Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755784Ab0KKOPb (ORCPT ); Thu, 11 Nov 2010 09:15:31 -0500 Received: from kroah.org ([198.145.64.141]:33485 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754902Ab0KKOP3 (ORCPT ); Thu, 11 Nov 2010 09:15:29 -0500 Date: Thu, 11 Nov 2010 06:16:11 -0800 From: Greg KH To: Boaz Harrosh Cc: Vladislav Bolkhovitin , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, scst-devel , James Bottomley , Andrew Morton , FUJITA Tomonori , Mike Christie , Vu Pham , Bart Van Assche , James Smart , Joe Eykholt , Andy Yan , Chetan Loke , Dmitry Torokhov , Hannes Reinecke , Richard Sharpe , Daniel Henrique Debonzi Subject: Re: [PATCH 8/19]: SCST SYSFS interface implementation Message-ID: <20101111141611.GA4679@kroah.com> References: <4CC1DAA2.7030602@vlnb.net> <20101022185437.GA9103@kroah.com> <4CD8566D.1020202@vlnb.net> <20101109002829.GA22633@kroah.com> <4CD9A9B8.70708@vlnb.net> <4CDA6CD4.3010308@panasas.com> <4CDAFE6E.7050200@vlnb.net> <4CDBBE80.40908@panasas.com> <20101111120453.GA672@kroah.com> <4CDBF837.7050608@panasas.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4CDBF837.7050608@panasas.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1480 Lines: 44 On Thu, Nov 11, 2010 at 04:05:43PM +0200, Boaz Harrosh wrote: > On 11/11/2010 02:04 PM, Greg KH wrote: > > On Thu, Nov 11, 2010 at 11:59:28AM +0200, Boaz Harrosh wrote: > >> 4. Exactly Like 3 but without the extra kref member > >> Only x_put() changes and x_kref_release() now receives > >> an x_object > >> > >> int x_put(struct object_x *x) > >> { > >> if (kobject_put(&x->kobj) == 1) > >> // Like above [3] x_kref_release() > >> x_kref_release(x); > >> } > > > > This is racy, please never do this. > > > > The last ref belongs to the core code. 1 means there are no > more external clients on the object. So it can not race with > decrements. But I guess there is a possibility that it can > race with new increments. Exactly. > If it is the case that new increments > can only come from, say, sysfs access, then if we call the > x_put() == 1 after we are unregistered from sysfs and no new > users are allowed then the counter can only go down and we > have the last reference. No? Just don't do this, it's not worth it and will break over time when others mess with the code. Also note that kobject_put() does not even return a value, so the code above will not even compile, let alone work. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/