linux-kernel - Re: [PATCH v2 -next] cgroup: remove offline draining in root destruction to avoid hung

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Message-ID: <btaaerpdl3bolxbysbqcig6kiccdgsoo32td64sk6yo4m5l5zy@nds6s35p6e6w>
Date: Thu, 14 Aug 2025 17:17:28 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Chen Ridong <chenridong@...weicloud.com>
Cc: tj@...nel.org, hannes@...xchg.org, lizefan@...wei.com, 
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, lujialin4@...wei.com, 
	chenridong@...wei.com, gaoyingjie@...ontech.com
Subject: Re: [PATCH v2 -next] cgroup: remove offline draining in root
 destruction to avoid hung_tasks

Hi Ridong.

On Thu, Jul 31, 2025 at 07:53:02PM +0800, Chen Ridong <chenridong@...weicloud.com> wrote:
> Have you come up with a better solution for this?
> Would appreciate your thoughts when you have time.

Sorry for taking so long. (Also expect my next response here may be
slow.)
I tried reproducing it with the described LTP tests [1] (to get a better
idea about what and why needs to be offlined) but I cannot bring it to a
hang nor lockdep report. How do you launch the particular LTP tests to
trigger this?

Thanks,
Michal

[1]
while true ; do
	/opt/ltp/testcases/bin/cgroup_fj_function.sh net_cls $pp
	/opt/ltp/testcases/bin/cgroup_fj_function.sh perf_event
done
(with pp both `;` or `&` for concurrent runs, two vCPUs)

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