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Date:   Wed, 18 Nov 2020 09:45:40 +0800
From:   Boqun Feng <boqun.feng@gmail.com>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Byungchul Park <byungchul.park@lge.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>, torvalds@linux-foundation.org,
        peterz@infradead.org, mingo@redhat.com, will@kernel.org,
        linux-kernel@vger.kernel.org, joel@joelfernandes.org,
        alexander.levin@microsoft.com, daniel.vetter@ffwll.ch,
        chris@chris-wilson.co.uk, duyuyang@gmail.com,
        johannes.berg@intel.com, tj@kernel.org, tytso@mit.edu,
        david@fromorbit.com, amir73il@gmail.com, bfields@fieldses.org,
        gregkh@linuxfoundation.org, kernel-team@lge.com
Subject: Re: [RFC] Are you good with Lockdep?
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Hi Matthew,

On Mon, Nov 16, 2020 at 03:37:29PM +0000, Matthew Wilcox wrote:
[...]
> 
> It's not just about lockdep for semaphores.  Mutexes will spin if the
> current owner is still running, so to convert an interrupt-released
> semaphore to a mutex, we need a way to mark the mutex as being released

Could you provide an example for the conversion from interrupt-released
semaphore to a mutex? I'd like to see if we can improve lockdep to help
on that case.

Regards,
Boqun

> by the new owner.
> 
> I really don't think you want to report subsequent lockdep splats.