Helgrind already has 

{
   helgrind-glibc-io-xsputn-mempcpy
   Helgrind:Race
   fun:__GI_mempcpy
   fun:_IO_*xsputn*
   obj:@GLIBC_LIBC_PATH@
}

DRD has no equivalent, and I see hazard reports for uses of "std::cerr <<" with std::thread. I would expect there us a similar issue with (f)printf/pthreads in C.

I suggest

{                                                                                                                                                           
   drd-glibc-io-xsputn-mempcpy
   drd:ConflictingAccess                                                                                                                                    
   fun:__GI_mempcpy                                                                                                                                         
   fun:_IO_*xsputn*
   obj:@GLIBC_LIBC_PATH@ 
}