From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S1758988AbZLOBX0@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1758988AbZLOBX0 (ORCPT <rfc822;w@1wt.eu>);
	Mon, 14 Dec 2009 20:23:26 -0500
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758945AbZLOBX0
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Mon, 14 Dec 2009 20:23:26 -0500
Received: from e8.ny.us.ibm.com ([32.97.182.138]:59508 "EHLO e8.ny.us.ibm.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1758391AbZLOBXY (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 14 Dec 2009 20:23:24 -0500
Date: Mon, 14 Dec 2009 17:23:22 -0800
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       LKML <linux-kernel@vger.kernel.org>,
       Dipankar Sarma <dipankar@in.ibm.com>, Ingo Molnar <mingo@elte.hu>,
       Oleg Nesterov <oleg@tv-sign.ru>, Al Viro <viro@zeniv.linux.org.uk>,
       James Morris <jmorris@namei.org>, David Howells <dhowells@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [patch 0/9] Fix various __task_cred related invalid RCU
	assumptions
Message-ID: <20091215012322.GI6679@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
References: <20091210001308.247025548@linutronix.de> <20091210022825.GG6938@linux.vnet.ibm.com> <alpine.LFD.2.00.0912091914540.3560@localhost.localdomain> <1260422031.4165.1.camel@twins> <20091210053457.GB6720@linux.vnet.ibm.com> <1260730577.4165.7.camel@twins> <20091214015347.GB7710@linux.vnet.ibm.com> <1260785859.4165.136.camel@twins> <20091214141607.GD7710@linux.vnet.ibm.com> <1260801039.4165.323.camel@twins>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1260801039.4165.323.camel@twins>
User-Agent: Mutt/1.5.15+20070412 (2007-04-11)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Dec 14, 2009 at 03:30:39PM +0100, Peter Zijlstra wrote:
> On Mon, 2009-12-14 at 06:16 -0800, Paul E. McKenney wrote:
> 
> > > I think you can use lock_is_held(&rcu_lock_map), except you need to deal
> > > with the !debug_locks case, because lockdep stops once debug_locks
> > > becomes false, which means lock_is_held() will return rubbish.
> > 
> > OK, so I need to do something like the following, then?
> > 
> > 	debug_locks ? lock_is_held(&rcu_lock_map) : 1
> 
> Depending on what the safe return value is, yeah. If you want an assert
> like function, false is usually the safe one.
> 
> #define lockdep_assert_held(l)  WARN_ON(debug_locks && !lockdep_is_held(l))
> 
> is the one in-tree user of this.

Sounds good, thank you for the tip!!!

							Thanx, Paul