Messages in this thread | | | Date | Mon, 19 May 2014 10:28:02 -0400 | From | Jeff Layton <> | Subject | Re: OFD locks and deadlock detection |
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On Mon, 19 May 2014 15:18:13 +0200 "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> wrote:
> Hi Jeff, > > I just happened to notice : > > commit 57b65325fe34ec4c917bc4e555144b4a94d9e1f7 > Author: Jeff Layton <jlayton@redhat.com> > Date: Mon Feb 3 12:13:09 2014 -0500 > > locks: skip deadlock detection on FL_FILE_PVT locks > > And then this thread: > > http://thread.gmane.org/gmane.linux.file-systems/81318/focus=81327 > From: Jeff Layton <jlayton <at> redhat.com> > Subject: [PATCH v5 13/14] locks: skip deadlock detection on FL_FILE_PVT locks > Date: 2014-01-09 14:19:46 GMT > > I think it's pretty important to document that. All implementations > of traditional process-associated (.k.a. "POSIX") locks that I've ever > come across do detect deadlocks, so it's important to note that OFD locks > do not. > > I plan to add the following text to the fcntl(2) page: > > [[ > In the current implementation, > no deadlock detection is performed for open file description locks. > (This contrasts with process-associated record locks, > for which the kernel does perform deadlock detection.) > ]] > > Okay? > > cheers, > > Michael > >
(note: I'm no longer with Red Hat, so jlayton@redhat.com no longer works)
Sounds fine to me.
FWIW, the deadlock detection for process-associated record locks is pretty worthless except in certain narrow circumstances.
At some point, we probably should have a discussion as to whether deadlock detection is really something we want to keep. The current implementation requires a global spinlock which has obvious consequences for scalability.
Thanks, -- Jeff Layton <jlayton@poochiereds.net>
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