From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S933025AbXGRXQL@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S933025AbXGRXQL (ORCPT <rfc822;w@1wt.eu>);
	Wed, 18 Jul 2007 19:16:11 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754369AbXGRXP6
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Wed, 18 Jul 2007 19:15:58 -0400
Received: from smtp-out.google.com ([216.239.33.17]:33568 "EHLO
	smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1759405AbXGRXP4 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 18 Jul 2007 19:15:56 -0400
DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns;
	h=received:message-id:date:from:to:subject:cc:in-reply-to:
	mime-version:content-type:content-transfer-encoding:
	content-disposition:references;
	b=ehwJX6t++X7y7qkGd5zyotSmrW/ylvOBLTXboqRmDtfSrUyOwIOZP9r+H1tMzouta
	IQ5xI3JxKPFqBYyQWxZXA==
Message-ID: <6599ad830707181615w4f2e4078j58473090691e36eb@mail.gmail.com>
Date: Wed, 18 Jul 2007 16:15:38 -0700
From: "Paul Menage" <menage@google.com>
To: balbir@linux.vnet.ibm.com
Subject: Re: Containers: css_put() dilemma
Cc: dhaval@linux.vnet.ibm.com,
       "linux kernel mailing list" <linux-kernel@vger.kernel.org>,
       "Pavel Emelianov" <xemul@sw.ru>, "Paul Jackson" <pj@sgi.com>,
       "Linux Containers" <containers@lists.osdl.org>,
       "Andrew Morton" <akpm@linux-foundation.org>
In-Reply-To: <469DA57F.9050302@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
References: <469BBE00.8000709@linux.vnet.ibm.com>
	 <6599ad830707170018p180cb7dfr53e609fd0b186e30@mail.gmail.com>
	 <469C99D1.7090807@linux.vnet.ibm.com>
	 <6599ad830707170849v11fe8cecs6d172cd38d247e09@mail.gmail.com>
	 <469CFF2B.1080702@linux.vnet.ibm.com>
	 <6599ad830707171044u38c0a940r12d2bc80b475ead4@mail.gmail.com>
	 <469D066B.6050606@linux.vnet.ibm.com>
	 <6599ad830707171126o7c431277p84f532d0122a8a98@mail.gmail.com>
	 <469D9728.2080701@linux.vnet.ibm.com>
	 <469DA57F.9050302@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org

On 7/17/07, Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>
> Thinking out loud again, can we add can_destroy() callbacks?
>

What would the exact semantics of such a callback be?

Since for proper interaction with release agents we need the subsystem
to notify the framework when a subsystem object becomes releasable
(currently as part of css_put()), what would a can_destroy() callback
let you do that you couldn't do just by taking an extra css refcount
to prevent destruction and releasing that refcount to allow
destruction?

Paul