linux-kernel - Re: [PATCH 00/24] Complete EEVDF

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Message-ID: <20240822155503.GC17097@noisy.programming.kicks-ass.net>
Date: Thu, 22 Aug 2024 17:55:03 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Hongyan Xia <hongyan.xia2@....com>
Cc: 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,
	kprateek.nayak@....com, wuyun.abel@...edance.com,
	youssefesmat@...omium.org, tglx@...utronix.de, efault@....de
Subject: Re: [PATCH 00/24] Complete EEVDF

On Wed, Aug 21, 2024 at 10:46:07AM +0100, Hongyan Xia wrote:
> Okay, in case the trace I provided isn't clear enough, I traced the crash to
> a call chain like this:
> 
> dl_server_start()
> 	enqueue_dl_entity()
> 		update_stats_enqueue_dl()
> 			update_stats_enqueue_sleeper_dl()
> 				__schedstats_from_dl_se()
> 					dl_task_of() <---------- crash
> 
> If I undefine CONFIG_SCHEDSTATS, then it boots fine, and I wonder if this is
> the reason why other people are not seeing this. This is probably not EEVDF
> but DL refactoring related.

Thanks for the report -- I'll see if I can spot something. Since you
initially fingered these eevdf patches, could you confirm or deny that
changing:

  kernel/sched/features.h:SCHED_FEAT(DELAY_DEQUEUE, true)

to false, makes any difference in the previously failing case?