linux-kernel - Re: [PATCH v5 13/14] locks: skip deadlock detection on FL_FILE

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Message-ID: <20140114213044.GD23999@fieldses.org>
Date:	Tue, 14 Jan 2014 16:30:44 -0500
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Richard Hipp <drh@...ite.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Jeff Layton <jlayton@...hat.com>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	nfs-ganesha-devel@...ts.sourceforge.net,
	samba-technical@...ts.samba.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Richard Hipp <drh@...ci.com>
Subject: Re: [PATCH v5 13/14] locks: skip deadlock detection on FL_FILE_PVT
 locks

On Tue, Jan 14, 2014 at 04:21:53PM -0500, Richard Hipp wrote:
> SQLite uses only F_SETLK, never F_SETLKW.  Doesn't that mean that SQLite
> will work the same with or without deadlock detection?  Doesn't deadlock
> detection only come into play with F_SETLKW?

That's correct.

> > >> (Actually, what happens if you receive a signal which waiting on a file
> > lock?)
> > >
> > > Return -EINTR.
> >
> 
> Huh.  SQLite is not checking for EINTR if fcntl(F_SETLK,...) fails.  Should
> it be?  Or does EINTR only come up for F_SETLKW?

I don't know--I wonder if a distributed filesystem, for example, might
allow even a non-blocking lock request to be interrupted?  Might be
interesting to check what nfs does.

--b.

> 
> We do check for EINTR and retry for other system calls (read(), write(),
> fallocate(), ftruncate(), close(), chmod(), open(), maybe others too).
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