c++ - boost::asio::deadline_timer::async_wait 内部的段错误

Question

当我在方法 SendMessageAgain 中调用 deadline_timer::async_wait 时，偶尔会抛出段错误。它可以通过以下两种方式之一发生；我在下面包含了回溯。它似乎是随机的，这让我觉得不知何故涉及竞争条件。我有一个包含 io_service 对象 ioService 的类，以及多个线程，每个线程都有连接到 ioService 的计时器。我可能需要在调用 async_wait 之前锁定 ioService 吗？不过我认为它可以解决这个问题。

也许这与计时器滴答时中断的任何代码有关。当其他代码也在执行时，设置截止时间计时器的正确方法是什么？

我在SendMessageAgain中使用的代码是

void Node::SendMessageAgain(unsigned long seqNum) {
  // figure out if and what to send (using object fields)
  if (should_send_again) {
    Send(...);
    timer->expires_from_now(INTERVAL);
    timer->async_wait(bind(&Node::SendMessageAgain, this, seqNum));
  }
}

#0  0x08060609 in boost::asio::detail::deadline_timer_service<boost::asio::time_traits<boost::posix_time::ptime> >::async_wait<boost::_bi::bind_t<void, boost::_mfi::mf1<void, Node, unsigned long>, boost::_bi::list2<boost::_bi::value<Node*>, boost::_bi::value<unsigned long> > > > (this=0x14, impl=..., handler=...)    at /usr/include/boost/asio/detail/deadline_timer_service.hpp:170#1  0x0805e2e7 in boost::asio::deadline_timer_service<boost::posix_time::ptime, boost::asio::time_traits<boost::posix_time::ptime> >::async_wait<boost::_bi::bind_t<void, boost::_mfi::mf1<void, Node, unsigned long>, boost::_bi::list2<boost::_bi::value<Node*>, boost::_bi::value<unsigned long> > > > (this=0x0, impl=...,     handler=...) at /usr/include/boost/asio/deadline_timer_service.hpp:135#2  0x0805bcbb in boost::asio::basic_deadline_timer<boost::posix_time::ptime, boost::asio::time_traits<boost::posix_time::ptime>, boost::asio::deadline_timer_service<boost::posix_time::ptime, boost::asio::time_traits<boost::posix_time::ptime> > >::async_wait<boost::_bi::bind_t<void, boost::_mfi::mf1<void, Node, unsigned long>, boost::_bi::list2<boost::_bi::value<Node*>, boost::_bi::value<unsigned long> > > > (this=0x807fc50, handler=...)    at /usr/include/boost/asio/basic_deadline_timer.hpp:435#3  0x080555a2 in Node::SendMessageAgain (this=0xbfffefdc, seqNum=8)    at node.cpp:147

#0  __pthread_mutex_lock (mutex=0x2f200c4) at pthread_mutex_lock.c:50#1  0x08056c79 in boost::asio::detail::posix_mutex::lock (this=0x2f200c4)    at /usr/include/boost/asio/detail/posix_mutex.hpp:52#2  0x0805a036 in boost::asio::detail::scoped_lock<boost::asio::detail::posix_mutex>::scoped_lock (this=0xbfffeb04, m=...)    at /usr/include/boost/asio/detail/scoped_lock.hpp:36#3  0x08061dd0 in boost::asio::detail::epoll_reactor::schedule_timer<boost::asio::time_traits<boost::posix_time::ptime> > (this=0x2f200ac, queue=...,     time=..., timer=..., op=0x807fca0)    at /usr/include/boost/asio/detail/impl/epoll_reactor.hpp:43#4  0x0806063a in boost::asio::detail::deadline_timer_service<boost::asio::time_traits<boost::posix_time::ptime> >::async_wait<boost::_bi::bind_t<void, boost::_mfi::mf1<void, Node, unsigned long>, boost::_bi::list2<boost::_bi::value<Node*>, boost::_bi::value<unsigned long> > > > (this=0xb6b005fc, impl=...,     handler=...)    at /usr/include/boost/asio/detail/deadline_timer_service.hpp:170#5  0x0805e2fd in boost::asio::deadline_timer_service<boost::posix_time::ptime, boost::asio::time_traits<boost::posix_time::ptime> >::async_wait<boost::_bi::bind_t<void, boost::_mfi::mf1<void, Node, unsigned long>, boost::_bi::list2<boost::_bi::value<Node*>, boost::_bi::value<unsigned long> > > > (this=0xb6b005e8,     impl=..., handler=...)    at /usr/include/boost/asio/deadline_timer_service.hpp:135#6  0x0805bcd1 in boost::asio::basic_deadline_timer<boost::posix_time::ptime, bo---Type <return> to continue, or q <return> to quit---ost::asio::time_traits<boost::posix_time::ptime>, boost::asio::deadline_timer_service<boost::posix_time::ptime, boost::asio::time_traits<boost::posix_time::ptime> > >::async_wait<boost::_bi::bind_t<void, boost::_mfi::mf1<void, Node, unsigned long>, boost::_bi::list2<boost::_bi::value<Node*>, boost::_bi::value<unsigned long> > > > (this=0xb6b005a0, handler=...)    at /usr/include/boost/asio/basic_deadline_timer.hpp:435#7  0x080555a7 in Node::SendMessageAgain (this=0xbfffefdc, seqNum=9)    at node.cpp:148

Answer 1

好的，已经解决了。正如 Sam 所建议的那样，这是一个对象生命周期问题，尽管不是 Node。我在 Node 拥有的对象中有一个计时器。我的代码中有一个竞争条件，我在关键部分之外重置计时器，它的所有者在关键部分结束和计时器重置之间被销毁。我只是扩展了关键部分并修复了它。

不过，我不确定为什么段错误会在 async_wait 中出现这么远，因为回调(和关联的 this 指针)属于 Node，它仍然存在。