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Date:   Thu, 3 Feb 2022 15:19:12 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Roman Gushchin <guro@fb.com>
Cc:     <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        Alexander Egorenkov <egorenar@linux.ibm.com>,
        Waiman Long <longman@redhat.com>, Tejun Heo <tj@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Shakeel Butt <shakeelb@google.com>,
        Jeremy Linton <jeremy.linton@arm.com>,
        <cgroups@vger.kernel.org>
Subject: Re: [PATCH RESEND] mm: memcg: synchronize objcg lists with a
 dedicated spinlock
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On Tue, 1 Feb 2022 14:33:04 -0800 Roman Gushchin <guro@fb.com> wrote:

> Alexander reported a circular lock dependency revealed by the mmap1
> ltp test:
>   LOCKDEP_CIRCULAR (suite: ltp, case: mtest06 (mmap1))
> 
> ...
>
> Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API")

I'm thinking it needs cc:stable.  It sounds unlikely that we'll hit it
in real life, but lockdep splats are concerning and I expect downstream
kernel consumers will end up merging this anyway, for this reason.