linux-kernel - Re: [PATCH] sched/schedutil: Fix deadlock between cpuset and cpu hotplug when using schedutil

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Message-ID: <CAB8ipk-8cbur-m733py-cw4bXCt7gkd8gAOXtKO+-fV1B2EeZw@mail.gmail.com>
Date:   Wed, 20 Jul 2022 15:45:27 +0800
From:   Xuewen Yan <xuewen.yan94@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Waiman Long <longman@...hat.com>,
        Qais Yousef <qais.yousef@....com>,
        Xuewen Yan <xuewen.yan@...soc.com>, rafael@...nel.org,
        viresh.kumar@...aro.org, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, linux-kernel@...r.kernel.org,
        ke.wang@...soc.com, xuewyan@...mail.com, linux-pm@...r.kernel.org,
        Lukasz Luba <Lukasz.Luba@....com>
Subject: Re: [PATCH] sched/schedutil: Fix deadlock between cpuset and cpu
 hotplug when using schedutil

Dear all

On Wed, Jul 13, 2022 at 11:20 AM Tejun Heo <tj@...nel.org> wrote:
>
> On Tue, Jul 12, 2022 at 10:49:57PM -0400, Waiman Long wrote:
> > > Well, the only thing I can think of is always grabbing cpus_read_lock()
> > > before grabbing threadgroup_rwsem. Waiman, what do you think?
> >
> > That is a possible solution as cpus_read_lock() is rather lightweight. It is
> > a good practice to acquire it first.
>
> On a similar note, I think we probably should re-enable percpu operations on
> threadgroup_rwsem too by default and allow users who are affected by slower
> write path operations to opt-in. After the new CLONE_INTO_CGROUP which
> doesn't need the rwsem, we have far fewer write lockers after all.
>

 If there's any patch for me to try? I would be very grateful.

Thanks!

---
xw.yan