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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 BL6PEPF0001AB77.mail.protection.outlook.com (10.167.242.170) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9160.9 via Frontend Transport; Mon, 29 Sep 2025 03:53:17 +0000 Received: from SATLEXMB06.amd.com (10.181.40.147) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.2.2562.17; Sun, 28 Sep 2025 20:53:17 -0700 Received: from satlexmb08.amd.com (10.181.42.217) by SATLEXMB06.amd.com (10.181.40.147) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Sun, 28 Sep 2025 22:53:17 -0500 Received: from [172.31.184.125] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.17 via Frontend Transport; Sun, 28 Sep 2025 20:53:12 -0700 Message-ID: <0fc0943c-8ec1-47dd-9b3a-82c68c6bde34@amd.com> Date: Mon, 29 Sep 2025 09:23:06 +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] Revert "sched/core: Tweak wait_task_inactive() to force dequeue sched_delayed tasks" To: Matt Fleming CC: John Stultz , Ingo Molnar , "Peter Zijlstra" , Juri Lelli , "Vincent Guittot" , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , , , Matt Fleming , "Oleg Nesterov" , Chris Arges , References: <20250925133310.1843863-1-matt@readmodwrite.com> <105ae6f1-f629-4fe7-9644-4242c3bed035@amd.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Sep 2025 03:53:17.9013 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b75e166b-b90a-4fab-31be-08ddff0bb990 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: BL6PEPF0001AB77.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9419 Hello Matt, On 9/26/2025 9:04 PM, Matt Fleming wrote: > On Fri, Sep 26, 2025 at 3:43 AM K Prateek Nayak wrote: >> >> Hello John, Matt, >> >> On 9/26/2025 5:35 AM, John Stultz wrote: >>> >>> However, there are two spots where we might exit dequeue_entities() >>> early when cfs_rq_throttled(rq), so maybe that's what's catching us >>> here? >> >> That could very likely be it. > > That tracks -- we're heavy users of cgroups and this particular issue > only appeared on our kubernetes nodes. > >> Matt, if possible can you try the patch attached below to check if the >> bailout for throttled hierarchy is indeed the root cause. Thanks in >> advance. > > I've been running our reproducer with this patch for the last few > hours without any issues, so the fix looks good to me. > > Tested-by: Matt Fleming Thank you for testing the diff. I see Ingo has already posted the scheduler pull for v6.18 which indirectly solves this by removing those early returns. Once that lands, I'll attach a formal commit log and send out a patch targeting the stable kernels >= 6.12. -- Thanks and Regards, Prateek