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Sat, 21 Mar 2026 07:47:45 +0000 Message-ID: <470ce693-ee2e-414e-930b-d6581d649110@intel.com> Date: Sat, 21 Mar 2026 15:47:34 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [tip: sched/core] sched/topology: Compute sd_weight considering cpuset partitions From: "Chen, Yu C" To: K Prateek Nayak CC: , , Shrikanth Hegde , Valentin Schneider , Dietmar Eggemann , , Nathan Chancellor , Peter Zijlstra References: <20260312044434.1974-2-kprateek.nayak@amd.com> <177382132440.1647592.1849180094328011054.tip-bot2@tip-bot2> <20260320235824.GA1176840@ax162> <60406550-d90e-4efa-a4d9-f901421887f8@intel.com> Content-Language: en-US In-Reply-To: <60406550-d90e-4efa-a4d9-f901421887f8@intel.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SI1PR02CA0003.apcprd02.prod.outlook.com (2603:1096:4:1f7::20) 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_|MN0PR11MB6009:EE_ X-MS-Office365-Filtering-Correlation-Id: f15204ea-45d4-4c77-034b-08de871e2379 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|1800799024|56012099003|22082099003|18002099003; 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>> >> which should have crashed too if we had a NULL pointer in the >> cpumask range. So I'm at a loss. Maybe the pc points to a >> different location in your build? >> > > A wild guess, the major change is that we access sd->span, before > initializing  the sd structure with *sd = { ... }. The sd is allocated > via alloc_percpu() uninitialized, the span at the end of the sd structure > remain uninitialized. It is unclear how cpumask_weight(sd->span) might be > affected by this uninitialized state. Before this patch, after *sd = > { ... } > is executed, the contents of  sd->span are explicitly set to 0, which might > be safer? > I replied too fast, please ignore above comments, the sd->span should have been set via cpumask_and(sd_span, cpu_map, tl->mask(tl, cpu))