drd和helgrind的当前状态支持std :: thread [英] Current state of drd and helgrind support for std::thread
问题描述
当我将代码转换为C ++ 11时，我非常希望将我的pthread代码转换为std :: thread。但是，我似乎在drd和helgrind中的非常简单的程序中得到了错误的竞争条件。
As I transition my code to C++11, I would very much like to convert my pthread code to std::thread. However, I seem to be getting false race conditions on very simple programs in drd and in helgrind.
#include <thread>
int main(int argc, char** argv)
{
std::thread t( []() { } );
t.join();
return 0;
}
。 1，在Ubuntu 11.11 amd64上使用valgrind 3.7.0。
Helgrind output snippet - I also get similar errors in drd, using gcc 4.6.1, valgrind 3.7.0 on Ubuntu 11.11 amd64.
我的问题是：
- 健康检查：我做错了什么吗？
- std :: thread的当前用户是什么用来检测竞争条件的？
我不太愿意从pthread到 std :: thread 移植一些代码，直到一些关键的工具，如helgrind / drd已赶上。
I am reluctant to port a ton of code from pthread to std::thread until some crucial tools like helgrind/drd have caught up.
==19347== ---Thread-Announcement------------------------------------------
==19347==
==19347== Thread #1 is the program's root thread
==19347==
==19347== ---Thread-Announcement------------------------------------------
==19347==
==19347== Thread #2 was created
==19347== at 0x564C85E: clone (clone.S:77)
==19347== by 0x4E37E7F: do_clone.constprop.3 (createthread.c:75)
==19347== by 0x4E39604: pthread_create@@GLIBC_2.2.5 (createthread.c:256)
==19347== by 0x4C2B3DA: pthread_create_WRK (hg_intercepts.c:255)
==19347== by 0x4C2B55E: pthread_create@* (hg_intercepts.c:286)
==19347== by 0x50BED02: std::thread::_M_start_thread(std::shared_ptr<std::thread::_Impl_base>) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.16)
==19347== by 0x400D51: _ZNSt6threadC1IZ4mainEUlvE_IEEEOT_DpOT0_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x400C60: main (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347==
==19347== ----------------------------------------------------------------
==19347==
==19347== Possible data race during write of size 8 at 0x5B8E060 by thread #1
==19347== Locks held: none
==19347== at 0x40165E: _ZNSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEED1Ev (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x401895: _ZNKSt19_Sp_destroy_inplaceINSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEEEEclEPS6_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x4016D8: _ZNSt19_Sp_counted_deleterIPNSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEEESt19_Sp_destroy_inplaceIS6_ESaIS6_ELN9__gnu_cxx12_Lock_policyE2EE10_M_disposeEv (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x401B83: std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release() (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x401B3E: std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count() (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x401A93: std::__shared_ptr<std::thread::_Impl_base, (__gnu_cxx::_Lock_policy)2>::~__shared_ptr() (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x401AAD: std::shared_ptr<std::thread::_Impl_base>::~shared_ptr() (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x400D5D: _ZNSt6threadC1IZ4mainEUlvE_IEEEOT_DpOT0_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x400C60: main (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347==
==19347== This conflicts with a previous read of size 8 by thread #2
==19347== Locks held: none
==19347== at 0x50BEABE: ??? (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.16)
==19347== by 0x4C2B547: mythread_wrapper (hg_intercepts.c:219)
==19347== by 0x4E38EFB: start_thread (pthread_create.c:304)
==19347== by 0x564C89C: clone (clone.S:112)
==19347==
==19347== Address 0x5B8E060 is 32 bytes inside a block of size 64 alloc'd
==19347== at 0x4C29059: operator new(unsigned long) (vg_replace_malloc.c:287)
==19347== by 0x4012E9: _ZN9__gnu_cxx13new_allocatorISt23_Sp_counted_ptr_inplaceINSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEEESaIS8_ELNS_12_Lock_policyE2EEE8allocateEmPKv (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x40117C: _ZNSt14__shared_countILN9__gnu_cxx12_Lock_policyE2EEC1INSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEEESaISA_EIS9_EEESt19_Sp_make_shared_tagPT_RKT0_DpOT1_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x4010B9: _ZNSt12__shared_ptrINSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEEELN9__gnu_cxx12_Lock_policyE2EEC1ISaIS6_EIS5_EEESt19_Sp_make_shared_tagRKT_DpOT0_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x401063: _ZNSt10shared_ptrINSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEEEEC1ISaIS6_EIS5_EEESt19_Sp_make_shared_tagRKT_DpOT0_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x401009: _ZSt15allocate_sharedINSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEEESaIS6_EIS5_EESt10shared_ptrIT_ERKT0_DpOT1_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x400EF7: _ZSt11make_sharedINSt6thread5_ImplISt12_Bind_resultIvFZ4mainEUlvE_vEEEEIS5_EESt10shared_ptrIT_EDpOT0_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x400E17: _ZNSt6thread15_M_make_routineISt12_Bind_resultIvFZ4mainEUlvE_vEEEESt10shared_ptrINS_5_ImplIT_EEEOS7_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x400D2B: _ZNSt6threadC1IZ4mainEUlvE_IEEEOT_DpOT0_ (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347== by 0x400C60: main (in /mnt/home/kfeng/dev/robolab/cpp/sbx/sandbox)
==19347==
==19347== ----------------------------------------------------------------
==19347==
推荐答案
std :: thread在内部使用一个共享指针。你所看到的是对该共享指针对象的引用计数的误报。您可以通过在每个源文件中添加下面显示的四行代码，避免这些错误，这些代码在C ++头包含伪指令之前。注意：这只适用于gcc 4.6.0或更高版本中包含的libstdc ++版本。
std::thread uses a shared pointer internally. What you are seeing are false positives on the reference count of that shared pointer object. You can avoid these false positives by adding the four lines of code shown below in each source file just before the C++ header include directives. Note: this only works with the version of libstdc++ included with gcc 4.6.0 or later.
#include <valgrind/drd.h>
#define _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(addr) ANNOTATE_HAPPENS_BEFORE(addr)
#define _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(addr) ANNOTATE_HAPPENS_AFTER(addr)
#define _GLIBCXX_EXTERN_TEMPLATE -1
有关详细信息，也看到的libstdc数据争狩猎节++手册（的http://gcc.gnu.org/onlinedocs/libstdc++/manual/debug.html ）。
For more information, see also the Data Race Hunting section in the libstdc++ manual (http://gcc.gnu.org/onlinedocs/libstdc++/manual/debug.html).
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