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Date: Thu, 10 Apr 2025 10:04:54 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: kvm@vger.kernel.org, Alexander Potapenko <glider@google.com>,
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Subject: Re: [PATCH v2 1/4] locking/mutex: implement mutex_trylock_nested
Message-ID: <20250410080454.GW9833@noisy.programming.kicks-ass.net>
References: <20250409014136.2816971-1-mlevitsk@redhat.com>
 <20250409014136.2816971-2-mlevitsk@redhat.com>
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In-Reply-To: <20250409014136.2816971-2-mlevitsk@redhat.com>

On Tue, Apr 08, 2025 at 09:41:33PM -0400, Maxim Levitsky wrote:
> Allow to specify the lockdep subclass in mutex_trylock
> instead of hardcoding it to 0.

We disable a whole bunch of checks for trylock, simply because they do
not wait, therefore they cannot deadlock.

But I can't remember if they disable all the cases required to make
subclasses completely redundant -- memory suggests they do, but I've not
verified.

Please expand this Changelog to include definite proof that subclasses
make sense with trylock.