Re: fcntl always fails to delete lock file, and PID is always -6464

On Sun, Oct 3, 2010 at 8:37 PM, Daichi GOTO <daichi_at_ongs.co.jp> wrote:
> It looks very strange. fcntl() always fails to delete lock file
> and command.l_pid is always -6464. This issue is disclosed in
> porting Google's Japanese input system called "mozc".
>
>  details follow:
>    http://code.google.com/p/mozc/issues/detail?id=40
>
> % uname -a
> FreeBSD parancell.ongs.co.jp 9.0-CURRENT FreeBSD 9.0-CURRENT #6 r213257: Thu Sep 30 10:30:06 JST 2010     root_at_parancell.ongs.co.jp:/usr/obj/usr/src/sys/PARANCELL  amd64
> %
>
> My home directory on NFS server.  Does anyone have any ideas?


    I see some bad assumptions in the code:

    const int result = ::fcntl(*fd, F_SETLK, &command);
    if (-1 == result) {  // failed
      ::close(*fd);
      LOG(WARNING) << "already locked";
      return false;   // another server is already running
    }

    If the developer actually coded to POSIX expectations, he/she
would be checking for EACCES/EAGAIN; there are a myriad of other
issues that might be occurring with the software, as per my copy of
SUSv4 (see the ERRORS section of fcntl). I would print out the
strerror for that case.
    Providing a backtrace of the application's execution and the
architecture and what version of FreeBSD you're using would be
helpful.
Thanks,
-Garrett

PS Quickly looking over this code, it has portability issues assuming
that all Unix based OSes (that aren't under some Mac OSX guard) are
Linux, based on the number of /proc filesystem opens and reads I see
in the code.