From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751416Ab1ADVAY (ORCPT ); Tue, 4 Jan 2011 16:00:24 -0500 Received: from kroah.org ([198.145.64.141]:39643 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750994Ab1ADVAX (ORCPT ); Tue, 4 Jan 2011 16:00:23 -0500 Date: Tue, 4 Jan 2011 12:57:20 -0800 From: Greg KH To: Jerome Marchand Cc: Vivek Goyal , Jens Axboe , Satoru Takeuchi , Linus Torvalds , Yasuaki Ishimatsu , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] kref: add kref_test_and_get Message-ID: <20110104205720.GA4180@kroah.com> References: <4D025154.8030400@redhat.com> <20101210165553.GE31737@redhat.com> <4D07D2AC.6000500@fusionio.com> <4D0B68AF.80804@redhat.com> <4D0BB4A1.8080305@fusionio.com> <4D13664C.3020500@redhat.com> <20101223153915.GE9502@redhat.com> <4D13810B.8000304@redhat.com> <20101224192916.GB2082@redhat.com> <4D23423A.60707@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D23423A.60707@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 04, 2011 at 04:52:26PM +0100, Jerome Marchand wrote: > > Add kref_test_and_get() function, which atomically add a reference only if > refcount is not zero. This prevent to add a reference to an object that is > already being removed. We just removed a function like this recently as it really isn't the solution for what you need here at all. Please use a lock that protects the desctruction of the kref, like the rest of the kernel, to keep someone from grabing a reference while the device could be going away. That's the only way to safely do this. See the archives for why this overall, isn't a good idea for a kref to have this type of function. thanks, greg k-h