linux-kernel - OFD locks and deadlock detection

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Date:	Mon, 19 May 2014 15:18:13 +0200
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	Jeff Layton <jlayton@...hat.com>,
	"linux-man@...r.kernel.org" <linux-man@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>
CC:	mtk.manpages@...il.com
Subject: OFD locks and deadlock detection

Hi Jeff,

I just happened to notice :

    commit 57b65325fe34ec4c917bc4e555144b4a94d9e1f7
    Author: Jeff Layton <jlayton@...hat.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

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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