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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by BN1PEPF00004688.mail.protection.outlook.com (10.167.243.133) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8207.12 via Frontend Transport; Fri, 29 Nov 2024 17:53:20 +0000 Received: from [10.252.205.52] (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Fri, 29 Nov 2024 11:53:14 -0600 Message-ID: <2ab494a6-e5d7-45a9-800a-d104f905f12f@amd.com> Date: Fri, 29 Nov 2024 23:23:11 +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 v2 1/3] sched/fair: Fix warning if NEXT_BUDDY enabled From: K Prateek Nayak To: Peter Zijlstra CC: Adam Li , , , , , , , , , , , , , References: <20241127055610.7076-1-adamli@os.amperecomputing.com> <20241127055610.7076-2-adamli@os.amperecomputing.com> <670a0d54-e398-4b1f-8a6e-90784e2fdf89@amd.com> <20241129095500.GD15382@noisy.programming.kicks-ass.net> <6683a7dc-b83b-489c-bdfc-ad225ab816c6@amd.com> Content-Language: en-US In-Reply-To: <6683a7dc-b83b-489c-bdfc-ad225ab816c6@amd.com> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Nov 2024 17:53:20.8160 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ed82c141-933b-4c29-b747-08dd109eb679 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=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN1PEPF00004688.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB8787 On 11/29/2024 11:16 PM, K Prateek Nayak wrote: > [..snip..] > newidle balance pulls a delayed entity which goes through the > check_preempt_wakeup_fair() path in attach_task() and is set as the next > buddy. On a second thought this is perhaps not required since even if > this delayed entity is picked, it'll go thorough a full dequeue and the > clear_buddies() change above should take care of it. That said, it'll still trigger the following warning in pick_next_entity(): /* ->next will never be delayed */ SCHED_WARN_ON(cfs_rq->next->sched_delayed); which is also why I added that check in check_preempt_wakeup_fair() :) -- Thanks and Regards, Prateek