如何解决当“ this”成为nullptr时,如何处理类成员线程中的quick_exit?
我有这小段代码:
// (...)
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,而gdb的backtrace命令显示了这一点:
(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)
这意味着我的类被破坏了,而没有调用析构函数。
据我所知/怀疑,当我的应用程序的操作系统/监视程序强制退出/快速终止时,这可能是可行的。
有什么办法可以解决这个问题?也许我在其中可以检查shared_ptr是否为nullptr的某些shared_ptr原子包装,是否有一些原子的if-not-null-execute-this?再说一次..这实际上是在执行中发生的。
我知道可以添加快速退出挂钩,但是出于某些合理的原因有时会使用快速退出,这将是减慢快速退出速度的设计。解决此问题成为nullptr的最佳方法是什么?
还是应该让SEGFALT发生,因为无论如何该应用都在快速退出?
这里是完整的堆栈,但是可能不会添加更多有用的信息:
(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,__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
解决方法
您的代码具有竞争条件。
Time::Time()
{
// ...
m_running = true;
m_worker = std::move(std::thread(std::bind(&Time::Worker,this)));
}
胎面开始于
std::shared_ptr<Time> time_data(std::make_shared<Time>());
完成。
仅在monitor::Time::HasTimedOut
完成之前线程到达std::shared_ptr<Time> time_data(std::make_shared<Time>());
。
Spawn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
后调用该线程。
无论如何,如果您的Timer
根本不使用time_data
全局变量会更好。
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