linux-kernel - Re: [PATCH v2 1/3] sched/fair: Fix warning if NEXT

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Message-ID: <2ab494a6-e5d7-45a9-800a-d104f905f12f@amd.com>
Date: Fri, 29 Nov 2024 23:23:11 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Peter Zijlstra <peterz@...radead.org>
CC: Adam Li <adamli@...amperecomputing.com>, <mingo@...hat.com>,
	<juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
	<dietmar.eggemann@....com>, <rostedt@...dmis.org>, <bsegall@...gle.com>,
	<mgorman@...e.de>, <vschneid@...hat.com>, <linux-kernel@...r.kernel.org>,
	<patches@...erecomputing.com>, <cl@...ux.com>, <christian.loehle@....com>,
	<vineethr@...ux.ibm.com>
Subject: Re: [PATCH v2 1/3] sched/fair: Fix warning if NEXT_BUDDY enabled

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