std::thread helgrind

From:

Garrett Hartshaw <ghartshaw@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sat, 01 Jan 2011 21:44:41 -0500

Message-ID:

<ifoorv$r51$1@speranza.aioe.org>

Running helgrind (valgrind --tool=helgrind) gives a bunch of warnings
about race conditions on the following code. Is it correct, and if so
how do I fix it?

-- The code
#include <thread>

class threads {
public:
  void run() {
    std::thread thread( &threads::run_thread, this );
    thread.join();
  }

private:
  void run_thread() {}
};

int main() {
  threads().run();
}

--the output from helgrind
$ valgrind --tool=helgrind ./a.out
==15668== Helgrind, a thread error detector
==15668== Copyright (C) 2007-2009, and GNU GPL'd, by OpenWorks LLP et al.
==15668== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==15668== Command: ./a.out
==15668==
==15668== Thread #2 was created
==15668== at 0x58C612E: clone (clone.S:77)
==15668== by 0x55DDEDF: T.124 (createthread.c:75)
==15668== by 0x55DE3E1: pthread_create@@GLIBC_2.2.5 (createthread.c:256)
==15668== by 0x4C2B163: ??? (in
/usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==15668== by 0x4EEEB76:
std::thread::_M_start_thread(std::shared_ptr<std::thread::_Impl_base>)
(in /usr/lib64/gcc/x86_64-pc-linux-gnu/4.4.2/libstdc++.so.6.0.13)
==15668== by 0x400F23: std::thread::thread<void (threads::*)(),
threads* const>(void (threads::*&&)(), threads* const&&) (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400DE5: threads::run() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400CC7: main (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668==
==15668== Thread #1 is the program's root thread
==15668==
==15668== Possible data race during write of size 8 at 0x7fefffbc0 by
thread #2
==15668== at 0x4C2B2A3: ??? (in
/usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==15668== This conflicts with a previous read of size 8 by thread #1
==15668== at 0x4C2B178: ??? (in
/usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==15668== by 0x4EEEB76:
std::thread::_M_start_thread(std::shared_ptr<std::thread::_Impl_base>)
(in /usr/lib64/gcc/x86_64-pc-linux-gnu/4.4.2/libstdc++.so.6.0.13)
==15668== by 0x400F23: std::thread::thread<void (threads::*)(),
threads* const>(void (threads::*&&)(), threads* const&&) (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400DE5: threads::run() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400CC7: main (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668==
==15668== Possible data race during read of size 8 at 0x7fefffbc0 by
thread #1
==15668== at 0x4C2B18D: ??? (in
/usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==15668== by 0x4EEEB76:
std::thread::_M_start_thread(std::shared_ptr<std::thread::_Impl_base>)
(in /usr/lib64/gcc/x86_64-pc-linux-gnu/4.4.2/libstdc++.so.6.0.13)
==15668== by 0x400F23: std::thread::thread<void (threads::*)(),
threads* const>(void (threads::*&&)(), threads* const&&) (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400DE5: threads::run() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400CC7: main (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== This conflicts with a previous write of size 8 by thread #2
==15668== at 0x4C2B2A3: ??? (in
/usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==15668==
==15668== Possible data race during write of size 8 at 0x7fefffbb8 by
thread #1
==15668== at 0x400C31: __gnu_cxx::__exchange_and_add(int volatile*,
int) (in /home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400C9E: __gnu_cxx::__exchange_and_add_dispatch(int*,
int) (in /home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x40128E:
std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x4010A4:
std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400E83: std::__shared_ptr<std::thread::_Impl_base,
(__gnu_cxx::_Lock_policy)2>::~__shared_ptr() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400E9D:
std::shared_ptr<std::thread::_Impl_base>::~shared_ptr() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400F2F: std::thread::thread<void (threads::*)(),
threads* const>(void (threads::*&&)(), threads* const&&) (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400DE5: threads::run() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400CC7: main (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== This conflicts with a previous read of size 8 by thread #2
==15668== at 0x4C2B24A: ??? (in
/usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==15668==
==15668== Possible data race during write of size 4 at 0x7fefffbb4 by
thread #1
==15668== at 0x400C35: __gnu_cxx::__exchange_and_add(int volatile*,
int) (in /home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400C9E: __gnu_cxx::__exchange_and_add_dispatch(int*,
int) (in /home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x40128E:
std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x4010A4:
std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400E83: std::__shared_ptr<std::thread::_Impl_base,
(__gnu_cxx::_Lock_policy)2>::~__shared_ptr() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400E9D:
std::shared_ptr<std::thread::_Impl_base>::~shared_ptr() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400F2F: std::thread::thread<void (threads::*)(),
threads* const>(void (threads::*&&)(), threads* const&&) (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400DE5: threads::run() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400CC7: main (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== This conflicts with a previous read of size 8 by thread #2
==15668== at 0x4C2B247: ??? (in
/usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so)
==15668==
==15668== Possible data race during write of size 8 at 0x5b5a060 by
thread #1
==15668== at 0x4021B0:
std::thread::_Impl<std::_Bind<std::_Mem_fn<void (threads::*)()>
()(threads*)> >::~_Impl() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x402491:
std::_Sp_destroy_inplace<std::thread::_Impl<std::_Bind<std::_Mem_fn<void
(threads::*)()> ()(threads*)> >

::operator()(std::thread::_Impl<std::_Bind<std::_Mem_fn<void

(threads::*)()> ()(threads*)> >*) const (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x40223A:
std::_Sp_counted_deleter<std::thread::_Impl<std::_Bind<std::_Mem_fn<void
(threads::*)()> ()(threads*)> >*,
std::_Sp_destroy_inplace<std::thread::_Impl<std::_Bind<std::_Mem_fn<void
(threads::*)()> ()(threads*)> > >,
std::allocator<std::thread::_Impl<std::_Bind<std::_Mem_fn<void
(threads::*)()> ()(threads*)> > >,
(__gnu_cxx::_Lock_policy)2>::_M_dispose() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x4012AF:
std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x4010A4:
std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400E83: std::__shared_ptr<std::thread::_Impl_base,
(__gnu_cxx::_Lock_policy)2>::~__shared_ptr() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400E9D:
std::shared_ptr<std::thread::_Impl_base>::~shared_ptr() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400F2F: std::thread::thread<void (threads::*)(),
threads* const>(void (threads::*&&)(), threads* const&&) (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400DE5: threads::run() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400CC7: main (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== This conflicts with a previous read of size 8 by thread #2
==15668== at 0x4EEEA26: ??? (in
/usr/lib64/gcc/x86_64-pc-linux-gnu/4.4.2/libstdc++.so.6.0.13)
==15668==
==15668== Possible data race during read of size 8 at 0x5b5a070 by thread #1
==15668== at 0x40108E:
std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400E83: std::__shared_ptr<std::thread::_Impl_base,
(__gnu_cxx::_Lock_policy)2>::~__shared_ptr() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x400E9D:
std::shared_ptr<std::thread::_Impl_base>::~shared_ptr() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x401F0C: std::thread::_Impl_base::~_Impl_base() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x4021C2:
std::thread::_Impl<std::_Bind<std::_Mem_fn<void (threads::*)()>
()(threads*)> >::~_Impl() (in
/home/garrett/Programming/game/__rewrite_valgrind/a.out)
==15668== by 0x402491:
std::_Sp_destroy_inplace<std::thread::_Impl<std::_Bind<std::_Mem_fn<void
(threads::*)()> ()(threads*)> >

::operator()(std::thread::_Impl<std::_Bind<std::_Mem_fn<void