当 `this` 变为 nullptr 时,如何在 class 成员线程中处理 quick_exit?
How to handle quick_exit in a class member thread when `this` becomes a nullptr?
我有这么一小段代码:
// (...)
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 的回溯命令显示:
(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 class 在没有调用析构函数的情况下被销毁了。
当我的应用程序 OS/watchdog 在我 know/suspect 执行强制退出/快速终止时,这可能是可能的。
有什么办法可以解决这个问题吗?也许一些 shared_ptr 原子包装我可以检查 shared_ptr 是否是 nullptr,是否有一些原子 if-not-null-execute-this?然后又一次..这实际上是在执行过程中发生的。
我知道可以添加快速退出挂钩,但有时使用快速退出是出于很好的理由,减慢快速退出的速度又是一种设计。处理这个成为 nullptr 的最佳方法是什么?
或者我应该让 SEGFALT 发生,因为应用程序无论如何都在快速退出?
这是完整的堆栈,但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, 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
您的代码存在竞争条件。
Time::Time()
{
// ...
m_running = true;
m_worker = std::move(std::thread(std::bind(&Time::Worker, this)));
}
此处胎面开始于
std::shared_ptr<Time> time_data(std::make_shared<Time>());
已完成。
只需线程在 std::shared_ptr<Time> time_data(std::make_shared<Time>());
完成之前到达 monitor::Time::HasTimedOut
。
生成线程不在构造函数中,而是在您将在 time_data
分配后调用的单独方法中。
无论如何,如果您的 Timer
完全不使用 time_data
全局变量会更好。
我有这么一小段代码:
// (...)
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 的回溯命令显示:
(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 class 在没有调用析构函数的情况下被销毁了。
当我的应用程序 OS/watchdog 在我 know/suspect 执行强制退出/快速终止时,这可能是可能的。
有什么办法可以解决这个问题吗?也许一些 shared_ptr 原子包装我可以检查 shared_ptr 是否是 nullptr,是否有一些原子 if-not-null-execute-this?然后又一次..这实际上是在执行过程中发生的。
我知道可以添加快速退出挂钩,但有时使用快速退出是出于很好的理由,减慢快速退出的速度又是一种设计。处理这个成为 nullptr 的最佳方法是什么?
或者我应该让 SEGFALT 发生,因为应用程序无论如何都在快速退出?
这是完整的堆栈,但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, 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
您的代码存在竞争条件。
Time::Time()
{
// ...
m_running = true;
m_worker = std::move(std::thread(std::bind(&Time::Worker, this)));
}
此处胎面开始于
std::shared_ptr<Time> time_data(std::make_shared<Time>());
已完成。
只需线程在 std::shared_ptr<Time> time_data(std::make_shared<Time>());
完成之前到达 monitor::Time::HasTimedOut
。
生成线程不在构造函数中,而是在您将在 time_data
分配后调用的单独方法中。
无论如何,如果您的 Timer
完全不使用 time_data
全局变量会更好。