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Tue, 2 Jul 2024 22:02:00 +0000 Message-ID: Date: Tue, 2 Jul 2024 15:01:57 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] selftests/resctrl: Adjust SNC support messages To: Tony Luck CC: "Wieczor-Retman, Maciej" , "shuah@kernel.org" , "Yu, Fenghua" , "linux-kernel@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "ilpo.jarvinen@linux.intel.com" References: <484aef5f10e2a13a7c4f575f4a0b3eb726271277.1719842207.git.maciej.wieczor-retman@intel.com> <4fdc8cc0-0b04-4879-9337-9eda3b83f603@intel.com> From: Reinette Chatre Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4PR04CA0114.namprd04.prod.outlook.com (2603:10b6:303:83::29) To SJ2PR11MB7573.namprd11.prod.outlook.com (2603:10b6:a03:4d2::10) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ2PR11MB7573:EE_|MN0PR11MB6277:EE_ X-MS-Office365-Filtering-Correlation-Id: f9312034-64be-4e81-8864-08dc9ae298e8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024; 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>>> + FILE *fp; >>> + >>> + fp = fopen("/sys/devices/system/cpu/offline", "r"); >>> >>> Check for fp == NULL before using it. >>> >>> + if (fscanf(fp, "%s", offline_cpus_str) < 0) { >>> >>> fscanf() seems like a heavy hammer. >> >> Do you perhaps have any recommendations that should be used instead of >> fscanf()? I checked with stat() but could not see a difference between >> file with a CPU and a file without. Other alternative is >> open()/read()/close()? Looks like when there are no offline CPUs then >> the file will only contain '\n' so it may be possible to read one byte >> from the file and confirm it is '\n' as a check for "cpus_offline_empty()". > > Sorry. I replied with Outlook and didn't quote things properly > so my alternate suggestion didn't stand out. Here it is again: > > if (fgets(offline_cpus_str, sizeof(offline_cpus_str), fp) == NULL) { > fclose(fp); > return true; > } Apologies, missed this. > > But that was with the assumption that /sys/devices/system/cpu/offline > would be empty. Not that it would conatain a single "\n" as you say > above. > > So fgets( ...) followed with "if (offline_cpus_str[0] == '\n') "? How about simplifying it more to "if (fgetc(fp) == '\n')" ? Reinette