linux-kernel - Re: [PATCH] KVM: Move VM's worker kthreads back to the original cgroups before exiting.

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Message-ID: <CAHVum0eh8CvyH7EjsnxzBbHG_UZi-8_OikZv146a7_bvUvUU6A@mail.gmail.com>
Date:   Wed, 22 Dec 2021 12:12:12 -0800
From:   Vipin Sharma <vipinsh@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     seanjc@...gle.com, "Michael S. Tsirkin" <mst@...hat.com>,
        dmatlack@...gle.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: Move VM's worker kthreads back to the original
 cgroups before exiting.

On Wed, Dec 15, 2021 at 10:27 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> So the issue is that the kthread_stop happens around the time
> exit_task_work() destroys the VM, but the process can go on and signal
> its demise to the parent process before the kthread has been completely
> dropped.  Not even close() can fix it, though it may reduce the window
> completely, so I agree that this is a bug and vhost has the same bug too.
>
> Due to the issue with kthreadd_task not being exported, perhaps you can
> change cgroup_attach_task_all to use kthreadd_task if the "from"
> argument is NULL?

Thanks for the suggestion. This also works, I will send out a patch.