c++ - boost Asio : waiting until thread_group has processed all posted tasks?

Question

我有一个对象，一旦创建就会在后台执行许多任务，但应该阻塞直到/所有/发布的任务完成。即:

struct run_many{
    boost::asio::io_service       m_io_service;
    boost::thread_group           m_threads;
    boost::asio::signal_set       m_signals;

    void evaluate(std::string work, int i){ /*...*/ }

    void run_tasks(int tasks, std::string work){
        {
          boost::asio::io_service::work w(m_io_service); //
          for(int i=0;i<tasks;i++)
               m_io_service.post(boost::bind(&run_many::evaluate, this, work, i));
        }

        //m_io_service.run();  // blocks forever
        m_io_service.stop();   // seems to cut off queued jobs
        m_threads.join_all();  // works only after m_io_service.stop()
    }

    run_many(int n_workers)
    {
        m_threads.create_thread(boost::bind(&boost::asio::io_service::run,m_io_service);
    }
};

所以我卡住了……看来我要么永远等待，要么在每个线程中当前运行的作业之后切断队列。文档中一定有我遗漏的东西吗？

Answer 1

根据文档，这个想法应该可行(伪代码):

...

// put a few handlers into io_service

...

// don't forget to destroy all boost::asio::io_service::work objects
while (m_io_service.stopped())
{
m_io_service.run();
}

// when code reaches this line m_io_service will be in stopped state and all handlers will be executed

// this code can be called without any doubts about being locked

m_threads.join_all();