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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 BL02EPF00029927.mail.protection.outlook.com (10.167.249.52) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8230.7 via Frontend Transport; Tue, 3 Dec 2024 16:48:47 +0000 Received: from [10.252.216.179] (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; Tue, 3 Dec 2024 10:48:43 -0600 Message-ID: Date: Tue, 3 Dec 2024 22:18:40 +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 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> <20241203160514.GI35539@noisy.programming.kicks-ass.net> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20241203160514.GI35539@noisy.programming.kicks-ass.net> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Dec 2024 16:48:47.3445 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f253af9f-cfcc-4b2f-3f69-08dd13ba5b5e 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: BL02EPF00029927.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB8052 Hello Peter, On 12/3/2024 9:35 PM, Peter Zijlstra wrote: > On Thu, Nov 28, 2024 at 12:59:54PM +0530, K Prateek Nayak wrote: > >> Can you please try the following diff instead of the first two patches >> and see if you still hit these warnings, stalls, and pick_eevdf() >> returning NULL? >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index ff7cae9274c5..61e74eb5af22 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -5478,6 +5478,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) >> bool sleep = flags & DEQUEUE_SLEEP; >> update_curr(cfs_rq); >> + clear_buddies(cfs_rq, se); >> if (flags & DEQUEUE_DELAYED) { >> SCHED_WARN_ON(!se->sched_delayed); >> @@ -5520,8 +5521,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) >> update_stats_dequeue_fair(cfs_rq, se, flags); >> - clear_buddies(cfs_rq, se); >> - >> update_entity_lag(cfs_rq, se); >> if (sched_feat(PLACE_REL_DEADLINE) && !sleep) { >> se->deadline -= se->vruntime; >> @@ -8767,7 +8766,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int >> if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) >> return; >> - if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK)) { >> + if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK) && !pse->sched_delayed) { >> set_next_buddy(pse); >> } > > > Prateek, I've presumed your SoB on this change: > > https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=sched/urgent&id=d1139307fe97ffefcf90212772f7516732a11034 No objections from my side! While at it, perhaps you can also squash in: diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3ed4af8be76b..eadcd64c03e9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5519,8 +5519,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) if (sched_feat(DELAY_DEQUEUE) && delay && !entity_eligible(cfs_rq, se)) { - if (cfs_rq->next == se) - cfs_rq->next = NULL; update_load_avg(cfs_rq, se, 0); set_delayed(se); return false; -- Since we do a clear_buddy() upfront, we no longer need this special case for delayed entities. Tested it on top of queue:sched/urgent with hackbench and I didn't run into any problems / splats. Thank you. > > Holler if you want it modified. > > Thanks! -- Thanks and Regards, Prateek