This could be the same issue as discussed in
http://permalink.gmane.org/gmane.comp.debugging.valgrind/10043
<http://permalink.gmane.org/gmane.comp.debugging.valgrind/10043>--kcc
On Tue, Apr 6, 2010 at 9:53 AM, Jorge Moraleda <[email protected]>wrote:
> Dear all,
>
> When I compile the following program with:
> $ g++ -g -pthread threads.cpp
>
> // begin program /////////////////////////////////////////////
> // file: threads.cpp
> #include <pthread.h>
> #include <iostream>
> #include <sstream>
>
> void *threadEntry(void *threadid)
> {
> long tid;
> tid = (long)threadid;
> for (int i = 0; i<5; i++) {
> std::stringstream myStream;
> myStream << "this thread is " << tid;
> std::string myString(myStream.str());
> pthread_yield();
> }
> pthread_exit(NULL);
> }
>
> int main (int argc, char *argv[])
> {
> pthread_t threads[2];
> int rc;
> long t;
> for(t=0; t<2; t++) {
> rc = pthread_create(&threads[t], NULL, threadEntry, (void *)t);
> }
> pthread_exit(NULL);
> }
> // end program /////////////////////////////////////////////
>
> and run drd on it with:
> $ valgrind --tool=drd ./a.out
>
> I get the following output:
>
> ==16240== drd, a thread error detector
> ==16240== Copyright (C) 2006-2009, and GNU GPL'd, by Bart Van Assche.
> ==16240== Using Valgrind-3.5.0-Debian and LibVEX; rerun with -h for
> copyright info
> ==16240== Command: ./a.out
> ==16240==
> ==16240== Thread 3:
> ==16240== Conflicting load by thread 3 at 0x05132e98 size 1
> ==16240== at 0x4ED44C8: std::ostream&
> std::ostream::_M_insert<long>(long) (in /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x400C48: threadEntry(void*) (threads.cpp:12)
> ==16240== by 0x4C32870: vgDrd_thread_wrapper
> (drd_pthread_intercepts.c:272)
> ==16240== by 0x55E8A03: start_thread (pthread_create.c:300)
> ==16240== by 0x58DD80C: clone (clone.S:112)
> ==16240== Allocation context: BSS section of /usr/lib/libstdc++.so.6.0.13
> ==16240== Other segment start (thread 2)
> ==16240== at 0x4C29F2F: pthread_mutex_unlock
> (drd_pthread_intercepts.c:633)
> ==16240== by 0x4EA387E: std::locale::locale() (in
> /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x4E9FE5F: std::ios_base::_M_init() (in
> /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x4EB4768: std::basic_ios<char, std::char_traits<char>
> >::init(std::basic_streambuf<char, std::char_traits<char> >*) (in
> /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x4ED7DEA: std::basic_stringstream<char,
> std::char_traits<char>, std::allocator<char>
> >::basic_stringstream(std::_Ios_Openmode) (in
> /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x400C21: threadEntry(void*) (threads.cpp:11)
> ==16240== by 0x4C32870: vgDrd_thread_wrapper
> (drd_pthread_intercepts.c:272)
> ==16240== by 0x55E8A03: start_thread (pthread_create.c:300)
> ==16240== by 0x58DD80C: clone (clone.S:112)
> ==16240== Other segment end (thread 2)
> ==16240== at 0x58ACEB7: sched_yield (in /lib/libc-2.10.1.so)
> ==16240== by 0x400C63: threadEntry(void*) (threads.cpp:14)
> ==16240== by 0x4C32870: vgDrd_thread_wrapper
> (drd_pthread_intercepts.c:272)
> ==16240== by 0x55E8A03: start_thread (pthread_create.c:300)
> ==16240== by 0x58DD80C: clone (clone.S:112)
> ==16240==
> ==16240== Conflicting load by thread 3 at 0x05132eb9 size 1
> ==16240== at 0x4ED44D3: std::ostream&
> std::ostream::_M_insert<long>(long) (in /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x400C48: threadEntry(void*) (threads.cpp:12)
> ==16240== by 0x4C32870: vgDrd_thread_wrapper
> (drd_pthread_intercepts.c:272)
> ==16240== by 0x55E8A03: start_thread (pthread_create.c:300)
> ==16240== by 0x58DD80C: clone (clone.S:112)
> ==16240== Allocation context: BSS section of /usr/lib/libstdc++.so.6.0.13
> ==16240== Other segment start (thread 2)
> ==16240== at 0x4C29F2F: pthread_mutex_unlock
> (drd_pthread_intercepts.c:633)
> ==16240== by 0x4EA387E: std::locale::locale() (in
> /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x4E9FE5F: std::ios_base::_M_init() (in
> /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x4EB4768: std::basic_ios<char, std::char_traits<char>
> >::init(std::basic_streambuf<char, std::char_traits<char> >*) (in
> /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x4ED7DEA: std::basic_stringstream<char,
> std::char_traits<char>, std::allocator<char>
> >::basic_stringstream(std::_Ios_Openmode) (in
> /usr/lib/libstdc++.so.6.0.13)
> ==16240== by 0x400C21: threadEntry(void*) (threads.cpp:11)
> ==16240== by 0x4C32870: vgDrd_thread_wrapper
> (drd_pthread_intercepts.c:272)
> ==16240== by 0x55E8A03: start_thread (pthread_create.c:300)
> ==16240== by 0x58DD80C: clone (clone.S:112)
> ==16240== Other segment end (thread 2)
> ==16240== at 0x58ACEB7: sched_yield (in /lib/libc-2.10.1.so)
> ==16240== by 0x400C63: threadEntry(void*) (threads.cpp:14)
> ==16240== by 0x4C32870: vgDrd_thread_wrapper
> (drd_pthread_intercepts.c:272)
> ==16240== by 0x55E8A03: start_thread (pthread_create.c:300)
> ==16240== by 0x58DD80C: clone (clone.S:112)
> ==16240==
> ==16240==
> ==16240== For counts of detected and suppressed errors, rerun with: -v
> ==16240== ERROR SUMMARY: 6 errors from 2 contexts (suppressed: 208 from
> 140)
>
> My question is: Are the errors reported real multi threading errors?
> If not, how can I tell drd to suppress them? (In my real world program, I
> have thousands of errors in hundreds of contexts, and I am trying to
> find the real ones.)
> If yes, can you help me understand what is wrong? Both threads only
> use local variables. I have been reading about the global object
> "locale" used by streams for localization, but I have read that it is
> protected by a global mutex.
>
> By the way, if in the program above I don't include iostream, then drd
> reports almost a thousand errors from a hundred contexts!
>
> Thank you very much!
>
> Jorge Moraleda
>
> FYI: I am running ubuntu linux 9.10. This is my system:
>
> $ valgrind --version
> valgrind-3.5.0-Debian
>
> $ uname -r
> 2.6.31-20-generic
>
> $ gcc -v
> Using built-in specs.
> Target: x86_64-linux-gnu
> Configured with: ../src/configure -v --with-pkgversion='Ubuntu
> 4.4.1-4ubuntu9'
> --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs
> --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr
> --enable-shared --enable-multiarch --enable-linker-build-id
> --with-system-zlib --libexecdir=/usr/lib --without-included-gettext
> --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4
> --program-suffix=-4.4 --enable-nls --enable-clocale=gnu
> --enable-libstdcxx-debug --enable-objc-gc --disable-werror
> --with-arch-32=i486 --with-tune=generic --enable-checking=release
> --build=x86_64-linux-gnu --host=x86_64-linux-gnu
> --target=x86_64-linux-gnu
> Thread model: posix
> gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9)
>
>
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proactively, and fine-tune applications for parallel performance.
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