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Received-SPF: SoftFail (protection.outlook.com: domain of transitioning amd.com discourages use of 149.199.90.133 as permitted sender) Received: from satlexmb07.amd.com (149.199.90.133) by CH2PEPF00000145.mail.protection.outlook.com (10.167.244.102) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.360.3 via Frontend Transport; Wed, 26 Aug 2026 06:30:21 +0000 Received: from BLRKPRNAYAK.amd.com (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Wed, 26 Aug 2026 01:30:15 -0500 From: K Prateek Nayak To: John Stultz , Suleiman Souhlal , Ingo Molnar , Peter Zijlstra , "Juri Lelli" , Vincent Guittot , Will Deacon , Boqun Feng , Andrea Righi , CC: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Waiman Long , K Prateek Nayak Subject: [RFC PATCH 03/16] sched/fair: Use enqueue flags for DO_ATTACH in update_load_avg() Date: Wed, 26 Aug 2026 06:28:47 +0000 Message-ID: <20260826062901.2137-4-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260826062901.2137-1-kprateek.nayak@amd.com> References: <20260826062901.2137-1-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: 8bit Content-Type: text/plain 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: CH2PEPF00000145:EE_|PH7PR12MB7380:EE_ X-MS-Office365-Filtering-Correlation-Id: 0f795cc5-1b02-4de5-a5f3-08df033b8165 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|82310400026|36860700016|23010399003|7416014|1800799024|10067099003|56012099006|11063799006|22082099003|18002099003|921020; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: j0cZ+efSGRbUJf9+T/koWHL2vSqa+TrjWdQrXI5OLdTnH4+C67eGPoUqHcTa+jWLNp44dx56JmManzo3IzTEwdtJyy5meGLcv1BczADn9tGjufGUqhDIyhQf9jO4Prr98y2RTtM4ikd6jHUe9rGxnS0CyjuARSNTgcGQKM8cc+dSydkanW3Rz5xFdPUMCIAVlahGn4V8IiGgTku933vK3Bry1eRUN3PRgPZIhqhYKcEXdsBGqDVF+L/LtZf0yug6z5X5W7ZlhWPbkJJly8JVOE6/giTzorHFTovoAzM+HdC+TByqXFJsGSvxcVzwvwN8RZKMmtWUWqRSNmFH1jSW+U1moib1TZULMmTc9xhDhV/vBmz4YsP6LJoE4EI9yAdg0YFxDvFyYyPQV2icDRi7+MfMqZ8dBf8hMg+rhVgThWkm+QaRb9p25Us5hWMQ6VcD X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Aug 2026 06:30:21.7362 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0f795cc5-1b02-4de5-a5f3-08df033b8165 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[149.199.90.133];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CH2PEPF00000145.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB7380 proxy_set_cpu() skips calling ->migrate_task_rq() callback for blocked donor migrations and can lead to incorrect PELT accounting. enqueue_task() -> update_load_avg() depends on migrate_task_rq_fair() to clear the p->se.avg.last_update_time and use this as a gating condition to do DO_ATTACH which is skipped for blocked donors. Use migrate instead of se->avg.last_update_time indicator for adding DO_ATTACH action. Add a defensive WARN_ON_ONCE() to catch any cases that are not covered by the MIGRATING | MIGRATED | INITIAL flags. Fixes: b049b81bdff6 ("sched: Handle blocked-waiter migration (and return migration)") Signed-off-by: K Prateek Nayak --- kernel/sched/fair.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 244f1c68c041..ed397c259509 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5654,7 +5654,7 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s decayed = update_cfs_rq_load_avg(now, cfs_rq); decayed |= propagate_entity_load_avg(se); - if (!se->avg.last_update_time && (flags & DO_ATTACH)) { + if (flags & DO_ATTACH) { /* * DO_ATTACH means we're here from enqueue_entity(). @@ -6110,6 +6110,7 @@ static void enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { bool curr = cfs_rq->curr == se; + int action = UPDATE_TG; /* * If we're the current task, we must renormalise before calling @@ -6120,6 +6121,11 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) update_curr(cfs_rq); + if (flags & (ENQUEUE_MIGRATING | ENQUEUE_MIGRATED | ENQUEUE_INITIAL)) + action |= DO_ATTACH; + else + WARN_ON_ONCE(!se->avg.last_update_time); + /* * When enqueuing a sched_entity, we must: * - Update loads to have both entity and cfs_rq synced with now. @@ -6129,7 +6135,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) * its group cfs_rq * - Add its new weight to cfs_rq->load.weight */ - update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH); + update_load_avg(cfs_rq, se, action); se_update_runnable(se); /* * XXX update_load_avg() above will have attached us to the pelt sum; -- 2.34.1