linux-kernel - Re: [RFC] Are you good with Lockdep?

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Message-ID: <20201118014540.GA1278700@boqun-archlinux>
Date:   Wed, 18 Nov 2020 09:45:40 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Byungchul Park <byungchul.park@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, torvalds@...ux-foundation.org,
        peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        linux-kernel@...r.kernel.org, joel@...lfernandes.org,
        alexander.levin@...rosoft.com, daniel.vetter@...ll.ch,
        chris@...is-wilson.co.uk, duyuyang@...il.com,
        johannes.berg@...el.com, tj@...nel.org, tytso@....edu,
        david@...morbit.com, amir73il@...il.com, bfields@...ldses.org,
        gregkh@...uxfoundation.org, kernel-team@....com
Subject: Re: [RFC] Are you good with Lockdep?

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.