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From: "Frank Filz" <ffilzlnx@mindspring.com>
To: <Volker.Lendecke@SerNet.DE>
Cc: "'Jeff Layton'" <jlayton@redhat.com>,
	"'Scott Lovenberg'" <scott.lovenberg@gmail.com>,
	"'Jeremy Allison'" <jra@samba.org>,
	"'Andreas Dilger'" <adilger@dilger.ca>,
	<linux-fsdevel@vger.kernel.org>,
	"'Ganesha NFS List'" <nfs-ganesha-devel@lists.sourceforge.net>,
	<samba-technical@lists.samba.org>,
	"'Linux Kernel Mailing List'" <linux-kernel@vger.kernel.org>
Subject: RE: [RFC PATCH 0/5] locks: implement "filp-private" (aka UNPOSIX) locks
Date: Mon, 14 Oct 2013 08:23:03 -0700	[thread overview]
Message-ID: <02a901cec8f1$47ce0280$d76a0780$@mindspring.com> (raw)
In-Reply-To: <E1VVcWF-00HTkJ-B9@intern.SerNet.DE>

> 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

  reply	other threads:[~2013-10-14 15:23 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-11 12:25 [RFC PATCH 0/5] locks: implement "filp-private" (aka UNPOSIX) locks Jeff Layton
2013-10-11 12:25 ` [RFC PATCH 1/5] locks: consolidate checks for compatible filp->f_mode values in setlk handlers Jeff Layton
2013-10-11 12:25 ` [RFC PATCH 2/5] locks: add definitions for F_RDLCKP and F_WRLCKP Jeff Layton
2013-10-11 12:25 ` [RFC PATCH 3/5] locks: skip FL_FILP_PRIVATE locks on close unless we're closing the correct filp Jeff Layton
2013-10-11 12:25 ` [RFC PATCH 4/5] locks: handle merging of locks when FL_FILP_PRIVATE is set Jeff Layton
2013-10-11 12:25 ` [RFC PATCH 5/5] locks: show private lock types in /proc/locks Jeff Layton
2013-10-11 13:35 ` [RFC PATCH 0/5] locks: implement "filp-private" (aka UNPOSIX) locks Jeff Layton
2013-10-11 15:20   ` Frank Filz
2013-10-11 15:50     ` Jeff Layton
2013-10-11 17:07       ` Frank Filz
2013-10-11 18:42         ` Jeff Layton
2013-10-11 18:53           ` Frank Filz
2013-10-12  9:10             ` Volker Lendecke
2013-10-11 20:07 ` J. Bruce Fields
2013-10-11 21:36   ` Andreas Dilger
2013-10-11 23:21     ` Jeff Layton
2013-10-11 23:49       ` Jeremy Allison
2013-10-12  0:18         ` Scott Lovenberg
2013-10-12  0:42           ` Jeff Layton
2013-10-12 18:12             ` Frank Filz
2013-10-14  7:24               ` Volker Lendecke
2013-10-14 15:23                 ` Frank Filz [this message]
2013-10-15  8:56                   ` Volker Lendecke
2013-10-12 20:56             ` Scott Lovenberg
2013-10-12  9:20 ` Stefan (metze) Metzmacher
2013-10-12 11:47   ` Jeff Layton
2013-10-12 18:10     ` [Nfs-ganesha-devel] " Frank Filz

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