From mboxrd@z Thu Jan  1 00:00:00 1970
From: James Bottomley <James.Bottomley@suse.de>
Subject: Re: [PATCH 02/36] scsi,rcu: convert call_rcu(fc_rport_free_rcu) to
 kfree_rcu()
Date: Wed, 23 Mar 2011 09:05:51 -0500
Message-ID: <1300889151.15899.4.camel@mulgrave.site>
References: <4D82D071.5020703@cn.fujitsu.com>
	 <4D82D3FF.2080303@cn.fujitsu.com> <4D82D45A.30102@cn.fujitsu.com>
	 <1300814913.19083.427.camel@fritz>
	 <20110323065014.GU2322@linux.vnet.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Cc: Robert Love <robert.w.love@intel.com>,
	Lai Jiangshan <laijs@cn.fujitsu.com>,
	Ingo Molnar <mingo@elte.hu>, Jens Axboe <axboe@kernel.dk>,
	Neil Horman <nhorman@tuxdriver.com>,
	"David S. Miller" <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	"Pekka Savola (ipv6)" <pekkas@netcore.fi>,
	James Morris <jmorris@namei.org>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	Patrick McHardy <kaber@trash.net>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Stephen Hemminger <shemminger@vyatta.com>,
	Tejun Heo <tj@kernel.org>, Jarek Poplawski <jarkao2@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"devel@open-fcoe.org" <devel@open-fcoe.org>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>
To: paulmck@linux.vnet.ibm.com
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20110323065014.GU2322@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: netdev.vger.kernel.org

On Tue, 2011-03-22 at 23:50 -0700, Paul E. McKenney wrote:
> The kfree_rcu() definition is as
> follows:
> 
> #define kfree_rcu(ptr, rcu_head)					\
> 	__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))

Isn't this one of those cases where the obvious use of the interface is
definitely wrong?

It's also another nasty pseudo C prototype.  I know we do this sort of
thing for container_of et al, but I don't really think we want to extend
it.

Why not make the interface take a pointer to the embedding structure and
one to the rcu_head ... that way all pointer mathematics can be
contained inside the RCU routines.

James