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Date: Tue, 22 Oct 2024 09:21:12 +0200
From: Christoph Hellwig <hch@lst.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>, Ming Lei <ming.lei@redhat.com>,
	Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Waiman Long <longman@redhat.com>, Boqun Feng <boqun.feng@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] block: model freeze & enter queue as rwsem for
 supporting lockdep
Message-ID: <20241022072112.GA12249@lst.de>
References: <20241018013542.3013963-1-ming.lei@redhat.com> <20241022061805.GA10573@lst.de> <20241022071905.GB16066@noisy.programming.kicks-ass.net>
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On Tue, Oct 22, 2024 at 09:19:05AM +0200, Peter Zijlstra wrote:
> > Not sure modelling it as a trylock is the right approach here,
> > I've added the lockdep maintainers if they have an idea.
> 
> So lockdep supports recursive reader state, but you're looking at
> recursive exclusive state?

Yes.

> If you achieve this using an external nest count, then it is probably (I
> haven't yet had morning juice) sufficient to use the regular exclusive
> state on the outermost lock / unlock pair and simply ignore the inner
> locks.

There obviosuly is an external nest count here, so I guess that should
do the job.  Ming?