当"this"变成nullptr时,如何在类成员线程中处理quick_exit

How to handle quick_exit in a class member thread when `this` becomes a nullptr?

本文关键字:quot 线程 成员 处理 exit quick nullptr 变成 this      更新时间:2024-04-29

我有一小段代码:

// (...)
class Time 
{
std::atomic<bool> m_running;
std::thread m_worker;
// ...
};

Time::Time()
{
// ...
m_running = true;
m_worker  = std::move(std::thread(std::bind(&Time::Worker, this)));
}

bool Time::HasTimedOut() const
{
return (!m_disabled) &&
(IsPending() && (GetRunTime() >= m_maximum_timeout) && (CloseHandlesDiff() >= m_minimum_close_time));
}
Time::~Time()
{
if (m_running)
{
m_running = false;
m_worker.join();
}
}
void Time::Worker()
{
while (m_running)
{
if (time_data->HasTimedOut())
{
time_data->RunTimedOutCallback();
}
if (m_count < 0)
{
m_count = 0;
}
if (m_running)
{
std::this_thread::sleep_for(std::chrono::milliseconds(20));
}
}
}
std::shared_ptr<Time> time_data(std::make_shared<Time>());

令我惊讶的是,我得到了一个coredump,gdb的backtrace命令显示如下:

(gdb) bt
#0  0x09438408 in monitor::Time::HasTimedOut (this=0x0)
at monitor.cxx: // return (!m_disabled) &&
#1  0x09438a84 in monitor::Time::Worker (this=0xbd96dd8)
monitor.cxx: // if(time_data->HasTimedOut()
#2  0x0943cf81 in std::__invoke_impl<void, void (monitor::Time::*&)(), monitor::Time*&> (
__f=@0xbd96e54: (void (monitor::Time::*)(monitor::Time * const)) 0x94389f0 <monitor::Time::Worker()>, __t=@0xbd96e5c: 0xbd96dd8)

nullptr似乎是问题所在(SEGFAULT(:

(this=0x0)

这意味着我的类被销毁了,没有调用析构函数。

据我所知/怀疑,当我的应用程序的操作系统/看门狗执行强制退出/快速终止时,这可能是可能的。

有什么办法解决这个问题吗?也许有一些shared_ptr原子包装,我可以检查shared_ptr是否是nullptr,是否有一些原子(如果不是null(执行此操作?再说一遍。。这确实发生在执行过程中。

我知道可以添加快速退出挂钩,但有时使用快速退出是因为有充分的理由,放慢快速退出的速度是违反设计的。处理这种情况成为nullptr的最佳方法是什么?

或者我应该让SEGFLT发生,因为无论如何应用程序都在快速退出?

这是完整的堆栈,但可能不会添加任何有用的信息:

(gdb) bt
(gdb) bt
#0  0x09438408 in monitor::Time::HasTimedOut (this=0x0)
at /opt/procesleiding/vptlib/lib/oracle_monitor.cxx:111
#1  0x09438a84 in monitor::Time::Worker (this=0xbd96dd8)
at /opt/procesleiding/vptlib/lib/oracle_monitor.cxx:142
#2  0x0943cf81 in std::__invoke_impl<void, void (monitor::Time::*&)(), monitor::Time*&> (
__f=@0xbd96e54: (void (monitor::Time::*)(monitor::Time * const)) 0x94389f0 <monitor::Time::Worker()>, __t=@0xbd96e5c: 0xbd96dd8)
at /usr/include/c++/7/bits/invoke.h:73
#3  0x0943c99f in std::__invoke<void (monitor::Time::*&)(), monitor::Time*&> (
__fn=@0xbd96e54: (void (monitor::Time::*)(monitor::Time * const)) 0x94389f0 <monitor::Time::Worker()>, __args#0=@0xbd96e5c: 0xbd96dd8)
at /usr/include/c++/7/bits/invoke.h:95
#4  0x0943c70c in std::_Bind<void (monitor::Time::*(monitor::Time*))()>::__call<void, , 0u>(std::tuple<>&&, std::_Index_tuple<0u>) (
this=0xbd96e54, __args=...)
at /usr/include/c++/7/functional:467
#5  0x0943c28c in std::_Bind<void (monitor::Time::*(monitor::Time*))()>::operator()<, void>() (this=0xbd96e54)
at /usr/include/c++/7/functional:551
#6  0x0943bcaf in std::__invoke_impl<void, std::_Bind<void (monitor::Time::*(monitor::Time*))()>>(std::__invoke_other, std::_Bind<void (monitor::Time::*(monitor::Time*))()>&&) (__f=...) at /usr/include/c++/7/bits/invoke.h:60
#7  0x0943b022 in std::__invoke<std::_Bind<void (monitor::Time::*(monitor::Time*))()>>(std::_Bind<void (monitor::Time::*(monitor::Time*))()>&&) (__fn=...) at /usr/include/c++/7/bits/invoke.h:95
#8  0x0943e2a6 in std::thread::_Invoker<std::tuple<std::_Bind<void (monitor::Time::*(monitor::Time*))()> > >::_M_invoke<0u>(std::_Index_tuple<0u>) (this=0xbd96e54) at /usr/include/c++/7/thread:234
#9  0x0943e15c in std::thread::_Invoker<std::tuple<std::_Bind<void (monitor::Time::*(monitor::Time*))()> > >::operator()() (this=0xbd96e54) at /usr/include/c++/7/thread:243
#10 0x0943e067 in std::thread::_State_impl<std::thread::_Invoker<std::tuple<std::_Bind<void (monitor::Time::*(monitor::Time*))()> > > >::_M_run() (this=0xbd96e50) at /usr/include/c++/7/thread:186

您的代码有一个竞争条件。

Time::Time()
{
// ...
m_running = true;
m_worker  = std::move(std::thread(std::bind(&Time::Worker, this)));
}

此处胎面在之前开始

std::shared_ptr<Time> time_data(std::make_shared<Time>());

完成。

简单地说,线程在std::shared_ptr<Time> time_data(std::make_shared<Time>());完成之前到达monitor::Time::HasTimedOut

派生线程不在构造函数中,而是在单独的方法中,您将在分配time_data后调用该方法。

无论如何,如果您的Timer根本不使用time_data全局变量会更好。