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Date: Fri, 24 Nov 2023 10:58:04 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Kent Overstreet <kent.overstreet@linux.dev>
Cc: linux-kernel@vger.kernel.org, linux-bcachefs@vger.kernel.org,
	boqun.feng@gmail.com, longman@redhat.com, will@kernel.org,
	mingo@redhat.com
Subject: Re: [PATCH 2/6] locking/lockdep: lockdep_set_no_check_recursion()
Message-ID: <20231124095804.GO3818@noisy.programming.kicks-ass.net>
References: <20231122235113.180132-1-kent.overstreet@linux.dev>
 <20231122235113.180132-3-kent.overstreet@linux.dev>
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In-Reply-To: <20231122235113.180132-3-kent.overstreet@linux.dev>

On Wed, Nov 22, 2023 at 06:51:09PM -0500, Kent Overstreet wrote:
> This adds a method to tell lockdep not to check lock ordering within a
> lock class - but to still check lock ordering w.r.t. other lock types.
> 
> This is for bcachefs, where for btree node locks we have our own
> deadlock avoidance strategy w.r.t. other btree node locks (cycle
> detection), but we still want lockdep to check lock ordering w.r.t.
> other lock types.

So earlier you added custom sort order.

Additionally there is the wound-wait mutexes that also have semantics
similar to what you describe.

Explain why you can't use either your own added feature or the existing
infrastructure to solve this?