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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 BL6PEPF0001AB50.mail.protection.outlook.com (10.167.242.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8534.20 via Frontend Transport; Fri, 14 Mar 2025 04:14:56 +0000 Received: from [10.136.37.23] (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; Thu, 13 Mar 2025 23:14:53 -0500 Message-ID: <28267ba4-94a2-4a77-9c34-7273a102c183@amd.com> Date: Fri, 14 Mar 2025 09:44:45 +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 6/7] sched/fair: fix tasks_rcu with task based throttle To: Aaron Lu , Valentin Schneider , Ben Segall , Peter Zijlstra , Josh Don , Ingo Molnar , Vincent Guittot CC: , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Mel Gorman , Chengming Zhou , Chuyi Zhou References: <20250313072030.1032893-1-ziqianlu@bytedance.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: 14 Mar 2025 04:14:56.8314 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 374c0ba4-ccfb-4e09-a6f2-08dd62aec795 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: BL6PEPF0001AB50.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6371 Hello Aaron, On 3/13/2025 12:52 PM, Aaron Lu wrote: > Taskes throttled on exit to user path are scheduled by cond_resched() in > task_work_run() but that is a preempt schedule and doesn't mark a task > rcu quiescent state. > > Fix this by directly calling schedule() in throttle_cfs_rq_work(). Perhaps that can be gotten around by just using set_ti_thread_flag() resched_curr() will also call set_preempt_need_resched() which allows cond_resched() to resched the task. Since exit_to_user_mode_loop() will run once again seeing that TIF_NEED_RESCHED is set, schedule() should follow soon. Thoughts? > > Signed-off-by: Aaron Lu > --- > kernel/sched/fair.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index f26d53ac143fe..be96f7d32998c 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5847,6 +5847,7 @@ static void throttle_cfs_rq_work(struct > callback_head *work) > struct cfs_rq *cfs_rq; > struct rq *rq; > struct rq_flags rf; > + bool sched = false; > > WARN_ON_ONCE(p != current); > p->sched_throttle_work.next = &p->sched_throttle_work; > @@ -5879,9 +5880,13 @@ static void throttle_cfs_rq_work(struct > callback_head *work) > dequeue_task_fair(rq, p, DEQUEUE_SLEEP | DEQUEUE_SPECIAL); > list_add(&p->throttle_node, &cfs_rq->throttled_limbo_list); > resched_curr(rq); > + sched = true; > > out_unlock: > task_rq_unlock(rq, p, &rf); > + > + if (sched) > + schedule(); > } > > void init_cfs_throttle_work(struct task_struct *p) -- Thanks and Regards, Prateek