On Mon, Aug 1, 2016 at 1:45 PM, CJ YAMIGOS <cjyami...@gmail.com> wrote: > Hi everyone, > > I started recently using Valgrind (Helgrind and DRD), and I mainly want to > detect data races in my program composed of two processes that communicate > via a POSIX shared memory object. I found quite a lot of examples showing > how Valgrind can detect data races in multithreaded applications (where all > threads belong to the same process). However, this is not the case I am > interested in. > > Basically, my program is composed of two processes, namely Server and > Client. The Server is responsible of creating a named shared memory object > with "shm_open", sets the size with "ftruncate" and maps the shared memory > object to Server's virtual address space with "mmap". On the other hand, the > Client opens/gets this shared memory object with "shm_open" and then maps it > to Client's virtual address space with "mmap". Both Server and Client > processes have Read & Write access to this shared memory object. There is a > nice example in: > https://www.softprayog.in/programming/interprocess-communication-using-posix-shared-memory-in-linux; > the main difference between this example and my program is I am not using > any semaphore (i.e., any kind of protection mechanism neither) at all. > > When running my program with Valgrind (v 3.7.0) in Linux, I am getting no > warnings about potential data races in my program. In fact, when both Server > and Client processes are running in parallel (i.e., each in a different > processor core) and there is not a mechanism protecting the access to the > shared memory object (e.g., a data structure), I expect somehow to see some > data races warnings. Neither Helgrind nor DRD are able to detect data races between shared memory pages. This is hard, because the tool needs to track the happens-before relation between threads belonging to different processes. Because Valgrind itself is single-threaded (i.e. it serializes the threads of the inspected program), synchronizing the states of two Valgrind processes that have just a common shared memory page is going to be quite painful.
> So, I wonder whether I am missing something here or Valgrind just does not > support data race detection in Inter-Process Communications (like the one I > have in my program). Many thanks in advance for your helps! > > Best, > > Carlos H. > > ------------------------------------------------------------------------------ > > _______________________________________________ > Valgrind-users mailing list > Valgrind-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/valgrind-users > -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg ------------------------------------------------------------------------------ _______________________________________________ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
