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Sun, 4 Oct 2026 06:07:28 +0000 Date: Sun, 4 Oct 2026 13:54:20 +0800 From: Chen Yu To: Reinette Chatre CC: , , , , , , , , , , , , "Hongyu Ning" Subject: Re: [PATCH v8 7/9] fs/resctrl: Do not invoke smp_processor_id() in preemptible context Message-ID: References: <6e0ff955200ead6a2ac689d492a5e5c73ebc3552.1789705667.git.yu.c.chen@intel.com> <432f616b-314f-4b46-bfa0-28759a493cae@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <432f616b-314f-4b46-bfa0-28759a493cae@intel.com> X-ClientProxiedBy: TP0P295CA0038.TWNP295.PROD.OUTLOOK.COM (2603:1096:910:4::11) To DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) 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: DM4PR11MB6020:EE_|CH0PR11MB5316:EE_ X-MS-Office365-Filtering-Correlation-Id: 48fe23b4-2a5e-4ee9-df9e-08df21ddc4cc X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|366016|1800799024|376014|7416014|22082099003|18002099003|4143699003|10067099003|56012099006|11063799006; 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Only > > Intel AET events set this flag, so __mon_event_count() rejects an any_cpu L3 > > event with WARN_ON_ONCE(). The L3 read paths can therefore call > > smp_processor_id() unconditionally to check that the current CPU belongs to the > > domain being read. > > > > MMIO-based LLC occupancy counters can be read from any CPU, so the L3 read > > paths have to tolerate an any_cpu event. Move that check into a helper which > > returns early for any_cpu events, avoiding smp_processor_id() in preemptible > > context, and report a wrong CPU via rmid_read::err. > > "report a wrong CPU via rmid_read::err" is obvious from the patch. > OK, will remove this. > > > > +/** > > + * cpu_on_correct_domain() - Check if current CPU is in the correct > > + * domain for the event. > > The domain is not always relevant. When considering "Return: true if the > current CPU can read this event" ... could something like "cpu_can_read_event()" > be more descriptive? > Yes, that is more accurate, let me rename it. thanks, Chenyu