From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Frank Filz" Subject: RE: [RFC PATCH 0/5] locks: implement "filp-private" (aka UNPOSIX) locks Date: Mon, 14 Oct 2013 08:23:03 -0700 Message-ID: <02a901cec8f1$47ce0280$d76a0780$@mindspring.com> References: <1381494322-2426-1-git-send-email-jlayton@redhat.com> <20131011200756.GB22160@fieldses.org> <20131011192118.483e436f@tlielax.poochiereds.net> <20131011234923.GD8688@samba2> <20131011204244.72c2d672@corrin.poochiereds.net> <024101cec776$8f004130$ad00c390$@mindspring.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: "'Jeff Layton'" , "'Scott Lovenberg'" , "'Jeremy Allison'" , "'Andreas Dilger'" , , "'Ganesha NFS List'" , , "'Linux Kernel Mailing List'" To: Return-path: In-Reply-To: Content-Language: en-us Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org > http://www.samba.org/samba/news/articles/low_point/tale_two_stds_os2 > > > .html > > > > > > See the section entitled "First Implementation Past the Post". > > > > Interesting that Jeremy actually suggested the implementation should > > have had an arbitrary lock owner as part of the flock structure: > > > > "This is an example of a POSIX interface not being future-proofed > > against modern techniques such as threading. A simple amendment to the > > original primitive allowing a user-defined "locking context" (like a > > process id) to be entered in the struct flock structure used to define > > the lock would have fixed this problem, along with extra flags > > allowing the number of locks per context to be recorded if needed." > > > > But I'm happy with the lock context per kernel struct file as a > > solution, especially since that will allow locks to be sensibly passed > > to a forked process. > > > > Another next step would be an asynchronous blocking lock... > > Yes, please :-) What model would be useful to you (and for what project)? One thing I could think of is since we have a file descriptor for each lock owner/file pair, we could do something like select on those descriptors, got to think about how that would actually work though... The vfs lock layer does inherently support a kernel call back when a blocked lock can be unblocked, so we just need to figure out the best way to hook that up to user space in a way that doesn't require a thread per blocked lock. Frank