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client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by BL02EPF0001A0FC.mail.protection.outlook.com (10.167.242.103) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.292.8 via Frontend Transport; Tue, 4 Aug 2026 08:45:05 +0000 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.41; Tue, 4 Aug 2026 03:45:05 -0500 Received: from [10.136.47.95] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.41 via Frontend Transport; Tue, 4 Aug 2026 03:45:00 -0500 Message-ID: <7bf9d48c-2a74-45b6-bfdc-faf10830f3f1@amd.com> Date: Tue, 4 Aug 2026 14:14:59 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] sched/numa: Prevent race on sysctl_numa_balancing static key To: chenjinghuang , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Paolo Bonzini CC: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , References: <20260803123046.297426-1-chenjinghuang2@huawei.com> <3149b834-b4bc-485c-8ea5-6b5c6d2d4db1@amd.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: nbEutdGlwxMZ0TWF1J0Ok0+fap2wHAu3/ouAE7K/zMvEDKW3uE7UkFA7woe73QoM5GXCxknwKkxR+rksyWaZwrXWks9yWSrJrT7p63hXg5SM7uDwrK4V2ThdnmeV29GJB1MB6wJTI5Z0rofF7CqBUmUYSLWI1wWRb3At1xPj5yazlgBrNYXmAvxQr5hMXHziHgQRnUvFzT2CV4Z1HawPZJHprOXq+VWKVyrCi/z5hL8JJy0DAi1174XZ05Lkf3EiqchSdTqGAZzuevzT2qvLvh2mDH0ZY4snwrNhv8rJPFTo41gJ+gvjTxDbLGKKkhohgoeuHfmJfusehFZkCDu5L0/vljdUz2uKg9aQ/fB1iL1P09TGnffEnBRAgCrdRTHVxoKPtx+5JjjnX7ngG60b5r3mKR5uprlUkthLQ8mKRVma1W890IMTJYxaIB430vds X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Aug 2026 08:45:05.3168 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 02194543-eedf-4253-9ea6-08def204ae70 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF0001A0FC.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB6046 Hello Chen, On 8/4/2026 2:05 PM, chenjinghuang wrote: > You're right - my mistake, I'll move numabalancing_mutex into sysctl_numa_balancing() > and drop it from the early-init path. No one races during init, so the lock is only > needed for sysfs writes: > > +static DEFINE_MUTEX(numabalancing_mutex); > + > static int sysctl_numa_balancing(const struct ctl_table *table, int write, > void *buffer, size_t *lenp, loff_t *ppos) > { > @@ -4666,11 +4668,13 @@ static int sysctl_numa_balancing(const struct ctl_table *table, int write, > if (err < 0) > return err; > if (write) { > + mutex_lock(&numabalancing_mutex); nit. You can just use a: guard(mutex)(&numabalancing_mutex); > if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && > (state & NUMA_BALANCING_MEMORY_TIERING)) > reset_memory_tiering(); > sysctl_numa_balancing_mode = state; > __set_numabalancing_state(state); > + mutex_unlock(&numabalancing_mutex); ... and save on the need to explicitly call unlock here. > } > return err; > } -- Thanks and Regards, Prateek