linux-kernel - Re: [PATCH] cgroup: wait for css offline when rmdir

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Message-ID: <YpZO26mJ3Wm0AeHo@slm.duckdns.org>
Date:   Tue, 31 May 2022 07:22:35 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Hongchen Zhang <zhanghongchen@...ngson.cn>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cgroup: wait for css offline when rmdir

On Tue, May 31, 2022 at 07:19:31AM -1000, Tejun Heo wrote:
> Maybe just keep the sequence numbers for started and completed offline
> operations and wait for completed# to reach the started# on memcg alloc
> failure and retry? Note that we can get live locked, so have to remember the
> sequence number to wait for at the beginning. Or, even simpler, maybe it'd
> be enough to just do synchronize_rcu() and then wait for the offline wait
> once and retry.

Also, given that it's an memcg ID issue. It probably makes sense to
implement it on the memcg side.

Thanks.

-- 
tejun