From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755863Ab0IBAfm (ORCPT ); Wed, 1 Sep 2010 20:35:42 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:38198 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752793Ab0IBAfl (ORCPT ); Wed, 1 Sep 2010 20:35:41 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.5.1 Message-ID: <4C7EF175.1090005@np.css.fujitsu.com> Date: Thu, 02 Sep 2010 09:36:05 +0900 From: Jin Dongming User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; ja; rv:1.9.2.7) Gecko/20100713 Thunderbird/3.1.1 MIME-Version: 1.0 To: Jean Delvare CC: Fenghua Yu , "Brown, Len" , Hidetoshi Seto , "H. Peter Anvin" , LKLM , "lm-sensors@lm-sensors.org" , mingo Redhat , Thomas Gleixner Subject: Re: [Patch-next] Trival fixes in thermal_throttle_add_dev(). References: <4C75D3C4.6040802@np.css.fujitsu.com> <20100826060822.GA15021@fenghua-desk.sc.intel.com> <4C7625D1.4060201@np.css.fujitsu.com> <20100827152007.27636fa5@hyperion.delvare> <4C7B64A8.2030208@np.css.fujitsu.com> <493994B35A117E4F832F97C4719C4C04A111EEDF@orsmsx505.amr.corp.intel.com> <4C7C5314.7090404@np.css.fujitsu.com> <20100831010251.GA28885@fenghua-desk.sc.intel.com> <20100831090725.5d83eedb@hyperion.delvare> <20100831170443.GA30454@fenghua-desk.sc.intel.com> <20100831213002.73e2f57d@hyperion.delvare> In-Reply-To: <20100831213002.73e2f57d@hyperion.delvare> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jean and Fenghua, Sorry for replying late. (2010/09/01 4:30), Jean Delvare wrote: > On Tue, 31 Aug 2010 10:04:43 -0700, Fenghua Yu wrote: >> On Tue, Aug 31, 2010 at 12:07:25AM -0700, Jean Delvare wrote: >>> On Mon, 30 Aug 2010 18:02:52 -0700, Fenghua Yu wrote: >>>> On Mon, Aug 30, 2010 at 05:55:48PM -0700, Jin Dongming wrote: >>>>> diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c >>>>> index d9368ee..79d563a 100644 >>>>> --- a/arch/x86/kernel/cpu/mcheck/therm_throt.c >>>>> +++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c >>>>> @@ -216,14 +216,27 @@ static __cpuinit int thermal_throttle_add_dev(struct sys_device *sys_dev, >>>>> err = sysfs_add_file_to_group(&sys_dev->kobj, >>>>> &attr_core_power_limit_count.attr, >>>>> thermal_attr_group.name); >>>>> - if (cpu_has(c, X86_FEATURE_PTS)) >>>>> + if (err) >>>>> + goto error; >>>>> + >>>>> + if (cpu_has(c, X86_FEATURE_PTS)) { >>>>> err = sysfs_add_file_to_group(&sys_dev->kobj, >>>>> &attr_package_throttle_count.attr, >>>>> thermal_attr_group.name); >>>>> + if (err) >>>>> + goto error; >>>>> + >>>>> if (cpu_has(c, X86_FEATURE_PLN)) >>>>> err = sysfs_add_file_to_group(&sys_dev->kobj, >>>>> &attr_package_power_limit_count.attr, >>>>> thermal_attr_group.name); >>>>> + if (err) >>>>> + goto error; >>>>> + } >>>>> + >>>>> + return 0; >>>>> +error: >>>>> + sysfs_remove_group(&sys_dev->kobj, &thermal_attr_group); >>>>> >>>>> return err; >>>>> } >>>> >>>> This fix is incorrect. In this patch, a previous error prevents from adding any >>>> further devices. There shouldn't be such dependency among the devices. >>> >>> I don't quite follow you. Did you mean to write that a previous error >>> prevents from creating further _attributes_ for the same device? This >>> would be true. >>> >>> Now I don't think this is a problem because 1* such errors should never >>> happen anyway and 2* if they do happen then further attempts to create >>> the other attributes are unlikely to succeed either. >> >> I don't think there is dependency among the count files, i.e. failure to add a >> count file to the group shouldn't impact other files. Other filles can still be >> added to the group. In this case, user application only sees part of count >> numbers. And kernel may just warn on the failure instead of providing nothing >> to user. >> >> In the patch, any failure to add a file will remove the whole group. This is >> too strict. Kernel doesn't provide any count number to user application. > > Oh, my bad. I missed the call to sysfs_remove_group() when reviewing > the code. I agree with you that it shouldn't be added. > >> Agree with you that such errors should never happen anyway. So original code >> works fine. > > The original code works indeed (except for the missing curly braces) > but is confusing for the reader (which is why I raised the point and we > are discussing it now). If you are voluntarily ignoring errors, you > should add a comment saying so. And it is also a good practice to use a > dummy variable to store the error value you'll ignore, so that the > intent is clear. > I agree with your option. So I will cancel error handling of this patch and resend a patch just for missing { and } only. And I think Fenghua could make a new patch for a comment. Best Regards, Jin Dongming >> If to be picky to the error handling, a patch may just ignore returning errors >> from sysfs_add_file_to_group. > > This is an option, yes. Unfortunately this also means that such errors > won't be even logged, while I think this would be desirable. > >> Or use err |= sysfs_add_file_to_group to collect >> all errors and return err but without calling sysfs_remove_group. > > Please never use |= on non-bitwise values, it can only lead to bugs and > confusion. >