
          callbacks_.pop();
          lock.unlock();
          cb();
        } else if (shutdown_) {
          return;
        }
      }
    }));
  }
}

ThreadPool::~ThreadPool() {
  {
    std::lock_guard<std::mutex> lock(mu_);
    shutdown_ = true;
    cv_.notify_all();
  }
  for (auto &t : threads_) {
    t.join();
  }
}

void ThreadPool::ScheduleCallback(const std::function<void()> &callback) {
  std::lock_guard<std::mutex> lock(mu_);
  callbacks_.push(callback);
  cv_.notify_one();
}

}  // namespace grpc