linux-kernel - Re: [PATCH] sched/fair: Fix DELAY_DEQUEUE issue related to cgroup throttling

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Message-ID: <tencent_DB76A6B5C83E21339A969893A285312A1F07@qq.com>
Date: Wed,  1 Oct 2025 08:49:24 +0800
From: Han Guangjiang <gj.han@...mail.com>
To: pierre.gondois@....com
Cc: bsegall@...gle.com,
	dietmar.eggemann@....com,
	fanggeng@...iang.com,
	gj.han@...mail.com,
	hanguangjiang@...iang.com,
	juri.lelli@...hat.com,
	linux-kernel@...r.kernel.org,
	mgorman@...e.de,
	mingo@...hat.com,
	peterz@...radead.org,
	rostedt@...dmis.org,
	vincent.guittot@...aro.org,
	vschneid@...hat.com,
	yangchen11@...iang.com
Subject: Re: [PATCH] sched/fair: Fix DELAY_DEQUEUE issue related to cgroup throttling

>> When both CPU cgroup and memory cgroup are enabled with parent cgroup
>> resource limits much smaller than child cgroup's, the system frequently
>> hangs with NULL pointer dereference:
> Is it happening while running a specific workload ?
> Would it be possible to provide a reproducer ?

Hi,

Yes, this happens on our complex workload. We are using PREEMPT_RT option,
and from the error log, we can see that rt mutex PI operation is
being executed, and it needs to switch scheduler for a delay_dequeued task.
The parent group of this delay_dequeued task is being throttled by
cgroup at this time. And We currently do not have a minimal bug reproduction
program constructed.

similar issue: https://lore.kernel.org/all/87254ef1-fa58-4747-b2e1-5c85ecde15bf@windriver.com/
 
Thanks,
Han Guangjiang