On Tue, Feb 26, 2002 at 09:35:30AM -0500, Theo Van Dinter wrote:
> On Tue, Feb 26, 2002 at 03:04:27AM -0800, Craig Hughes wrote:
> > FYI, your code example is not even close to concurrency-safe. If one
> > instance checks (-f $path) and finds no file, then context switches, and
> > instance #2 performs the same check, then both instances will try to
> > create a new file, and you'll probably end up with some weird mangled DB
> > file.
> >
> > > if ( -f $path ) {
> > > tie %{$self->{accum}},"AnyDBM_File",$path, O_RDWR, #open rw w/lock
> > > (oct ($main->{conf}->{auto_whitelist_file_mode}) & 0666)
> > > or die "Cannot open existing auto_whitelist_path $path: $!\n";
> > >
> > > } else {
> > > tie %{$self->{accum}},"AnyDBM_File",$path, O_RDWR|O_CREAT, #open rw
>w/lock
> > > (oct ($main->{conf}->{auto_whitelist_file_mode}) & 0666)
> > > or die "Cannot open auto_whitelist_path $path for creation: $!\n";
> > > }
>
> Is there a reason you do a check for O_CREAT? O_CREAT just says "create if
> it doesn't already exist", it won't truncate the current data (that's
> O_TRUNC). I would elliminate this code and just have a single tie with
> O_CREAT.
I just noticed the comment in the code about "with lock", which O_CREAT
won't give you either. You'd want to do this check if you're using
O_CREAT|O_EXCL (which will error if the file already exists.)
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