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Shenoy" , Swapnil Sapkal , Shrikanth Hegde , Chen Yu Subject: [RESEND RFC PATCH v2 10/29] sched/fair: Use xchg() to set sd->nohz_idle state Date: Mon, 8 Dec 2025 09:26:56 +0000 Message-ID: <20251208092744.32737-10-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251208083602.31898-1-kprateek.nayak@amd.com> References: <20251208083602.31898-1-kprateek.nayak@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS3PEPF0000C37D:EE_|SA0PR12MB4493:EE_ X-MS-Office365-Filtering-Correlation-Id: 4e47ee7b-14dd-430b-4291-08de363c72a2 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|82310400026|7416014|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?dph2pjiXFHnGx2xEbBEQzvxlsLcRv40p8fDO+79SZknqfPyLPQ82MXRj1yfv?= =?us-ascii?Q?RU3UQSkTo6cFEZ34vyrrSeDQxbbKmi5h3nTYWCm82fPOj8KrUAmyK+H51Z22?= =?us-ascii?Q?jIiGFn5hSe7BbYv1goei0IRSuuG3DlSQfc85hCidcvCOSaoD3lSONQw+NeAN?= =?us-ascii?Q?XcYEu4XzpHetcUgeLPQN3YB5QXPfAYTO+S36sEKut3vdhUoXj5amPrUYN2fX?= =?us-ascii?Q?IjAT643aQU/QbnqEMZe5Ub6C19VZVG5Y6FhJMQx0aoV1oipGraOphndSCJsE?= =?us-ascii?Q?i8ugvLPGRI/BixrO0MhLTOZAj696nfpp4GQBJ9udtVMFhwggzXplWZLEdU01?= =?us-ascii?Q?GMFHFatfsySy8+UDxbogxCX6aH04e/E2SMsqkxjlL3m7ifmpItRxfQks/DLA?= =?us-ascii?Q?0G/PSa+cIwmVLjTdXertdAqaQUVt3G96b9cAk1jGLeWc/bFdoWqIpfsdeM1h?= =?us-ascii?Q?4vClHxKu/YpofPuujcTBDY1jTyi/1P351GUWybjmXKLGW3bQUzHVvU0p9YhV?= =?us-ascii?Q?BqjCnY8Gfa53kSiIhnWP606gpurt4lDesF5ZZuuqJrXm8BFSiMMeYF08BeYs?= =?us-ascii?Q?437GK1xNdOi5gObJxUhWfymmBVU+xlake6kvf1lmWBrBGaP2u7N7RRzDU0+e?= =?us-ascii?Q?oDqVAPXl09GodOftLUPeh5viVIW76qCFsipiJHf1KeL3LqSH8K4p+gQL84xw?= =?us-ascii?Q?jkYYw45pTPQVxVAf9052DhiG8GrEdmvKLnSRtUS4EBUjzcEPRUCXnpUc4wZb?= =?us-ascii?Q?1dzXmIgJTGWvuP6D5TnGFWT2HcfGGoYklWhfbuQqDz8NHnP74s/DktY2Hxhu?= =?us-ascii?Q?EhFUqNalm8YcjXXxdng+XaK3a7UjfAyExGsPMIzEDiQ3dPn0/MOK0x2z3IAV?= =?us-ascii?Q?BBdJOgbpCdyhFp0+z4pycYBDLc9Mt9rtfIsvII2UPyESImXS2JsauYbfyIcn?= =?us-ascii?Q?2+PfMKyrYIYL7VpW4j0KlKs9ceYR25IqUZ+7YAu4ZitNZW71KSrKobJKols6?= =?us-ascii?Q?vS61c35RTi77DRMfDPiDb/utTeFsNiWFA6l53jTrDVorgjGdhRNt+2I1VmI/?= =?us-ascii?Q?aftO5r7r5m9TG3VsYA+o5SWNz17cesBwOnc+jH2CLKNII/Z3jRPWJmkL+BQg?= =?us-ascii?Q?/EoEHW6D0l7mkWtPonvgY0qtd0ZMyMmgZCt/VvMkTV0cMi5yA2SyUUwMrAhH?= =?us-ascii?Q?Dv3tPFeduAhDl57mqTBL005oHA3glCm5VkkOiQG3y78VC3ih2URGUND7CWle?= =?us-ascii?Q?q/ZiWkEStqj67GYrefGUHzb5xgMS7xfie2SvHJdxnzC5n1/miziCYNr3DZy8?= =?us-ascii?Q?TfEGVsBhdH3wEXIS2ZlmUHt87aXQvzIBi/nHhPI9lLrlXjtOUAinmzrANLHd?= =?us-ascii?Q?m7MiTcfXcCqoOUfLbIpro6IcTGInypinmnRPjVIKtDJ4wajeMBU7eXiCfgjn?= =?us-ascii?Q?DT12YN74XX/D1dm6wx3sp8I15uxU6HDhDin6uZHTeULLf2YPgyFUdQyJAEAV?= =?us-ascii?Q?isc4RHVopMpOxXqAIXPrCCyEJ8h4Qf9beS1ddSwJGfjO1LqqMueqw2hrlfY1?= =?us-ascii?Q?WPxybfUa4ug3IwFBLS8=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(376014)(82310400026)(7416014)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Dec 2025 09:30:38.1573 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4e47ee7b-14dd-430b-4291-08de363c72a2 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF0000C37D.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR12MB4493 Content-Type: text/plain; charset="utf-8" "sd->nohz_idle" currently relies on the fact that it is always modified from the local CPU to keep consistency however, the subsequent commits will use the rq->online() callback to correct the "sd->nohz_idle" status from a remote CPU during sched domain rebuild. Use xchg() instead to prevent double accounting of "nr_busy_cpus" if the status update on the local CPU races with a correction from a remote CPU. No functional changes intended. Reviewed-by: Gautham R. Shenoy Signed-off-by: K Prateek Nayak --- kernel/sched/fair.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e3935903d9c5..3128daf1d5d4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12559,7 +12559,9 @@ static void set_cpu_sd_state_busy(int cpu) if (!sd || !sd->nohz_idle) return; =20 - sd->nohz_idle =3D 0; + if (!xchg(&sd->nohz_idle, 0)) + return; + atomic_inc(&sd->shared->nr_busy_cpus); } =20 @@ -12587,7 +12589,9 @@ static void set_cpu_sd_state_idle(int cpu) if (!sd || sd->nohz_idle) return; =20 - sd->nohz_idle =3D 1; + if (xchg(&sd->nohz_idle, 1)) + return; + atomic_dec(&sd->shared->nr_busy_cpus); } =20 --=20 2.43.0