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Date:   Sat, 2 Sep 2023 18:28:28 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc:     linux-kernel@vger.kernel.org, Zqiang <qiang.zhang1211@gmail.com>,
        Zhen Lei <thunder.leizhen@huaweicloud.com>,
        "Paul E . McKenney" <paulmck@kernel.org>, rcu@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH 2/2] rcu: Dump vmalloc memory info safely
Message-Id: <20230902182828.e42c6ec7b4a7beb1e4b2b042@linux-foundation.org>
In-Reply-To: <20230830110402.386898-2-joel@joelfernandes.org>
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On Wed, 30 Aug 2023 11:04:00 +0000 "Joel Fernandes (Google)" <joel@joelfernandes.org> wrote:

> Currently, for double invoke call_rcu(), will dump rcu_head objects
> memory info, if the objects is not allocated from the slab allocator,
> the vmalloc_dump_obj() will be invoke and the vmap_area_lock spinlock
> need to be held, since the call_rcu() can be invoked in interrupt context,
> therefore, there is a possibility of spinlock deadlock scenarios.
> 
> And in Preempt-RT kernel, the rcutorture test also trigger the following
> lockdep warning:

"possibility of deadlock" sounds like something -stable kernels would
like to have fixed.

Did you consider the desirability of a -stable backport?

If so, are we able to identify a suitable Fixes: target?