為什么boost boost shared_ptr原子操作會導致SIGSEGV
[英]Why boost shared_ptr atomic operation causes a SIGSEGV
問題描述
我一直在監視運行多線程程序的服務器。 信息如下。
- 操作系統：CentOS版本6.4 x86_64
- 提升：BOOST_LIB_VERSION“ 1_41”
- ACE版本6.2.3
- 4月版本2.0
- apr-util版本2.0
- log4cxx版本2.0
- 多線程主程序
在GDB核心文件中的程序信息中發現間歇性死亡，如下所示。
情況1
Using host libthread_db library "/lib64/libthread_db.so.1".
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007f709cda7c8c in boost::detail::atomic_increment (pw=0x2d) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:66
#1 0x00007f709cda7d68 in boost::detail::sp_counted_base::add_ref_copy (this=0x25)
at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:133
#2 0x00007f709cda7e77 in boost::detail::shared_count::shared_count (this=0x7f708fffe8d8, r=...)
at /usr/include/boost/smart_ptr/detail/shared_count.hpp:228
#3 0x00007f709cda848d in boost::shared_ptr<AudioChunk>::shared_ptr (this=0x7f708fffe8d0) at /usr/include/boost/smart_ptr/shared_ptr.hpp:169
#4 0x00007f709cdb6ae4 in MediaData::GetPacketDescription (this=0x7f705cd1edd0) at MediaData.cpp:955
源代碼＃0和＃4如下所示。
#0 0x00007f709cda7c8c in boost::detail::atomic_increment (pw=0x2d) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:66
56 inline void atomic_increment( int * pw )
57 {
58 //atomic_exchange_and_add( pw, 1 );
59 __asm__
60 (
61 "lock\n\t" //
62 "incl %0":
63 "=m"( *pw ): // output (%0)
64 "m"( *pw ): // input (%1)
65 "cc" // clobbers
66 );
67 }
#4 0x00007f709cdb6ae4 in MediaData::GetPacketDescription (this=0x7f705cd1edd0) at MediaData.cpp:955
953 MediaPacketDescriptionRef MediaData::GetPacketDescription()
954 {
955 MediaPacketDescriptionRef packetDescriptionRef = m_mediaPacketDescriptionQueue.front();
956 m_mediaPacketDescriptionQueue.pop();
957 return packetDescriptionRef;
958 }
“ M_mediaPacketDescriptionQueue”的定義如下：
typedef boost::shared_ptr<MediaPacketDescription> MediaPacketDescriptionRef
std :: queue <MediaPacketDescriptionRef> m_mediaPacketDescriptionQueue;
案例2
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x0000000000415e60 in boost::detail::atomic_exchange_and_add (pw=0x5d, dv=-1) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:50
#1 0x0000000000415f39 in boost::detail::sp_counted_base::release (this=0x55) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:143
#2 0x0000000000415fe9 in boost::detail::shared_count::~shared_count (this=0x7fe8042a09f8, __in_chrg=<optimized out>) at /usr/include/boost/smart_ptr/detail/shared_count.hpp:217
#3 0x0000000000416408 in boost::shared_ptr<MediaPacketDescription>::~shared_ptr (this=0x7fe8042a09f0, __in_chrg=<optimized out>) at /usr/include/boost/smart_ptr/shared_ptr.hpp:169
#4 0x000000000041bf3c in std::_Destroy<boost::shared_ptr<MediaPacketDescription> > (__pointer=0x7fe8042a09f0) at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_construct.h:90
#5 0x000000000041bed0 in std::_Destroy_aux<false>::__destroy<boost::shared_ptr<MediaPacketDescription>*> (__first=0x7fe8042a09f0, __last=0x7fe804244f30)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_construct.h:100
#6 0x000000000041be27 in std::_Destroy<boost::shared_ptr<MediaPacketDescription>*> (__first=0x7fe8042a07f0, __last=0x7fe804244f30)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_construct.h:123
#7 0x000000000041bcbb in std::_Destroy<boost::shared_ptr<MediaPacketDescription>*, boost::shared_ptr<MediaPacketDescription> > (__first=0x7fe8042a07f0, __last=0x7fe804244f30)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_construct.h:149
#8 0x000000000041b9af in std::deque<boost::shared_ptr<MediaPacketDescription>, std::allocator<boost::shared_ptr<MediaPacketDescription> > >::_M_destroy_data_aux (this=0x7fe804a29a38, __first=..., __last=...)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/deque.tcc:733
#9 0x000000000041b661 in std::deque<boost::shared_ptr<MediaPacketDescription>, std::allocator<boost::shared_ptr<MediaPacketDescription> > >::_M_destroy_data (this=0x7fe804a29a38, __first=..., __last=...)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_deque.h:1653
#10 0x000000000041a3fe in std::deque<boost::shared_ptr<MediaPacketDescription>, std::allocator<boost::shared_ptr<MediaPacketDescription> > >::~deque (this=0x7fe804a29a38, __in_chrg=<optimized out>)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_deque.h:790
#11 0x000000000041930c in std::queue<boost::shared_ptr<MediaPacketDescription>, std::deque<boost::shared_ptr<MediaPacketDescription>, std::allocator<boost::shared_ptr<MediaPacketDescription> > > >::~queue (this=0x7fe804a29a38,
__in_chrg=<optimized out>) at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_queue.h:90
#12 0x0000000000419433 in MediaData::~MediaData (this=0x7fe804a29860, __in_chrg=<optimized out>) at ../orkbasecxx/MediaData.h:55
#13 0x0000000000419863 in boost::checked_delete<MediaData> (x=0x7fe804a29860) at /usr/include/boost/checked_delete.hpp:34
#14 0x000000000041ca96 in boost::detail::sp_counted_impl_p<MediaData>::dispose (this=0x7fe804263ac0) at /usr/include/boost/smart_ptr/detail/sp_counted_impl.hpp:78
#15 0x0000000000415f5a in boost::detail::sp_counted_base::release (this=0x7fe804263ac0) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:145
#16 0x0000000000415fe9 in boost::detail::shared_count::~shared_count (this=0x7fe804391f10, __in_chrg=<optimized out>) at /usr/include/boost/smart_ptr/detail/shared_count.hpp:217
#17 0x00000000004164ce in boost::shared_ptr<MediaData>::~shared_ptr (this=0x7fe804391f08, __in_chrg=<optimized out>) at /usr/include/boost/smart_ptr/shared_ptr.hpp:169
#18 0x00007fe857208d8d in ReportData::~ReportData (this=0x7fe804391f00, __in_chrg=<optimized out>) at ReportData.h:34
#19 0x00007fe857208de1 in boost::checked_delete<ReportData> (x=0x7fe804391f00) at /usr/include/boost/checked_delete.hpp:34
#20 0x00007fe85720a0b6 in boost::detail::sp_counted_impl_p<ReportData>::dispose (this=0x7fe8044cf900) at /usr/include/boost/smart_ptr/detail/sp_counted_impl.hpp:78
#21 0x0000000000415f5a in boost::detail::sp_counted_base::release (this=0x7fe8044cf900) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:145
#22 0x0000000000415fe9 in boost::detail::shared_count::~shared_count (this=0x7fe804b25838, __in_chrg=<optimized out>) at /usr/include/boost/smart_ptr/detail/shared_count.hpp:217
#23 0x00007fe8572036ae in boost::shared_ptr<ReportData>::~shared_ptr (this=0x7fe804b25830, __in_chrg=<optimized out>) at /usr/include/boost/smart_ptr/shared_ptr.hpp:169
#24 0x00007fe857209038 in __gnu_cxx::new_allocator<boost::shared_ptr<ReportData> >::destroy (this=0x7fe8261fab1f, __p=0x7fe804b25830)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/ext/new_allocator.h:115
#25 0x00007fe857208699 in std::_List_base<boost::shared_ptr<ReportData>, std::allocator<boost::shared_ptr<ReportData> > >::_M_clear (this=0x7fe8261fac20)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/list.tcc:76
#26 0x00007fe857207b63 in std::_List_base<boost::shared_ptr<ReportData>, std::allocator<boost::shared_ptr<ReportData> > >::~_List_base (this=0x7fe8261fac20, __in_chrg=<optimized out>)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_list.h:360
#27 0x00007fe8572074e0 in std::list<boost::shared_ptr<ReportData>, std::allocator<boost::shared_ptr<ReportData> > >::~list (this=0x7fe8261fac20, __in_chrg=<optimized out>)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_list.h:418
#28 0x00007fe857207365 in ReportDatas::Refresh (this=0x7fe8040291e8) at ReportData.cpp:479
源代碼＃0和＃28如下所示。
#0 0x0000000000415e60 in boost::detail::atomic_exchange_and_add (pw=0x5d, dv=-1) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:50
35 inline int atomic_exchange_and_add( int * pw, int dv )
36 {
37 // int r = *pw;
38 // *pw += dv;
39 // return r;
40
41 int r;
42
43 __asm__ __volatile__
44 (
45 "lock\n\t"
46 "xadd %1, %0":
47 "=m"( *pw ), "=r"( r ): // outputs (%0, %1)
48 "m"( *pw ), "1"( dv ): // inputs (%2, %3 == %1)
49 "memory", "cc" // clobbers
50 );
51
52 return r;
53 }
#28 0x00007fe857207365 in ReportDatas::Refresh (this=0x7fe8040291e8) at ReportData.cpp:479
471 for (std::list<ReportDataRef>::iterator it = toEmpty.begin(); it != toEmpty.end() ; it++)
472 {
473 ReportDataRef data = *it;
474 data->Empty();
475 m_datas.erase(data->GetId());
476 LOG4CXX_DEBUG(s_log, data->GetId() + ": Become empty");
477 }
478 logMsg.Format("Refreshed %d datas. New data size:%d", (data - m_datas.size()), m_datas.size());
479 LOG4CXX_DEBUG(s_log, logMsg);
對於CASE1和Queue.front（），假定這不是問題。 我認為它必須正常執行Queue.front（）來執行引用計數器shared_ptr的增加。
問題是我不明白為什么在boost lib原子操作中會發生間歇性SIGSEGV。
================================================== ======
抱歉。 很難在注釋中描述細節以編輯問題文本。
謝謝您的回答erikzenker。
我在運行您的代碼時，可能得到與GDB相同的結果。
Program received signal SIGSEGV, Segmentation fault.
0x000000000040092b in boost::detail::atomic_exchange_and_add (pw=0x20b49, dv=-1) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:50
/usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:50:1141:beg:0x40092b
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.192.el6.x86_64 libgcc-4.4.7-16.el6.x86_64 libstdc++-4.4.7-16.el6.x86_64
(gdb) bt
#0 0x000000000040092b in boost::detail::atomic_exchange_and_add (pw=0x20b49, dv=-1) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:50
#1 0x000000000040098b in boost::detail::sp_counted_base::release (this=0x20b41) at /usr/include/boost/smart_ptr/detail/sp_counted_base_gcc_x86.hpp:143
#2 0x0000000000400a25 in boost::detail::shared_count::~shared_count (this=0x6044c8, __in_chrg=<value optimized out>) at /usr/include/boost/smart_ptr/detail/shared_count.hpp:217
#3 0x0000000000400ad6 in boost::shared_ptr<int>::~shared_ptr (this=0x6044c0, __in_chrg=<value optimized out>) at /usr/include/boost/smart_ptr/shared_ptr.hpp:169
#4 0x0000000000401e86 in std::_Destroy<boost::shared_ptr<int> > (__pointer=0x6044c0) at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_construct.h:90
#5 0x0000000000401cb4 in std::_Destroy_aux<false>::__destroy<boost::shared_ptr<int>*> (__first=0x6044c0, __last=0x6042c0)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_construct.h:100
#6 0x0000000000401b25 in std::_Destroy<boost::shared_ptr<int>*> (__first=0x6042d0, __last=0x6042c0) at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_construct.h:123
#7 0x000000000040185b in std::_Destroy<boost::shared_ptr<int>*, boost::shared_ptr<int> > (__first=0x6042d0, __last=0x6042c0)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_construct.h:149
#8 0x0000000000401366 in std::deque<boost::shared_ptr<int>, std::allocator<boost::shared_ptr<int> > >::_M_destroy_data_aux (this=0x7fffffffe350, __first=..., __last=...)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/deque.tcc:739
#9 0x0000000000400df9 in std::deque<boost::shared_ptr<int>, std::allocator<boost::shared_ptr<int> > >::_M_destroy_data (this=0x7fffffffe350, __first=..., __last=...)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_deque.h:1653
#10 0x0000000000400b50 in std::deque<boost::shared_ptr<int>, std::allocator<boost::shared_ptr<int> > >::~deque (this=0x7fffffffe350, __in_chrg=<value optimized out>)
at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_deque.h:790
#11 0x0000000000400a7c in std::queue<boost::shared_ptr<int>, std::deque<boost::shared_ptr<int>, std::allocator<boost::shared_ptr<int> > > >::~queue (this=0x7fffffffe350,
__in_chrg=<value optimized out>) at /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_queue.h:90
#12 0x00000000004008be in main () at testc2.cpp:12
當我想到這一點時，我認為它與案例2非常相似。
但是我還不明白。
我認為操作＃0的引用計數器增加了CASE 1 shared_ptr。
由於非空隊列元素方法成功，因此請嘗試嘗試“＃0 atomic_increment”。
1 個解決方案
解決方案1
0 2016-08-17 12:38:51
我認為這里的問題是刪除std::queue為空的元素。 您可以使用以下簡單示例重現該錯誤：
// Simplified example
#include <queue>
#include <boost/shared_ptr.hpp>
int main(){
std::queue<boost::shared_ptr<int> > queue;
boost::shared_ptr<int> ptr = queue.front();
// Remove element from empty queue
queue.pop();
return 0;
}
在空隊列上調用pop方法是未定義的。 您必須先檢查隊列是否為空：
// Solving the problem
if (!queue.empty()) {
boost::shared_ptr<int> ptr = queue.front();
queue.pop();
}
編輯
正如我上面提到的：沒有定義從空隊列中刪除元素。 如果仍要彈出或擦除元素，會發生什么情況取決於您的stl實現。 看一下gcc 6.1使用的實現（pop（）調用std :: deque的pop_front（））：
void
pop_front() _GLIBCXX_NOEXCEPT
{
if (this->_M_impl._M_start._M_cur != this->_M_impl._M_start._M_last - 1)
{
_Alloc_traits::destroy(this->_M_impl,
this->_M_impl._M_start._M_cur);
++this->_M_impl._M_start._M_cur;
}
else
_M_pop_front_aux();
}
...
template <typename _Tp, typename _Alloc>
void deque<_Tp, _Alloc>::
_M_pop_front_aux()
{
this->_M_impl.destroy(this->_M_impl._M_start._M_cur);
_M_deallocate_node(this->_M_impl._M_start._M_first);
this->_M_impl._M_start._M_set_node(this->_M_impl._M_start._M_node + 1);
this->_M_impl._M_start._M_cur = this->_M_impl._M_start._M_first;
}
通過不詳細介紹，您會看到實現嘗試破壞（破壞）隊列的第一個元素。 破壞共享指針意味着修改參考計數器。 但是沒有可以修改的對象，因此它將嘗試修改不擁有的內存（分段錯誤）。
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