linux-kernel - Re: [PATCH v2] KVM: Move VM's worker kthreads back to the original cgroups before exiting.

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Message-ID: <Yeclbe3GNdCMLlHz@slm.duckdns.org>
Date:   Tue, 18 Jan 2022 10:39:09 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Vipin Sharma <vipinsh@...gle.com>
Cc:     Michal Koutný <mkoutny@...e.com>,
        pbonzini@...hat.com, seanjc@...gle.com, lizefan.x@...edance.com,
        hannes@...xchg.org, dmatlack@...gle.com, jiangshanlai@...il.com,
        kvm@...r.kernel.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: Move VM's worker kthreads back to the original
 cgroups before exiting.

Hello,

On Tue, Jan 18, 2022 at 12:25:48PM -0800, Vipin Sharma wrote:
> Automated tools/scripts which delete VM cgroups after the main KVM
> process ends were seeing deletion errors because kernel worker threads
> were still running inside those cgroups. This is not a very frequent
> issue but we noticed it happens every now and then.

So, these are normally driven by the !populated events. That's how everyone
else is doing it. If you want to tie the kvm workers lifetimes to kvm
process, wouldn't it be cleaner to do so from kvm side? ie. let kvm process
exit wait for the workers to be cleaned up.

Thanks.

-- 
tejun