Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760513Ab2EKTGv (ORCPT ); Fri, 11 May 2012 15:06:51 -0400 Received: from rcsinet15.oracle.com ([148.87.113.117]:37880 "EHLO rcsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758861Ab2EKTGu (ORCPT ); Fri, 11 May 2012 15:06:50 -0400 Date: Fri, 11 May 2012 15:00:41 -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: <20120511190041.GA3785@phenom.dumpdata.com> References: <20120420192439.GA32170@phenom.dumpdata.com> <20120510145745.GO26152@phenom.dumpdata.com> <20120511142758.GA29677@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: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3100 Lines: 81 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. -- 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/