linux-kernel - Re: Query regarding deadlock involving cgroup_threadgroup_rwsem and cpu_hotplug

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Date:   Mon, 15 Aug 2022 11:39:35 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Xuewen Yan <xuewen.yan94@...il.com>
Cc:     Mukesh Ojha <quic_mojha@...cinc.com>, Tejun Heo <tj@...nel.org>,
        Imran Khan <imran.f.khan@...cle.com>, lizefan.x@...edance.com,
        hannes@...xchg.org, tglx@...utronix.de, steven.price@....com,
        peterz@...radead.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, Zhao Gongyi <zhaogongyi@...wei.com>,
        Zhang Qiao <zhangqiao22@...wei.com>
Subject: Re: Query regarding deadlock involving cgroup_threadgroup_rwsem and
 cpu_hotplug_lock

On Mon, Aug 15, 2022 at 05:25:52PM +0800, Xuewen Yan <xuewen.yan94@...il.com> wrote:
> Your means is that the problem should be fixed by [1]+[2]'s revert ?

I understood that was already the combination you had tested.
You write in [T] that [1] alone causes (another) deadlock and therefore
the revert of [2] was suggested.

> I just tested the case which reverted the [2]. Need I test with [1] and [2]?

It'd be better (unless you haven't already :-), my reasoning is for the
[1]+[2] combo.

Thanks,
Michal

[T] https://lore.kernel.org/r/CAB8ipk_gCLtvEahsp2DvPJf4NxRsM8WCYmmH=yTd7zQE+81_Yg@mail.gmail.com/