Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761037Ab2EKUyg (ORCPT ); Fri, 11 May 2012 16:54:36 -0400 Received: from acsinet15.oracle.com ([141.146.126.227]:32756 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760950Ab2EKUyd (ORCPT ); Fri, 11 May 2012 16:54:33 -0400 Date: Fri, 11 May 2012 16:48:24 -0400 From: Konrad Rzeszutek Wilk To: "Liu, Jinsong" Cc: "'xen-devel@lists.xensource.com'" , "'linux-kernel@vger.kernel.org'" Subject: Re: [Xen-devel] [PATCH 3/3] Xen physical cpus interface Message-ID: <20120511204824.GA2156@phenom.dumpdata.com> References: <20120420192439.GA32170@phenom.dumpdata.com> <20120510145745.GO26152@phenom.dumpdata.com> <20120511142758.GA29677@phenom.dumpdata.com> <20120511190041.GA3785@phenom.dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3557 Lines: 90 On Fri, May 11, 2012 at 08:31:15PM +0000, Liu, Jinsong wrote: > Konrad Rzeszutek Wilk wrote: > > On Fri, May 11, 2012 at 06:04:21PM +0000, Liu, Jinsong wrote: > >> Konrad Rzeszutek Wilk wrote: > >>> On Fri, May 11, 2012 at 01:12:13PM +0000, Liu, Jinsong wrote: > >>>> Liu, Jinsong wrote: > >>>>> Just notice your reply (so quick :) > >>>>> > >>>>> Agree and will update later, except 1 concern below. > >>>>> > >>>>> Konrad Rzeszutek Wilk wrote: > >>>>>>> > >>>>>>> Hmm, it's good if it's convenient to do it automatically via > >>>>>>> dev->release. However, dev container (pcpu) would be free at > >>>>>>> some other error cases, so I prefer do it 'manually'. > >>>>>> > >>>>>> You could also call pcpu_release(..) to do it manually. > >>>>>> > >>>>> > >>>>> that means kfree(pcpu) would be done twice at some error cases, > >>>>> do you think it really good? > >>>>> > >>>> > >>>> Ping. > >>>> > >>>> I think error recovery should be kept inside error logic level > >>>> itself, if try to recover upper level error would bring trouble. > >>>> > >>>> In our example, there are 2 logic levels: > >>>> pcpu level (as container), and dev level (subfield used for sys) > >>> > >>> So you need to untangle free_pcpu from doing both. Meaning one does > >>> the SysFS and the other deals with free-ing the structure and > >>> removing itself from the list. > >>> > >> > >> free_cpu is very samll, just consist of the 2 parts your said: > >> * pcpu_sys_remove() deal with sysfs > >> * list_del/kfree(pcpu) deal with pcpu > >> > >>> > >>>> dev->release should only recover error occurred at dev/sys level, > >>>> and the pcpu error should be recovered at pcpu level. > >>>> > >>>> If dev->release try to recover its container pcpu level error, like > >>>> list_del/kfree(pcpu), it would make confusing. i.e., considering > >>>> pcpu_sys_create(), 2 error cases: device_register fail, and > >>>> device_create_file fail --> how can the caller decide kfree(pcpu) > >>>> or not? > >>> > >>> Then you should free it manually. But you can do this by a wrapper > >>> function: > >>> > >>> __pcpu_release(..) { > >>> .. > >>> /* Does the removing itself from the list and kfree the pcpu */ } > >>> pcpu_release(..) { > >>> struct pcpcu *p= container_of(..) > >>> __pcpu_release(p); > >>> } > >>> > >>> dev->release = &pcpu_release; > >>> > >> > >> Too weird way. If we want to release dev itself it's good to use > >> dev->release, but for pcpu I doubt it. (consider the example I gave > >> --> why we create issue (it maybe solved in weird method I agree), > >> just for using dev->release?) > >> > >> In kernel many dev->release keep NULL. > >> An example of using dev->release is cpu/mcheck/mce.c --> > >> mce_device_release(), it *just* deal dev itself. > > > > OK? I am not sure what are we arguing here anymore? > > I think using 'kfree(pcpu)' on the error paths (as long as it is > > done before device_register) is OK. I think that seperating > > the SysFS deletion from the pcpu deletion should be done to > > avoid races. Perhaps the SysFS deletion function should also > > remove the pcpu from the list. > > How about static array pcpu[NR_CPUS]? > It seems solve all issues we argued :) Ugh. That could mean a structure of more than 4K of items. Lets stick with making it dynamic. -- 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/