在我的多线程程序中,我经常使用如下所示的方法来同步访问数据:等待异步方法来完成
class MyAsyncClass
{
public: // public thread safe interface of MyAsyncClass
void start()
{
// add work to io_service
_ioServiceWork.reset(new boost::asio::io_service::work(_ioService));
// start io service
_ioServiceThread = boost::shared_ptr<boost::thread>(new boost::thread(boost::bind(&boost::asio::io_service::run, &_ioService)));
}
void stop()
{
_ioService.post(boost::bind(&MyAsyncClass::stop_internal, this));
// QUESTION:
// how do I wait for stop_internal to finish here?
// remove work
_ioServiceWork.reset();
// wait for the io_service to return from run()
if (_ioServiceThread && _ioServiceThread->joinable())
_ioServiceThread->join();
// allow subsequent calls to run()
_ioService.reset();
// delete thread
_ioServiceThread.reset();
}
void doSometing()
{
_ioService.post(boost::bind(&MyAsyncClass::doSometing_internal, this));
}
private: // internal handlers
void stop_internal()
{
_myMember = 0;
}
void doSomething_internal()
{
_myMember++;
}
private: // private variables
// io service and its thread
boost::asio::io_service _ioService;
boost::shared_ptr<boost::thread> _ioServiceThread;
// work object to prevent io service from running out of work
std::unique_ptr<boost::asio::io_service::work> _ioServiceWork;
// some member that should be modified only from _ioServiceThread
int _myMember;
};
这个类的公共接口是线程安全的意义它的公共方法可以从任何线程调用,并且boost::asio::io_service
注意同步对此类的私有成员的访问。因此,公众doSomething()
除了将实际工作发布到io_service
之外不做任何事情。
start()
和stop()
方法MyAsyncClass
明显在MyAsyncClass
开始和停止处理。我希望能够从任何线程调用MyAsyncClass::stop()
,并且在MyAsyncClass
的未初始化完成之前它不应该返回。
因为在这种特殊情况下,我需要在停止时修改其中一个私人成员(需要同步访问),我引入了一个stop_internal()
方法,我从stop()
发布到io_service
。
现在的问题是:我如何等待执行stop_internal()
完成stop()
?请注意,我不能直接调用stop_internal()
,因为它会在错误的线程中运行。
编辑:
这将是很好有一个解决方案,同时工作,如果MyAsyncClass::stop()
从_ioServiceThread
叫,让MyAsyncClass
也可自行停止。