From mboxrd@z Thu Jan  1 00:00:00 1970
From: "J. Bruce Fields" <bfields@fieldses.org>
Subject: Re: file locks: Use wait_event_interruptible_timeout()
Date: Tue, 15 Jan 2008 13:54:48 -0500
Message-ID: <20080115185448.GL17937@fieldses.org>
References: <48611B2F-1587-48C5-9F30-8DCFA1121CF6@Sun.COM> <20071129190848.GA17907@fieldses.org> <71BCABE5-52AD-4573-8DC0-5C57152A397B@Sun.COM> <20080114204419.GD16926@fieldses.org> <20080115042605.GT18741@parisc-linux.org> <20080115042830.GU18741@parisc-linux.org> <20080115144851.GB10971@fieldses.org> <20080115150447.GZ18741@parisc-linux.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Oleg Drokin <Oleg.Drokin@Sun.COM>, linux-fsdevel@vger.kernel.org
To: Matthew Wilcox <matthew@wil.cx>
Return-path: <linux-fsdevel-owner@vger.kernel.org>
Received: from mail.fieldses.org ([66.93.2.214]:53295 "EHLO fieldses.org"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1750801AbYAOSyu (ORCPT <rfc822;linux-fsdevel@vger.kernel.org>);
	Tue, 15 Jan 2008 13:54:50 -0500
Content-Disposition: inline
In-Reply-To: <20080115150447.GZ18741@parisc-linux.org>
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

On Tue, Jan 15, 2008 at 08:04:47AM -0700, Matthew Wilcox wrote:
> On Tue, Jan 15, 2008 at 09:48:51AM -0500, J. Bruce Fields wrote:
> > On Mon, Jan 14, 2008 at 09:28:30PM -0700, Matthew Wilcox wrote:
> > > interruptible_sleep_on_locked() is just an open-coded
> > > wait_event_interruptible_timeout() with a few assumptions since we know
> > > we hold the BKL.  locks_block_on_timeout() is only used in one place, so
> > > it's actually simpler to inline it into its caller.
> > 
> > Makes sense, thanks.  So the assumption we were depending on the BKL for
> > was that we could count on the wake-up not coming till after we block,
> > so we could skip a check ->fl_next that's normally needed to resolve the
> > usual sleeping-on-some-condition race?
> 
> That's right.

OK, thanks, applied just with the "few assumptions" replaced by a
description of that particular problem:

	"interruptible_sleep_on_locked() is just an open-coded
	wait_event_interruptible_timeout(), with the one difference that
	interruptible_sleep_on_locked() doesn't bother to check the
	condition on which it waits, depending instead on the BKL to
	avoid the case where it blocks after the wakeup has already been
	called.

	locks_block_on_timeout() is only used in one place, so it's
	actually simpler to inline it into its caller."

Pending locks patches available from:

	git://linux-nfs.org/~bfields/linux.git locks


--b.