On Mon, 23 Aug 1999, Christopher Masto wrote: > > The thing about well-intentioned but incorrect locking code is that > > it will appear to work fine, until it trips over the one code path > > where it forgets to lock some file that it should have locked. And > > even then, the code will "work" just fine, until multiple processes > > are accessing that file at the same time. > > > > I think it is appropriate for an operating system to provide an option > > such that *it* (the system) will enforce the locking, and not have to > > trust that all code-paths in all programs will do the right thing > > WRT advisory locking. > > Dunno about that.. if you're using advisory locking, you know to say > "lock the file, then read the data, do your calculation, write it out, > and unlock". This manditory locking sounds like an invitation for > disaster. "I don't need to pay attention to the details because > the kernel will take care of it for me." > > Actually, I don't really understand the paradigm. Two processes need > to safely update a file, so one of them aquires a mandatory lock, and > the other.. uh.. just blocks trying to open the file? How does it > know it's not the first one?
It means that if user A puts data in (and follows locking procedure correctly) then he doesn't have to worry that user B might not be following correct locking procedure, because user B is mandatorily forced to follow the procedure. There isn't any added sloppiness, just a guarantee that if one user locks a file, no other rogues can get into it while the lock exists. ---------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data [email protected] | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | picnic.mat.net: FreeBSD/i386 (301) 220-2114 | jaunt.mat.net : FreeBSD/Alpha ---------------------------+----------------------------------------------- To Unsubscribe: send mail to [email protected] with "unsubscribe freebsd-hackers" in the body of the message
