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Wed, 26 Aug 2026 22:51:54 -0500 Message-ID: Date: Thu, 27 Aug 2026 09:21:53 +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: [RFC PATCH 06/16] sched/core: Queue blocked donor onto sleeping owner for chain-wakeup To: Andrea Righi CC: John Stultz , Suleiman Souhlal , Ingo Molnar , Peter Zijlstra , "Juri Lelli" , Vincent Guittot , Will Deacon , Boqun Feng , , Dietmar Eggemann , Steven Rostedt , Ben Segall , "Mel Gorman" , Valentin Schneider , "Waiman Long" References: <20260826062901.2137-1-kprateek.nayak@amd.com> <20260826062901.2137-7-kprateek.nayak@amd.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH1PEPF0000A345:EE_|PH7PR12MB8039:EE_ X-MS-Office365-Filtering-Correlation-Id: 033bcf42-b258-47ac-fff2-08df03ee8bef X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|82310400026|376014|7416014|1800799024|23010399003|10067099003|56012099006|11063799006|4143699003|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: cNG4LlBkJqVmrSHkpBWxfmZgjPDI4UIJ/DBzrX53OlLrs1B7jk3hKnqR6ax8rFx7lhvRKPq+YZimkscZCTSzkmLCV0OmL7zGxHf9tRfkHxcoNIWwdkxCi3bB2FLy56I0NKYs8sUzqtmFPNO9VJTK3rDQ1gkdMRRACPPThaD8peM204fCUvWTkzu/85Wj9NmesAlzgp+W00eKS0IIfx7DbKmcJ1rlOlRDXB0MBOUSV4bZa9zWBkZnc4sQIelaMVF587sFUKLj7yw+Qt8lL+FV1oIs3w9gTvDAGpl1TX4AMRyJvv42123v9Ejqh29No+U7JyASHxegL8H5/pJfxxhjSE3/raHQzMMdud9gQ2MGeC3ftVQOnSo8DUqx87OKS/xo42J8n3o91jq/qkwLFgSiqiDrc+EnUUQeBbECSWllClejzWHZEmQb4yFzlgGva8EX X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Aug 2026 03:51:59.3425 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 033bcf42-b258-47ac-fff2-08df03ee8bef 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=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CH1PEPF0000A345.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB8039 Hello Andrea, On 8/26/2026 9:50 PM, Andrea Righi wrote: >> +static void proxy_enqueue_on_owner(struct rq *rq, struct task_struct *owner, >> + struct task_struct *p) >> +{ >> + lockdep_assert_rq_held(rq); >> + lockdep_assert_held(&owner->blocked_lock); >> + >> + WARN_ON(!p->on_rq); >> + WARN_ON(p->sleeping_owner); >> + >> + WRITE_ONCE(p->sleeping_owner, owner); >> + list_add(&p->blocked_node, &owner->blocked_head); >> + proxy_resched_idle(rq); >> + >> + /* >> + * Order against __activate_blocked_task_slowpath() checking >> + * owner->blocked_list after setting owner->on_rq. > > This should be owner->blocked_head not owner->blocked_list, right? Correct! My bad. Also the slow-path is proxy_activate_blocked_task() that gets introduced in Patch 14. I missed renaming it here. And ack on other comments too above. > >> + */ >> + smp_mb(); >> + >> + if (READ_ONCE(owner->on_rq)) { >> + /* >> + * owner has woken up and may miss activating us. >> + * Remove ourself from "owner->blocked_head" and try >> + * find_proxy_task() again considering the owner's >> + * new state. >> + */ >> + __proxy_dequeue_from_owner(p); >> + return; >> + } >> + >> + /* >> + * Owner is fully blocked. __activate_blocked_task_slowpath() >> + * will see us on the list during wakeup and DTRT. >> + */ >> + block_task(rq, p, READ_ONCE(p->__state)); >> +} -- Thanks and Regards, Prateek