On Mon, 19 May 2014 15:18:13 +0200
"Michael Kerrisk (man-pages)" [off-list ref] wrote:

Hi Jeff,

I just happened to notice :

    commit 57b65325fe34ec4c917bc4e555144b4a94d9e1f7
    Author: Jeff Layton [off-list ref]
    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-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org 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 [off-list ref]
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