On Tue, Apr 6, 2010 at 7:53 AM, Jorge Moraleda <jorge.moral...@gmail.com> 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.
Hello Jorge,
Unfortunately not all libraries have been designed with data-race
detection tools in mind. Several libraries contain code that triggers
benign data races. Examples are the I/O code in libstdc++ and in libc.
You can either create a suppression pattern to suppress the above
races, or even simpler, add the following code in main() before thread
creation starts:
std::ostringstream dummy;
dummy << 0;
The above code will make sure that locale initialization, which is
triggered by sending an number to an I/O stream, will happen before
any threads are created and hence no races will be reported anymore on
locale initialization.
Bart.
------------------------------------------------------------------------------
Download Intel® Parallel Studio Eval
Try the new software tools for yourself. Speed compiling, find bugs
proactively, and fine-tune applications for parallel performance.
See why Intel Parallel Studio got high marks during beta.
http://p.sf.net/sfu/intel-sw-dev
_______________________________________________
Valgrind-users mailing list
Valgrind-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/valgrind-users
